N A S A T E G H N I C A L M E M O R A N D U M

N 1 1 - 2 1 1 1 3 NASA TM X-67846

PERFORMANCE OF A BRAYTON-CYCLE POWER CONVERSION

SYSTEM USING A HELIUM-XENON GAS MIXTURE

by Alfred S. Valerino and Lloyd W. Ream Lewis Research Center Cleveland, Ohio

TECHNICAL PAPER proposed for presentation at 19"1 Intersociety Energy Conversion Engineering Conference sponsored by the Society of Automotive Engineers Boston, Massachusetts, August 3-6, 1971

https://ntrs.nasa.gov/search.jsp?R=19710018237 2020-03-12T15:38:45+00:00Z

ABSTRACT

A Brayton power conversion system was oper- a t e d i n an ambient environment with a gas mix- t u r e of h e i i w , and xecon. The system was oper- .

a t e d a t a compressor i n l e t temperature of 80' F through a compressor discharge pressure range from 20 to'45 p s i a and through a turbine i n l e t temperature range from 1300° t o 1600' F. Resul ts of system and component performances through the operat ing range of p a r m e t e r s a r e discussed.

Resul ts of the inves t iga t ion ind ica ted a s e t engine e f f i c i e n c y (excluding heat l o s s e s from the h e a t source) of approximately 30 percent a t a compressor discharge pressure of 45 p s i a and a turbine i n l e t temperature of 1600° F. The gross power output measured a t the a l t e r n a t o r terminals f o r t h i s condit ion was 15.2 kW. Good, agreement was obtained i n a comparison of t h e compressor ad iaba t ic e f f i c i e n c y with t h a t ob- t a ined with the compressor t e s t e d with argon gas; compressor e f f i c i e n c i e s of the order of 79 per- cent were obtained. With the blend of helium and xenon and with high tu rb ine i n l e t tempera- t u r e s ( 1 3 0 0 ~ t o 1600' F) turbine s t a t i c e f f i - ciency was s l i g h t l y lower than with cold argon; t h e values were 87.5 percent and 88.8 percent with hot helium-xenon and co ld argon, respect ive- l y . The hea t - t rans fe r e f fec t iveness of 0 .95 of t h e gas-to-gas recuperator agreed w;th the pre- d i c t e d value a t a system pressure l e v e l of 45 ps ia . The head r i s e of the l i q u i d coolant pump, approximately 193 f t a t a design capaci ty of 3.7 gal/min, was considerably higher than the spec i f ied minimum value of approximately 159 f t .

ZONSIDERABLE EFFORT HAS BEEN expecde a by the ;TASA, Lewis Research Center, t o aemoxstra.l;e the c a p a b i l i t i e s of a l o n g - l i f e , space-oriented, mult i -ki lowatt Brayton cycle power sysiem. The 3rayton engine was designed t o produce 2 t o 10 kW of e l e c t r i c a l power with a gas mixture of helium-xenon (molecular weight of 83.8) a s the working f l u i d . The power conversion sy-tcm of the engine employs a r o t a t i n g u n i t ( 'URU) c lose- coupled t o a hea t exchanger wit (BIIXU) . 'She r o t a t i n g u n i t cons i s t s of a turbine, an a . l terna- t o r and a compressor on a s ing le s h a f t which i s supported a n i re ta ined by journal. and t h r u s t bearings operat ing on a f i lm of the systems work- ing f l u i d . Design r o t a t i v e speed i s 36,000 rpm. The hea t exchanger un i t cons i s t s of a gas-to-gas recuperator, a gas- to- l iquid waste heal; exchang- e r , and assoc ia ted ducting. Much da ta or: the be- havior of the components and of the p o y r con- '

version system operat ing with e i t h e r arr argon, or l c r n t o n has been published ( 1 t o IS)*: Few experimental data , however, have been dbtained o r published on the components afid system perform- a w e with the helium-xenon gas mixture a s the working f l u i d . The experlmental perform,nce o f . a power conversion system operatin, in a vacuum en- vironment with helium-xenor. i s re?ort,ed i n Hef. 14.

This p a p e r p r e s e n t s da ta obtained with a power conversion system operat ing i n an ambient envirotment with the helium-xenor, gas mixture a s the wopking f l u i d . T e s t s f var iab les include a turbine i n l e t temperature range of 1 3 0 0 ~ t o 1600' I, a compressor discharge pressure range of 2G t o 45 p s i a a t a compressor i n l e t temperature of 80' F. Performance of the turbine, the com- pressor , the recuperator , the waste heat ex- changer, the engine l i q u i d coolant pump, a s well a s the power conversion system, are presented.

GENERAI, DESCRIPTION

A schematic diagram of the Erayton power conversion system i s presented m Fig. 1. An e l e c t r i c hea t source wag i n s t a l l e d between the BKXU high-pressure s ide o u t l e t and Lhc Lurblne i n l e t t o provide the thermal energy f o r Lhe sys- tem. Gas flows from the compressor drscharge, through the gas-to-gas recuperator i n t o the hea t source. The heated gas passes througn the t u r - bine, i n t o the BHXLi low-pressure s lde where i t

gives up some of i t s heat content t o the gas

umbers i n parentheses designate Ref- erences a t end of paper.

cntering cne recuperator from the compressor. Gas then :Lows in to the waste heat exchanger where suff ic ient heat i s released t o the l i qu id coolant t o maintain a compressor i n l e t tempera- ture of 80° F.

The Dow Corning l i qu id coolant i s circu- l a t ed by the coolant pump through the y x t e heat exchanger v ia a single path and through the al- ternator v i a e i the r one and/or two paths. Heat added t o the coolant i s removed by means of a ref r igera t ion unit .

Photographs of the BRU, BHXU and the elec- t r i c heat source in s t a l l ed i n the power conver- sion f a c i l i t y are presented i n Figs. 2 and 3. The heat source-BHXU ins t a l l a t ion i n the system support frame i s shown i n Fig. 2. The heat source and i t s i n l e t and out le t piping are cover- ed with a micro-quartz blanket type insulat ion. The ins ta l la t ion of the vertically-mounted BRU, with tbe turbine end up, andathe BHXU i s shown i n Fig. 3.

High gas temperatures were measured with chromel-alumel type thermocouples; low gas tem- peratures and l iquid temperatures were measured

.with iron constantin thermocouples. Strain-gage type transducers were employed to measure a l l of the absolute and d i f f e ren t i a l pressures required for pressure measurements and fo r gas flow r a t e computations. Liquid flow ra tes were sensed by a turbine-type flow meter.

Rotative speed of the BRU shaft was obtained by means of a capacitance probe located near the BRU compressor journal bearings and by means of the a l te rnator frequency. A speed -controller described in Ref. 13 was u t i l i z e d t o operate i n a safe-speed band.

The e l e c t r i c a l power output of the a l te rna- t o r ' s three phases were each measured with root- mean square instruments.

PROmDURE

During the t e s t , constant values of t u r b i ~ e i n l e t and compressor i n l e t temperatures were maintained while the compressor dischmge pres- sure was varied. Turbine in le t temperature was controlled by a closed-loop contr'oller regulating the e l e c t r i c a l power t o the heat source. The compressor i n l e t temperature was mai'ntained a t 80° F by controlling the l i qu id coolant flow ra t e t o the waste heat exchanger. Temperature of the coolant entering the waste heat exchanger was f ixed a t approximately 68' F. The compressor discharge pressure was varied by varying the gas system inventory.

The ,?eed cont ro l le~" was 110s "roperly tuned p i i n g th i s t c s t . The resul tant ro ta t lve speed ana, therefore, the a l te rnator frequency l a r e approximately 101 t o 104 percent above the de- sign values. Dcsign rotat,lve speed was 36,000 rpm; design a l te rnator frequency was 1200 Ha.

DISCUSSION

COMPRESSOR - The radial-outflow compressor was designed fo r a nominal. 6-kW net output (1). A photograph of the compressor vaned diffuser-

' sc ro l l assembly and the impeller i s shomm. in Fig. 4.

The charac ter i s t ics of the BXU cmlpressor are shown in Figs. 5, 6, and 7, The effecss of compressor discharge s t a t i c press.me on the s t a t i c pressure r a t i o across the compressor and the adiabatic efficiency are presented i n Pig. 5. A t a constant turbine i n l e t temperature, the compressor discharge pressure lias no s igni f icant e f fec t on neither the s t a t i c press i re r a t i o nor the efficiency; however, increasing the turbine i n l e t temperature resulted i n s l i gh t increases in s t a t i c pressure r a t io . The s t a t i c pressure r a t i o increased from approximately 1 .91 'to 1.94 when the turbine in l e t temperature was illcreased from 1300° t o 1600° F. The pressure r a t i o ob- tained a t 1600' F i s s l i gh t ly higher than ihe value obtained with argon as reported i n Ref. 8.

The adiabatic efficiency (Fig. 5(6)) i s essent ia l ly independent of the turbine i-nlet temperature. The experimental eff iciency of ap- proximately 79 percent i s i n goo$ agreement with the 79.5 percent obtained from the argon t e s t of Ref. 8.

The ef f ic iencies and the s t a t i c pressure r a t io s of the compressor are presented in Fig. 6 i n the conventional compressor format-viz., pres- sure r a t i o and efficiency versus equivalent flow ra te .

The e f f ec t of the equivdent weight flow on the temperature r i s e r a t i o i s presented i n Fig. 7. There i s r e l a t ive ly good agreemelit bk- tween the experimental data with helium-xenon and the .argon data of Ref. 8-approximately 0.38 compared t o 0.37 with argon.

TURaIrjE - Photographs of the rotor housing and the sc ro l l assembly are presented i n Figs. 8 and 9, respectively. The radial-inflow tulrbine was a lso designed for a nominal 6-kW system e l e c t r i c power ( 2 ) .

The operating charac ter i s t ics of the turbine are presented i n Figs. 10, U. and 12. Effects of the compressor discharge s t a t i c pressure on

the turbine inlet to discharge static pressure ratio and on thc turbine efficiency are s h m in Fie. 10. Compressor discharge pressure shows no significant effect on the static pressure ratio (Fig. 10(a)). A slight increase in pressure ra- tio resulted with increasing turbine inlet tem- perature. Pressure ratios of approximately 1.77 and approximately 1.79 were obtained at turbine inlet temperatures of 1300~ and 1600~ F, re- spectively.

Increasing compressor discharge static pres- sure from 25 to 45 psia resulted in a slight in- crease of approximately 2 percentage points in turbine efficiency (~ig. 10(b)). The data indi- cates a slightly lower efficiency (87.5 percent at a compressor discharge pressure of 25 psia) when compared to the cold argon tests of Ref. 7 (88.8 prcent). The turbine efficiency and the equivalent inlet-to-discharge static pressure' ratios are plotted in the conventional manner against blade-to-jet speed ratio and equivalent weight flow in Figs. 11 and 12, \respectively. Scatter exists in the data but, in general, the data is in close agreement with the' argon data of Ref. 7.

HEAT EXCHANGER UNIT (BW) I. The BHXU, shown in Fig. 13, consists of a gas-to-gas re- cuperator, a gas-to-liquid waste heat exchanger and the interconnecting ducting. The recuper- ator is a counterflow plate-fin unit with cross- flow, tri-angular end sections. The waste heat exchanger is a cross-counterflow, plate-fin unit. Manifolds are provided for the two units and are shaped to provide uniform flow. Ducts are attached to the manifolds for connections to the heat source and the rotating unit. A more de- tailed description of the BHXLJ and some perfom- ance data are presented in Ref. 3.

The performance characteristics of the BHXU has been determined for the operating conditions of the power conversion system. The performance is expressed in terms of the heat srarisfer effectiveness-i.e., the ratio of the temperature drop to the difference between the inlet temper- ature through each heat exchanger passage. To demonstrate the behavior of the BHXU in relation to the system operating conditions, the perfom- ance is presented as a function of the system pressure level at the compressor discharge.

The variation of recuperator heat transfer effectiveness with compressor discharge pressure at turbine inlet temperatures of 1600~ and 1 3 0 0 ~ ~ is shown in Fig. 14. The effectiveness is rela- zively constant at a turbine inlet temperature of 1600' F through the compressor discharge pres-

sure range. The expermental effectiveness of 0.95 obtalned at a turbine iliiet temperatue of 1600' F at a compressor discharge prcssurc of 42.5 psla is In agreement with the predicted value. The effectiveness decreased sllgbtly wlth increasing compressor discharge pressure when the turbine inlet teinperaiure was reduced to 1300' F.

The change in heat transfer cfiec tlveness of the waste heat exchanger obtained at a turb- ine inlet temperature of 1600' E wlCh compressor dlscharge pressure 1s shown in Fig, 15. A small decrease, from approxmately 0.97 to 0.95, re- sulted when the compressor aischarge pressure was increased from 25 to 45 psla. The smalL drop in effectiveness occurs because of the c m - bined lncrease of both the heat load m a the heat transfer coefficient

The variation of overall pressure arop ra- t ~ o across the BHXU wlth compressor dlscbarge pressure at a turbine lnlet tenperatme of 1600' F 1s presented In Fig. 16. 1ncreasl)ig compressor discharge pressure from 20 to 45 psia resulted in a decrease In the overall pressure drop ratio from approximately 3.056 to 0.038.

LIQUID COOLANT PUMP - The mosor dnverl pump, shown in Flg. 17, 1s an rntegral, hermetically- sealed unit consisting of a centrrfugal, pimp and a three-phase 400-Hz motor mounted in a conmon housing. A complete descx lptlon of the coolant pump unlt is presented In Ref. 4. Input power to the pump unit was supplled by a three-pliase, 400-Hz motor-generat~on set. The liomnal speed of the pump unit is 11,OOC rpn.

The head rise characteristic of the coolant p'mp is shown in Fig. 18, The opezating charac- teristics indlcate that the pwnp nead rlse is well over the specified mxnimum requlrelnent of 159 ft at a flowrate of 3.7 gail/nlin. Experl- mental value of approximately 192 ft was obtain- ed at the deslgn flow conalslon,

ENGINE - The effects of compressor discharge pressure and turblne Inlet temperature on the power output measured at the alternator terminals (gross power output) are presenteo ln Flg. 19. Increasing compressor dlscharge pressure and the turbine inlet temperature resulted ln Increases in the gross power output. At turbine inlet temperatures of 1600' and 140O0 F, at a conlpres- sor discharge pressure of 45 psla, the gross electrical power outputs were approxmately 13.2 and 10 kW, respectively. At a compressor drscharge pressure of 20 psla, the gross power outputs were approximately 4.5 and 3.3 kW, re- spectlvely.

The ef f ic iencies of' tine engine are presented i n Fig. 20. Since t'le e l ec t r i c heat source does not provide a good exyine-heat-source simulation, the efficiency of the e l e c t r i c heat source i s not taken in to account i n the computation of the en- gine efficiency. The thermal input t o the engine i s defined a s the r a t e of enthalpy addition across the heater-that i s , ~ ~ $ 2 2 , where w i s flow ra te , cp i s specific heat a t constant pres- sure and AT i s temperature r i s e from recuper- ,

ator out le t t o turbine in l e t . The engine gross efficiencies, based on the

gross power outputs, are presented as a function of tine system pressure l eve l a t various turbine i n l e t temperatures i n Fig. 20(a). A t a compres- sor discharge pressure of 45 ps ia the gross e f f i - ciency decreased from approximately 33.5 percent t o approximately 28.5 percent when the turbine i n l e t temperature was decreased from 16000 t o 1 4 0 0 ~ F. A t a l l turbine i n l e t temperatures, de- creasing the compressor discharge pressure re- sulted i n decreases i n gross efficiency.

Since the operation of the Brayton engine i s self-sustaining, a housekeeping power requirement for engine auxi l ia r ies must be considered. This auxil iary power requirement i s 1 . 4 kW (5). The net power or the useful engine power therefpre i s the gross power output minus 1.4 kW.

The ef fec ts of compressor discharge pressure and turbine i n l e t temperature on the engine net efficiency i s shown i n Fig. 20(b). The'net e f f i - ciency i s defined i n the Appendix. A t 1600° and 1 4 0 0 ~ F turbine i n l e t temperatures a t a compres- sor discharge s t a t i c pressure of 45 psia, the net e f f ic iencies obtained were approximately 30 and 25 percent, respectively. A t a compressor dis- charge pressure of 20 psia, the net e f f ic iencies were approximately 19 and 13 percenr;, respective- ly.

CONCLUDING REMARKS

The performance charac ter i s t ics of a Brayton cycle power conversion system and of i t s compo- nents were 'obtained with a gas mixture of helium- xenon as the working f lu id . Tests were conducted i n an ambient environment through a compressor discharge pressure range, a turbine i n l e t temper- ature range, and a t a constant compressor i n l e t temperature of 80' F. Results of the investiga- t ion indicate:

1. A t a turbine i n l e t temperature of 1 6 0 0 ~ F and a compressor discharge pressure of 45 psia, a system net eff iciency of approximately 30 percent resulted. The system efficiency does not include

the e l e c t r i c heat source efficiency since IC does not adequately simulate the engine heat source,

2. The compressor adiabatic efficiency, ap- proximately 79 percent, i s i n good agreement with the 79.5 percent value obtained from the compo- nent t e s t with argon gas.

3. The t u b i n s dfficioncy el' 87.5 psresnt was approximately one percentage point lower than the value obtained when the turbine was tes ted with cold argon gas.

4. The effectiveness of the recuperatar portion of the heat exchanger uni t was approxi- mately 95 percent. This value agrees with the predicted effectiveness.

5. The head r i s e of approxrrnately 193 ' f t obtained with the l i qu id coolant pump f a r ex- ceeded the specified minimum requirement of 159 f t a t a capacity of 3.7 gd/min.

APPENDIX

APG al ternator gross output power, k'G.1

Cp speci f ic heat a t constant pressure, f t - l b / ( l b -OR)

ER recuperator heat t ransfer effectiveness, (TRI-TR~ / ( T R ~ - T R ~ )

Ew waste heat exchanger effectiveness (gas side), (TRz-Tw~)/(TR~"T~z)

g gravi ta t ional constant, 32.174 f t / see2 - &hi ideal specific work, ~ t u / l b J mechj~nical equivalent of heat, 770.16

f t -lb/Btu P s t a t i c pressure, ps ia T t o t a l temperature; OF U t blade t i p velocity, f t / s ec

V absolute gas velocity, f t / sec

Vj idea l j e t speed corresponding to s t a t i c pressure r a t i o across the turbine, 2gJ(Ahi), f t / sec

w f l o w r a t e , l b / s e c

y r a t i o of specific heats, 1.667 fo r heliuin- xenon mixture .

6 r a t i o of i n l e t s t a t i c pressure t o U.S. standard sea-level pressure P/P3'

E function of y used in re la t ing parameters t o those using a i r i n l e t conditions a t U.S. standard-se - level conditions, (&Pa) ( y y / r -?

qc compress" ad iaba t ic temperature r i s e e f f i - ciency,

qT turbine e l f i c iency

qG engine system gross e f f ic iency , ~ J 1 . 0 5 4 w c p ( T ~ 1 - T ~ 4 )

QN engine system n e t e f f ic iency , (WG-1. 4) /I.. 054 w C ~ ( T ~ ~ - T ~ ~ )

8, r a t i o of compressor i n l e t t o t a l tempkra- t u r e t o U.S. s tandard sea- level tempera- ture, T~*/T*

BCR squared r a t i o of c r i t i c a l v e l o c i t y a t t h e turbine i n l e t t o c r i t i c a l v e l o c i t y a t U.S. s tandard sea- leve l temperature, ( VCR/V&)

v b lade- je t speed r a t i o , Ut/Vj ~ u ~ e r s c r i p t s

* U.S. s tandard sea- level condit ions (tem- pera ture equal t o 518.7O R; pressure equal, t o 14.7 p s i a ) .

Subscripts CD compressor discharge CI compressor i n l e t CR condit ion corresponding t o Mach number of

un'ity

EQ equivalent TD turbine discharge' TI turbine i n l e t

R1 recuperator i n l e t low pressure s ide

R2 recuperator o u t l e t low pressure s ide

R3 recuperator i n l e t high pressure s i d e

I14 recuperator o u t l e t high pressure s ide

W l gas o u t l e t s ide of waste heat exchanger '

W2 l i q u i d i n l e t s ide o f waste hea t exchanges

1. Anon., "Design and Fabricat ion of t h e Brayton Cycle High Performance Compressor Re- search Package." AiResearch Mfg. Co. Rep. APS- 5269-R, NASA CR-72533, November 29, 1967.

2. Anon., "Design and Fabricat ion of the Brayton Cycle High Performance Turbine Research Package." Report APS-5281-R, AiResearch Mfg. Co. Rep. APS-5281-R, NASA CR-72478, February 14, 1968.

3 . G. N. Kaykaty, "Design Description and Performance Test Resul ts from Two I d e n t i c a l Brayton Heat Exchanger Units." NASA TM X-52844, 1970.

4. A., C. Spagnuolo, R. R . Secunde, and J. R. Vrancilc, "Performance of' a Hermetic Induction Slotor-Driven Pump f o r Brayton Cycle Heat Rejec- t i o n Loop." NASA TM X-,52698, 1969.

5 . D. B. Fenn, J. N. Deyo, T. ;. Miller , and R . W. Vernon, "ExperimentaJ. Performance of a 2-15 Kilowatt Brayton Power System i n t h e Space Power F a c i l i t y Using Krypton." NASA TM X-52750, 1970.

6. A. S. Valerino, R . P. Macosko, A. $, Asadourian, T. P. Hecker, and R. Xruchowy, "h- liminary Performance of a Brayton-Cycle-Power- . System Gas Loop Operating with Krypton over a Turbine I n l e t Temperature Range of 1 2 0 0 ~ F t o 1600Q F." NASA TM X-52769, 1970.

7. W . J. Nusbaum and M. G. Kofskey, "Cold Performance Evaluation ,of 4.97-Inch Radial- Inflow Turbine Designed f o r Single-Shaft Brayton Cycle Space-Power System." NASA Tfi D-5090, 1969.

8. C. Weigel, Jr., E . R. Tysi, and C. L. Bal l , "Overall Performance i n Argon of 4.25-Inch Sweptback-Bladed Centrifugal. Compressor." NASA TM X-2129, 1970.

9. D. G. Beremand, D. Namkoong, and R. Y. Wong, "Experimental Performance Charac te r i s t i cs of Three IdenticaL Brayton Rotating Units ." NASA TM X-52826, 1970.

10. R. Y. Wong, H. A. Klassen, R . C . Evans, and C. B. Winzig, "Preliminary Inves t iga t ion of a Single-Shaft Brayton Rotating Unit Designed f o r a 2-to-10 Kilowatt Space Power Generatioii'Sys- tem. " W A TM X-1869, 1969.

ll. D. S. Repas and R . A. Edkin, "Perfom- ance Charac te r i s t i cs of a 14.3-Kilowatt-Ampere Modified Lundell Al te rna tor f o r 1200 Hertz Brayton-Cycle Space-Power System." NASA TN D- 5405, 1969.

12. J . L. KLann, " S t e a d y ~ S t a t e Analysis of a Brayton Space-Power System." NASA TN D-5673, 1970. . .

13. B. D. Ingle, H. L. Winner, and R. C. Bainbridge, "Steady-State .Charac te r i s t i cs of a Voltage Regulator and a P a r a s i t i c Speed Con- t r o l l e r on a 14.3-Kilovolt-Ampere, 1200-Hertz Modified Lundell Alternat'or. " NASA TN D-5924, 1970.

14. R. W . Vernon and T . J. Mil ler , " E q e r i - mental Performance of a 2-15 Kilowatt Brayton Power System Using a Mixture of Helium and Xenon. ". NASA TM X-52936, 1970.

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F igure 10. - Effect of compressor dis- charge pressure on t u r b i n e static pressure ra t io and on eff iciency.

TURBINE INLET TEMPERATURE,

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TURBINE INLET TEMPERATURE,

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F igure 13. - Brayton heat exchanger unit.

o TURBINE INLET TEMPERATIIRE, 1 6 0 0 ~ F A TURBINE INLET TEMPERATIIRE, 1300' F @ DESIGN POINT

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F igu re 14. - Effects of t u r b i n e i n l e t tempera ture and pres- s u r e level o n t h e recupera tor effectiveness.

0 TURBINE INLEI TEMPERATURE, 1600' F

COMPRESSOR DISCHARGE PRESSURE, PSlA

F igu re 15. - Effect of p ressu re level o n heat s i n k exchanger effectiveness.

o TURBINE INLET TEMPERATURE, 1600' F

.031 1 I 1 0 10 20 30 40 50

COMPRESSOR DISCHARGE PRESSURE, PS lA

F igu re 16. - Effect of p ressu re level o n BHXU p ressu re drop.

TURB

INE

INLE

T TE

MPE

RATU

RE,

TT

TUR

BIN

E IN

LET

TEM

PERA

TURE

,

TT

o?

0

1600

-

r 1M

O

(A) G

ROSS

EFF

ICIE

NCY.

- - CO

MPR

ESSO

R DI

SCHA

RGE

PRES

SURE

, P

CD

(PS

lA)

Figu

re 1

9. -

Effe

ct o

f sys

tem

pre

ssur

e le

vel o

n th

e al

tern

ator

gro

ss p

ower

ou

tput

.

COM

PRES

SOR

DISC

HARG

E PR

ESSU

RE,

P PS

lA

C D'

(B) N

ET E

FFIC

IENC

Y

Figu

re 26. -

Effe

ct o

f sy

stem

pre

ssur

e le

vel o

n th

e en

gine

gro

ss a

nd n

et

effic

ienc

ies.