APPENDIX A
, NACA liRRNo. KK06 9 APPENDIX A . . . .
. . mDIcAToR-cARD ANALY81S h order to find the temperatures d pressures before release, an analysis of Hioator cerds was made.
The release pressure can- not be direotly read frau the Indioator o-s obtained with a modl- fled Rarnboro engine Indioator beoause the pressure soale is lnaoou- rate below 300 pounds per square Inoh.
An snalysls was made cd the oycle shown In figure 10 using the folloulng synibols : exponent for oaupression stroke In equation # = k ‘c ,>, exponent for expansion stroke ‘e T volume above piston at cut-off co cleexance volume ‘c Vd displacement volume ‘co cut-off ratio, — ‘c ‘c Vc + v~ r compression ratio, ‘c temperature at release, OR T4 pressure at release, lb/sq ft absolute ‘4 inlet-air temperature, % T1 Inlet-air pressure, lb/sq ft absolute ‘1 Experimental values d ne, no, and rc for rich mlrtures were obtained frau indicator O-S taken In the tests reported herein.
The otis used for lean mixtures were taken frcm figure 4 of referenoe 7. These cards were taken with en optioal indicator with the engine under power for only one oycle. The compression ratio was 1.3.9. The exponent nc was foud to be apprmlmately 1.35, as almwn In figure 13. Figure 13 also shows ne for a range of fuel-alr ratios fra 0.0581 to 0.0027. The value of the cut-fl ratio was available only for rich mlrtures frciuthe indicator oards .
obtained In the present test. It was asswned that the cut-off ratio is constent’ for rich mixtures and Is propcn%ional to the fuel-air ratio up to the theoretloally correct mlrture. The variation d ne, end rc with fuel-alr ratios are shown In figure 14.
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IVACA~ NO. E~06 Release temperatures and pressures for most operating condi- tions at a compression ratio of 13.1 are plotted In figure 11.
These values were obtained by substituting ths experimental values of tbe constants from f@re;14, in the following equations: T4 . Tl@-%c~ (1) (2) With tl?lsInfmmatlon, the exhaust energy can be calculated for almost any condition.
APPENDIX B
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IVACAARR NO. E~06 APPENDIX B .. -—_. ., ---- --- . ..+. -r . . . . . . . . . . . . . .
CALCULATION OF lKEAUST-GAS ~ AND AVAILAELE ENERGY Tho temperature of the exhaust gns can be calculated from the ccntitions before *lease. During the release process two nctlons occur.
ll~chsmall volume of @s escapflngfrom the cylinder Is clssumodto undergo a fre~ oxp~~on wltb practically no change of teuiperature. The gases.remaining h the cylinder undm?go an approx- imately adiabatic expansion. The relation between the temperature and tho density will then be apprcxlmntely as shown”in the following figure:
‘1
-.. + dp l“ Both the temuoratur6 T md the dcnslty P decreaeo until the pres- sure becomes equcl to the exhaust pressure. The temperature remains constarit while the ro!mlnder of the gases are exhcuated from tho cyl- indc.r. The cver~go tcmpercturo cf the afiaust gns can tker~’fore be nbtclncd by intogr,~tl~ tho mxja “mder the curve and dividing by tbc l:bs,.ls~~ .
The equation for the average tmuperature Is derived as follows: P5 TdP + T+5 (1) T av “ P4
“J
P4 &cm the *6 equations: .
. .
.!..- .
in Oquation (1) Substituting the ~EIsion for T, T5) “ ~ P5 and integrating (2) ‘=”~i+(’-l)fi .
When the release conditions and the ahaust-b.ok pressure ae knuwn, the exhaust-gas tempomtuw oan be caloulatod frcunequation (2). The values of 7 wure obtained frcxufigures 2 and 4 d reference 8.
“After the exhaust-gas temperature was oaloulated frcm equa- tion (2), thtienergy available for a turbtie cycle was obtained frcxn figure 9 & referenoo 8. The results are shown plotted in figure 12.
1. Ehnlth,G. Geoffrey: Aircraft Propulsion Systems. An laminat- ion & the Possibilities @ the CcxnbustionGas Turbine: Tur- bines in ConJunotlnn with Airscrews. Flight, vol. XLII, no. 1764, Ott. 15, 1942, pp. 417-421.
2. Piening, Werner: The I!Xflclenoyof Cmbustion Turbines with Constant-Pressure Cmbuetl.on. lWICATM No. 975, 1941.
3. Moore, C. S., and Foster, H. H.: Perfomano e Tests at’a S@le- Cylindor Canpression-Ignition -no with a Dlsplaoer Piston.
NACA TN No. 518, 1935. U 4. Foster, H. H .“: The Quiescent-Chsmber Type Cccnpresslon-Ignition Engine. NACA Rep. No. 568, 1936.
5. Collins, John H., Jr. : Alterations and Tests aF the “Farnboro” Engine Indicator. NACA TN No. 349, 1930.
6. lUng. W. J.: Measurement of High Temperatures In High-Velocity Gas Streams. A.S.M.E. Trans., vol. 65, no. 5, July 1943, pp. 421-428.
7. Rothrock, A. M., and Waldron, C. D. : Effects of Air-Fuel Ratio on Fuel Spr~ and Fl&uneFormetion in a Ccuupress lon-Ignit$on Engine.
NACA Rep. No. 545, 1935.
8. Plnkel, BenJamIn, and Turner, L. Richard: Thermodynamic ~ta for the Ccmputatian of the Performance af Exhaust-Gas Turbines.
NACA ARR RO . 4325, 1944. .
-i- u End U $lde cylinder.
E%gUP8 I*- Combustion chamber in the water-cooled NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS HACA ARR NO- E5K06 Fig. 2 *O Max . mum Cyl .nder n bs .
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‘u : d NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS ~ H q A- :b w H ,0 / ) 1200- ()= ()’ r\ 1000.
( )’ 800 ~ r () x )’ 600 ~ )- ( 400jo 40 50 60 70 80 Inlet-air pressure, in. Hg abs.
Fbzure 2. - Effect of Inlet-air pressure on maximum power and com- ~ression pressure in a pressure-limited cycle. Compression ratio, 13.1; engine speed, 2200 rpm; inlet-air temperature 95° F.
I
NACA ARR No. E5K06 Fig. 3 o 100 20G 300 400 500 Indicated mean effective pressure, lb\sq in.
Figure 3.
- Comparison of Inlet-alr pressures and maximum cylinder pressures in compression-ignition and spark-ignition engines.
NACA ARR NO. E5K06 Fig. U NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS :ompressia n rat10 0 13.1 + j d < ~ c ! t . n--0 ( i’ / @ c 1 e +.
d. — CJ w $ +/’< r / ‘ ~ ./+ c‘ /( ) a 220 s a o z d /< 60 70 m ~“ m lm 20 50 W&t-air pressure, In. X@ aba.
Figure 40 - Effect Of compressionr~tlo Onthe ~xlm~ Power;:~::~le from pressure-limited cycles in a compression-lgnltlon engine.
cyllnderpressure,1225 pounds per square Inch; engine speed, 2200 rpm; fnlet-alrtemperature, 95° F.
. . . .-——. ——.. —....—— Fig. 5 NACA ARR HO. E5K06 NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS Inlet-air pres~ iure adv abs. Qeg ! .n. ~ o 84 4 + 81 ,& x 76 ,5 10 I-I 73, ,0 12 0 68 ,2 3*4 3.0 ‘ .
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\ \ 2.6 ‘ D < 1!
k 2.2 ‘ s .
\ : u) < ~ 1.8 \x\ \\ 1.4 1.0 .02 .06 .08 ,12 0 .10 l @ Fuel-air ratio TUgure ~.- Effect of Injection advance angle and fuel-alr ratio on fuel consumption of’compression-lgnltionengine when maximum cylinder pressure is maintained at 1400 pounds per square inch.
Compression ratio, 13.1; engine speed, 2200 rpm.
— HACA ARR MOO E5K06 Fig, 6 NATIONAL ADVISORY COuMiTTEE FOR AERONAUTICS b 1.00 z G-1 G-J + ) u .
.90 ‘ g ~ .80 .70 80 100 120 Brake mean effective pressure, lb\sq in.
Volumetric efficiency of compression-ignition engine with Figure 6.- Engine speed, 2250 rpm; Inlet-air pressure, displacer type piston.
40 inches mercury absolute.
—.—, .,----- —— 80, ,
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Preseure. lb /sq in.” . .
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Cylinder pressure, lb/sq in.
[1400
m Inlet-air
Hg abs. lb/sq in.
/1 / /1/I 80 \ \\
IIlit 70
60 294
Jftt’t300 \E
NATIONAL ADVISORY CWITTEE FOR AERONAUTICS J’
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Ho o 20 60 100 Crank angle, deg Figure 8.- Effect of inlet-air pressure on cyclic pressure when the maximum cylinder pressure 1s held at 1310 pounds per square inch. Compression ratio, 13.1; engine speed, 2200 rpm; inlet-air temperature, 95° F.
Cylinde pressure, lb~q in.
&cu Ou ml Luu u Crank <&@e, #e”g
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Figure 9.- Effect of maximum cylinder prissure & cyclic pressure when the maximum Compression ratio, 13.1; engine “ cylinder pressure equals the compression pressure.
w speed, 2200 rpm; i.nlet-a~r temperature, 95° F.
NACA ARR NOO E51(06 Fig. 10 140 ~ “v&l bl NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS 0 1 4 5 volasm above piston, arbltr-y =~ts Figure 10. - High-pressure diagram obtained with Farnboro indicator and translated to pressure-volume card.
CompressIon ratio, 13.1; engine speed, 2200 rpm; inlet-alr pressure, 80 Inches mercury absolute; inlet- air temperature, 95° F; measured indicated mean effective pressure, 335 POLUIdSper square Inch: area of card, 8.’7lJ square inches; equivalent mean effective pressure, 3~8 pounds per square Inch.
NACA ARR NOO E5K06 Fig. II t NATIONAL ADVISORY CWITTEE FOR AERONAUTICS ,, Pressure at release a t rel ease Teu perat ure / / / 1800 ‘ / } .
.
/ al $ / % a) / 160 “ l-l a) // h u’ / m v D to r+ d M / 120 .: f I / t-l m o d / v .-i et-a.. r In. / / I / L in.
80 % , / 1200, w L !s m /a .
Ww 1 - E 50 / &o a 1000.
// “ J , .02 l 04 .06 . Ou Fuel-air ratio - Release temperatures and pressures estimated from Figure 11.
an analysls of indicator cards obtained on a compression- ignltion engine.
Compression ratio, 13.1; Inlet-air tempera- ture, 95° F.
Fig. 12 NACA ARR )iO. E5K06 Inlet-air pressure, in.Hg abs.
F@ure 12.- Exhaust-gas temperaturesand energy available to turbine estimated from analysis of indicator cards obtained on a compression- Ignltlon engine.
Compression ratio, 13.1; fuel-air ratio, 0.067; inlet-alr temperature, 950 F; engine speed, 2200 rpm; exhaust back pressure 1s equal to the inlet-air pressure.
Fig. 13 NACA ARR HO. E5K06 50RY NATIONAL ADVIS COMMITTEE FOR AERONAUTICS Curve lFueliaiIi r+l~ I Inel I Ill I I I I I I I I I II &56 .1 .2 2 8 10 .3 .4 .5 .6 ~ l.o 3 Volume, arbitrary units Figure 13. - Varlatlon of expansion exponent no with fuel-alr ratio.
Compression ratio, 13.9. (Data from reference 7.)
Fig. 14 ltACA ARR No”. E5K06 NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS G u“ g 1.4 ~ @ a) 5, ~ 1.2 h A E ‘e 1.0 , 1.8 ‘ / 1.6 i?
/ o“ ~ E / ~ 1.4 “ % o 4!
~ 1.2 1.0 l 02 l 04 .06 .08 .10 .12 Fuel-air ratio Figure’u. - Effect of fuel-air ratio on cycle exponents and cut-off ratio of compression-ignition engine.
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