What was the purpose of the CF6 Jet Engine Diagnostics Program?

The purpose was to determine the causes of performance degradation for each component of revenue service engines.

What improvements were noted in turbine efficiency?

Improvements in roundness were established at approximately 0.38 mm, which translated to a 0.86 percent increase in turbine efficiency.

How was the performance of the high pressure turbine Stage 1 tip clearance measured?

The performance was measured as 0.44 mm per percent of turbine efficiency at take-off power.

What correlation was found in the test results?

A good correlation was found between the analytical model of round engine clearance response and the measured data.

CF6 jet engine diagnostics program. High pressure turbine roundness/clearance investigation

Q: What were the findings regarding high pressure turbine clearance?

The findings indicated that increased airfoil tip radial clearances in the high pressure turbine significantly contributed to performance degradation.

Document

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N A _ C R -165581 ; i I ' i I CF6 Jet En g i ne D ia gnos tics Prosr _ - _ gh P reSsur e Tu:b i ne Jun e 19 ,89 ii "4, Tl|hl a n d Sul _ i|lll §, Rig h t OIl _ l _; Ko und nils / Cl e & r a nc a I n va s_i g a_ i on 0 , Pu _ or ml_ Or98nttltlo _ @ od e :: i 7. Author(1) ' 8, PlrformJngOrgenlsttlon Report No,.

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...... 0 . Ftff oC mina O r aen i u tlotl NilnU _ AddlllSl General El ec r. ric Co= p arty , ; 11. Contr K t or Grant No, Ai r c r a f t En g i n e G : o up _ C l n cl nn at i , _ Ohi o N AS 3-2063 1 n . r n . o f ,. _ _d _ rl _ Cov., d 12 . S pon _ :xi n a _ Y N a memd A(Xlrm Contra c t o r t _ a p o rt Na ti ona l Aero na U tics and Spa c e A d m in i s t ra ti on _ " Wa s h i n g_ or _D . C . 2054 5 - 14. _en_ l _ A le_ Cod e I S , S. _ lem _ ary No te s Pr oj ec t M an a ge r - J , KcAula y, P r o _ e c t En gi neer - R . P, D an g l er : NASA _ Lew is Resear c h Cancer, Cleveland , O h i o • m, i 16, A_ s c t A s ys t e m a tic t es t progra m w as c o nd u cte d t o e valuate . oth e e f fe ct s of h i g h pressure t urb in e cl earan c e c h a n g e s o n e n g i ne a n d m odu l e p e rf or ma n c e and t o measure C F 6 - SOC h i gh pr essure _ urb i na-- S t a ge 1 . tip c lea r a nce and _t a t on ou t- of -r o u ndness dur in g e _ aady- st a t e a n d tr ans i e nt o _ e r a ti ou .

T h e r emt lt s i nd icate d a good c or relati o n of t h _ anal y tic a l m n de l of rou n d e n g i ne cl ear anc e re spo n s e w ith me asu red d ata. Th e stat o r ou t- of - rou n d n es s meas u r emen t s v er i f ie d tha t the a n al y tical tech - n i q u e for p r edicti n g th e d i s to r ti on e _ £e cts of m e cha n ical l o a ds i s acc ur at e, where as th e t e c h ni- q u e f or c al c u l a ti ng t h e ef f e ct s o f cert a i n circ_m_e reu tia l t h e r mal gr ad ie n ts re q u i r e s so me m od i f ic a _i on s . A p o te n ti al for. imp rovemen t s in r ound n e s s w a s es t abl i shed i n t h e o rder o f 0.38 (0.015 i n. ), e q ui vale£ t t o 0 , 86 p er c e nt t ur bi ne , ef f ici en cy wh ich t ran sl a te s t oe c ru is e S FC im_ ove m en _ of 0.36 _ e rc en t , Th e _ P t u r b i ne S t age 1 .t ip c l earan c e p e rf orman c e de ri va tive w as esta bli s h ed as 0 , 44 =m ( 17 mi ls ) p ar p er ce n t of t u rbin e eff ici en c y a t _ ak e -of f p o wer, s o me wha t s_ alle r , _ h are_ o _ e, m ore sen siti v e • th an p red ict ed f ro m pr ev ious i nv estig a ti on s .

Je t E n8 1 ne l Un c l a sb i f i ed Unl imit ed Kigh P r e s s ur e T ur bi ne C learance / K _ ndne s e I e. Turbofan Engi ne Un c las sifie d ' _m salebytheNational Technical Inf m mtio _ Service, $ _ ingfield, Virginia 2 218 1 _ AS _ -C - I_ (R e v. I0.75) The work wa s p e r formed by the E ven da le Pr o duc t E nsineerins O p e ra_i o n of Gene r al E lectr ic' s A i r c raft E ng i ne Group, Ai rcraft E ns i no E ng i neer i ns D i v £ - | s i on, Evendale, Oh i o. The pro s ra m w as conduc t ed fo r the N a ti onal A e ronau tic s and Space Ad mini strat i o n , Lew i s R esea rc h Center, Cl e veland , Oh i o, under Sub- task 5 .2 o f t h e CY6 J et E nsU e D i a g nos tic s P r o s ra m , Con tr a c t Number NAS3-20631.

The CF6 Jet En gi ne D i a g nost ic s Pro s ram i s pa r t of t he En s £ne Compon en t _ nprove- • ' m e n t (EC I_ Pro j ect, w h ic h i s pa r t o f the NASA A ircr aft gnersy Eff ici en cy (ACE E) _ Pro g ra m . The NASA Pro j e ct En gi neer for th i s pro g ram w as R. P. D eng ler. Th e pro g ram w as i n i t i ated i n January 1980 and c ompleted i n M a y 1981.- The report w as prepared b y W. A. Fas c h£u g , G enera l E l e c t ric Pro gr a m - M ana g er, and W. D . Howard, Pro J e c t - En $i neer, wi th the ass i sta nc e of M . W ............

Tho ma s, M . P. M urph y, and B. D. Beck.

t l • I / / TABLE OF CONTENTS Section Page ,- 1. 0 SUMMAR Y i !

2.0 I NTRODUCT I ON 2 - 3 . 0 B AC K GR O UND 4 3 _ I Hig h P ressure Turbine C le a rance R esp o nse 4 3.2 H ish P res su r e Tu rb in e R o undnes s 9.

3. 2 . 1. Tur bi ne Midf r ame Effec t s 9 3.2.2 H PT Shr o u d Sup po rt Tem p erature E ffec t s 11 3 . 2 . 3 Low__P l ess u re • Tu rbi n e Ca s i n g Eff ec t s 1 8 4.0 TEST VE HI CL E AND I NSTEUME NTA TZON 1 9 4. 1 EnB l n e C o nf l Burat l on .............................. 1 9 4 .2 _ n s t r um e ntati o n 20 4 .2 . 1 G e neral _ nf o rma t i o n 20. - 4 .2. 2 Aer o dyna mi c I nstrumentat io n 22 I 4 .2.3 St r uc t u r al _ n s t rum entati o n 2 3. .

4 .2. 4 Clearanc e om eter Pr o be Instrumentati o n 2 3 5 . 0 - TES T F A C I LI T Y 2 6 6.0 TE S T PR OCE DU RE 2 8 6. 1 P erfo rman c e Tee = 2 8 6.2 PoS t t est Tea r d o wn and Hardware Analy s is 32. ..

7._ _---TEST RESULTS 33 7. 1 En Ei n e Performan c e 33 7.1.1 D i s c uss i on o f . Results 3 4 7.2 HP Tu r h l ne Stase 1 Clearance Map 38 7 .2.1 Clearance As a Fun ctio n o f T lm e f o r a 10-Se co nd A c cel fr o m Ground Idle to Takeoff Power 38 7.2.2 C l earance As a Fun c t i on of T lm e f o r a De e e l from St eady- St ate Takeoff P owe r t o Gr o und I dl e 40 7 .2.3 Reburst 40 ' -- 7.2. 4 Clearance A s a Function of Core Speed, R2; Compressor Ex it Te m perature, T3 ; a nd Compressor E x it Pre s sure , P 3 _ 44 V .

PRECE D ING.PAGE _ L ANI( N O T FILM ED TABLE OF CONTENTS (CONCLUDED_ _ Section PaR0 il _i 7. 3 En si n e Shu t down (S to pcock) Te st 44 i 7 . 4 . C o ld Motor in g D ata 49 7.5 H ig h Pres s ur e Turbine S t a re r Roundnes s _ 9 _i 7 .5.1 L o w Pressure Turbine T e m p e r a t u r e s 53 ._ __ . .

7.5. 1 . 1 H or iz o n t a l F l ange / Skln Tempera t ure G r ad i en t s 5 3 7.5.1. I Ci r c u mfe r en ti al Tem p era t ure G r adien t s 53 7 .5.2 Turbine M idf r ame Tem p era t u r e s 53 7 .5.3 H ig h Pre s sure Tu r bin e S t a to r Tempera t u r es 67 _i_i 7 .5. 4 L o wP re ssur e Tu rb ine Eff e ct s 8 2 _: 7 .5.5 Turbine Mi d fra m e. Effec t s 8 2 !i i 7.5. 5 Mea s ured Trans le n t HPT S t a rer Roundness 87 _ i 7 .5.7 Discussi o n o f R o undness Da t a 8 7 i i 7 .6 . E l e arance an d R o undness Q uan tit a ti ve Ba se l i n e 8 7 & .0 - D I SCUSS I ON OF RESULTS i 06

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LI STOF ILLUST T!O S I

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J | I. C F6 -5 0 HP Tur bi ne Cro ss Se c t i on .... 5 +I 2. Typ i cal CLASS MASS Model of liFT Sta g e 1 Noz z le SuPport. 5 1 3. Typ ic al CLASS MA SS M o d e l of HPT Shroud Suppor t , S t a ge 2 No zz le _ S upp o rt and Tur b i ne Mid fra m e. 7 ..... ':!

4. Typ ic al H o t R otor Re bu r st. 8 . + : 5. . C F 6-50 M oJ o rCas e s and Frames. i0 + :_ 6. Tu r b i n e Midf r a me . 12 7. T ypic al Tu rbl n r Mi df r ame Fo rwa rd Ha t Sec ti o n Defl ect i o n R e lat iV e t o H u b_ R e sult l n s fr o m,Tak e o ff T r an si e nt O p e r at io n. 13 8 . Typ i cal EF T S h r oud Support Defle c ti o n Rela t ive to TMF Hub _ I | (Caused b y TMFHa t Sec t ion D i sto rt i o n) R esulting from Ta k eoff I ' :: _' Transi e n t Opera t i o n .... .... 1 4.... I :, 9. C o mpari so n of Calculated V ersus M ea s u r edDi s t or t lo n in Static .

Te st , Ver tlc al M ountReact i on Load l n g , 15, I0 . Com p aris o n of Calculated . Versus M easured +D istort lo n in S tatic Test, T o rque R eac t i o n Mo unt L o ad i n g . 1 6 Ii ............... Comparis o n o f Calculated Versus M easured Distorti o n i n Static _ T est , TMF S t r uts Number 2 ,4, 5 Heated A bove Rest of Structure. 1 7 .

12 , Engine I nstru m entat lo n. 21 13. HP Tur b ine .Pr o be L o cati o n / Rew o rked.-C omP onent s . ° - 4 P 1 4. Probe Angular Po siti on A f t Looking Forward 25 1 5 . CF 6 E ng i n e i n Te st Cel l. 2 7 1 6.. Te s t Seque n ce ( Co n t in ued o n F ig ure 1 7). 29 :1 ............ 1 7 +. Test Sequence. 30 . ,_ i 1 8. H P Tu rb i ne E ff i c i en c y Loss A s s o ci ated s ith Tip C l earan c e Chan g e t of 0. 3 0 5 m m ( 0 .012 inc h ). 3 5 1 9. E xhaus t Gas Te m pe r ature I ncrease As soc i a t ed wit h 0. 305 m m ( 0 . 012 inch) Increa s e i n HP Tur bin e T ip Clearance. 35 i 20 . Loss Overall E n gi ne Perfor m an c e As so ci ated w ith HP T urbine Tip i Clearance Change of 0 . 305 m m (0 . 012 •in ch ) . 37 +i J vi i i

k +

LIST OF ILLUSTRATIONS (Contln ued) nll 0

Fig ure _

21. S t a g e 1 Blade Clearance a s a Fun cti on of _im e Du ri n g a n A cc e l - I st a ti on from Ground _ dle t o Takeoff Power. 39 22. S t age 1 Blade C l ea r an c e as a Func tio n of Time Dur l n g a D ec e l - era ti on fro m Takeoff Power t o Ground Idle. 41 23. Clearance VersusTime Af t er R ebu r s t f o rVarl o us Gr o und I dle Dw e ll I n t ervals . 42 24. Clearance E ffe cts from E ng i ne R e b urs t Af t er Two M i nu t e Dwell Ti m e . 4 3 25 . _ __Co r e S peed as a F u n cti on of T i m e Exh i b it ln g a 2 Minu te Dw e ll Pr i or t o Reburs t . 4 3 2 6. Clearance as a 2 un ctl on of Core Speed. 4 5 2 7. Cl e arance as a Func t i o n of Co mpressor. Exl t Te m pera t ure. 46 28 . Clearan c e asaFun ctlo n o f C o mpressor Exi t Pressure. 47 29 . Clearance Versus Tim e Aft e r S t o p cock . 4 8 30 . Core S peed Ve r sus Tim e Af t erS t cp co c k. 4 8 3 1 . The o re t ical Appr o xima t i o n o f S t age I B lade T i p Clearance F o ll o wing a S t opcock from Takeoff P o we r. 50 32. Cold Mo t or Roundness, Dev i a tio n o f I nd l vd u al Probe Re a d l n g fr o m t he Averase o f All Readinss. 5 1 33. P o s tt es t S t age l Shr o ud Su r face Ro undness I nspe ct i o n. 52 3 4. L P T u r bi ne S t a t or Ca se _Ins _r um en t a tl on. 54 35. LP Tu r b ine S t a to r Case Ax i a l T em pera t u r e Di st r l bu tlo n , Gr o und 1 41 e. 55 36 . LP Tu rb l ne:S t a t or Case Axi al T e m pe r a t ure D _st r l bu tl on, Takeoff. 56 3 7 . LP Tu rb i ne S t a to r Ca s e Circumferen t la l Te m pera t u re Dis t r l bu tlo n _ Axi al L o cation N u mb er i , Ground I dle . 5 7 38. LP Tu r b ine S t a tor Ca s e C i r c um feren ti a l Te mp era t u r e D i s t r i bu tio n, A x i a l L oc a ti on Num b er 2 , Gr o u nd I d l e. 58 39 . LP Tu rbine S t a t or Case Ci r cu m feren ti al Tem pera t ure D i s t ribu t ion, Axial Loc a ti onNu mb er 3, Gro u nd Idl e. 59 40 , LP Turbine S t aCorCase Ci r cumferenC l al Te m perat u re Distr l buC lo n, Axi al Lo c a ti on N u m ber 4 , Ground Idl e. 6 0 , .

41, LP Turb i ne St a t or Case C i r c u m feren t ia l Te m pera t ure Dis t r i bu ti on, , : Axi al A verase, Ground Idle. 61 VIii i : LIST OF ILLUST R ATIONS (CONTINUED)

ill Fig ure

I 42. LP Turbine Stator Case Circumferenti al Temperature D is trlbut _ on,_ " Ax l aiLocation N um ber I, Take o ff. 62 4 3. LP T u rbine Stat o r Case Circ um ferent i al Temperature D i st ri but io n, A xial L o cat io n N um ber 2, Take o ff. 63 44. . LP Turbine Stat o r Case C i roum f erent l alTe m perature Dis _ r l butl o n, Ax i al L o cati o n N u mber 3 , T a keoff. 64 4 5. LP Tur bi ne Stat o r Case Clrc um fe r ent l alTe m per@. t ure D i str ib ut io n , Ax i al Locat io n Num ber 4, Take o ff ._, 6 5 _i_ 46. LP Turbine Stator Case C ir c um ferent i al Te m p e rature D is tr lb ut l on, Ax i al Average, Take o ff. 66 47 . Tur bi ne M i dframeTempe r ature , Gr o und I d l e. 6 8 4 8. Tur b ine Midframe Ca sl ng Hat Sect io n Average Te m perature , Gr o und I dle . 69 _ 49 . Tu rb ine M i dfr a m e C a s i ng H a t Section_R a di al Te m pe ra tu r e G ra d i e n t, Gro und I d l e _ 7 0.

50 ....... Tur bi ne M / dfram e Te m per a tur e , T a ke o ff. 7 1 5 1 . Tu rbl neN l d fr ame Casing Hat S e ct io n Average Te m perature, Take o ff. 72 52. Tur b ine M i dfram e Casing Hat Sect io n Rad i al Te m pera t ure Gradient, Take o ff. 7 3 53. Turb i ne Midframe / C om p r ess o r Rear Frame F la nse Average Te m pe r ature, Ground I dle. ? 4 ____ ......

5 _. Turbine Midfra m e / C om pre s s o r Re a r Fr a m e F l ange A verage Temper a ture, Take o ff. 7 5 55. HP Turbine St a torTe m per a ture, Gr o und Idle ( Loc a t i on A ) . 76 5 6. HP Turb i ne S t at o r Te m per a tur e , Gr o und l dle (Locatl o nB). . _ 7 5 7 . HP Turb l neStat o r Te m perature, Gr o und Id l e (Locat io n C). 7 8 58. HPTurb l ne Stator Temperature, Take o ff(L o cat lo n A). 7 9 5 9 . HP Turb i ne Stat o rTemper a ture , Take o ff (L o cat io n B). 8 0 6 0 . HP Turb i ne St a t o r Temperature, Take o ff (.L o cat io n C). 81 6 1, C a lculated HPTS t ator Out-of-R o undness D ue to TMF , Ground Idle. 83 6 2. C a lculated HPT Stator O u t -of-Roundness Due to TMF , T a ke o ff. 8 4 6 3." Ca l cu l ated HPTStat o r O ut-of- R oundne ss Due t o SEat o r Tem per- ature Variat io n, Gr o und Id l e. 85 Ix k il LIST OF ILLUST R AT IO NS (Concluded) !i ' !ii_ 64 . Calculated I _ PT Stato r O ut- of -Roundness Due to Stato r Temperature I Variat io n, Tak eo ff. 86 65. T o ta l EPTu rbl ne Stat o rOut- o f- Ro undnes s , Gr o und I dle. 88 66. To tal HP Tu r b l neStator Out-of- Ro undne s s, Takeoff. 89 _ ....

6 7 . HP Turbine S t at o rOut- o f-R o undne s s, Bur s t + 0 Sec o nds. 90 68. HP Turbine Stat o r Out- o f-R o undness, Burst % 9 Sec o nds. 91 69. HP Turbine Stat o r Out- o f-Roundness, Burst • 20 Seconds ...... -92 7 0. HP Turbine Stator Out-of- R ou nd ness, Burst+123 Sec o nds. 93 " 7 2 . HP Turbin e Stat o r Out- o f-Roun d ne s s, Burst + 747 Sec o nds. 95 _ 7 3. HP Turbine Stat or Out-o f -. Ro undn e ss, Ch Qp + 0 Sec o nds. 96 7 4. H P Turbine Stat o r Out,of-Roundness, Ch o p + lOSec o n d s. 9 7 -- i 7 5. HP Turb i n e Stat or _Ou t -of-R o undness, Chop +20 Seconds. 98 7 6 . _ HP_Turb l ne Stato r Out-of-R o undness, Ch o p + 40 Second s . 99 7 7. HP Tur bl ne_Stat _ r O_ t _ of-R o undness s Chop + I 0 0 Seconds. i00 7 8. - / _ P Turbine Stat or_O ut _ of-R o undness, Ch o p + 308 Sec o nds. i01 7 9. HPTurbine Stator Out , of-R o undness, Ch o p + 425 Sec o nds. 102 80. HP Turbine Stat o rOut- o f- Ro undness, Ch o p +1020Se co nds. 103 8 1 . Max i mu m and M i n i m um Pr o be Readings During An A c ce l . 10 4 82. _Maxim u mandMin l , ium Pr o be R ead i ngs During a Dece l . 1 05 X_ I n the CF6Jet E ng i ne D i ag n o s t i c s P r o gr a m , the causes of per forman ce de g rad a t i on were de t erm i n e d f or each c o m pon en t of reve nue s erv i ce en gi n es .

It was found that a s i gn i f ic ant c ont ri but i on to p e rforman ce degrada ti on w as caused by i n cr ea se d a i rfoil t ip radial c learan ces i n t h e h i gh pressure t urb ine .

_ Since t he i n fl uen c e of these c l earance s on e ngi ne per f orma n ce and fue l _ c onsu m p ti on i s s i gn i fican t, i t is im po rt an t Co e st abl is h t he s e rela ti on s h i p s , i especially c on si der i n g t h e h i gh price of fuel. I t i s equally im portant co l unders t a n d t he c au s es of c lea r ance de t er i orat io n so t ha t t hey c an be reduced or e l i mi nated.

The obje cti ve o f t h i s _ nve sCi ga ti on w as to c ondu ct a s ys t ema ti c t es t i pr og ra m t o evalua t e t he effe ct s o f h i gh pressure t urb i ne clearance c hanges i: o n eng i ne and m odule perf o rmance and to m easure CF6-50C h i gh pressure t urbine Stage 1 t i p clearance and SC atorou c -of- r oundnes s du ri n g steady-s t a t e and if: trans i en t operation.

_ An in st r u m e n t ed en gi n e te s t wa s conduc t ed w i th eig ht c learan c eo m et e r probes i n st alled i n the Stage 1 h ig h pressure t urb i ne shrouds. S t a g e 1 t i p !_ clearances a nd sca t or o ur-of-roundness were measured du ri ng steady-s t a t e a n d t rans i en t ope r a ti ng c ond iti on s . The t urb i ne s t a tic par t s were i nstr um en t ed w it h pressure and t e mp era t ure probes C o m on it or t he behavior of c hese s t ru cc ures and t he c o r re sp ondin g c lea r an c eo m e c er da t e. The effe ct of clearance on en g ine _ and m o dule perfo rm an c e was establ i she d fr o m pe rf orm an c e c al i bra ti ons before _: - and after the basic r u nnin g clearance of t h e S t age 1 tur b ine wa s increased by blade- tl p- o n- s hr o udrubs.

_ e da t a fr o m t he pr o gram were analyzed to de t erm i ne (1) t he effete of I: h i gh pressure tur b ine clearance c hanges o n eng i ne and m o dule perf orm an c e , ( 2) the S ta Re 1 high pre s sure tu rbi n e clearance m ap , (3) t he high pres s ure I tur b ine sta t orou t -of-roundne ss m a p , (4) a c orrelation b etween m easured ::< r and pred i c t ed clearances, and (5) a quant it ative b aseline to which clearance .....

co ntrol im prove m en t s c an be co m pared.

,, The re s ul t s indicated a good c orrelat io n of the analyc l cal m odel o f I round en g ine clearance re s pon s e w it h measured data. The stator ou t -of-round- ' nes s m e a sure m en t s ver l f l ed.Chat the analyC lc al t e c hn l que for predi c ting t he d i s- i t or $ in g effe ct s of mechanical loads i s accuraEe, whereas t he t echn iq ue _ for c alcula ti ng t he effec t s of cer t a i n c i r cum ferent i al t hermal srad l en ts !! requires s o m e m odlflcat l on s . A poten ti al for improve m en t s in roundne s s was _ e s tabl is hed i n the order of 0 .38 mm ( 0 .015 i n.), equivalen t to 0.86 per c ent i n i " t urb i ne eff ici en c y which tran s la t es t o a cruise SFC Im prove m ent of 0.36 percen t .

_i The HP t urb i ne Stage 1 t i p clearance performance der i va t ive was establ is hed w a s 0. 4 4 mm (17 mils) per percen t of t urb i ne eff ic iency at take- of f power, so m e- wha t sm aller , t heref o re, m o re s en siti ve t han pred ict ed fr o m p r evi o u s I nve sti Sa fil ons.

2.0 INTRODUCTION The rece n t e n ergy d e m a nd has o u t pa ce d do mestic f uel supplies creat ln 8 ; an increased Un i ted States de p e n d sn c_ on fo r e i sn oil. This i n cre a sed _: ' dependence was a cc en t ua t ed by t h e O P E C e mb ar g o i n t he w i n te r of 197 3 - 7 4 , : wh ic h trigge red a rapid rise i n t he p rice of f u el. Th i s pric e r is e , alon g ' w it h s u bs equen t in c rea s es , br ought ab o ut a set of c han gi n g e c onomic circ u mst an c e s i . + w it h re g ard t o t he u s e of ener g y. These even ts were fel t in a ll s e ct or s of i" t he tr anspo rt a ti on i ndus t ry. A s a r e sul t, t he Governmen t , w it h th e suppo rt of t he + avia ti on indus tr y, in iti a t ed p r o g ra m s a i med a t bo t h t he supply and ' de m andaspe cts of t he problem. T _ e supply a s pe c t is be i n g i nve s t ig a t ed by . _ I !: de te rm i n i ng t he fue l avai l abi l i t y from new sources s u ch as c oa l and oi l : shale, wi t h con c u rr en t pro g ra m s i n pro g re s s t o develop e ng ine co m bus t o r s and i! fuel sys t e ms t o a cc ep t the s e br o ader based fuels. . • :, i Eeduced fue l co nsu m p t i o n i s t h e appr o ach bein g e m p lo yed to dea l wi t h _!.: ' : t he demand a s p ect o f t h e probl em . A cc ordingly, NASA is s p o nso ri n g t he A i r- i::!:i craf t Energy Efficiency (ACEE) pr og ram which is di rec t ed t oward redu cl n _ :.: fuel c o n s ump t i o n f or co m me r cial a i r t ranspor t s. The long-range e ffor t t o .

r edu c e _ fue l c o ns umptio n is ex p ec t ed to ev o lve new t e c hn olo g y which will i: permi t de velop me n t of e m o te e ne r gy eff ici en t t urb o fan, o r an impr o ved p r o pul T_ i!: si o n cycle such as th a t f or t u r b o pr o ps. S t udies h ave i ndica t ed larg e r e - d u ct i o ns i n fu el usage are p o ssi bl e { e.g., 1 5 to 40 per c en t ) fr o m t his ap- -- _ proa c h, however, s ig nif ic an t I m pac t in fuel usa ge i s considered to be i0 i: o r m o re years away. I n t h e near term , t he only p ra ctic al pr o pulsi o n a p - i proa c h is t o impr o ve t h e fuel effi ci ency o f cur r en t en gi nes since t hese engine s will co n t inu e to b e t he si E nlf lc an t fuel users f o r t he nex t 15 t o :: 2 0 yea r s .....

! The Engin e C ompo nent Imp r o ve me n t (ECl) . pr o gra m I s t he ele m en t o f t he ,i. ACEE pr o gram dir e c t ed a t imp r o v i n g t he fuel efficiency of curren t e ng i nes.

; ..... The EC I+ pr og ra m c o nsis t s o f t w o p ar t s: ( I ) Perf o rman c e Imp r o ve me n t and i: / (2) En g ln e D i a g n o s t l c s . The P erf o rmance I m p r o vem e n t pr o gram i s di rec t e d a t .............

:_ : d e vel o ping engin e perf orm ance im pr o vem e n t and re t en t ion c o n c ep t s for new _:" p r od uc t i o n and re t r o fi t engines. Th e En g ine Diagnostics eff o r t ls t opro- ::. vide inf o rma t i o n rela t ed t o determ in i ng t he s ources and ma g n it ude s of p er- : .: forman c e de t eriora t ion for . the h i gh bypass ra tio t urb o fan engines u t ili z ed on ": wida bo dy #i r craf t .

i _: A s part of th e E ngine Diagn o sti c s effort, N A SA-Lewls ini t ia t e d a pr o - _ : gr am wi t h t he General Electr i c Comp a ny t o condu c t high press u re turbine i nves t i g a ti ons.

:.!i_ i cle a rance The modern air c raf t g as t urb i ne en gi ne t y p i c ally uses hi g hly loaded • _ c o mpressor a nd t urb i ne st ages . Al t hou g h t h i s de si gn a ppr o ach t ends t o _" r e duce w e ish t and imp rove o ve rall e ff i c ie ncy, t h e hig h pr e ssure ra ti o t urb i ne ii bladin8 is more sens it ive t o b lade tip-to-shroud clearance. Since clearance i i s d i re ct ly rela t ed t o _ as leaka g e, aerodyna mic losses resul t, _......

i As . a Je t en g ine a cc umula t e s opera ti ng ti m e in revenue s ervi c e , i t s ; • . performance de t eriorates as a function of time and operatin g cycles. A _ ,. l ar g e pa rt of t he CF6-5 0 engine pe r forman c e de t eriorat i on has been deter- ,_ ; m ined t o be cha _ ge a ble to the high pressure turbine (Ref. i). This de t erlor- a tio n is pri m ar i ly due t o an increase i n b l ade tl p- to - s hr o ud c l earance which .........

results from loss of ti p or shroud mat e ri al s by rubbing of b l ade t i ps on the shrouds. The major cause of CF6-50 rubs i s s t ator out-of-roundness br o u g h t abou t by t hermal 8 radients and trans i en t t he rm al responses of adjacent s t ru c - tures, such as t he compressor rear fra m e, turb i ne mi dfra m e a n d low pre s sure turb i ne case.

| It i s very im port a nt to th e en g i n e d esi gn er co d e c e rn _ .n e th e e_ fe c c of c l e ar an ce on tu r b in e pe r forman c e and Co u nd e rst and the relat i on s hip of the r a d i a l gro w th of t h e rotor and s c a c o r for both tr ansi ent a nd s te a dy- s Care o perat i ng c on di t i on s ; Ach i ev i nga nd m a i nt ai n i ng sma ll t i p c l ea ranc es r equ i r e s thaC rubs b e avo i ded,or aC lea s t closely c ontrolle d .

' Stud i e s have shown thac s i gn i f i c a n tim prove me nt s i n eng i ne p e rform an ce (reduced fuel c on s u mp tion) and engine l i fe ex t en si on ( c o s t s av i ng s ) can resul t i f proper tip c learan c e t e ch n iq u e s a re im ple m en t ed. It is very im por t an t , _ t h erefore , to o bt a i n r u nning c learan c e m ea s u r e m en t s dur i ng eng i ne opera t ion, quan tit a ti v e l y evaluate t he e ffe ct of c le a ran c e on p erfor m an c e and to under st and t h e nature of s hroud ou t- of -r ou n dne s s. .

_n or d er to c le a rly ide nt if y causes a nd effe ct s of turb i ne c learan c e c hanges, m ea su re m en t s of these c lear a n c es in t he t urb i ne te mp era t ure e n viron m e nt of an eng i ne to an accuracy o f _ 0 . 05 m m ( 0. 0 02 in,) a r e required. Vari o us m e a sur i n g devices have been u s ed ln t he p as t , b u t most o f t he m have seri o us li m i t a t i o ns.

Ru b pins have been used which sh o w o n l y t he min im u m cl earan c e r equ i re m en ts, b ut wi t h n o r eferen c e as to when t he even t o ccurred in tim e. Highener g y X-ray has been u sed, b u t is d l ff lc u ltto de t erm i ne r o u n d ness an d requires sp e cl a ll y equipped test s i t e s. Th e to uch pr o be device i s widely u s ed, h o wever, it cann ot m eas u re i nd i v i dua l b l a d e cl earan c es or c l earance d u r l n g t rans i en t s. The c a p a- c ltance sens o r Isals o b ein g used increasin g ly , b u t has sh o wn li m i t a t i o ns pr e- c lud l n g us e i n t he h o t t ur bi ne env l r o n m en _ .

A c learan c e m easur i ng d ev i ce which o ver co mes a ll o f t he a bo v e p r obl e m s and pro vides _ ac c ura t e clearance m easure m en t s i s an o p ti cal, n o n-c o n t a ct lng sen so r called a cleara nc e om e t er pr o be. Such a device has been de si gned , b u i lt , an d de mo nstra t ed _by t heGeneral Elec t ri c C o mp a ny. Aben c h m o del wasfa b r l c at ed and t e st ed i n a c o n t r o lled la bo ra to ry envir o n m en t to asses s accuracy a nd t ou g hne ss i n a si m ula t e d t ur b ine envir o nmen t . Thi s ini t ial evalua t i o n was f o ll o wed b y a fac to ry engine t es t o n a J7 9 engin e in Augu st 19 7 9. The success o f bot h d e mo ns t ra t i o ns pr o vided t he ne c essary too l to a tt ain ac c ura t e m easure m en t s o f' high p ressur et urb l ne blade t i p clearances, s t ato r r o undnes s and r ot or / sta to r c o n c en t rici t y o n t he CF 6 -50 engine.

An ins tr u me n t e d engine t es t was c o ndu ct ed a t t he Genera l Ele ct r i c, Even d ale, ! Ohio, test facili t y. This test w a s concluded in Septe m ber, 198 0 . The objectives.

i o f th l s effor t were t o m easure CF 6 -5 0 h i gh press u re t ur bln eStage 1 t lp clearanc e an d st a to r oU t - o f-r o undnes s , and to evalua t e t he e ffe ct s of high pres s ure t ur bi ne s teady- st a te and transient engine oper a t ing co ndi t i o n s .

i clearanc e changes o n engi ne and mo dule perfor ma nces. The testi ng i ncluded bot h The data o b t ain e d fr o m t hi s t es t pr o g r am have been ana l yzed to de t erm i ne: (1) th e effec t of high pressure turb i ne clearance ch a nges on engine and mod u le p er f ormance , (2) t he h i ghp r es s ure turbine S t age 1 cl earan c e m ap, (3) t he high pressure turb i ne st ator ou t -of-roundne s s m a p , ( 4 ) a c orrelation be t ween experi- m en t ally measured and analyt i cally p red ic ted average clearan c es and roundness, and (5) a quantitative b aseli n e t o which clearance control i mp rovemen ts can be com p ared.

3 . 0. B ACKGROLTHD ) ', }_. Z t h ad p rev i ou s ly b een de t erm i ne d t h at turb in e bla d e- t o- sh rou d c lear an ce i ncre as es a re o n e of th e lead i n g causes of en gi ne p e r formance de t er i ora t_ o n ; (R ef . 1) T h e mos t needed i nform ati on p er tai n i n g t o t h e cl earan c e / p erfo rm ance )_ rela ti onshi p w as a quan tit a t ive m ea s u r e m e nt of th e effe ct of c le a ran c e ch an g e s ' upon e ngi ne p erfo rm an c e . Once thi s rela t ionsh ip i s e st a b l i s h ed , t he round )i!i , en g ine cl ea r an ce- re sp o n se wi th respe ct t o d i ffe r en t en gin e ope rati n g p ara m e t ers , j i : such as core speed ( N2 ) and compressor d i s c ha rg e pressure ( P 3)) is required t o .... de t e rm ine when c learan c e i n c reas i n g rubs could occur. Fi nall y, shroud su r fa c e II_ , I roundness m us t b e addressed because the c o mbi ned effe ct s of ou t -of-roundness )._ a n d rou n d eng in e respo n se de t e rmin e when ru b s occ u r.

R o t or e cce n t r icity i s a to pic of t e n d i s c ussed wi t h res p ec t t o bla de- t o - shr o ud cl earan c e an d p e r forman c e d eteri o rati o n. B ec a use the CF 6 -5 0 hig h p res s ure i_<: ._ turbine ro t or (F ig ure 1 ) i s su pp or t ed by b earin g s a t each end, t he ecce nt ric i ty _ !:_ : : i s a fun ct ion on ly o f the b e a ring c l ear an ces, runou t of b e a r in g c e nt ers a nd re p ea t a bl e, and kn own effec t in t he CF6-50 en _ ne an d is n ot addressed in t his Ii r e la ti ve s t ruc t ural s t lffness e s . This e c c entri c i ty has been s h own to be a sm all, i ill ! reRo t .

i!i_ 3 . 1 High Pr e ssure Turbine Clearance Response , , _'i:_ : _, Clearance resp o nse m a y b_ d et ermin e d anal yt icall y th r o ugh deflec t i o n anal y ses i l o f b o th t he r ot a t ing and s t a t ic e ngine s t ruc t ures . Heat t ransfer and aer o d y - L _ n amic mo dels o f t h e c om p o ne nt s ar e required to pr o vide app rop ria t e and c o nsis- -- } _ . _.- te n t t emp era t ure and pressure bo undary c o ndi t i o ns as i npu t s to t he s tr uc t ural _i m o dels.

T y pical p o r t i o ns o f t he s t r u c t u r al model o f th e CF 6 -50 hig h pressu re t ur b ine s t a to r are sh own in Figure s 2 and3. These hlgh pressure t ur b ine co mpo nen t s have b een analyzed p ri m a r i l y wi t h a Gene r a l E l ec t r i c comp u t er p r og ra m called CLASS / MASS ) e mplo yin g an axisynnne gr lc ana l ysis.

E ngine t hr ott le mo ve me n t s, such as s te els, decels , an d r e b u rst s have b een ._ analyzed u sl ng t his m o del. The st ea d y-s t a t e op era ti n g p o in ts o f gr o und Idle, t ake o ff p o wer, and cruise p o wer have als o been analyzed ....

E x p erien c e has sh own C ha t s t ead y -s t a t e engine op era t in g clearances are usua ll y de t er m ined as a r esu lt o f eng i ne t rans i en t op era ti ng co nd itio n s . A • calcula t ed o r o b served ml ni m u m w hlc h occurs during t rans i en t man e uve r s w i ll d ict a t e th e c learance whi ch m us t b e se t ini ti all y i n order to avoid ru b s .

The w o r st case, i . e . , minimum clearance o r ru b co nd it i o n f o r t he CF 6 -5 0 eng i ne ) ha s b een p r edi c ted to occ ur during a h ot r oto r re b ur s t. A re b ur st i s defined as an eng i ne de c el fr o m hig h po wer t o idle, h ol d ing a t idle f o r a peri o d of _ tim e (genera ll y l ess t han f i ve mi nu t e s ) and t hen a cc e l era t ing t he en gi ne b ack to hi g h po wer. The t u rb ine s hr o u d s u pport mem b er i s co n s idera b ly le ss m as s ive t han t he t ur b ine di s k an d , co nse q uen tl y, i t c oo ls m o re q u lc k ly t han t he di s k dur i ng th e t i m e a t idle. A rea cc elera t i o n o f t he eng i ne add s ro t a ti onal s t res s gr o w t h and b lade t herma l gr o w t h to t he a l ready ex ist en _ disk t he rm a l st re ss gr o w t h . - Th e re s ul t is a h ot b la d e t ip radiu s grea t er t han t ha t o f t he s hr o ud surfa c e which t here b y p r o duces bl ade tip ru bbi ng. The t y p i c a l gr o w t h ; ch ara ct er i s tic s for b o th t he r o tor a nd th e s t a t or during s re b u r st maneuver are p resen t ed in F ig ure _ a s a fun cti on of tim e ......

.I

!i

A s ig n ifican t p a rt o f en g i ne de t er i or a t io n may be caused by w arm rotor r ebu r s t s (t im e at gr ound idle more _ han five mi nute s ) f o r wh ic h l i ttle da t a are available. This test i n c lud e d war m r ot or r e b urats t o provide data relat i ve t o t h i s t ype of en gi ne o p erat i on.

3.2 High Pressure Turbine Ro un dnes s The c on t rol of the roundness of a g as turb i ne en gi ne s t ruc t ure requires an evaluation o f the material prope rti es and c haracter is ti c s a s well as environ- _ m enta l in fluen c e s for all the prima_ y en gi ne st ru c tural m e mbers . Fi g u r e 5 h ig hl ig ht s and defines the cr i t ic al structural members of th is en gi ne. These c o mp onents i n c lude the fan cas i ng, the c ompres s or cas i n g , the compressor rear frame (CRF), hig h pressure turb i ne (HPT) Sta g e i and 2 nozzle supports, the tur bi ne m l dfra m e (TM F ), th e l o w pre ss ure turbin e (LPT) c a s l n g and th e turb i ne rear frame (TRF).

Each o f these com p o nents is sub j e c ted t o vary i n g leve ls o f b o th n on -axi- sy m metr ic lo ad i n g and c l rcu m ferent l al l y n o n u n i f o rm rad l a l the rm a l grad i en t s.

• These effe c ts t end to induce o u t - o f-r o undness d l st o rt lo ns l n t hese c o mp o nen t s which can pr o pa g ate thr o u g h o u t the ent i re len g th o f the en gi n e . The re s ult i s that the study o f ther oun dness o f an en gi ne s truct u re m ust i n c l u de not o nly it s I nherent-ability t o re ma in r o u ndSut als o m u s t include the dist o rting In- f l uen ca of n e l g hb o r _ s _ / uc t ures.

The r o undness s tudy u ti l i zed General Electr ic S t ruc t ural Analys i s pr o - g r am s "CLASS / MASS " and "MA SS " , o f the en ti re CF6-50 stru c tura l sys t e m . The s e m o dels w _ re used to evaluat e t he m agn i tudes o f _ t- o f-r o u ndness o f each c om - p o nent and the effects tha t dlst o rt lo n s o f the var io us c ompo nents have o n S t a g e i HPT shroud r o undnes s .

Non-ax l sy m met r l c frame st r u c tu r es m ust f i r s t be m o d e led w i th th e " MASS " pr o gram and t h e c alculat e d def o rmat io ns a pp ll ed t o the " C LA SS / MASS " pr o gr am .a s b o undary c o ndit io ns. The "MA SS " pr og r am empl o ys three-d lme nsl o nal analysis and has the c apab i l i ty o f handling non-axl s y m metr l c s tructure s co ns i st i n g o f p l ate, br l c _ , s ha ll and beam elements. Transient engine c o ndit io ns were I n- ! c luded in the s e analy s es s_ n c e the most s evere t hermal effects d o n o t ne c es _ - s a r ily coincide, tl me wi se, w _ th the mos t s eve r e mec h ani cal lo a d i ng eff ec ts.

The c o n t r ib ut io n s o f each en gl ne c o mp o nent t o b o th h i gh press u re t ur- bine r o u ndness and t _ ans i_ nt clearances were t hen determ i ned u s i n g F o ur l er Serie s a ppr o xlmat l c _s. Th e s e co ntr ib u ti on s wer e s uper impos e d to o btain the roundnes s and clearance re s pon s e maps o f the high pres s ure tur b ine.

The a n alytical studies i nd ic ated tha t the co m p r essor rear f r a me has a negl i g i ble effe c t o n HPT o ut- o f-r o u ndne ss .

3.2.1 TurblneMidframe Effects The blade tip c l earan c e Is i nfluenc e d by t he a m o unt of di s t o rti o n and o ut- o f-r oun dne ss IL the s hr o ud s . The hi g h pre ss ure turb i ne s hr o udsln the CF6-50 engine are supported from the mldf ram e forward flange. This flange i s 1 0 .

_L_rpv r¸ L_ _ _, _ i _ ' _ ............... ..... • _ _' _ _ ' 1

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t c onnected to the stru c tu r a l hat s e c t i on s o f t he turb i ne mi d f ra m e b y a sheet _t m etal cone. The turb i ne mi df r a m e i s shown sc h em a ti call y i n F ig ure 6.

!i_ Turbine Midframe Temperature and Pressure Effect_ !i Distort io ns of the turb i ne midfr am e stru c tural h a t se c t i ons a re trans mi tted thr o ug h the s upp o rt i ng s t ru c ture t o t he h ig h pressure turbine shrouds• F ig ures i 7 and 8 s h ow typ ic ally the kind o f turb i ne m i dframe f o rward hat se c t i on a nd f _ tr a ns i ents f o ll o w i n g the en g ine a c celerat i on fr o m Idle to max im u m power. These i : _ re su lt a nt h ig h pressure turb i ne shr o ud d i stort i on s which result from the d i stort i ons primarily o ccur due to (a) mechanical l o ad i n g on the t urb i ne mi d- _ ture differences i n the en gi ne st r ucture. Structural te mp erature g rad i ents are • caused by d i fferent t h ermal response rates, g as strea m ci r c umferential te m perature variat i ons and strut i nternal a i rte m peratur e var i at i ons. Three o f the s tru t s i frame, ( b ) pressure l oad i n g s transmitted to the tur bi ne mid fra m e, an d ( c ) te mp era- operate approx im ately ll0OC (200OF) hotter than the other f i ve struts. The vary i n g strut te m peratures result i n different amounts of the rm al expans i on i n the struts. Th i s causes a non uni fo rm d i stort i on of the turb i ne mi dfra m e hat se c t i ons and an out-of-roundness d i stort i o n of the h ig h _ ressure turb i ne shrouds.

Turbine Midframe Deformation Due to En_ine Mounting Loads • !

_ T he tur bln e m idfra m e i sals o def orm ed b y l o ads fr o m t h e mo unt ing o f t h e i en gine. T h e aft en g ine mount is an in te g ral p ar t of t h e stru c tural h at se c t io n.

T heseeffects are in cl uded in the_ o veral l struc t ura l m o de l .

Correlation of AnalyslsTechnlques of High Pressure Turbine Stator Distortion Resultln_ from Turbine Midframe Distortion i An an alys i s o f HPT s tat o r dist o rti o n resultin g fro m TMF dist o rt io n was perf o rmed using the General Electri c Structural An alys i s c o mpu t er pr o grams.

The analys l s m eth o d had been c o rrelated by means o f stat l c test l n g ( I ndependent o f and p rl o rto th i s c o n t ract) o f the fu ll eng ln estructure dur l n g whi c h both - were co ndu c ted f o r thef o ll o wln g ! o a dl n g s: . _ _ I TMF h at se c t io n and HPT stator o ut-of-r o undne s ses were m ea s ured. Three te s ts a . Vert ic al load rea c t i on at en gi ne aft m o unt p oints 1 b . T o rque l o ad rea c tion at en gi ne aft m ount p oi nt I c . T h e rm al load i n g where three of the e igh t TMF struts were I h eated 9 0 °C (162°F) above the r e s t of the structure The c orrelat i on between measured and c a lc ulated out-of-roundness is shown " -- i n Fig ures 9 t h rou gh ii 3.2.2 HPT Shroud Support Temperat u re Effects Since roun dnes s m ust be as s ured before any si gnif i cant work can be d i rected toward blade t i p clearance redu c t i on , the turb i ne shroud stru c ture it s e l f m ust stay round, In add i t i on to be i n g influenced by other engine s tru c tures, turb i ne stru c tures ma_ lose the i r ro un dness due to rec i r c ulat i on of hot flowpath gases i nto the c ab i ties between the turb i ne flowpath hardware• This re ci r c ulat i on of hot g ases c an induce local overheat i n g of the turb i ne stru c tural m e m bers, causing the m to elast ic ally d i s t ort.

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ALF _ F iK ure 7 . Typical Turb i ne Mi d f rame Forward H a t Section De f lec ti on Rel ati ve t o Hub _ Re s ul ti n g f ron Takeoff Transient Operation.

F i sur e 8. Typ i cal HPT Shroud Suppor t Deflection R elat i ve t o TMFHub _ (Caused by T _ F Hat S_ t i on D ist or ti on) Re sult i n _ from Takeo f f Transient Operat i on.

OF POORQ U A L ITY

16 ... """ ..... _" ' / . T i,i , !'__ ,• ....... ' ............................. _ . , ........................... , ; ,. ....... __........................ • , " ___--_ _ " " _°_,_ , iI 3 .2. 3 Low Pressure Turbine Castn 8 DistOrtion Effects i_ T he lo w pressure turb i n e c a si n g, li ke _ he turb i ne mid fram e , i s sub j e c t- :_ ed t o b ot hax i ally and ci r c umferent i ally vary i n g temperatures and loads. Two _ m e c han i sms were Judged t o be possible contr i b u tors to HPT out-of- r oundnes s, i_ These m e c han i s m s are: _ 1, Te m pera t ure d i fferent i al s between the LPT s tator c aee . hor i zontal _ ., . flanges and skin cause the hor i zontal flan g es to g row relative .

_-'[ to t h e s kin, thereby d i stort i ng the LPT forwardflan g e , These il d i stort i ons are transmitted forward to the HPT stator. _ 2 ......... Cir c u m ferential te m perature g radients in the LPT sta t or c ase sk i n . , if! f o rce the LPT-stator case i nt o an out- o f-round shape and . props- The HPT o ut- o f- roun dness caused by the hor i z o ntal f l an g e / sk i n tempera- i g ate f orw ard to induce HPT sta t or o ut- o f.roundnes s . I __ : _ ture gr adients and cl rcumferen tl al thermal g radients was evaluat e d by us i n g _• _i b o th c o m pute r and.emplrlcal m o dels, Th e m eth o d. o fdetermln l ng out-of-roundnes s i had been verified by tests in which th e flan g e s and skin o f the LPT casing _ = were heate d and the result l ngHPT deflec t i o n s measured.

4 ,0 TEST VEIIZCLE AND X.NRTRUMRNTAT]ON T he teat v oh i cl e u sed in t hin £nve st ig a tio n w en a CF5- $ 0C engin e , wh i c h h ad boon a s s e m bled u s i n g s t a nda r d t u r bine c ompon e n t s rapr e zen t otive o _' \ produ c tion e ngine s C urrently opor at i n s in rev e n u e so rvi c o, S eve r a l c o m ponen t s _., were mod i fie d for th e installa tio n of the c l e aran _ eo m e t er pr o b e s and oth e r _ii required I na tr u me n t a t L on I o a do ut z, for t h e S t ag e I hi g h p r.es au r o tur bi n e ( I I P T) . , By bu ildi n g only t h e St ag e i HP.T wl t h i T he a ng le s wa s as se m b l ed w l th l a r go r o t o r -t o - s eater cl e aranc es e xc ep t tl g ll t Cl ea ranc es, t h e in tent w ee to iso lat e t h e o f fa c t u po n per f or manc e o f l: S t age 1 b la de=to-sh r oud cl ear an ce , by su zt al ulug a b l ad e -on shroud rub, P rov i d e d _ }. t hac n o o t h e r C o m po n e n ts de te ri o r ated dur in g. th e ti me t he ru b . w a s su st a i n ed, o r that any dete ri orat i on wh i ch d i d occur co ul d be i d en t i fi e d a n d . quant i ta ti ve l y a m aassed, the c l e arauc a o me tor read i ngs before , a nd afte r , th e rub could be c o r rolat a d wi th cos i n e pe r for m anc e m on i tor e d b e fore and after the r ub to dete rmi n e a r el at i onsh i p bet w een,c h a ns o n i n t l p C lea r an ca m a nd cha ng e s I n e ng i n e he alth p arama t e rs ( Ex i t G a s T am p a ratura ( E GT), Turb i ne E ff iciency (S T), Sp ecific F u el Co n su m ption ( ar c ). , Th ru st (F ), . o t c. ) ., In-p a rt ic u lar , t h e r e l a t i ons hi p , of clea ran ce a nd q e f ficie n c y - d e t e rm i n e d t h rou gh t hi s te nt C ou l d b a Comp a r e d wi t h t h os e e st a b li sh e d t n oth er te n t s to det er mi n e wh e t he r or not the r e l a t l v e 8 i gu iflca n ca o f H P T t l p i _ c l ea ran ce d e t e r i or a t i o n wa s w ea ker, s tronger Or about th e s ame a m had be e n azs e zae d pr e v i ou alz .

P ; , 4. 1 RNOZNE CON FZ_ URATION A d e s c r i p ti on o f til e ca s t ve h icle and i t s a ss o c i at e d co m p o n e n t co nf i s u - i ra ti on i s.giv en as f o ll o w s: • • ........... . F au . . F r am e .................................................................. A st a nd a rd CF 6- 5 0C f ro u_ fr a m e wit h r a k e p a d ca p a b ili ty t o re c ord C ompress o r ln l_ c b . _ r - ect ari n t ic s, if n oe d oA .

• C O mpress o r Star e r St a nd ar d C F 6- _fi C co, pr e ene r - o r & c a r , • Com p r e soor RO t Or ... St a n dard CF 6-, 5 0 C rot or, i • Co mp r es s o r Re a r Fr a me A C F 6-5 0 C fr a me m od i f i ed t O rec ei v e .c l ea r a ncoo mo ta r _ prob es ............

• Co m buzt or St a nd a rd .C F _ 6-50 C c o m bu a t o r _ _ ,i • , F ue l . _ ozzle CF 6-50C f ue l n ozzl e s. ' 1 • S ta g e I H i gh P ressur e Turbine __C F 6-50 C a s s e m bly , N ozzle Azz a mb ly (i nc lu di n g - i m i n i - n oz zlo) E' t : _ ,!. • St age 2 Hig h Pres s ure T ur bi n e CF 6 - 5 0C co n f ig u rati on _ od if i a d _: , : Nos s le A s se mb ly . Co r ec ei v e c lea r an c eomeC er p robes i . i _; , e. H_g h Press ure Turb i n e R e , o r CF6-5 0 C : : • _Turbi ne_Midf r ame- . CF6-50C ii: a LOW Pressure Turb i n e C F 6-50 fll_;; s E xhaus _N ozzl e CF 6 -50C c onf i gura t ion ! : : 4. 2 INSTRUMENTATION :_., E n gi ne st a ti on (p l ane) de sig na _i on s .used for t he te s t i n g were i n accordance wI_ hARP 7 55A. F ig ure 12 i llustra t es the plane loca ti on s on a CF6-5 0 e n gi ne cr o ss I_.. s ec ti on and i den Clfl e s _ he I ns t rumen t a ti on used. Th e i ns t ru m en t a ti on i s broken i_ ' down i n _ o four g roup s : g eneral i n s_ r um en _ a _t on _ aerodyna mi c i n s_ ru m en _ a _i on, i_'. turbine s _ ru c_ ural in s _ r _m en _ a _i on, and clearan ce o m e _ er probe in s_r u m en _ a _i on.

i;._ _ . 2 .1 General _ns_r u meneaC_on f : • Br- _m e _ ic _ re s sur e - The local baro m e _ r ic pressure m easuned _ u si ng.

[!; a cord i n g mi cr o haro g ra p h. .

e .. H u m i di t y - The ab s olu t e h umi d it y m easured i n g ra i n s o f.m o ls_ ure pe r p c und of dry air u s ing a hu m idi _ y indi c a t or.

• Cell S_ a _ i c P re s s u r e ( P o ) - _ T es_ cell s_ a _ i c pr ess u re mea s ured a _ four loca _i ons i n _ he cell, !.

• Fan Speed (XNL) - Low pressure r oto r speed m ea s ur _ .d _ us i n _c wo fan case m ounC e d _ fan ' speed aen s oc s.

o _ Core Speed (XNH) - Hi g h pressure rotor speed measured u sin g en gi ne core- s peed sensor dr i ven off the and of Che _ lub e . and s c aveng e p u mp .

e_ Main Fuel Flow (WFM).-Volume_ r lc f lowm e_ e r , faclll _ y m ou n_ ed.

• Veri f i ca _i on FuelFlow .. (WFV) -.-Second fuel flowme _ er m oun _ ed i n ser i es wl C h WFM.

2 O L_ d k . ...........

i

• F uel Te m per at ure - Te m p er a t u r e of fuel m easu r ed a _ t h e fac i li t y flo w - m eter u si n g a +si n gl e c hr om e l / alumel probe i n the f u el l ine+ • Fuel Sam p le Spec i f ic Gravit y (SGSAMP ) - Spe ci f ic 8 rar it y o f t he fuel s a m ple m e a sured us i n g a hyd r o meter .

• Fuel Sa m pl e Te m pera t ure (TSAMP) -F u el s a m ple t empera tu re m easu r ed \ durin g t he s pe c if ic Br ev it y m ea s u r e me n t .

a • Fuel Lower Heati n _ Value (LHV) - L o wer hea _ ins value o f t he fu el ] sample a• det erm i ned by a bomb c alo rim e t er, _ s Thrus t ( F G) - Th ru s t -fra me , axial force m ea s ur i n g u s in g three _ s t r a t n- g a _ e t ype load c e ll s_f o r redundan t m ea s ure m en t .

• Var i ableS t a t or Vane Po si tion (VSV) - Readou t of t he LVDT a tt a c hed to t he h ig h p re s s u r e com pre ss o _ va ri able s ta t o r pump handle.

• Var i abl e Bleed Valv e Po si t i on (VBV) - Eeadout of t he LVDT a tt ached to t he variable b leed valvea c t ua t ion me c hanism. _ , • 4 °2.2 gerod_namic Instru m entation

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The f ol low i n _ rakes, probes, andstat ic pressu r e t ap s we r e i ns t a l led t o measure ai r flow, t e m pera t ure,and pres s ure as : r e qu i red t o define co m ponen t performan c e . (See Fi g ure 1 _ .)

Fan.Inlet (Plane i_ Bellm ou t hrake s were i ns t al l ed t o meas ure s t a tic pressure, t o t al.pre s - sure, and t o t al t e m p er a t ure at _ he fan inle t . F o un r akes, each ha vl n E s ix _ o t al pres s ure probe s , s l x st a t i c pres s ure pr o bes, and t w o total temperature probes were us ed ....

Booster Discharge (Plane 23_ Fi ve ar c rakes, ea c h hav i n _ si x t e m pera t ureand s ix pressure probes j

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were_ i n s tal l ed t o m easure b oo s te r d i s c ha r_e total te mp e r atu r e and total p r e s - s ure. Ten taps were in s talled t o m ea s u r e boo st er d i s c ha r ge s t a ti c pressure.

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Compressor Inlet (Plane 25) _i Five flowpa t h,wall static pressure taps were installed. " Compressor Discharge (Plane 3) Five of the borescope port plugs in t he c ompres s or rear frame were " _ modified to perm it co m presso r di sc harge sta t i c pressure m ea s u rem en t . A s i ngle 5-el em ent t her m ocou p le probe was used to measu re co m pressor d isc harge te m p e ratu r e.

• ! i........i .... ....

!i L ow Pressure Turbine Inlet .. _ Plane 49_ I Te m peratu r e i n thi s plane i s m easured by eleven 5-ele m ent rake s w i th i i ndiv i dua l probe r eadout to perm i t moni t o r in g o f te m p er at ur e profi l es P r es - sure is m easuredu si n g f i ve probes, each hav i n g f i ve ele m ents all f ee d i n g a s i n gl e f i tt i n g .

I c: Low Press u re T_rhine DJ.scharae (Plane 5_ _ L ow pressure turb i ne d i s c har g e pressure is measured u s i ng four rakes, !_ hav i n g , five ele m ent s each.. ' ....

_ / " 4 -.2.3 Turbine Structural Instrumentation _i s HPT Stator Ther m o c ouples: 2 4 im bedded i n stru c tu re a_ d 2 a ir _ : t h ermoc o uples • HPT Sta t or Pressure Probes: 4 basket-t y pe p res su re probes i nthe Sta g e 1 shroud c oo li n g a i r supp l] , c av i t _ s E n gi ne Str uc tu r e 2 hermocou p le s : 1 _ 6 m eta l and 1 4 air thermoco u pSes _ _ a En g ine Stru c tur e Coo l ing A i r Te m perature s_ dn__Pr_e _s ure s : 1 4 a i r thermocoup l es a n d 10 pre ss u r e, probes .....

• LPT Case Thermoco up les: 4 8 m eta l t h ermo c oup l es • L P T CaseCoo li n g M a nif o l d and Under Co wlI nstrumenta ti o n : 17 pressure probes under c ow l and in supply tubes 4 .2. 4 Clearanceometer Probe Instrumentatlon E ig ht cl ea r anceo m eter p r obe s were i n s talled i n the test v eh icl e above the St g . I b l ade t l ps as s hown I nF i gure 13. These probe s were used to obta lu rea l , t im e, i nd i v i dual h ig h pressure t u rb i ne b l ade tlp-to- s hroud c l earance m ea s uremen ts to an accuracy o f_ O.0 _ u _ (0.002 i n.). The h i gh pressure t u rb i ne stator on the test veh i cle was m od ell ed to re c e l ve • the probes. The reworked statorco m ponents i ncluded _ Stage 1 shrouds , Sta g e 2 nozzle support, fil ter screen and 10th sta g e a i r s ea l . The c l earanceo m eter probes were l ocated a t _- e i ght c l rcu mf eren _ a l po s it l ons, a s near l y e qual ly spaced as w a s pract ical (F i gure i _ ).

• Each c l ea r anceon _ ter probe w a s i nd i v i dua l ly cal i brated a n d checked dur i ng asse m b l y on the HPT stato r . A fi na l reference c alibrat i on w a s obta i ned dur i n g i n i tial cold rot a t i g n and _ otor i n g o f the engine..

A proven lig ht-bea m tr ia n g ulat i on techn i que w as ut i l iz ed f or t he c lear- a nce m easur i n g sensors. Data were co ll ected f or fi xed-t i me intervals and i nd i v i dual blade clearances were obta i ned from each probe. Ind i v i dual probe processors were used to store clearance data and the processor cal c ulated blade m inimum, m ax im u m a nd average clearances from a l l the da t a collected.

A h ig h speed data tape recorder w as used to i ndependen t_ y record i nd i v i dual blade clearances.

_ 3 2 4 ¸ 32405 6 104 ° 19 !

2 5 ': 5 . 0 TEST FACILITY All testi n g w a s c ond uc ted i n Test Cell 2 , B ui ld i n g 500, at the General E le c t ric Company plant i n Evendal e , Oh i o _ A photo g ra p h of an en gi ne i nstalle d i n the t e s t c e l l i s s h o wn i n Fi2 ur e 1 5 .

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_ Cell 2 has access to t he data re c ord i n g sys t ems i n t he I nstrumenta ti on Data ° R oo m. I n add i t io n to the standard t e s t cell equ i p m ent , a c learan c eo m eter probe c omputer and h l gh speed s i gnal processor were used t o c olle c t and rec o rd the c learan c e om ete r data.

The _ data a c qu isi t io n and pro c e ssi n g syste m i n u s e i n Evendale c ons i st _,_ , o f a Cell Sy s te m and a S i te Sy stem. The Cell Syste m performs s teady-sta t e and t r ans i ent data a c qu is it io n , c o nve zs i o n to eng i neer i ng un i t s , qulck-l oo k perf orm an c e c alculat io n s , and sh o rt-te rm s t o ra ge . C o nver te d data i s aut o - m atically tran sm i t ted C o the Si t e Syst em f o r further o n-l l ne p r o ce s s i n g and _! hard-copy output. The Site Sy s t em ut i lizes a data-base co nc e pt for eff ici ent c ool i ng sys tem was pr o vided which ut i l i zed eng i ne compressor bleed a i r. A micr o - _ " _ storage, retr i eval, and r e pr oc ess l n g of current and h i stori c al data. In add i t io n , data m ay b e trans m itted t o the Genera l Elect r ic E venda l e Time Shar i n g ....

, Computer Cen t er for further pr o cess l n s, s uch as cycle deck analys i s and : ' i ' com pa r is o n..

Data a c quis i t io n capa b i ll ty co n si s t s o f : 400 pres s ure channel s , 4 00 te m perature c hanne l s, I0 frequency channe l s, and 28 d. c . v olt a g es, su c h a s : load cells, i ndiv i dual pressure transduc e rs, po si ti o n potentio me te rs , e tc .............

The pressure syst em c o nsists o f t en 4 0 -p o rt s c ann l va l v es w l th ava il ab l e p re s sure ran g es from + 6.9 N / c m 2 (i 0 p s l g) thr o ugh + 3 4 5 N / cm 2 (5 0 0 p sl g).

The syst em i n co rp o ra tes aut o -rang l n s and m u l t i ple s_mpll ns c a p a b i ll ty f o r _ all _ _ data c hannels t o a s sure op timal res o lut io n and p recisi o n i n add itio n t o variable averaging t lm e for frequency m ea s ur em ents. Data m ay be achieved and pr o cessed i n e it he r a steady- s tate o r tran si ent m o de. Typical acqu i s itio n t lm e f o r a ll data t o be rec o rded f o r a steady state test p oi nt (c o nd i t io n) i s 30 ......

sec o nds and each m ea s ure m ent (parameter) i s sampled 4 0 . t im es o ver t hat time period. Transi ent a c qu i s itio n rates are variable from one sample per second per c hannel to 250 s amples per second per c ha nn el. R edundant m easur em ents are m ade of key para m eters such as fuel fl o w, fan speed, and thrust. Auto m at i c .... data r eje c tion _ e c hn i ques, ratio of redundant measure m ents , and on-line syste m - verifi c at i on analysi s fur t he r enhance overall data qual i ty.

All data is c onverted to eng i nee ri ng un i ts on the Cell Sy s te m and aut o - m at ic ally tran s fe rr ed t o the S i te Sy s te m . The s e are then u s ed i n various data-analy sis c o m puter progra ms . Q u ic k-look pro g r ams ar e ava i lable on the Cell Syst em to prov i de on-line and hard copy of overall engine perfo rm ance t and health calculat i on s . S im ultaneou sl y, the s e d ata are ava i lable at the !

Site Sy s t em for hard copy and plott i ng of co r rected overall and i nter s tage perfo rm ance charac t er is t i c s . E as i neer in g un it s and / or calculated data m ay be trans mi tted to the General E l e ct ri c E vendale Ti m e,Shar i n g Co m puter Center for archival st orage and add i t i onal analysis such as cycle deck comparison.

2 6 ORIGINAL I_ , _ _S OF PO O R QU A LITY

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| , ¸ ....... - , .......... ...... ....... , 6, 0 TEST PROCEDURE ._ _ i_ The te st obje cti ve s were to secur e round e n gin e c l e arance ma p s, i . e . , _ b lade t ip clearances as a fun cti on of core s p eed, co mp ressor ex i t te mp e r ature, c o m pre s sor ex it p re s sure, and t im e; and b oth s teady- s tate and tran si ent out- o f- .. r o undness map s. The effe ct of vary i n g c learance u p o n eng i ne p erfor ma n c e wa s .

_ ' also to be evaluated. The clearance and out-of-roundn e ss ma p s were to be de- term i ned from t he data generated by c lea r an c eome t er probe _ . • ii ; 4 .... I norder to achieve these o bj ect i ves, a te s t p lan w a s developed which co ns i sted of o p erat i n g the en gi ne a t the follow i n g t est c ond l tlons z ' i_!.i "_ _i • C o ld m otor i n g _. • Gr o und Idle _ • Sl o w ac c els to, and de c els from takeoff p ower . _ _! • St eady-state o perati o n at takeoff power .._ time i nte r vals at takeoff • Severa l re b ur s ts t o take o ff p o wer after specified time i ntervals a t g r o u n d I dle ( dwelltl m e) _ il. • Suffi ci ent eng i ne sp eed s ett i ngs to e s tabl is h th e p erf o rm a n c e b> _. p o wer cali b rat io n ._. e. Stopc o ck _.. As c hema tlc presentat io n of the . t est sequence, sh o w i ng power level condl- _ t i o ns or s e t ti ngs for sp e cif ie d ti m e s, is g i ven i n F i gures 1 6,and 17. There were actual ly tw o type s o f t es t o perat io ns. One wa s pe r f o rmed t o pr o vide ac c u- : ra t e t rans i en t resp o nse; t he o ther was used to. eval u ate t he relati o n s hip of cl earance t o perf o rmance. The s t o pc o ck, o r engine shutd o wn fr o m cruise p o wer , b y turnin g the fuel fl o w o ff, c o ncluded the sec o nd t est sequence. The intent o f th l s Inve s t l gat l onwas to ob t a i n d a t a on the effect of th i s o p era t ion , which is pe r f o rmed i n a i r c raft ac c eptance test i ng , o n sh o rt te rm perf o r m ance deter io r a t io n.

6 _ I PERFORMANCE TEST The perf o rman c e te s t pr o gram was des ls ned t o eva l uate the perf o r m an ce and Stage i r o t o r t i p clearance o ver a range o f p o wer s ett i ng s after the engi ne reached s teady- s tate cond i tion s . E ach power cal i brat i on con sis ted of ba c k-to-ba c k sets of power levels i n des c end i n g order of fan speed w i th a short s hutdown i n-between. The en gi ne shutdown was included to a s su r e t e s t i n g repea t ab i l i ty.

A lis t o f the s peed se t t i n g s and stab i l i zat i on t i m e s for the power calibration chec ks ( bo t h " A " and " B " ) i s p resented i n the f ollow l n 8 tabl ez O_ lGll '_ gL PAG e : iS .i O F P OO R QUALI T Y ' 3O POWER CALIBRATION TEST RUNS C o rre c te d Fan Speed _ r pm ) Stabilization Time (_in) P o wer Cal i brat i o n " A " G ro und Z dl e 12 \ 3600 . _ 1 2 3785 5 35 8 5 4 . 3323 4 2093_ . 4 Gr o und I dle 3 Shut d o wn, o bta i n new thru s t balance m easure m en u ( or readln g ) an d res t art eng l n _o wer-Calibration " B " u r o und Idle 12 3600 12 _ ' 382 0 5 ......

!i , i . 3 700, 4 " ii . 3 64 0 ...... 4 ................ ] . .

3 410 4 .

i 3123 4 Gr o und I dle 3.

Shut D own .

Data Analysis Technique The data were analyzed usingthe Gene ral Elec t ri c Pha s e II co mp ut e r pro - 8 r am. This program has for it s basls a status cycle deck representat i ve of the p articu l a r en gi ne mo de l b ein g t ested. S o me o f the key fea t ure s o f thi s data •analysis progra m are = .-

il

a. Fo r each te at r eadl n g,a pretes t p r ed i cti _ n poi n t i s r un on t he cyc l e . _!

_ deck a t the tested c o nditions ( am b i ent temper a ture, p ressure , hu mi di.

• ty, e t c.), _ nd_th i s p retest po i nt is used :o check raw data quality _ ......

_ b. Sever a l a ltern a te a nalysi s paths a re bu i lt in for de t erm i nat i on of c o re f lo w, l o w pressure s y s te m w o rk, etc. I nadditl o n . i t i s p os sib l e " f o r the user t o se l ect his own analysi s setup. A l l o f these ana l y sis path s guaran t ee a ba l anced cyc l e; that i s, the s ol utl o n i s self-c o n- s i s tent and s ati s fie s thecontinulty , m o m entum, and energy_ 9 _quat l ons.

3 1 _ c . Th e built - in ana l ysis o pti o n s f ea t ure m i ss ion data protec t i on , Whe n a m ea s u r e m ent is missi n g , a suitable assump ti on i s made to replace the me asureme n t i n theanalysi s ; for example, when comp r es s or d is - • c ha r ge te mp er a ture is unavaila b le, co mp ressor e ff i c ienc y i s held a t the pred i cted level t o ef f e c t i vel y take its place. For a few ke y , i_. m easu r e m en ts , the analysis Is t erm i nated when they are unava i la b le,.

but fo r th e ma j or i ty o f t he m ea s u r e m ents, a n alternate analys i s i s , i : _ p erformed i n s tead.

t I_ d. At . th e c on cl u si on o f the ana l ysi s, th e c y c le dec k is m a t ch e d to th e ". tes t da t a; tha t i s , th e c y cle d eck m aps, e t c . , h a v e b ee n r e sc a le d lill t o b e c ons i s te n t w it h t he me a s u r em e n ts .

e. The d ata is adjusted to dry, sea level, stati c, s t anda r d-day condi-- tion by runn i n g theres c aled cycle deck at the _ tandard c on di tion.

i i This m etho d for c o r re c t i n g thedata el imi nates the p ro b le m , en c oun- _i_ t ere d i n t he past , of t ry i n g t o selec t a s i n g len um berto repre s ent, ii- for exam p le, the te mp erature e ffec t on fuel fl o w i n d e p en d ent of pow e r se tti ng or typ e of day . This i s p ar ti cula r l y s i gn i f ic an t in mo dern engines b e caus e t hey _empl o y m ore variable geome t ry.

ii 6 .2 POSTTEST TEAEDOWN AND HARDWARE ANALYSES Iii A f t er th e co nclu sio n o f t he engine t e st ing , the t urb i ne s ec t ion of t h e : if! en g ine, incl u d i n g the high pressure tu r bine r o t o r, Sta g e 2 n o zz l e asse mbl y (w it h S t a g e 1 and 2 shr o uds) an d turb i ne m ldfr am e , was disasse mbl e d and visu- i! / . . ally and d i m e n s ionally i nspec te d . These m easure me n t s were t hen c or r elated w i th t he c learan c e om ete r d a t a , es p ec i all y the data ob ta i ne d dur i n g c ol d mo t o r- "i ng .

7 ,0 TF.ST tumU LTS

7 . I. ENG ] '.NE PERF ORM ANCE Du r in g the cl e ara n ce p has e of the testing, pe rfo r m a nce w a s m e a s u red , se ve ra l time s throu g h out th e tes t to ascertai n a ny re s u l ti ng e ff ect s O n eng i n e par ame - t e r s.

' °Ana ly tl c a l s tu dlws p redic t e d a s t a g e one bla d e -o n - sh r o ud r ub to o cc u r d ur - lag b o th a two - mlnu t e and a n lnet y-s eCon d r e bu rst, P e rf o r man c e wa s mon it o r e d initiall y • pr ior t o any o f th e. r e bur st s a n d a g aln. pr lor - t o th e two - mlnut e rebu r s t, I _ a ft er t he tw O - m i me r s re b ur s t, p r io r t O _ h e nl n et-s_nd r eburs t, a n d a ft e r t he I n ine ty s e c on d r ebu r st .

probe , m ea s u r emen t s Ii The cl ea r anc e, shO w e d t ha t a r u b . o f .. 0. 3 05 mm ( 0 ,012 in) .... wa s s u st a ined d u ring th e reb u rs t t e stin g ._ T h e pe rform a nc e i n str ume n t a t i on _pr o- ' _.i v lde d d a t a f o r t h e .G,E. P hase IS c om put e r an a l ysi s o f e ng i ne p e rf o r ma nc e . . As- i a u mp t lons a nd d ata ad jus t m ent s ma de .l n th ls pe rf o r m a nce study w e r e : | q i a, All d a t a w ore a dj u s te d within t h e pr o gra m tO s ea le v e l, d ry, st an d ard , da y c on d itions, b , C o re f low w as ba sed on hi gh.pr e s s ur e t ur bine f low fu n c tion .

c, Com pres sor dis charge te m p e ra tu r e , was b a sed on th e i n itial . buil d s t a t us.

d ec k c ompressor , m a p a nd C om p ressor effl c len cy c h a r ac terl et l cs w e re a s sumed to re main co n s tan t t h r o u ghou t thi s t e sti n g. Th i s a s sum p tio n .

o r CO rr elation u se wa s ne c es s it at ed by d i ff i c ul t ie s encoun t e r e d wit h compre s sordi sc hnrg e in str umen tat ion. T his i s c onslde r ed a v a l i d d e- !. v iation , hOweve r, s in c e t h e c om p r ess or s tage s we r e in te ntion a ll y a sse m .......

_: b l e d w l t h l arg e tl p c learan c es tO avoid ru b bin g , w hi c h •coul d ve ry w all r e s ult in lo w er..e ff i c ie nc ies .

i_,. d, T h e H i g h Pressu re T u r bine e ff i c ien cy w a s calc u l a t e d fr om the t u r bine ' p r e ssur e rat i o ,, in l et t empera t u r e a n d wor k e xtract ion . Th e tu r bine _,: inl e t tempe r at ur e _ n o t mea sured) was d e ter mi n e d fr o m the c o mpre s s o r i_ d ischarg e t em peratur e and t h e. C omb u s t or- te m p eratu r e r i s e a ss o c i at ed .

: : wi t h t he m e a su r e d f uel f lo w . T h e t u rb i ne w o r k was det e rm i n e d fr om an i:- ene r g y ba h mC e w i th th e m e as u r e d compr e ss o r sy s t em . T hi s is a n acc ep t e d i" • pr O Ce du r e_ .

•....... Th e lo w pr e s su r e t urbin e f o r this test wa s. b uilt w l t h new stat l onary sea ls. Th u s. s o me L P : t u rb ine d e t e r i orat io n w as e x p e r ie nc e d . d u rin g t h e .........

' te s t: program and is a cc o unt ed f O r -l n the m eas ure d o v e rall- pe rfo rm anc e _ . _i re su l t s. T he P h a se II d a t a an al ysis I nd i Cated . the. a m o unt o f LP tur bi ne deter io rati on was on t he o rd e r Of .0. 1 % _ S FC and 0 . 6_ C ( I° F ) i ncr e as e i n exha u s t ga s te m perat u r e , The p e rf o r m anc e data rep o rt e d-h e r ein have i_ been a dju sted t o a cco u nt f o r th e LPT d e ter io r a t i on sO that t h e d a ta i C Oul d be c om p a r ed wi t h r e spect t o pe rf o r m a n c e e ff e c t s d ue to th e H PT i Oul y , l 33 !

7 .1 . 1 Discussion of Results Th e res ul ts s h o wn i n F ig u res 1 8, 1 9 an d 2 0 re p rese n t th ec hang es i n hig h pres s ure t ur bi n e effici e ncy, e xhau st g a s tem p e ra t u re an d o verall en gi ne s p e ci- fi c fu el . co n s um ptio n a ssoci a ted w i th a cle a r an ce c han ge o f 0 .3 0 5 mm ( 0 ,0 1 2 1 In ] £ r o m th e ba se lin e p e rf o rmanc e p o we r c a li bra ti on , A pr e d i c t i o n of c hang es i n t u rb ine e ff ici en c y , exhau st g a s temp er atu r e and specific fuel c onsu _ p tlo n was made f o r an 0 .3 0 5 m m ( 0 . 0 12 in) c han g e i n Sta g a 1 _ r oto r ti p cle a r an c e. This predicti o n was based up o n t he analysis o f t es t re - s ul t s o btained in several a ir t ur bi ne com p o n e n t te s ts and t he a tt en d an t en gi n e p e rf o rman c e mod e l s devel o ped a s a resul t o f t hes e and ot hers d e s i gned to i s ol a t e " .i t he perf orm an ce rela t ed c hara ct er isti c. A c omp ar l s o n o f t he t es t d a t a and pre- d iction s is sho _ n in t he f o ll o wing table: • Effect o_ 0.305 m m (12 mils> Sta_e 1 Tip Clearance _ncrease at Takeoff (F - 222kN / 50, 00 0 L b ) Test Results Pre-Test Prediction _ _ -0. 7 - 0 .5 7 i - _ EGT ° C 9 . 7 SFC X 0.3 7 0 . 55 Clearance (mm) -0. 4_ -0.53 An T .(_ ) Clearance (mils) -17 -2 1 • _n._ (_).

I f all o f t he calcula t ed de t er i ora t i o n i n en g ine p erf o rmance i s ass i g n, a b le to t he measured chan g e i n HPT S t a g e 1 blade t ip cl e arance, t he r e su lts o f t hi s t e s t s h o w a s t r o n ge r e ffec t o f S t age l . c learan ce on p e rf o rmance t han de te rmined b y previ o u s tests . • Theref o re, explanati o n s for th i s differ- ence were soug h t . I i • Men t i o ned previously was t he assu m pti o n dur i n g performance da t a reduc- " i tio n t ha t t he com p ressor had no t d e t er io ra t ed du ri n g t h i s t es t. T h ere is " no evidence, b _s edon ti p clearance, t ha t t he compressor changed.. :

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iJ T he de t e r ior ati o n of t he Lo w Pressure T u r bine w as assessed a t 0.1 Z i n SFC. I f th is n um b er w e r e in error, th e resul t s f o r _P T S t a g e 1 clea r ance der i va _ ive w ould c han g e.

T h ro ugh ou t th e CF6 d i a _ no s_ic pro g ra m, a cause of de t er i ora ti on , which has been c ons i s t en t l y i den ti f i ed as s i_ n i f i can t, _ i ncrea s ed a i rfo i l surface rou g hness on fan , HP compressor, HP Turb i ne and LP Tur bi ne a i rfo i ls. Al t hou g h it would n ot b e an ti c i pa t ed t ha t s i sn i f ic an t r oug hness in c rease s occur over t h e r ela ti vely shor t tim e en c o m pa s s e d by t h i s t es t, t he ti p c learan c eder i va- ti re wa s e st ablished on t he basis of small c han ge s i n performan c e fo r s mall chan g e s in measured clearance. This means t hen t ha t variable s , such a ssm all increases in rou g hnes s , may have some e f fec t on t hese t es t r e s ul t s t ha t i s no t readil y r eco g niza b le. Any unassessed de t eriora t ion which did occur would be in t h e dir ect ion of i mpr ovin g t h e a g ree m en t be t ween , t h e d e riva t ive measured in t hi s te s t and t he _ reviou s ly a cce p t ed de r iva t ive ....

One t h i n g i s cle a r. • The S t a g e 1 HPT blade tip c lear anc e has a s i g n i f i - can t effec t on en gi n e p erformance and t h e der i va ti ve o f S t a g e 1 c lear an ce on p erforman c e was assessed t o be . a t leas t_ as i nflue nti alas t ha t which i has b een _e v io usl y a cc e pt ed ....

_i !' 7 .2 B P TURBINE STAGE 1 CL_CE MAP '_ T h e r e sul ts o f t he clea r ance om e te r t es t ar e pr esen te d f o r sev e ral o pera- i - t i o nal c o n d i t i o ns. Tip cl e aranc e is p re s e n te d a s a func tio n o f t i me f or th e follo w i n g t hr ottl e m o v e m en t s; a n a cc el fr o m g roun d i d l e to s t ea dy -s tat e ..

_i t a k e o f f p o wer i n w h ich t a k e o ff p o wer I sa tt a i ned wl t h l n I0 sec o nds; - a d ecel fr o m s t ea d y-s t a t e t ake o f f co nd i_i ons to g ro u n d idle; an d vary l n g-t i m es a t g round Idle foll o we d by a burs t t o t a k e o ff powe r . In a dd iti on, clearance i s The c lea r an c es p resen t ed a r e t he avera g e of t he readin g s of t he eig ht pr ob es and da t a have been c orre ct ed where ne c e s sary t o refle ct a c on s is t en t se t o f a mb len t cond lt lon a .

I exi t t e m pera t ure ( T3 ) , an d as a f uncti on of compress o r ex itp ressure ( P 3).

/ _I 7 . 2 . 1 Clearance As a Function of Time for e lO-Second Accel from i, Gro u nd Idle _o.Takeoff Power .

_ T he me a s u red S t a g e 1 blade- t o-shroud cle a rance as a f u nct i on of tim e for • a lO-sec o nd accel i s shown i n F i g u re 21 . T he pred i c t ed clearance i s als o _i p lo tt ed. There i s a ppr ox im a t ely an 0. 25 _ ( 0 .0 10 i n) di ffe r en c e b e t ween .

measured a nd pred i c t ed clearanc e wi t h th e measured clear a nce be i n g larger - _' than th e p r ed i c t ed clearance . The ma jo r difference between th e predic t ed and m ea s ured clearance a p pears to occur at t he s teady- st a t e takeoff and 1 idle condi t i o ns. T h e sh ape of the curves, h owever , are very sim i la r . 1 _ Three d i s ti nc t areas o f c l earance b e ha vi or m ay be ob s erved. F i rs t , as • ro t or speed increases fr _ nO-10 se t. , t he cl e a ra nc e decreases due t o m e c han ic al (pr i _ a ri ly speed) effe cts. Fro m 10-35 s e c . t he s t a tic s t ru ct ure s b eco m e warmer t han t he ro t a ti n g st ru ct u r es, resultin g i n a clearance increa s e. Fro m 35-1000 se t . , the more m a s sive ro t a ti n g s t ru ct ureswarm u p c ausin g cl earan c e t o decrease and even t uall y reach a st eady-s _ a _ e value , i !

I 3 S I • 3 O • ..... , _ • _ ...... 7 , _,_ , _. • .... _ --_ _ ¢ ._ . _ _. . _ . ,. _

l

7 ,2 _ 2 Clearance As a F uncti on of T.Ime for a Deeel from.St g ady-State Takeoff Pow e r to Grou, d Idle Th e m ea s ur e d S t ag e 1 blad e -t o - s hr o ud cl e arance as a f u n ctio n o f t im e fo r a decel from steady-stat e t akeoff power t o g ro u nd idle i s presen t ed i n F ig ure 22.

The pred ic ted cle a rances are al s oplotted .... As i s ev id ent fr o m th i s f ig ure, the measured clearance c o mpares• very well w i th the analyt ic al pr ed ic t io n .

i ii_: Aga i n, c learance a s a funct i on o f tlm e for a d e c el i s c hara c terized b y__ \ three re g i o n s . As RPM de c rea s e s , c learance i n i t i ally increases (up. to l0 sec o nds). Then the s tat o r cools d o wn, cl o sin g ar o und the r o t o r (i 0 t o i 00 sec o nds)•; _I na ll y the r o t o r cool s, c ausin g a cl earan c e increa s e (I00 t o I 00 0 sec on ds) .

7 .2 . 3 Reburst Previ o us to this inves ti gat io n, t hrottl e rebu r sts were thought t o be ._ the s I E nlf l cantcause o f result an t clearance increases and c o nsequen t p e r fo rm- ance lo s s e s . One o f the o bje c tives o f this te s t was t o o btain clearance and _ em p eratur e data f o r va ri ou s r ebur s t o peratl o nal.conditi o ns. t o verlfythls, i Reburst-type d ata were o b t a i ned f or eng i n e Id le t im es o f 8, 6, 4, 2, I , and % ml nu te s. F i gure 23 p resen t s the ro und eng i ne c l earance d ata re s ul ti ng fro m t h ese t es t s. Th e start i ng po i nt fo r each of the plot t ed curves _,.

i s the be gi nn i ng of thereaccel from gr o und Idl e aft e r th e label e d dwell tim e.

A r e b u rst fr o m stab ill z e d gr o und Idl e ( i .e., 30 m i nutes) i s a l s o s h o wn fo r reference. This represents a " c o ld " r o t o r re b urs t o r a acc e l fr o m stab i l i z e d gr o u nd i dle . - ...........

_ t i s evid e nt fr o m F ig u r e 23 that a min im u m cl e arance exists f o r re- b ursts f o ll o win g a o ne t o tw o minu t e dwell t i me at g r o und idle. This is als o su p p o rted by data present e d i n Figure 22 which sh o ws that the m ln lm umcl e arance during a dec el o ccurs at a pp r oxi m ate l y I00 s ec o nds._ Clearance as a fun c ti o n o f ti m e fr o m the stea d y-state take o ff po wer point through the accel mini m um clearan ce p oi nt for a re b urst after a two- : mi nute dw e ll time at gro und idl e i s s hown i n Fi gure s 2 4 and 25 .• F i gu re 2 4 s ho ws the ef f e c t of rebur s ton clearance. Figure 25 shows H _ turb l ne rot o r _ RPM a s a fun c tlon o f ti me . durin g th i s t hro tt le se q uence. The additional i closurefr o m steady- s tate takeoff result i ng fr o m a two-mlnute rebur s t l s i 0 . 7 _ m m ( 0 . 0 29 i n.). Thi s ag r e e s extremely well w i th the predlctedc lo su r e o f 0. 7 9 _ n.(O.03 _ i n.).

Th is r e b u rst d a ta s h o w s that w a r m an d h o t r oto r (d e p e n d ent u p o n gr o und _ i d l e dwell t im e) reb u r s tsar e e n gl ne o perat l n g c o nd i t io ns wh i ch p ot ent l a ll y ca u se r u b s a nd c o ns e q u ent per fo rmance deter io rat io n. The t im e c o rrelated clear a nce and t e m perat u r e d a ta o b t a i ned fr o m th l s : te s t has s l gn l f l cantlyen- hanced the under s tand i ng o f rebur s tsand ver i f i ed t hat the c lo sure (and s u b- s eq u ent r u b) pred i ct i ons are c o rre c t .

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Ground Idle i 1 - ii O 50 cO0. 150 20 0 Ti m e, se c gnd s F igu re 25. Core Speed As a Function of T i me Exh i b i tin g a 2 Minute Dwell Prior _ o Reburst.

, : i Exit T em p e r a t u re , T3} an d C om p res s o r _E xlt Pressure, P 3 ; I !" T h e rela ti o n ships o f c learan c e a s a fun ct i o n of core sp e ed , c o m pres s or ex i t !

i te mp e ra= u r e and c o mp re us or ex i tpres s ure are p resented i n Y ig ur e s 26, 2 7 and 28.

; The da ta u s e d to con s t ru c t th ese c urves w e r e o b ta i ned from s t eady-state c o nd i ti o n s | L I achieved during th e p ower ca l ib rat i on work. Steady-st a te is defin e d as th a t t im e !" when all en g ine pa r a m eters hav e ceased to apprec i ably chan g e. Most of t h ese i I st e ady - s t ate da t a ar e" off _ des ig n " c ond iti o n s, i. e ., o th e r than g round i dle, t a k e, i off , and cruise, i _" The datawere us e d as the baselln e relatl o nsh i ps t o e sta b lish an e m p i r i- .........

L . t el mo del.t o pr e d i c t clearance f o r . an 7 st e ady - state op e rat i n g co nd i t i on.

i I, ' This i s a very use f ul t oo l b e c ause, t o ob ta i n a p pr o xi m ate clearances f o r a g l v e n o perating c o nd it i o n, it eliminat e s the need f o r heat transfer and aer omod elln g usin g t he result l ngheat t rans f er a n d ner o m o d e l te mp eratur e s a n d pressures. This e mplrl ca l m o del Is o nly an a pp r o x im ati o n and certain l y n o t a totally valid an a lytical pic t ur e. It i s e x t r eme l _ us e ful, h owe v e r, i in translating fr o m a new engine to a d e t e ri o rat e d o ne, fr o m a hot day : .

_, high alti t u d e t a keo ff t o a s e a l e v _ .is t andar d conditi o n t a ke off, etc.

Thes e func t i o na l relati o n s hi p s are a l s o quite usefu l in assessing the accuracy o f s t eady-state calculati o ns , e sp e cially th e h e at t r ansf e r po r t i o n o f such analyses.

! ; 7. 3 ENGINE SHUTDOWN (STOPCOCK) TEST " A n e ng i ne shutd o wn fr o m cruise, o r h i gh e r, p ow e r i s t e rm e d a s top c o c k.

The tes ti n g for this I nves £ igati o n included a st op c o ck f ro m cruis e in o rder t o esta b lish,he transient clearanc e r esp o ns e dur i ng this ty pe o f maneuv e r.

I t is c o m m o n in aircraft acceptance, testlng t o p erf orm st op c o cks. Th e in t ent o f this i nvestigati o n was to ga t he r data w h l ch w o uld b e o f valu e i n assessing the effect that aircraft acce p tance t e st st op c o cks might have o n sh o r t term performance deter io rat io n.

Th e st o pc o ck test sequence was in i tiated fr o m a c o re speed of 9500 RPM af t e r having st ab ilized at th i s s peed f o r ap p r o xi m at e ly i0 m inutes. Th e fue l fl o w t o t h e e n gi n e_ as cut. The e n gi ne coas te d d o wn an d was r e s t ar te d aft e r i 200 sec o nds. Thi s r e s t ar t was done to e l imi nat e t he poss i bil it y o f b oth hi gh I and l o w sp e e d r o tor s e izure and o f s ump and be ar i ng as a r e sult of l osi n g o il co o ling.

The avera g e Sta g e 1 b lade _ t o -shr o ud clearance versus ti m e dur i n g st o p- C o ck is presented in Fi g ur e 29. The c o re speed, N2 , ver s us t im e is pre s en t ed in Fi gure 3 0 a s a r e f e rence.

The cl e arance curve ma y b e d i v ide d i n t o th r ee r e g i ons of i n te r est. T he _ f i rs t r e gion i s wher e cl e arance i s i ncreasin g (up t o 6 0 s e conds). _Th i s cl e aranc e incr e ase is caused b y the l o ss o f m echanical effects (centr i fugal f o rces and pres sure loads). Th e sec o nd r e g i on is t ha t cl e arance decrease c aused by t he statorcool i n g do wn (60 to 24 0 seconds). Th is stator cool-down period was interrupted by the en g ine bein g restarted. Dur i n g t h e restart, t h e clearance reduct i onoccurs because mec h anical effects are so m e wh a t restored by returnin g to idle. T h e third region of in t e r est is where clearance increased because t h e rotor was coolin g (240 to 4 00 seconds).

44 _

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OF POOR Q U A L I TY ' i

100 200 300 400 _ 00 600 ,

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Compress or g x l t Te m pe r a t ure, . _ C -- Fig u re 27, Clea __r_t_ c _ As _ _ F . u n c t lo n o f C o mpressor E x lt Temperature, 46.

0 200 300 ........ 40 _ Time, _ conds .

F i gure 2 9 . C l e ara n c e V ersus T£me Af te r S_o pc ock .

xo, ooo .._ ., - --T _ , _ I i

Cr u £se =--=41m _ Stop Cock I n terrupted- t N2 . Ens£n e R e fir e d end - I 8000 Recu_ed to Idle Ground 4_ 0 k aOOO 0 • 0 1oo 200 300 400 Ttme , s e cond = F l_ re 30. Core Speed Versus Time After Stopcock.

A t heoret ic a l approx ima t i on o f a s t op c ock f ro m s t eady-state t a keo f f power, based on the c ru i se stopco c k m easured resu l t, is shown i n F ig ure 31. Th i s c urve m od ifi es the informa ti on sathe r ed i n t he stop c o c k test to ref l ec t t he h i gher power l eve l and re m oves the i nterrup ti o n i n the trans i ent w h ic h r esu l ted when the en gi ne w as re fi red . It c an be_seen tha t no round en gi ne rub i s pre- dicted f o r an uninterrupted st o pc oc k i n which n o en gi ne restart was made. \ 7.4 COLD MOTORING DATA w ..

Cold mo t or ing data wer e ob ta i n ed whil e turn i ng th e ro t or wlthan a ir sta r t er mo t o r. Ther e was n o c o mbusti o n occ u rr ing within the engln e_ an d pri or to th i s test t he engine ha d n o t b een running f o r at l e ast 8 h o urs. Clearance- I om e t er data were taken dur l n g t hls phase o f testing. These data are p resen t e d

I

in Figure 32. The c o ld mo t o r r o undne s s i s plo tted as da vla tlo nfr om t he average.

These d ata a re r equlr a d f o r a cc u r ateanalyses o f bo th c lear an ce resp o nse and ou t- o f- ro undness. The c o ld mo t o ring data r e p r esent the c o ld c learan c es and the shape o f the HP stat o r as asse mb led. These data , theref o re, a r e the basis f o r b o th c o ld clea r ance an d o ut -o f-r o undne s s. I tls t he co mp o site picture o f m anufacturlng-andasse mb ly c aus edo ut- o f-r o un d nes s . The average o f the clearance ome ter read i n g s d ur i n g c o ld mo t o ring is used to esta b lish the cold clearance. The c o ld mo tor i ng c learan c e sha p e is use d to es t a b lish the init i al engine o u t - o f-r o u ndness. This initial O ut- o f-r o undn e ss can th e n b e util i ze d t o modify the o ut- o f-r o un d ness data t o refle c t the r o und eng i ne assu m eda s t he analyt ic al s tart i ng p o int.

The Stag e 1 b lade-t o - s hr o ud clearance, as ob ta l ned b y po st t est i n s pec- ti o n , i s sh o wnln Figure 33. Aga i n , th i s r o undn e ssshape is plo tted as d e viati o n fr o m av e rage. _ f a sl i@ ht rotor e ccen t ric l tyls as s u m edan d assem b ly caused o u t , o f-r o undness i s c o nsidered, the s i milar i ty b etween the tw o shapes (F i gures 32 and 33) i s clo se. This Is verified b y the average o f the clearance om ete r d ata and the i nspe c t io n data b eing within 0 .025 m m (0. 0 01 in) o f o ne an o th e r.

7 .5 HIGH PRESSURE TURBINE STATOR ROUNDNESS The o bjec t ive o f th i s p o rti o n o f the pr o g r amwa s t o m easure th o se p a rameters believed t oinfluen ce high pr es sure t urbine r o undne ss , analytically determine the i r effect o n r o undness , and c o mpare the c alculated roundness to 1 the measured roundnes s ob tai ned fro m t he clearanceometer results. _

• 1 Theme a sured roundness was obtained by a vera gi n g t he data from the

clearance pro bes, subtract l n g o ut the cold m o to r i n g mea s ured assembly o ut- o f-r o undnes s , and then pl o tt i ng the deviations fr o m the average clearance i value. This relate s the roundne s s data t o the clearance respon s e data and to a theore ti cal round engine star t in g point. Therefore, the variation of readings from the e i ght clearance prob e s provides a me asure of t he roundness of the h i gh pressure t urbine Sta g e 1 shroud sy s te m .

49 i

I

'_" OF POO R ,QUAL IT Y ...............................

e_ ue _ t e o I_ L 5 0 Avern ge Figure 39. Cold Motor Roundness, Devi attonof Individual , Probe Re a d ing f ro m the Average of Ill Reading s .

5 1 Ro u nd Ftsure 33. Po= tte s t 8ta s e X Shro u d 8ur f aco . Roun d ne sl Xn|peetton, 7 . 5 . .1 L Ow Pressure Turbine Temperatures The LPT s t a t or case w as i ns t rumen t ed wit h 48 s k i n t her m o co u pl e s (S ee F i_ ' _ re 34 ) i n order t o o bt a i n dat a requ ir ed t o ana l y ticall y de t ermine LPT c on t r ib u ti ons t o HPT ou t -o f - r oundness. The tw o m e c han is ms b e li eved t o c on- t r ib u t e s ig n ific a ntl y t o H PT ou t -o f -ro un dne s s were t e mp era t u r e d iff eren ti a l s b e tw een t h e LPTs t a t or case hor i zon t a lfl an g es an d shee t m e t a l s ki n a n d ci r c um f eren ti a l _ e mp era tu re g rad i en t s i n t he LPT st a t or c asa sk i n. _ 7 . 5 . 1 . 1 H orizontal Flange / Skin Te m perature Gradients . The t e mp e r a t ure differences b e t ween t he LPT s t a to r c ase ho r izon t al _.

f lange s and skin were obt a i ned fr o m t h e t es t e n gi n e sk i n t herm oco u pl e _ da t a a t var io us s t eady-s t a t e p o i n t s i n c lud i n g t akeoff a nd g r oun d Idle. The m axl m u mt e m pe r a t u r e dlfferenc e be t w e en _h e LPTs t a to r ca s e h or i z on t al flanges and .s kin , fo r any o f t he axial stat ion s m easu r ed, was i 0 8°C (19 4 °F) a _ t ake- o ffand t he _ maxl m um difference b e t ween t he average t em p e r a t u r e o f t he fl ang e s and sk i n was 3 1° C (55 ° F) _- F i g u res 35 and 36 c om pare .t he ax l a l t e st t e mp era- t u re d i s t r ib u tio ns o f t he LPT st a to r case h o r i z o n t al fla- _ esand s k i n (as well a s t he _ veral _ _ay _ ra g e o f all T / C' s ) f o r g r o und idle and t ake o ff co n d i-

tions .... l....... ]

_i 7.5. 1 .2 Circumf e r entl al Tem p e ratur e Gradients

ii!i

_i : iI LPT,s t a to r cas e skin ci r cumfe r en t ial t e mp e r a t ur e dis tr i b u t i o ns w e re s o btained f or g ro und idle an d t ake o ff condi t i o n s using t h e t es t da t a. These dis t r ib u t i o ns _ e r e t hen rep r esen t ed b y Fourie r Series in o rder to de t ermine _ : I t he pr i n ci pal ha rm on i cs co n t r i bu tio n to t h e d ist or t ed LPT st a t or case mode s hap e s. F i g ur e s'3 7 t hr o u g h _ i illus t ra t e t he circu m feren ti al t es t t e m pera t ur e ] I ! d is trib u t i o ns o f each of t he f o ur axial st a t i o ns of t h e LPT st a t o r case an d i ! o f t he _ ave r age o f all axial s t a t i o ns f o r an engine _ ro u nd i dle con ditio n _ii (refer t o FI R ur e 3 _ f or axial s t a t i o n de s i g na tio n). F _ g _ re s _ 2 t hrough _ 6 : !i_ i i llu st ra t e circ u m fer e n ti al t e st t e mp er a t ure d ist r i bu tio ns a t t he s ame lo c a tio ns i_ , , ! for a n eng l ne t akeof f cond itio n.

7. 5 . 2 TurblneMidframe Temperatures Te mp era t ur e s o f t he-s t ru ct ural e l ements i n t he t ur bi ne m _ df r a m e wer e m e a s u red a t s t e a dy-s t a t e gro un d i dle and takeoff power at t he same t i me t h at I clearances i n t he h i gh pre s s u re turbine were being recorded. The s i gn i f i can t ' _ en gi ne parame t er s recorded a t t h ese con d i ti on s , which are used _ for de t e rm in i ng . t he m e c hani c a l lo ading o n t he TMF, are a s f o ll o w s : Ground Idle Takeoff • I "" Fan Speed, RPM 864 3785 • C o re.Speed, RPM 6_ 46 10 ,2 3 5 ! _ E ngine Thrust , N (Lb) 849 6 ( 1 9 10 ) 2 1 0 , 978 ( 4 7 4 30) RPT exit temp. , _°C . 4 0 0. 895 _ i HPT exit pressure, N / c m 2 (PSIA) 11.5 (16.7) 58.7 (85) 5 3 5S ................................

]1._ OF POofl _l . _ . _.t._-,_, ......

TAv Data Point M i ss i ng.. _ _ .

Between End Po i nts Figure 37. LP Turbine S t atorrCase Circu m ferent i al Temperature D l str i bu ti on , Ax i al Location Nu m ber I t " Ground Idle.

5 7

OF PO 0_ QUA L ITY

,, _ l _ 5 0 ° F _ 1 0 ° C TT .

TAv a F i gure 38. L P Turb i ne S t a t or Case C i r c_ n _ erent ia l . Tempera t ure D ist r i bUt i on, ..

Ax i al Location Number _ Ground . Idle.

I

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TAv

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Es tim a t ed ( Data _ % , N o t Ava i lable)__._ ............................ _q._ _ / B_ F i gure 39. L P Turb in e S t a t or Case Circumferential Te mp erature D ist r i bu t ion , Axial Location Nu m ber 3, (]round Idle.

ORIGINAL PAGE IS

OF POORQUALITY

TAvg

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J i • F i gure 40. LP Turb i ne Stator Came C i rcum f erent i al Tempera t ure Dist ri b ut ion, A x i al Location Number 4 _ Ground Idle. _

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TAvg Figure 41. LP Tu rb£ne Stator Case C£rcumferential.Temperature D is tribution,.

, A x£ a l A verase, Ground Idle.

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Fi g ure 42. LP Turbine S t atOr Case Ctrcumf e ren t_ al T e mper at ur e Dis t ribution, _ . _ Axial Location N u m ber 1,__ Tak@ _f.f_ ....................................................................................................................................

' i 6 2 ...........................

L , ,. • a Ft_ t l w 43 . I A _ Tu r bi n e $ t at_;r Ca Be C i rt'ttm terQu t l aX T e ml} e ratur Q D I ,t r ttatt_k o u, ..

• A. _ tal LOca_ t O u Numb_ " 2, T . k, _ff . .

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100° F- i • \ " 2 0 o C Figure 44. LP Turbine Stat or -C ase CLrcu m£ eren ti al Te m perature Di st ribu t ion | _ Ax ia l Location Number 3, Takeo££ . - 1

, 6 4 _ i

T Av Fi g ure 4 8 _ _ _ LP Turbine Stator Case _ C t rcumferent i al Temperature Distribution t o _ Axial Location Number 4 , Takeo f f.

6_ • TAv !

Figure 46. LP Turbine St a tor Case Circumferential Temperature . D i s t r i but io n, Ax ia l Aver a ge, T akeo ff .

il i_ T h e measured te m p e ratu r e s i n the TMF _s t r uctura l e l eme n t s a r e s hown i n I F i gu res 47 th r ou g h 4 9 fo r 8 r ound i d l e and F i gures 50 throu g h 52 fo r takeo ff .

, _ T h e te mp e r atures of each of the e ig ht struts was m easured to o b ta i n the s trut to st r ut var i at i on s h own on F ig ures 4 9 a nd 50. The hub te mp erature wa s m easured at severa l ci r c u m ferent i al l o c at i ons. No s i gn ific ant te m perature _i: _ • v a r i at io n wa s noted; therefore , only _ he_avera g e te m perature i s shown o n _ . . t , F i gures 4 7 and 50 . _ I_i" ' I' The te m peratures o n _ he TMF c a s i ng hat se c t i ons were m easured at .the base m easure m en t s were then used to calculate the area we i ghted average te m perat u re ii " a nd apex : of the hat se c t i on at a n u mber of ci rc um ferent i al locat i ons. These [_! and radial grad i ent at e ac h l oc at i on. Th i s was d o ne i n o rder to o bta i n the _! ! data pre s ented o n F igu res 48, 49, 51 and 52. Also sh o wn onF ig ures . 51 and 52 _:.i;_ d a t a i n a f o rm wh ic h w o u ld be u s able .l n the a n a lyt i c a l model. These are the _:.|+ are the est i mates of thes e te m p e rat u res made prior t o th i s test i ng. Th e se eng i n e te s t i ng. As the th e rma l mass and heat i n g / c ooll n g me chanism f or the hat se ct io n varies ar o und th e c i r c u mf ere n c e o f th e TMF caslng, t emp e r atu r e m easure - _ me nt s were made at t _ elv e ci rc u mf er ent i al l oc at io n s t o o bta i n an a cc u r at e re pr e - i !_ _i sen tat l on o f _ ha.tamp er atu r e va r la t i o n s in thi s area.

- o f b oth th e CRF and th e TMF flanges a s a m ea s ure of the average flange temper- ature an d_ are sh o wn. o n Fi gu Te s 53 and 5 4 .

ii_ ! T em p er atu r es on the TMF / CEF flange were measured at th e radial m id point / _! ' _: 7. 5 .3 High Pressure Turbine Stator Te m peratures ! Te m peratures were al so measured at three l oc at io n s o n t h e HPT ' stat o r at I the same eng i ne operat i n g point s . . The results a r e shown o n F io " ure s 5 6 thr o u g h 5 7 f o r g r o und Idle and F ig ure s 58 thr o u g h 60 f o r take o ff. _- 6 7 _ , , _ - ,, i , i I I I l l lII l II I

ORIGINALPA G _ , _ i : _

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7 0

7 2

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_ " j F i gure 55. HP Turb i neStator Temper a ture , Ground Idle (Locat i on A).

O R I G INA LPA GE L" J '

OF POORQUALITY

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• . _._

10 ° (3

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F i g ure $6 . _ _ HPTurbi n e S tat or Tempera t ure j Gr Q und __ dle ( Lo ca tion B) .

7 .......

1 84 ° :_ R e f er enc e F£gure 57. BP T urbine S t ator Temperature, Ground Id l e (Location C).

, : . , • • _' , ...... _ • • , _i_ ' ¸_ ' _. , .

ORIGI N P zL P_, , ,_._ [_

OF POORQUALITY

" Fi gure 58. HP Turo i ne Stator Te m perature, .

Takeof f ( Location A).

I 0 • o _ . _ : _ . _ .

' 20 ° C..

-r-

543 . o Ref e rence _i_ F _ ure 59. li _ Turb i ne S t ator Tempera t ure ,._ Tak e o ff (Location B).

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80 _

O F PO O RQUALI T Y

10 ° C e.

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" F i gure 60. HPTurb i ne S t ator_T e mperature j Takeof f (LocattonC).

7 . 5 . 4 Low Pressure Turbine Effects Horizontal Flange / Skin Temperature Gradient Effect s Based on the CF8-50 stru c tura l s y s te m m ode l , the g rad i ent of th e aver ag e s o f the LPT ho ri zonta l fl an ge / sk i n te mp e ra tur e s ( s ee F ig ures 35 an d 36) t r an s - .

l a r es i nto an HP T s ta to_ out - o f- roundne ss of l es s t h an 0. 02 5 _ n ( 0 , 00 1 i n ) . _ \ Ci rcumferential Temperature Gradients I i ' i Each of the c ir o u m ferent _al temperatu r e di str i but io n s dep ic ted i n F ig ure s f 37 throu g h 46 was represented bya Fourier Series. . These r epresenta ti ons l de m ons tr ated tha t no s i n g le harmon ic do m inat e d the m ode shapes at the g round d o mi na t ed. The Fourier Series representa ti on s of . the c ir c umferent i al avera g e i dle c ondit i on but that for thetak e off c ond it ion, the f irs t ha rm on ic c le a rly m ode shapes for both gr ound idle and t akeoff were used in c on j un c tion with the .

"CLASS / MASS " i nfluence c oeff ici ents to det e rm i n e that the L P T i ndu c ed HPT B ut-

!

of-roundnes s i s ap p rox i ma _ ely 0 _ 025 m m (0.001 _ for both g round idle and takeoff c o n d i tio n s.

Discussion Of LPT Caused HPT Out-Of-Roundness The LPT- c aused HPT ou = -of-roundn e ss of ap p rox i mately . 025 -_ (0.001 in. ) from the thermal g radient of th e flan g e / skin syst em and of ap p rox im ately 0.025 . m m (0.001 i n.) fro m the skin ci r c u m ferent i al gr adient are very small compared to the out-of-roundness caused b y the tur b in e m i df r a m e. Considerin g the complex- I ty of the .m odel and the many appro x imations m ade thro u ghout t he analys l. s . . _ te c hni%ue, these small o ut- o f- ro undne ss es wer_e _ _ILe _ lected. _ 7.5o5 Tur_Jine Midframe Effects 1 L _ L U s ing the measured t em peratu r es u u the tu r bine ml dframe st r uctural ele m ent s and TMF / CRF flang e , and the eng i ne o perating pa r ameters t o -e s tab ll sh m ech ani c al :_ loading on t he TMF, the out- o f-roundnes s i n the HPT s tator was c al c ulated for gr o und I d l e an d t akeoff. Thl i cal c ula t ed o ut-of-r o undne s s is shown i n Figure s 61 an d 62 .

High Pressure 5_rbine Stator Temperature Gradient Effects The c al c ula t ed stator out-of-roundnes s due to. the measured temperature var i a ti on i n the sta t or i s shown i n F ig ures 6 3 en d 64 .

Total Calcu!a_ed Out-Of-Roundness I The t otal cal c ulated HP Ts tator out- o f-r o undne ss , due t o turbine m l dfr am e e ff ec t s and h igh pressure t u rb i ne s tat o r temperature gradients is s h o wn in o. =5== (o.oz _ n. ) .

8 " F i gure 61. Calcula t ed HPT S t ator O _t -o f -Roundness Due t o T _ F, O round Idle.

@ 83 '

I

l F _s ure 62. Calculated. Hl = T Stator Out.-of- R oundness..Due to TMF _ _i Takeo f f.

, !

_ ' 84 i ALF

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Round Fi s u re 63. Calculated [ - I 1 3 '1' Stator Ou t -o ¢ - R ound n ess Due.to Sta t or , Temperature Varia ti on a Ground Idle.

I .]

t 85 ....

, Round F i gure 6 4 . Calculated HPT S t a t or Ou t -o 2 -Roundness. . Due .t o Sta t or !

Tempera t ure Variation, Takeof f .

6 _ - _ F ig ures 6 5 a n d 66 an d co m p a red to the measured data at these points f ro m the e n gi ne test.

7. 5 .6 Measured Transient HPT Starer Roundness T h e h ig h pressure turb in e starer out-o f -roundness f or a t h rntt l e burst i s_ presented i n Fig ure s 67 throu gh 72 andthe out-o f -roundn es s dur ing a t h rott l e ' chop _ s s hown i n Figures 73 throu g h 8 0 . These figures show the slowly chan gi_ n g r o undness relat io nsh i p wlth res p ect t o time during th e se thr o tt l e mo ve m ent s .

7 .5.7 Discussion of Roundness Data Themeasured versus c al c ulated o ut- o f-r o undness is used t o c o rrelate th e analyti c al m od e ls, te c hn i ques, and ass u mptions used in HPT out-of-roundness predi c tions. Comparison of c al c ulated to measured out-of-r o undness under ope r - atin g c ondit i ons has not been possible prior to the testin g c ondu c ted i n th is pr og ra m . C ompa r i s o n o f the HPT o ut- o f-r o undness measured dur i n g th i s te s t t o that c alculated fr o m th e ope rat i n g co n d iti o n s an d a dj acentst r u c ture te mp era- ture s ob tained at the . s ame t im e pr o vides the.data required to sh o w where im- p ro vements need t o b e made in t he analyt i cal p r edi c t io n m eth o ds. These d ata can a l s o be u s ed in the future to verify the effe c tiveness o f any such impr o v e - m ents.

The c o rrelati o n b et _ een measured and c a lc ulated o ut- o f-r o undn e ss is n o t goo d, especially at the take o ff c o nd i ti o n. A review of the measured t r ansient o u t - o f-r o undness d ata f ollo wl n g a rapid a c ce l fr o m gr o und id l e t o take o ff and a l s o f ollo w i n g a rapid dece l fr o m take o ff t o gr o und id l e, F i g ures 8 1 and 82, sh ows that the change in d i st o rted HPT sta _o r s hape o ccurs g radually o ver a ele m ent f or o ut- o f- ro undness i s the differentlalthermal resp o nse i n the engine "_ ! st ru ct ures which is .kn o wn to occ ur sl ow ly. M e cha nical l o ads w i ll re s ult i n a i l_il per io d o f several m i n utes. Fr o m this, it Is co n c lude d that t h e ma_or drlvln g ,l_i!i nea r ste p chan g e in _ ut- o f-r o undne s s a sthe pa rameters which• cause these load s , _' (thrust and + in t ernal p ressures) c han ge o nly durin g th e initial 10,2 0 second s and then remain r elat i vely co n s tant. Pri o r c om p o nent stat i c l o ad te s tin g ha s sh own goo d co rrelati o n o f m easured t o c al c ula t ed o ut- o f- ro un d ness f o rmechanlcal an d therma l lo a di n g w i th the TMF s tru c tu r a l e l e m ents. Fr o m t h e a bo ve dis c ussl o n , it i s c o nclu d e d that im p r ov e m ent s , ln o ut, o f-r ound ne ss pre d ict io n m eth ods are r e quired in t he a rea o f th erm all y i ndu ce d d isto r ti on i n_ _ he_eng i ne cas i ngs a nd HPT stare r structure..- , 7 .6 CLEARANCE AND ROUNDNESS _UANT_TAT_VE BASELINE A quanti tative base li ne has been defined from the c l earance curves and • the out-of-roundness plots obta i ned from t h i s test. Al t hou g h the relat i onsh i p ° between performance and clearance has n ot been exper im entally evaluated , the data obta i ned from tests c onducted do provide a b as i s for more ac c urate theo- retical predict i o n s.

Althou g h there i s a mi nor mis m atc h between the m easured and analytically p redlc t edclearance as a fun c t i on o f ti m e relationsh i ps, the curve shapes of _.

th e a n a l yt i ca l m ode l co rre l ate we ll (Ref. F ig ures 21 a n d 22). This will ena b le a c curate a ss e ssme nt s o f re s p o n s e rate s, total ti mes , s l op e change s , etc . o f prop os ed des ig n change s . 87 Fisure 65. T o_ al l i pTurbine S _ a _o r Ou r - o f-R o undness, Gr o und I dle.

r Fl 8 ure 67. HPTurbine Sta t or O ut- o f- R o undness, Burs t + 0 Seconds• I

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9O • F i sure 68. HPTurb L _ _ neStator Ou t- o f- Roundness p Burst SecOnds.

OF POOR QU / _!.I TY

F£ursEE_ 7 0 . HP Tu. r.blne _ sta ._.o r ..O u t - . o _ -Rqundn . .ess, _... B _ _ r_ s._ . . _. + 1 2 3.S. . e _ . o _ nd p............................ !

• i

i OF POOR QU _ Li _ C Y ,i , Fi gure 71. HPTurbine Stator Ou t -o _ -Boundness, Burst + 30 6 Seconds.

i O F _ .. P O OR ( _ LIALiTY 0, 25 e ml (0.01 :l.n.)

--f - .

, ! ° 1 Round , • ib Ftsure 72. HP ' A_ rbtne Stator O ut - o _ -Roundnes s t B u rst + 747 Seconds.

I...........

¥isure 7 4 . HP Turbine StatorOut-of-Roundne ss_ Chop + 10 Seconds. . !

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I F is ure 7 5 . HP Turb i ne S t ator Out - o f Roundn essj Chop Seconds.

ALF

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i_i 6 4 Fi g ure 75. HP Turbine Stator O ut-of-R0undness e Chop _ 40 SecondB, F _g ure 77. HP T urb i ne Stator Out-o g -Roundnes s , Chop + 10 0 " Seconds. I

1'

l oo I

7 ALF !

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¥ 1gure 79. HP Turbine S_ a t or Out-o: _ -Roundne u , Chop + 4 25 Seconds.

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Figure 80. HP T u rbine Stator Out-of-Roundne ss_ Chop + 109.0 Seco n ds.

1 03 :_ a N d _ ll i_ f _ am _ , _ ,, ,_m_ -, , _ . .................................. _ .......... :..... :_ : :_ ._. _ .... _ ..... , _ .. .. , , . , ,. ° .... 8.0 DISCUSSION OF RESULTS prov i de i ns i ght i nto the causes and ma g n i tudes o f Sta g e $ r turbo f an re l ate d en gi ne per f orman c e deter i orat i on of the CF6- 5 0 en gin e.

do i ng, i t w as Jud g ed that the pr inci pa l ga i n t o be real i zed wou l d be the eng i ne i dent i f i cat i on of im prove m en ts w h i ch cou l d be ma de t o the i n order to reduce i ts f ue l con s umpt i on.

Analyses co nducted prior t o this c o ntract indi c ated that a meaningful invest i gat io n would have t o In c lude t he following ele m ents: a) A survey o f n o rmal tran s ient and s teady s tate clear anc e behavi o r i! suchas: i) Accels fro m low t o h ig h p o wer _ 2) De c els fr o m h ig h to l o w power _! ., 3) Estab lish i ng clearances as functi o n s o f* N 2, P3, T3 h) A surve _ o f non- r a u tl ne tran s ients i n c lud i n g :

if

i_ I) Thr ott le reburs _ s wi t h varyin g g r o und i d l e dwell t imes__._ 2) Engine shu t d q wn (st opc o c k) fr o m hi g h p o wer c ) A surve y o f shr o ud surface o ut- o f-r o undness dur i n g transient and s te a d y sta te op .era t i o n and an assess me nt o f the •causes o f this o u t - o f,r o undness d) A d i rect m easure m ent o n a full-scale o perat i ng engine o f the effe ct that a c han g e in S t age 1 bl ade t ip clearan c e has o n en g ine fuel c o ns u mpti o n, ._.

The re sults o f thls _ In T estigatl o n hav e been m eanlngfu l i n a ll o f these areas: :.

a) Normal Translent and !!teadY State Clearance Behavior The results o f t h i s inv e s t i g a tio n s how t ha t a g ood unde r s t andin g ex ist s o f t h e behavi o r o f th e eng l newhen it i s as s umed to remain r o und and the r oto r and st a t or c o nc e n t ric, A rela t ively co ns t an t error ex i s ts be t ween t he m e asured and predi c ted c l earan c es f o r an a c ce l f ro m g r o und id l e t o takeoff p o wer (Fi g ure 2 1 ). Th e disagree m en t i s ab o ut' 0 .25 m m ( 0 , 01 in), The loc ati o n o f m axi mum and mi n imum clearance values i n time are in exc e llent agree m en t , These r esult s indi c ate t hat the analy t i c al to ols being employed and the a s s um pt i on s ma de w it h respec t to trans i ent t herma l and m e c han i ca l resp o nse wi 11 re s u l t i n.

reli able p red i ct i ons of round e ngi ne clearance s .

The above s t a t e m ent is furth e r s uppo r ted by the trans i ent decel response from takeoff to idle, (F ig ure 29) , which also exh i b i ts g ood correlat i on bo t h i n level of c l earance and i n t im ew i se locat i on o f ma x im um and mi n imum values.

10 6 W i t h res p e c t to the e s t ab l is_ m ent of clearance as a f un c t i o n o f powe r level ( N 2 , P 3 ' T _ ), that i nformat i on w i ll b e o f value i n the de t er mi na ti on o f th e i m pac t on f u el c ons u r_p t i on of p ar t -powe r and off- d e si gn p o i nt eng i ne opera- t i ou. _ tia ne ce s s a ry to know th e se relat i onsh ip s when c ond uc tin g _ n tegr ated fuel bu r n c al c ulat i on s , for exampl e ; c ond u c t i n g such s tud i es was not a ta s k or goal o f th i s i nves ti gat i on.

t b) Non-Routine Transient Behavior Th i s i nvest ig at i on prov i d e d a s urvey of an i mp o rtant class of tran si ent en gi ne operat i, ns called rebursts. A r ebur st i s defined as a decal fro m a " h ig h, s tab ili z e d pow er po i n t t o i d le fo ll ow e d by an a ceel ba c k to a h ig h p ower , po i nt. The variable wh i ch c har ac ter i zes the sev e r it y (nearness-to-rub) of a r e b ur st is t he len gt h o f time the e n g ine i s o p erated at i dle prior t o the a c - ce lera tio n to h ig h p ow er. This L _ terval is termed the dwel l t i m e. Figure 23 shows t he clearance b ehav i or du ri ng t here b urst ac c elerat i on for var i ous dwell t im e8.

Thi s inf o r m at io n is o f value f o r two major reasons. O ne reason i s t hat by kn o wing the dwell i nterva l s o ver which rubs are mo st likely t o occ urs, fact o ry • accep t ance test s and a i r c raft a c ce p tance and c o m merc i al o perat io n pr o cedures may be ad j usted, w h er p o s s ible, t o av o id b o th s h o rt te rm and l o nger term d e _ e- rl o ra tlo n caused by increased b l ade t i p clearances. The o ther i s that it pr o - vides a b ase l lne w i th which impr o ved des ig ns, i ntended t o m ake theeng l ne l ess s e nsi t ive t o re b u rs ts, m ay b e co m pared (Eefe r en c e 2 ma ke s u se o f the s e data t o sh o w t he impr o ve m e nt achieved i n a m od l f l ed d es l gn) .... _ The o ther n o n-r o ut l netran sl ent i nves tig ated was an eng i ne shutd o wn. There ; are two type s o f eng i ne shutd owns o f i n t e r es t , a s hutd o wn fr o m h ig h p o wer at o r n e ar s ea l e v e l ambien t condition ( st o p cock) and a shu tdo wn a t altitude foll o w e d by a dwell tim e dur l ngwh l ch the fan co nt i nues t o r o tate ( wi nd n Li 11 ) b y v i rtue o f t he a l rc r aft _s forwar d m o m ent u m an d f i nally an en gi ne r e st a r t and accel back t o the po wer l ev el fr o m which the en g ine had been s hut d o wn. The l atter ca s e is a form o f a rebur s t called a wi nd m i ll l ng a i r star t . Inve sti gat i on of wlnd mi ll l ng air s ta r t s wa s b ey o und the s c o pe o f this inve s tigati o n. Neve r thele ss , the a r e an impo rtan t s o urce o f deter io rat i on and data fr om t he ens l ne s hutd o wn ac t ually performed i n t he i nves ti ga ti on . wa s used t o predic t c learance behavior for w i nd- mi lllnga lr s t a r ts.

The engi ne shu t down actually per f ormed w as a stopcock. The clearance an d core speed tran si ent s are shown i n F ig ure s 29 and 30 respect i vely. The stopco c k was i nte r rupted, for reasons discu s sed earl i er, at 20 0 s a c . The en8 i ne was re- fired and r etu rn ed to idle. Figu re 31 i s an ext e n si on of th e s top c o c k data,a s - s umi ng that the a top c o c ked en gi ne wa s not r e s tarted an d adju s ted to i n i t i ate • fr om takeoff power ra t her than fro m cr u is e p ow er as actually c ondu c ted. It shows that a r ub wou l d not be expected to occur.

Two th i ngs s tand out. One is that a pure (un i nter ru pted) s top c ock will not re s ult in a rub. Secondly, a stopco c k which i s i nterrupted m ay very well re s ult i n a rub even though the eng i ne is bei n g ret urn ed to only idle power. This is significant. I t demon s trate s that more attent i on needs to b e paid to what on e prev i ou s lywo u ldhave considered to be o f l i ttle s i gni f icance: the tran s ient m ove m ent s fr o m shutdown t o moto r i ng and motorin g t o idle. Dep endin g on what p re c eded t he s e tr an si e nts and on t he l e n g th of s hu t do wn t im e, rubs (deter i ora- tion) are predi c table.

One final note on w i nd mi lling air s tart s . The data fro m t h is i nve stig a- tion were ad j u s t e d to analyt i cally pred ic t the c l e aran c e behavior dur i n g a windm i ll i ng a i r s ta r t performed durin g the flight te s t prog r am of a d i ff e rent m odel of the CF6 en gi ne. B e cause of g eo m etry differences between en gi ne s, pr o bable imp r e ci s i on i n the ex t rapolat io n t o d i fferent ambi e nt conditi o ns and \ other adjust m ent ina cc ura c ies , this analysis m ustbe considered an approx im a- - . '_ rich| however, rubs were pr e dicted of a ma g n i tude in reasonable asree m ent with those a c tually o bserved by boresc ope i nspe c t i on.

S i nce wind milli n 8 ai r s t arts a r e pe r f orm e d dur i n g ai r c ra ft ac cept ance - testi n g , t hey re p resent a potent i ally signlf ic ant s o urce o!_ short t erm deteri-.

o rati o n which m ay be r ec o v e ra b l e eithe r by adJu s t l ng ac c e pt an c e test pro c e du r es il or b y in co r po rating d e s i g n _) which are le ss sen si t i ve t o t h ese th ro ttl e mo ve m en ts .

c). Shroud Roundness Survey This inves tl gati o n wa s the f i rs t survey o f t ransien t and s t e a d y-s t ate r o undness p erf o rmed o n an a c tual full scale op erat i ng CF6-50 eng i ne. P r ev io us, an d unrelate d , co m po nent testing had e s ta b lishe d relat io n s h ip s b e tw een the o ut- o f-r o un d ness o f var io us en g ine s tr uctures and the re s ulting indu c ed shr o ud o ut- o f-r o u n d ness. These relati o nships were used in stress and defle c t io n m o dels _o es _ a b lish shr o ud sha p e s . This pre sent I nvesti g at lo n has de mo nst r ated t ha t pr evi o us l y esta b l i shed est i mates o f sha p es d o n o t mirr o r the actual sha p es well. Figure 66 il l ustrates t he p o in t an d d e monstrat es the value o f having r u n t h is .l nve s t i ga t l o n. Fr om empi r i c al inves t igat io ns , it : i s k n o wn that t he measured shape is an ac c urate refle c ti o n o f the n et o ut- o f-r o un d ness o f the Sta g e I shr o ud surface. En g ines which r un w i th a Sta g e I shr o ud surface gr oun d t o a r o und condi t io n have the highest l ike li h ood o fsu s tainlng ru bs b etwee n 2:30 - 3:30 and 7 :30 - 9: 00 o ' cloc k , aft loo king f o rward. The m easure d results o f th is inv e s ti gati o n _r e in agre em ent wi _ h thi s e m piric a lly det erm in e d o ut-_ o f-r o undne ss s hape.

Bo th the shape an d m a g nitude o f shr o ud o ut- o f-r oun dness can b e d eter- mined e mp ir ic a ll y a s has b een the p ra c ti c e. The sign l f l cant as p e c t f o r po ten-.

tla l fue l efficiency im p r o ve m ents i s the m agn i tu d e, not the s hape, o f o ut- o f- r o undness. Thi s i nvest i gati o n ha s esta b li s hed t ha t the p otential for im- prov em ents in roundness is on t he order o f 0.38 m m ( 0 .015 i n.) equivalent to ,f 0 .86 percent in turbine effl c iencyw hl ch tran s la t es t o a c ruise SFC i m p rove- m ent p o t e nt i al o f a pp r o ximat e ly 0. 36 p er c ent.

d ) Tip ClearancePe_formance Derivative The re s ult s o f thi s i nvestigati o n have a ss i g ned a n i mpo rtan c e t o Sta g e 1 blade ti p cl earance which is in reasonable a gr eementw i th u nre la ted pre- vious te s t i n g and with the i nvest ig at i on of Re f erence 1. Th i s present i n- vesti g ation indicates that the Stage 1 blade t i p clearance has a somewhat s t ron g er ef f ect on fuel efficiency than has been the accepted case.

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9. 0 CONCLUSIONS This te s t p ro g ram ha s provided m any outstandin g r e s u lt s . R eal-t im e Sta g e 1 ,i blade-to-shroud clearance m easurement s have been obta i ned for a CF6-50C en gi ne.

Since e ig ht c lea r au ca omete r p ro bes were lo c ated a r ound th e c i rc umfe r en c e of the _ St a ge 1 s hroud area, the ci rc u mf e rent i al var i at i on wa s used to obta i n the round- !

i_ hess of the Sta g e 1 shroud area. U si n g the c learanceo me ter p ro bes while sus- th e magn i tude I ta n n i n 8 a Sta g e l bl ade -on- s h r oud r u b es ta b lish e d of th e clearance i ncrease dur i n g the rub. By m on i tor i n g en g ine performan c e before and after the + rub + the effe ct of cleara nc e up o n perf o rman c e was expe rim entally determ i ned.

The test enslne w as very heavily i n s tr um ented. This i nstr u mentat io n pro- vldedte m pe r atures , pres s ure s , flow s , et c . f or many s IE n l floant e n gi ne p arameter s i !

a nd areas of in terest. These data poin ts a l l owed a c orrelat io n _I th these en- gin e p a ramet e r s and h is h p res s u re t ur b ln a Sta g e I clear a n c e s.

• I The pressure and t em p e r a t ure +m eas u re m en P_ p r o v i ded data tha t were used t o p redi c t th e ef f e c t o f b o th the tu rb ine ml d frame an d t he l o w pre ss ure t urbine up o n Sta g e 1 h i gh pressure tu r b i ne r o undne s s. Th e c o mparis o n o f th is p re dictio n and the measured ro u n d nesswas used t o verify t hat t h e c u r r e nt analy s is te c h- n i que f o r m echan lc a ll y c au s ed lo a d s and di st o r tio n s was co rre c t and that t he ,+ met h o d u se d to e valuat e +t h _ e ff ec t s o f cer tain clrcum f ere n t ia L+ t h erm al _ d _ n t e ,.

_; requ i red mo d l flcat _ on.

!+i The avera g e clearance data s h o wed t hat, alth o u g ha small steady st a t e error ! e xi sts, the analyt _ ca! i m o del o f ro u nd en sln e clearance r e spo n s e i s qu i_ e +g o p d .... '_

i

Areas o f i mpro v e me nt i n t he f u e l co ns u mpt io n c haracter i st i cs o f the CF6-5 0 I en gi ne exp! ore d i n the d i s c uss ion o f resu l ts are : t i 1. Des i gn c h a n g e s_ to m a ke the en gi ne less re b ura _ s ens i t i ve. !

2. Des i gn and / or a i rcraft ac c e p tan c e te s t c han g es to m ake the en gi ne less sens i t i ve t o w i ndm l ll l n 8 a i r starts.

!

h_ 3 . _ n c orPoratlon +o f de s i g ns which will imp r ov e shroud s urface r oundn ess .

i

i Reference 2 ex p lores a s pe c ts of the s e im prove m ents.

t

_P_ND_X% r m_FERENC_S

i. R .H. W u lf , " E n si ne Diasn o s t i csPro s r am p CF6-50 E n sine P e rf o rmanc e De t er i ora tio n ", NASA CR-159867 , Nove m ber 1980 . \ 2 . W. D . Howard and W.A. Faschln E," CF6 Je t E nE i ne Perf o rmance Impr o v e men t - H _g hPres s ure Tur bi ne R o undn ess", NASA CR - 1 6 $55 5 December 1 981 . _ ........................

_J A_PENDZXC IN T R O O UCTIO N The qua lit y pro g ram app li ed to th i s c ontra ct is a do c ume n ted sys tem _ t h r oughou t th e des i gn , m anu f a c tur e, repair , ove r hau l and m od ific at i o n c yc le • f or g a s t urbine a i rcra ft en gi ne s . Th e qua li t y s y s te m ha s been c on s tructed - to comply wi th mi l it ary s pe ci f ic at i ons M _ L- Q -9858A, M I L-I- 4 5208, and MIL-STD- 4 5662 a nd F e d er a l A v i ati o n R egulat io n s ¥AR-145 and a p pl! c ablep or tl o n o f F AR-21.

The q u a lit y sys t em and it s Im p l e m en t at lo n are def i ned by a c om p l ete s e t o f procedures wh i ch ha s been c oo r d i natedwith t he DODand ¥AAandhae t h eir . _, c o ncurrence. I n addit io n, t h e quality sy s tem as described i n the qual i ty p ro g ra m m ee t s the c ontra c tor requ i rements requ i red by t h e N A S A -L e w _s Research C en t er. The following i s a br i ef synopsis of t he sy s tem.

sYsm, 1

Th e qua lit y syst em is - docume n ted by o p e rat i n g procedures which c oordinat e the qual lt y-related a c t i v i t i es i n the funct i onal areas of Engi neer i n g , Manu- 1 fa ct ur l ng, Ma t er i al s , P u rchasin g , an d En gi n e P ro g r a m s. The q ual i ty s y s t em is a s ln g l eas tan d ard syst em w he reinall p ro du ct line s are c o n t r o lled by t h e c o m m o n quali t y sy st em . The a cti ons and ac t iv i ti es as s o c iate d wi t h d ete rminat l on o f _ q ua ll t y a r e re c orded, and doc umentat lo n i s avai l able f or rev le w.

I nh e ren t in t he sy s te m is the assuran c e o f conforman c e to th e q ual i t y r equ ir eme n t s . Thi s .i ncludes t he performan c e o f r equ ir ed i n s pe c tion s and te s t s ._ In add i t i on, the syste m provides chan ge c ont r ol r equ irem ents which assure that de sig n chan g e s are i n c orporated into m anufactur i n g , pro cu rement and qual i ty do cum entat io n, and i nto the produ c ts. Ma teri al used for p a r ts is ver if ie d fo r c onforman ce to a pp licable e ng i n eeri n g s peci f i cation s , u til i z i n g a p propr i ate physical and..ch emi cal t est i n g procedures.

Measu r in g devices used fo r produ c t a cc eptan ce and £netnm e n t at £ on used t o control, record, m on it or, or ind ic ate result s o f readin g s dur i n g i nsp ecti on " and test are i n i t i ally ins p e c ted and c al i brated a n d p er i od i cally are rever i f ie d or r e c al ib ratad at a p r e s c r ib ed f r equ e n cy . Such c al ibr at i on is pe r f o rme d by • t e c h nic ians a g ain s t etandards wh ic h are tra c eable t o t he Na ti onal B u rea u of Standards. Th e g a g e s are i dent i f i ed b y a c ontro l number and are on a recall s c h e dul e fo r re v eri f i cation a n d c al i b r a ti on. The calibra t ion fu n c t io n main- ta i ns a r eco rd of the lo c a ti on of each g a g e and t he date i t requires rec al i - brat i on. Instr u c t i ons im ple m ent the p rov i s io ns of MIL-STD- 4 5662 an d the a pp ro pri at e FAR r equ ir e m e nt s .

_ o r k i n sc ru cc_ ous •re i ssued fo r c o _pl_a_ c t b y o perat o rs , insp e cc o rs: c as te rs | and _ e c h an_c s. Co mp on e n t p•rc manufa ct u r e prov i des fo r l •b or a t ot _ ov e rv _ e _ of a _l s p ec i al and c r_c_ c•l proc e s ses , inc l u d in 8 qua li f i ca ti on and ce rc_c • t_ o n of p erson n_ : equipment an d p rocesses.

When work _s performed _ u ac c ordan c e _ r _C h work in s C ruc c_ on s , t he o pe ra - t ot / insp e ct or records c ha c t he w o r k ha s bean p e r formed. Th _ s _s a cc om pli sh e d by t he ope r a t o r / ins pe ct or s c am p_ ns o r s _ n _ ns t he + o p erat i on se q ue nc e shee r C o s _ sn _ gy c h• C t he ope r a c_ on ha s been p e rfo rm ed.

Va r_ ous d esi sn s of sc amps •re used c o _ nd _ c• C e t he _ n s pe cc_ o n of s t a t us of wo r k L n pr oc e ss an d _£ n _ shed _ c ams . Perg c rmmc e or a cc e ptanc e of speci a l p rocesses _ .8 _ .ud _ . c ace d b y dt st_ cctve sc am p s •s s_ , g ned s p e c lf _ .cal ly c o p erson- ne _ . perform in 8 on e process o r _ spect _ .on. Ac _ u _ . sC r•C i on of c ha s camp s ys t em and the _ .ssu ance of e c a _ ps • r e g unc C_ .ou s of the Q ual _ .Cy 0pers on .on. The scam ps • re ' app lie d co che paper w o r k i denC _ . f y _ .u S o r d e n 0C _ .u8 the _ . C mn s requ _ r in 8 con- Cr ol. Wh e n so • s p in 8 of h a rdwa re o c cu r s, only iabo r a c ory approved i nk _ , s used t o assu re 8sa in sc dsm _ se.

Th e t yp e and l oca te .on of ocher p •rc _ a r k in 8 ar e spec _ .f _ . e d by t h e d e s i i _ ens ineer on ch e dr •w in 8 C o assu re e ff e c t s d o n o c c oup r oucLse des _ sn requi te - sau c e an d p• t c q u a lit y.

.t Contr o l of p•rc h an d l_ s• , s o . t eS s an _ d ell .v e ry i s ma _ n C•ine d C h r oush c h e anC£re cycle. Ens ine e a n d •ssembl£es • re scored in sp e c£s _ dol l£es an d trans- po rt a ti on car e s. F in£ shed assembl e d pa re s • re s c o re d so •e C o pre clude d am •8 e an d c o nt am inati o n , o pe n in SS • re cov ered , l in ts ca p p e d an d pr o ce c c_ v e c ov ets • p pl£e d •J re q uire d.

Hour.uS. rein 8 ha r d war e i s con tr oll e d by a s y s tem of ma teri el r ev ie w • C t h e_ compon en t sou r c e . _ och • Qu _i c y re pr e s ent e ci v e an d an EnZ ineerin 8 re p re - s ent a t iv e prov id e t h e acc e p t (use-as-is or re pair ) decis i ons. Ho n co n fotu an c e s

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