Document
NATIONAL ADVISORY C O ~ M I T T E E
F O R AERO
I-.-- -__._ ---_“--- ” - - NACA RM Mo. E6L24 f o r the A i r Fateriel Command, Army A i r Forces B7 Howard C . Stevens? Jr.
A n investigation was candlocted on a m l t i c y l i n d e r airclra.ft e n g k e on a dynamometer stand t o determine the e f f e c t of ixduction- sg-stem icing on e n g b e operating c h a r a c t e r i s t i c s and t o compam t h e r e s u l t a with those of 8 previow laboratorg in-retrtigation in which .
o n l y t h e sarburetor and engine-stage supercharger assembly from the engine were used. The eqeriments were conducted at simulated glide gower, lm cruise power, and noma1 rated power through a range of h m i d i t y ratics and air temDemtures a t approximately sea-lave1 p s - 8Lire.
Iaductim-system icing was found t o occur within appmximte3-y the 8- lirsits as those established by the previozs laboratory imes- t i g a t i o n a f t e r making s u i t a b l e allowances f o r the difference i n PJel v o l a t i l l t y and t h r o t t l e angles. Rough operatioil or" t h e engine was experiences when ice caused a marked reduction i n the a i r flow.
Photographs of t $ T i c a l ice formations f r o m t h i s investigation indicate close s i n ' i l a r i t y t o icing previoualy observed in t h e laboratory.
A t the request of the A i r Materiel Command, Amy A i r Forces, 811 investigation has been conC!ucted at the XACA Cleveland laboratory of the icing and de-icing characteristics of an engine induction system.
Previous b v e s t i g a t ions included laboratory experiments t o determine the icing c h a r a c t e r l s t i c s (reference 1) and the e f f e c t s of a ; n auto- matic manifold-pressure regulator (reference 2 ) .
The puqose of the ex-perimeEts r e F r t e d herein was t o e s t a b l i e h c o r r e l a t i o n between the msults obtained in the previous laboratory NACA XM No. EGL24 investigation using a carburetor-superchrger assembly o p e r a t k g with v o l a t i l e nonleaded f u e l (referexce 1) with those obtained iming an engine operating with service f u e l of lower v o l a t i l i t y . Icing charac- t e r i s t i c s of the engine were obtained dxring operation at si.mulated glide Tower, low cruise power, and normal r a t e d power over a mange of humidity rat io6 a r d drz-bulb air temperatures a t approximately sea- l e v e l carbure tor-deck pressure. The e f f e c t s of icing on reiiucirg t h e air flow <and the cSlinder-head t e m y e r a t u A ~ , a l t e r i n g the f u e l - a l r r a t i o , and producing rough engine operation were obtained f o r low cruise end normal-rated power conditions. Photographic data of typ!.cal ice forma- t i o n s i n t h e induction system were obtained t o c s t a b l i s h c o r m l a t i o n with the previous leboratory r e s u l t s . The influeice of an automatic pressure regulator on the perfomance of the eagine during icing cond5- tiona at low cruiBe power w a s needid t o determine the l i m i t s of serious i c i n g f o r engins i n s t a l l a t i o n s incorporating t h a t type of control.
APPARATUS The experiments were made wl’th a multicylinder engine mounted on a dynamometer stand. Conditioned a i s was siiuplied through ducts t o t h e carburetor a t the desired dry-bulb temperature, humidf-ty, and pressure; simulated r a i n m s sprayed into the vertical portion of the duct ebove Thz dry rofrigercbed t h e carburetor entrance, as shown in figwe 1.
air was humlaified by steam sprayed i n t o the duct upstream of a f i l t e r t o ineure eqxalizaticn. The am-,mnt or“ steam reqcired f o r humId5fication w a s regulated by w e t -bulb and dry-bulb a i r temperahme indicatlons frm a special thermocouple psychrometer locatad upstream of t h e simulated- r a i n spray8 similar t o the i n s t a l l a t i o n described i n reference 3.
The engine had a superchezger impeller-to-engine apeed r a t i o of 9.6:l a8 conpared with the speed r a t i o of 8.l:l of t h e carburetor and engine -stage supercharger ossembiy, which was used i n the laboratory 1). The icing c h a r a c t e r i s t i c s of the engine investigation (reference were t h s e x p c t e d t o be s l i g h t l y d i f f e r e n t from t h e e of t h e carburetor- supercharger com5insttion because of the d i f f e r e n t t h r o t t l e angles f o r a given engine-syeed anC air-flow condition. I n both c a w s , a pressure- t y p * c a r b u r e t o r with a double t h r o a t w a s used; slizfit differencca between carburetcrs were considered t o be negllejble f o r the purpcjses of t h i s investigation. Both carburetors were f i t t e d w l t h special continuouoly variable f i o l - m e t e r i n g plates t o permft f i n e r udjus”ument or’ mixture rEtios.
A standard carbumtor-entrEnce screen was used In these exyerimente; screen w a s used i n the experlmnts of reference 1. Addi- no protective t i o n of t h e screen was expected t o introduce no Ioessurable e f f e c t on icing c NACA No. 36L24 3 c h a r a c t e r i s t i c s at t e q e r a t u r e s ebove 3 2 ' F, bLt the screen w a s e w c t e d t o accelerate the rate of impact-ice b l o c k i q below 52" F.
The duct s e c t i o c immediately above t h e carburetor waa so s r m e d that it could be readily disconnected end the c a r b m t o r rewved A special f o r i r i s p e t i o n and photographing of ice formatione.
suyercharger inlet elbow, provided f o r the investigation reported in reference 4, f i t t e d with special windowe w&8 used in these experi- ments to detect, t.hs p-eecce of fwl-euqoLmtition fe- &mj.ng e a h e operat ion.
A standard manifold-pressure regzlator, which automatically operates t h e t h r o t t l e t o maintain constant manifold pressure, waa i n s t a l l e d on the carburetor f o r two m s .
=;e flow and temperature of the engine air, f u e l , and Simulsted r a b were Indicated, together with carbxretor-deck pressure, nanlfold p r e s s m , m t e r i r g suction d i f f e r e n t l a l , czrburetor ~ ~ s s u r e drop, tfxottle =&le, engine torque and speed, and cylinder-head temperature.
Spark-plug-gasket them9cougles were i n s t a l l e d f o r one run. The fuel used in these experiments vas 28-R.
The conCitions f o r a l l r ~ n s are l i s t e d i n table I. The engine w a s operatcd a t a zarburetor-deck pressure of 29.3 inches of mercury absolute and selected air flows o f 1540, 4620, and 7708 punds per hour, corres?ondi,ag aogroximately t o glide ?owa-, l o w c r d l s e power, and ~ o r m a l rated FOWT, respectively.
The m i x t i a m control W&E used t o set thc: f u e l flow within the a r b i t r a r y llrjits shom in fjgm 21 which is approximately correct for the carbaretor. T ~ E ; carburetor-deck preaaure was controlled w l t h l n f 0 . 1 inch of mercury absolute t o simulate l e v e l flight at con- stant airspeed and the engine syeed waa maintained constant by manu- a l l y ad3usting t h e f i e l d rheostat of the dynamometer. Once set, t h e throttle and mixture-control settlws were not altered during a run except when t h e manifold-pressure regulator was used.
The simulated-rain injection was varied from 25 t o 1 0 0 0 grama per minute, corresponding t o conditions of moderate rain (less than 1/2 gram/cc meter) and excessive r a i n (more than 2 grms/cu meter).
Ths fhel tem- The r a i n temperature was varied betwecn 47O and 75O F.
gerature was maintained at about 6 0 ' F.
When t h e engine w a s operating irnder approximately the desired conditionsy steam and water s p r a p were turned on and adjustment8 4 NhCA IIM No. EGL24 made t o obtain the selected conditions of humidity z t i o and r e l a t i v e h m i d i t y of -the engine air. Steam and water sprays were then diverted t o b p s s l i n e s , thus removing any ice t h a t had f o m d and at the s m e time maintaining the correct s e t t i n g s f o r humid;fication and simulated rain. The air flow w a s then readJusted t o a r a t e lower than the desired r a t e t o compensate f o r the increase i n flow caussd by the i n j e c t i o n of steam and water. Injection w a s aipia s t a r t e d and air flow, fuel flow, engine speed and torque, carburetor preesure drop, manifold pressure, metering suction d i f f e r e n t i a l , carburetor-deck pruesure, and air tempera- t u r e were recorded ut regular i n t e r v a l s .
Durbg one ran spark-plug- gasket tcmperatnes were t a b n .
For two runs, when the manifold-pressure regulator was i n operation, t h e proceduvws were similar except that t h r o t t J e angle was automatically adjusted by the rsgulator dxring icing.
A t the end of each run, ice formations were observed through windows i n the supercharger i n l e t elbow or wcre studied and photographed by stopping the engine and quicklg removing the carburetor.
l?3SITLTS AND DISCUSSION 1 Results of the iiivestigation f a l l i n t o two categories: e f f e c t s that could be coirulzted with the r e s u l t s of the laboratory investiga- t i o n and e f f e c t s t h a t pertained t o engine opi?mtion and could not be obtained using tho carburetor and engine-stage supercharger aosembly.
Comvlat ion with Previous Laboratory Investigat ion For correlation with the laboratcry investigation, the r e s u l t s from t a b l e I f o r simulated l o w cruise and normal rated power are ?resented in figures 3 and 4, respectively, with the icing c h a r a c t e r i s t i c s from reference 1.
In t h i s r e p o r t , as i n reference 1, icing t h a t i n 15 minutus caused a 2-percent o r greater drop i n air flow w a s designated serious. The d i f f i c u l t y i n observing and obtaining rapid acces8 t o the supercharger inlet elbow prevented the detection of most nonserious icing, which is reported as v i s i b l e icing i n referonce 1 . The r e s u l t s of a11 runs a r e given in t a b l e I with verbal description of the type of icing.
O f t h e f i v e runs (1 t o 5) made at s i m l a t e d glide power, four were made with dry-bulb air temperatures from 41.5" t o 52' F and r e l a t i v e L humidities from 68 t o 100 percent and did not r e s u l t i n serious icing.
HACA I 3 4 NO Em24 5 The other run, with a dry-bulb air temperature of 4 0 ’ F and satu- r e t e d air plus simulated-rain injection of 50 grams yer minute, did resQlt i n serious icing. I n s p c t i o n at the end of each of these ~ u n s disclosed a n o i l f i l m on the under side of t h e throttlerr and.
on the walls of the i n l e t elbow caxsed by lea- of o i l past the s u p r c h m g e r seals at the low m i f o l d pressure, which would have reduced the tendency of ice to adhere t o theae surfaces. Presumably, icing would have been ~ e r i w s xitk; ell&. a t m s p i e r l c conditions and l o w t h r o t t l e o p n i q p had the oil f i b not been present.
Serious-icing conditioxs f o r the complete engine a t low cruise Imwer ( f i g , 3) f e l l below the limit established in the labomtory investigation as m i g h t be e q e c t e d becaEae the 26-R fuel is l e s s volatile and Lencs t i i l l :ji”o&..ice less evapomtive ~ 0 0 1 h g than AB-F-22 f u e l .
For t h e nornaf-rated-power conditions ( f i g . 4), however, serious- icing points more nearly correswnd t o the l i m i t established in t h e laboratory despite the less v o l a t i l e f u e l i n the engine mns.
Icing seriously a f f e c t s engine air flow a t reduced throttle angles because both the increased cfsburetor pressure drop and greater turbulence i n the fuel. spray below the t h r o t t l e e poduce a g r e a t e r temperature depression and the resultant increased icing qvlickly obstructs the a m l l e r t h r o t t l e o:ening.
Photograyns of t y p i c a l i c e forna-cions from t h l s investigation, shown i n f i g u r e s 5, 6, end 7 , fc;r runs 28, 29, and 30, respectively, at low cruise power indicate close aimilarity t o icing Treviously observed in the laboratory. T h r o t t l i n g and fuel-evaporatlon ice f o m d on the carburetor t h r o t t l e s and iniet elbow at a dry-bulb a i r teaperatrcre of 4Fjo F with saturated a i r (fig. 5). Heavier forma- t i o m r e m i t - from a dry-?mlb a i r temperature of 40° F, saturated air, and simulated-rain lnjection of 100 grams per minute are ahovn i n figure 6 . Figwe 7 shows i c e fornations a f t e r a run a t a dry- bulb air temperatime of ZOO F with saturated air plus sirmrlated-rain i n j e c t i o n of 50 grams per minute. Careful inspection of figure 7(a) reveals impact i c e remaining on t h e carburetor entrance screen, whereas i n figures 7(b) and 7(c): ice on the t h r o t t l e s and i n t h e inlet elbow is evident. Ice formations at t h e edge of the t h r o t t l e s t h a t serious13 r e s t r i c t e d air f i o w may be observed in flgures 5 t o 7.
NACA IiM No. E6L24 Effect on Engine Operatin;: Characteristics
Charge-air f l o ~ . - The primary e f f e c t of induction-system i c i n g
in the engine was -Lhrottling of the charge-air f l o t r with corresponding reductiona i n manifold pressure and ei-gine horsepower. TyTical r e s u l t s of serioue iclnG (run 1 4 ) are shewn i n figure 8. A t t h e end of 10 mln- U t e s , the air flow had dropped t o 63 percent, t h e manifoid. pressure t o 79 percent, and the homapower t o 62 perceni; of t h e i r i n i t i a l values.
I n f l i g h t operation with maniaally controll.ed t h r o t t l e s and conotant -
speed p o p e l l e m , the decrease i n manifol8 pressure normc.lly serves as a warning t h a t iiiitmtion-systern icing is o c c u r r i w . I n 1 2 of the low- cruise-power r u m ai; flxed t h r o t t l e scttlng, charge -air f l o w dropped a t l e a s t 2 percent. In r m s 31 and 32 und.er similar conditions, but with the manifold-preosure regulator i n operation, the t h r o t t l e was automatically opeced t o maintain nearly ccnstant a i r f l o w during i c i n g conditions. Figme 9 shows t,hat the throttles opeiied from 26" t o 3 8 ' during icing while the manifold prcssure was maintiilned nearly constant, thereby eliminating the n c m , l warning or" the occurrence of induction- system icing. If such a process were continued, the t h r o t t l e s m u l d e i t h e r reach the limit of opening o r vould be prematurely stopTed by ice formations. Bacause ncj f m t h e r opening could be effected, coztin- ued icing would caum a loss of manifold pressure t h a t could not be recovered.
Fuel-a5.r r a t i o . - In some case6 impact icing on t h e a i r - m t e r l n g
p a r t s of thb carbur&or adversely affected. the fuel molxring in the carbu- r e t o r , o r fwl-avaporat ion icI.ng interfered with the i n j e c t i o n of f u e l i n t o the s u y r c h a r g e r b l c t elbow by forming around t h e f u e l spray nozzle (roferwnce 1) and. causing rough engine operation. This rough opor- a t i o n was detGcted by abnormal engine vibration o r irregular erqine noise.
Four of th5 f i f t e e n serious-icing rims a-t l o w cruise power and a l l o f t h e a e r i o u s - i c i q runs at norinal ratcd power resulted in rough engine opers- t i o n . Rough o p r a t i o n occurred only after icing had reduced t h e shargc- air f l o w more thar, 2 percent.
I n order t o investigate thc3 p o s s i b i l i t y t h a t s i g n i f i c a n t changes i n f u e l - a i r r a t i o were the cause o f roughness or 10~18 of power i n c d d i t i m t o t h a t due t o thc reduction in a i r flow, t h c r a t i o of the observed v a l - ues of fuel-air r e t i o obtained during icing t o the value I'rom -Lhe lower l i m i t curve of the normal car$urctor-metcring c h a r a c t c r i s t i c s ( f i g . 2) a8 shown i n f i g w z s d md 9.
waa computed and plotted a@.inst t i m e , Large dcviations from 1.00 i n t h i s r a t i o m e a thEt the f u e l - a i r r a t i o has changed from the value t h a t would ncrmall; occur at the observcd air flow. The ratso of t h e obscr-rc,d horsepower t o t h e anticipated valuc? f o r the observed air f l o ~ ; was dotcmnined and plottcd i n a s i m i l a r m m .
NACA €84 Bo, EsL24 7 For run 14 both the horsepower and f i e l a i r ratio zmalned nearly equal t o the values normally anticipated f o r the mduced slr flm (fig. 3(a)), indicating t h a t the only measmd effect was the t h r o t t l w of the air flow. In t w o nure, 21 and 22 (footnote to table I), t b metering a c t i o n differential waa higher khan antic$- Fated because of impact i c e on the air-metering parts of the d u - r e t o r d the result- f u e l - a i r ratios wem also high, r e a - 0.097 and 0,127, respectively. 1 x 1 contrast, x u n 31 (fig. 9) 6howa ! R B excessive &creaeee in both f u e l - a i r r a t i o and horsepower, metering suction d i f f e r e n t i a l pressure decreaaed below the mrzd value for the observed alr flow but firel flow wzza normal f o r the observed metering d i f f e r e n t i a l . I n another run (33), the metering m c t i o n d i f f e r e n t i a l wag lower than anticiyzted. and the fwl-air O f t h e seven run8 h i which rough opem%iOn r a t i o dropped t o 0.056.
occurred, three ( r u n s 22, 31, and 33) were characterized by abnormal f u e l - a i r r a t i o s .
S p a r k - p l w - w k e t temperatum . - Spark-plug-gasket temperatures, All temper- aeasured only durhg run 14, am shown in figure 8(b), aturea after i c i n g started were lower t i the initial values with tbe exception of cylinder 2 in the r*&t bank. The d o - tread and t h e s i m i l a r i t y of the curvet3 is a l o g l c a ~ e f f e c t of t b iqjection in the n o m mixture d i s - of eimrrlated rain and indicate8 m change tribution. The iqjection of quantltiee of' eimulated rain greater than the r a t e of 50 grams per minute used i n x u n 14 would produce a corresyjondin@g g r e a t e r depression of cylinder-head temperatums and cause rough operation.
From a study of the e f f e c t s of induction-system icing in a roulticyfinder engine mounted on a dynamometer stand, the folloxing: results uere obtained: 1. Correlation exirjted between t h e icing c h a r a c t e r i s t i c e of the complete enQsine and those of a laboratory eetup (used in a p v i o u s investigation), coneieting only of the oarbumtor and supercfaarger aaeembly, after suitable allowancos were made f o r diffemnces in f b l v o l a t i l i t y and t h r o t t l e angle i n the two investigations.
2. Rough engine opemtion occurred onl:J a f t e r icing had reduced t h e charge-air flow more than 2 percent.
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8 NACA RM €10. E6L24 4. A n automatic manifold-pressure regulator prevented l o s s i n charge-air flow or mctnlfold preosure during two 15-minute mno at serious-icing conditions but did 80 without giving warning of the potentially oerious ice formations e x i s t i n g on the t h r o t t l e s .
Aircraft Engine Research Laboratory, National Advisory Committee f o r Aeronautics, Clevel-and, Ohio.
Howard C . Stevens, J k . , Mechanical Ihgineer .
Approved : Willson H. Bmtcr, Mechmice.1 Eng?necr.
Abe Silvcratein, Aeronautical Ene;ineer.
vab 1. %sex, Henry A , , KeSth: Wayne C . , and IhlholLand, Donald R.: Labora- tory Investigation of Icing i i i the Carburetor and Supercharger I n l o t
Elbow of the Lockheed P-38J Alrplane. I1 - Determination of t h e
NACA MR No, E51J18a, Ardy A i r Forces, 1945.
Limiting-Icing Conditions.
2. Chapman, G. E., and Zlotowski, E . D.: Laboratory Investigation of Icing m d Sii.perchal-ger I n l e t Elboir of tile Lockheed P-30J i n t h e Carburetor
Airplane.. I V - Effect of Four Throttle D e a i g i s and Method of' Throttle
MACA MR Operation on Induction-System Icing Characteristics.
no. E5L27, Army A i r Forces, 1946.
3 . Mulholland, Donald R., Rollin, V e r n G . , und Galvin, Herman B. : Labora- tory Investigation of Icing in t h e Cmbure'ior and Si-ipercharger I n l e t
Elbow of the Lockheed P-38J A-irplane, I - Description of Setup and
Testing Technique. NACA M R No, E5Ll.3, Army :2ir F O l ' C 6 8 , 1945.
Investigation of the Effectiveness of b t e r Model 4. Chapmn, Gilbert E.,: MA-33-24 Ice Indicator as a n Induction-System Ice Warning Device.
NACA MR No. E6F04, Army A i r Forces, 1946.
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N A C A R M N o . E 6 L 2 4 J
-
si* l n l t i r l )rJr-brilb Total Of brPark8 &m hitid
lated charge- bl-air rir tas humidity 1 icing
p r r 1 sir f l a n ratio I
?&%a la mt.*Lx?
( l b water/ (lb/hr) (9) l b dry air) - 1 Glide 1580 0.00530 N O W ~ ~ O P ~ 0 . 0 7 9 50.5 2 0 .00825 lonseriow 1565 . o m 52 .078 .OOi+70 lknserioua 3 1585 w.5 1600 0 4 .078 42 .O@& knscrious . w 0 8 Sariolm 5 1550 .w7 40 50 - Lsr 4655 2000 Soriaus 6 46 25 0.W39 cruise 4660 2000 s S r i O U 8 7 47 50 .00849 2Ooo 100 Seriow 8 4665 45 .ow39 2000 .Oll80 Serious 9 4635 4 7 175 LO 2ooo 48 . 0 1 2 0 0 )lonserious 4695 175 U 2000 .01362 Nonssrlous 4675 4 6 l 2 2000 4 6 0 k ~ r I 0 U S 4640 -00655 2Ooo lo00 tfobnsariow 1675 45 .03490 2000 serious (a) l4 4575 47 50 000829 2000 blonserlous 35.5 .00581 15 4425 50 L 6 2000 0 Nom 4655 33 .m9 2OOo 0 Nonserious 17 . W f 3 4405 51 L 8 2000 0 ! b M e f i O U S 4550 56 . m 5 5 2000 0 Nom L? 6655 55 . o w 5 ! O 2000 .01051 Nonserious 465 5 54.5 50 2 l 2000 20.5 .00356 Nonserious (b) 4635 50 2 2 2000 Serious (c),(d) 4655 25 250 .mm Serious (d) 2000 26 100 23 -5 .W65 0 Serious 2 4 2000 34 . w n 5 2000 0 Serious 2 5 4640 44 OOS65 2000 0 Serious 2 6 4640 51 . W 8 2000 0 Wonserious
n 4620 53 ,00673
23 0 4 m 2000 . o w 3 Serious 45.5 2000 100 Serious 29 4480 40 .o0802 2000 20 Seriow 30 @ l o 50 .00352 2000 .Ol238 SerioutJ (d)#(e)s(f Y 40 4625 250 2Ooo 100 Serious (d),(f) P 4790 40.5 -00796
-
33 40 0 . 0 9 4 3 4 .092 3 . 5 35 .oq3 35.5 .093 35
n 46
.01 F 46 .oqg
-
Spark-plug-gasket temperatures were nmasurod.
Metering suction differential increased above v a l w a n t l c l p t e d f o r o b m d air f l a , causing fuel-sir r a t i o to increase to 0.097.
di fISX# g+teriau s.uc.fsii Zfferefi<id ;iicrws& & L - - < e 7&>a &yt:ctst& fcr causing fuel-dr r a t i o to increase to 0.127.
hugh engins operation occur rod^ Metering rmction differential decreased belor v a l w anticipated for observed air flow, causing fuel-dr r a t i o t o decrease t o 0.059.
bnifol&pressure regulator operated throttles.
h t e r l n g mction differential decreased below v a l w anticipated f o r obssrved air flow, cauaing f’uol-dr r a t i o t o decreass to 0.056.
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F i e r e 3. - Cosparison of induction-systen i z l n c characteristics of rr.ulticy;inder
engine and carburetor-supercharger assembki at sinulztec iow c r u i s e corer.
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N A C A R M N O . E6L24 f i g . 5 t l a 1 B o t t o m v ew o f c a r b u r e t o r showing t h r o t t I i n g - i c e and f u e l - e v a p o r a t on- i c e f o r m a t i ons.
( b 1 View i n t o s u p e r c h a r g e r i n l e t e l b o w s h o w i n g f u e l - e v a p o r a t i o n - i c e f p m a t i ons.
N4CA c - 1 7 3 4 9 1 2 - 1 0 - 4 6 L F i g u r e 5 . - S e r i o u s i c i n g a f t e r 12 m i n u t e s o f e n g i n e o p e r a - t i o n . S i m u l a t e d p o w e r ; l o w c r u i s e ; i n i t i a l a i r f l o w , b 4 6 0 0 p o u n d s p e r n o u r ; d r y - b u l b a i r t e m p e r i i t ~ i r e , 4 5 . 5 ' F ; s i m u l a t e d - r a i n i n j e c t i o n , C g r a m s p e r m i n u t e ; s a t u r a t e d a i r ; t h r o t t l e a n g l e , 26'. ~ u n 2 8 .
N A C A R M N o . E6L24 F i g . 6 ( a ) Bottom v i e w o f c a r b u r e t o r showing t h r o t t I i n g - i c e and f u e l - e v a p o r a t i o n - i c e f o r m a t i o n s .
t b 1 V i e w i n t o s u p e r c h a r g e r i n l e t elbow showing f u e l - e v a p o r a t i o n - i c e f o rniat i o n s .
NACA C - 17350 12- 1 0 - 4 6 F i g u r e 6 . - S e r i o u s i c i n g a f t e r 6 m i n u t e s o f e n g i n e o p e r a - t i o n . S i m u l a t e d p o w e r , l o w c r u i s e ; i n i t i a l a i r f l o w , 4 6 8 0 p o u n d s p e r h o u r ; d r y - o u i b a ; i t s m p e r a t ~ ~ r e , 40° F; s i m u l a t e d - r a i n i n j e c t i o n , 100 G r a m s p e r m i n u t e ; s a t u r a t e d a i r ; t h r o t t l e a n g l e , 2 6 O . Run 2 9 .
F i g . 7 N A C A R M N o . E 6 L 2 4 f a ) Top view o f c a r b u r e t o r w i t h e n t r a n c e s c r e e n showing i m p a c t - i c e f o m a t i ons.
. - - ( b ) Bottom v i e w o f c a r b u r e t o r showing t n r c t t l I n g - i c e , f u e l - e v a p o r a t i o n - i c e , and i m p a c t - i c e f o r m a t i o n s .
NACA c - 1 7 3 5 1 1 2 - 1 0 - 4 6 ( c 1 View i n t o s u p e r c h a r g e r i n l e t elbow showing f u e l - e v a p o r a t i o n - i c e and i m p a c t - i c e f o r m a t i o n s .
F i g u r e 7 . - S e r i o u s i c i n g a f t e r 2 m i n u t e s o f e n g i n e o p e r a - t i o n . S i m u l a t e d p o w e r , l o w c r u i s e ; i n i t i a l a i r f l o w , 4 8 1 0 p o u n d s p e r h o u r ; d r y - b u l b a i r t e m p e r a t u r e , 20' F ; s i m u l a t e d - r a i n i n j e c t i o n , 50 g r a m s p e r m i n u t e ; s a t u r a t e d a i r ; t h r o t t l e a n g l e , 26'. Run 3 0 .
a H A C A RM N O . E6i.24 F i g . 8
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