Document
NASA Technical Memorandum 4486
Jet Engine Performance Enhancement
Through Use of a Wave-Rotor
Topping Cycle
Jack Wilson Sverdrup Technology, Inc.
Lewis Research Center Group Brook Park, Ohio Daniel E. Paxson Lewis Research Center Cleveland, Ohio
NASA
National Aeronautics and Space Administration ( _"i_,S A- "r hi- 4'_ 8 o ) J_-T £NGINE N94-1747( ;:: I:<,_ ,.)R _',,_, _" :_',,. S :__ 5i. HANC EH ENT THP_QUGH USE Office of Management _;;I- A _,tAVE-i,;,!-)TOA TK)PPING CYCLE Scientific and Technical Uncl as (#;ASA) ._.2 p Information Program HI/O? 0193045 OPR overall engine compression ratio, 193.2/po Summary free-stream static pressure Pa A simple model is used to calculate the thermal efficiency and total pressure at station i Pi specific power of simple jet engines and jet engines with a wave- M rotor topping cycle. The performance of the wave rotor is based flight Mach number on measurements from aprevious experiment.Applied to the case fuel-air ratio my of an aircraft flying at Mach 0.8, the calculations show that an PD combustor pressure ratio for simple jet; ducting engine with a wave-rotor topping cycle may have gains in thermal pressure ratio for engine with wave-rotor topping efficiency of approximately 1 to 2 percent and gains in specific cycle power of approximately 10 to 16 percent over a simple jet engine PM ratio of free-stream total to static pressure, with the same overall compression ratio. Even greater gains are (1 + 0.2M2) 3"5 possible if the wave rotor's performance can be improved.
PO ratio of pressure of gas leaving wave rotor to pressure of air entering wave rotor, P4. t/P3.1 Introduction PR compression ratio of wave rotor, P3.JP3.1 caloric value of fuel Q The wave rotor is a device that uses aerodynamic waves to R compression ratio of jet engine compressor (i.e., compress and expand gas instead of the mechanical compressors shaft compression ratio, P3/Po) and turbines of conventional turbomachinery. It is not new, having been invented by Seippel in 1940 (ref. 1). Although its free-stream static temperature, To/(1 + 0.2M 2) Ta major application has been as an automobile supercharger (refs. 2 total temperature at station i to 6), it was originally intended as a gas-turbine topping cycle V flight velocity (ref. 1). The advantage of a wave rotor as a topping cycle is that W specific work of engine/wave-rotor combination it allows combustion temperatures that are higher than the turbine inlet temperature because the gas entering the turbine has already specific work of engine compressor Wc been cooled by the expansion wave in the wave rotor. This was a We specific work of complete expansion after wave desirable feature for early jet engines, which suffered from a lack rotor of suitable turbine materials. However, the materials problem was WER specific work of wave-rotor expansion solved before the wave rotor was adequately developed for this WR specific work of wave-rotor compression purpose, and the use of the wave rotor as a gas-turbine topping Wr specific work of engine turbine cycle appears to have been shelved.
Currently, turbine inlet temperature is again alimitation on jet- specific heat ratio of air engine performance, and turbine inlet temperatures have been specific heat ratio of combustion gases almost constant over the last 10 years (ref. 7). Materials develop- efficiency of engine/wave-rotor combination ment is aimed at ceramic blades, which are brittle, expensive, and combustor efficiency difficult to machine. As a result, there is renewed interest in wave rl8 rotors (refs. 8 and 9). Despite the previous interest, little appears compressor polytropic efficiency tic to have been done to indicate generally the extent of the perform- expansion efficiency of wave rotor _E ance improvement that can be achieved. Consequently, in this mechanical efficiency rim report, simple models will be used to estimate this enhancement.
compression efficiency of wave rotor rlR turbine polytropic efficiency tiT" Symbols Subscripts specific heat ofairin compression stages of engine
G1
0,3,3.1,3.2, stations indicated in figure l(a) specific heat of gas in expansion stages of engine 4.1,4.2, 5
G2
Model Description Wave 3.1 rotor 4.1 Wave rotors can operate on a variety of cycles, depending on the intended application. For example, a three-port cycle has been used by Kentfield both as a flow divider and equalizer (ref. 10).
A flow divider takes in a single stream of gas at the input port and delivers it to two output ports: one at higher stagnation pressure than the input, the otherat lower stagnation pressure. An equalizer 0 1 3 4.0 3.2 4.2 5 6 does the reverse (i.e., it takes in two streams at different pressures Station and delivers a single stream at one pressure). Neither of these (a) Schematic diagram showing various stations.
cycles employs a combustion stage. In order to use a wave rotor as a topping cycle, assuming that combustion is performed outside the rotor, at least four ports are required: input, output to the combustion chamber, return from the combustion chamber, and final output. Taussig (ref. 8) considered a five-port cycle and liVER a variation, a nine-port cycle. The five-port cycle has two output streams, each at different stagnation pressures, and thus requires an extra turbine to extract the energy from the high-pressure EX W r = W C 3.2 stream. The cycle used by Brown Boveri (ref. 4) creates high stagnation pressure in the output to the combustor, from which
t
1.1.1 work must be extracted before retuming the gas to the wave rotor.
t
wR i/
W In contrast, the cycle proposed by General Electric, as reported by Mathur (ref. 11), is a four-port cycle with the single final output stream at higher pressure than the input stream. Such a cycle is O 1/t eminently suitable for application as a jet-engine topping cycle, requiting no special turbine. Calculations of the performance of four-port cycles have recently been made by Paxson (ref. 12), Entropy using a computational fluid dynamics (CFD) approach, and will (b) Enthalpy-entropy diagram.
be used in this work.
Figure 1 .---Schematic and enthalpy-entropy diagrams of jet The use of a four-port wave rotor as a topping cycle is engine with wave-rotor topping cycle.
illustrated in figure l(a). Compressed air from a conventional compressor (station 3) is sent to the wave rotor where it is further compressed, leaves the wave rotor (at station 3.2) to enter the the combustor, the mass of gas per pound of input air is (1+ mf).
combustor, exits from the combustor (at station 4.0) to reenter the This gas passes to the turbine, which drives the compressor. The wave rotor where it expands (compressing the input gas in the turbine must supply enough work, after losses in the mechanical process), and finally exits (station 4.1) to enter the conventional shaft connecting the two, to drive the compressor. Thus, the turbine. Because the gas is heated in a conventional, constant- temperature drop in the turbine is calculated from pressure combustor, the cycle is a Brayton cycle, and the whole cycleisas indicated in the enthalpy-entropy diagram of figure l(b).
The basic engine is assumed to be a simple jet engine, so that the (l + mf )Cp2(T4.1-T5)= CPI(T3-TO) (3) turbine work equals the compressor work.
rim If it is assumed that the compressor has a compression ratio R, called the shaft compression ratio to distinguish it from the overall that is, the temperature of the gas leaving the turbine 7"5is compression ratio OPR (which includes the wave-rotor compres- sion), and a polytropic efficiency r/c, then
: %, (r3-r°)
(4) (1) WC =Cp1To[R(71-1)/rlc?l-1] and the temperature after compression is and hence the pressure of the gas leaving the turbine is given by T3 = ToR(r1-1)/r_Tc (2) The compressed air passes through the wave-rotor-combustor P.____5( T5 I yz/(_'z-1)rlr (5) cycle and emerges at station 4.1. Because fuel has been added in P4.1 = _, T'_.I ) where the pressure P4.1 is found from (11) mfQ= -_B [(I+mf )Cp2T4.1--CplT3 ] (6) P4.1 = Pa xRxPMxPOxPD and the thermal efficiency can be written as The gas leaving the turbine can do work WE in expanding to ambient pressure Pa, given by r/BW (12) 7/= (1 + mf)Cp2T4.1-CplT3 (7) Thus if, for a given temperature rise across the wave-rotor- WE =(I+mf )Cp2T 5 1-- -_5 combustor system, T4.1 -T3, the pressure rise is known, so that P4.1 can be calculated, the specific work and efficiency of the engine can also be evaluated. The dependence of the wave-rotor This is the expansion work available from the cycle, which could pressure rise on the wave-rotor temperature rise will be called the be extracted in a turbine to drive a propeller or fan or used to wave-rotor characteristic. It is a measure of the wave-rotor's provide exhaust velocity in a jet. Each of these extraction schemes efficiency.
has its own inefficiencies, and so, for greater generality, the expansion work will simply be calculated as if it were extracted in a 100-percent-efficient turbine. However, not all the expansion
Wave-Rotor Characteristic
work WE is available: After exlxaction of the work there must be sufficient enthalpy left to produce a velocity in the exhaust equal to the flight velocity, or else there will be a net thrust or drag on A general approach to the wave-rotor characteristic can be the engine. Thus, the available specific work is made by way of thermodynamics, like the approach used earlier for the engine. Thus, if the wave rotor has a compression ratio denoted by PR, the compression work is W = WE----_-- = (1 + mf)Cp2T 5 1- 7, V2 I /pa"
W R = 91(T3.2-T3.1)-91T3.1 (13)
r/R [PR(rl-l,/rl-1]
-Cpl(rO-ra) (8)
and the expansion work is The overall thermal efficiency of the cycle is the available work divided by the heat added to produce it, that is, WER = Cp2(T4-T4"I)= TIECp2T4II (PO ](Yz-1)IY2 ]-k,-p-R j W 7-/= _ (9)
mlQ
(14) In order to evaluate this expression, it is necessary to calculate the where PO is the pressure ratio P4.1/P3.1.
fuel-air ratio my. By balancing the heat supplied in the combustor, Equating the compression work to the expansion work leads, after some algebra, to rlBmfQ = Cp2T4(1 + mf )-CplT3. 2 PO = PR %2 _E_R T4.1 1 Cpl (1--r/E) T3'l [PR(7'-l)/7'-l] 1+ Cpl T3I[pR(r'-O/r'-I] =(l+mf)Cp2T4.1-CplT 3 +(WER--WR) (10) %2 T]R Z4.1 But because the compression work in the wave rotor will equal the (15) expansion work, This relation is the desired wave-rotor characteristic equation WER-WR =0 giving the pressure rise across the wave rotor as a function of the temperature ratio across the wave rotor. Unfortunately, it includes and hence, increase, so will PR, but at the same time the efficiencies will drop.
the wave-rotor compression ratio PR, which isalso afunction of
However, unless the ratio PR and the efficiencies are obtained
the temperature ratio, and the wave-rotor compression and expan-
sion efficiencies, which are notknown. Inprinciple, if ananalyti- from the CFD program, there is no basis for determining their values more exactly. It is simpler to use constant values that
calmodel ofthe wave-rotor cycle could bedeveloped, the wave-
rotorcompression ratioandefficiencies could becalculated. generate a curve which should approximately equal an actual curve. In fact there will not be any single actual curve because the
However, thecycleis sufficiently complicated thatit proved
real curve will be a function of the efficiencies, which will vary impossible tocreate ananalytical model.
from rotor to rotor depending on the exact cycle used and the
Altemative means ofdetermining the wave-rotor characteristic
arethus needed. One wayis touse the CFD code developed by configuration of the hardware. For generic purposes, equation (15) will suffice, and for the balance of this report, the expression
Paxson (ref.12), and another istouse experimental data. Mathur
"wave-rotor characteristic" will mean equation (15) with PR = 1.8
(ref.11)has reported workby General Electric ona four-port
rotor.Thisworkincluded experimental determination of the and r/R = r/E = 0.83 unless otherwise indicated.
characteristic; the results are reproduced infigure 2.Also included In previous wave-rotor work it has not always been possible to infigure 2isanumerical calculation ofthe characteristic using the evaluate _TRand r/E separately; instead, their product has been determined. Thus, Taussig (ref. 8) reported rlRrlE = 0.7 tO 0.74, and
CFD code developed byPaxson (ref.12). There are twopossible
Moritz (ref. 13 ), in experiments at Rolls-Royce, found r/Rr/E = 0.6.
causes for thediscrepancy between theCFDresults andthe
Kollbrunner (ref. 2) measured r/R alone as 0.65 to 0.68. Approxi-
experimental points. One isthat the CFD calculation has different
mately then, the GE results correspond to rlRrlE = (0.83) 2 = 0.69.
timing foreach value oftemperature ratio, whereas theGeneral
This result is in reasonable agreement with Taussig and Moritz,
Eleclric data presumably are forafixed geometry. Another isthat
although rather higher then Kollbrunner. Thus, it appears that use
friction isincluded inthe code, but the calculation was performed
for a relatively large rotor,for which frictionshould beless of r/R = r/E = 0.83 is consistent with results from other work on wave rotors.
important than inthe small General Electric rotor. Two additional
In addition to cases calculated using this wave-rotor character-
curves areshown infigure 2.One isacurve generated byusing
istic, additional cases were run using an "advanced" wave rotor.
equation (15)withr/R = r/E=0.83, PR= 1.8, and 72 = 1.3. It is
The advanced wave-rotor characteristic was simply obtained by sufficiently close to both the General Electric results and the CFD code results that it can be used as the rotor characteristic for the doubling PR (i.e., using PR=3.6 in eq. (15) again with r/R = r/E = 0.83) and is also plotted in figure 2. Whether such a purpose of this report. This is not meant to imply that PR = 1.8 or that the efficiencies are constant. Indeed as the temperature ratios wave-rotor characteristic is possible is not currendy known-- certainly it is not with the four-port cycle of the kind explored by General Electric. Brown-Boveri has achieved compression ratios up to 7 according to L. Mathews in a private communication.
1.5 However, this was with a cycle that generates a large stagnation
- / /
pressure difference across the combustor, requiring a turbine in / .
this part of the cycle if this pressure difference is to be converted
/ /
/ .
to useful work efficiently. This may well prove to be the only way ,_ 1.4 v- to exploit large wave-rotor pressure ratios but will require a total 'n: engine redesign. Thus, it is not clear whether, or how, the d performance indicated by the advanced wave rotor will be obtain-
- /
able, but it is an interesting speculation.
m J' _ 1.3 ¢) ffl Q.
Application to Engine Performance
_ 1.2 With an expression for the wave-rotor characteristic given, it is possible to calculate the specific power and efficiency of engines with a wave-rotor topping cycle. A reasonable case to
I/- ° Eexpe.ment(ref,,l
• / ' Equation (15), PR = 1.8 consider is that of an aircraft flying at an altitude of 35 000 ft at g 1.1 r-- / / , CFD code results Mach 0.8. For this case the stagnation temperature of the incom- /// . Advanced rotor (eq. (15), ingairis444 °R, andthetotaltostaticpressureratioisPM = 1.524.
[// PR=3.6)
If a turbine inlet temperature T4.2 (assumed equal to T4.1) and
[1 I I I I
a shaft compression ratio are chosen, the temperature T3 is given 1.0 1.5 2.0 2.5 3.0 3.5 by equation (2), and hence the wave-rotor temperature ratio Wave-rotor temperature ratio, T4.1/T 3 T4.JT3 is known. The ratio PO follows from the wave-rotor characteristic, and thus the specific power and efficiency can be Figure 2.--Pressure ratio across wave rotor as function of found from equations (8) and (12). By setting PO = 1 the calcu- temperature ratio across it.
lation becomes that forasimple jetengine without awave rotor. I--I;_ Turbine inlet
I _'_,\\ temperature, ,=
Thermal efficiencies forsimple jet engines ofvarying compres-
I °R
sion ratio calculated this wayare shown infigure 3,together with
points calculated by usingtheONXprogram for jet engine
/ "."..\.'N 33oo
performanceofMattingly, Heiser, andDaly(ref. 14)withY1 = 1.4
and 72 = 1.3. Other values used were r/c= 0.9, r/T= 0.91, r/_ = 0.995, PD = 0.95, and T/M = 0.98. The agreement between
-- 2900
the results of the ONX program and those of the present calcula- tion is excellent, giving confidence in the method.
o E
Figure 4 shows that the wave-rotor temperature ratio is deter- o mined more by the value of R than by the choice of turbine inlet temperature for the range of turbine inlet temperatures chosen.
I I I I I
r_ For a fixed turbine inlet temperature using a high value of R leads 20 40 60 80 100 to a low wave-rotor temperature ratio because the value of T3A Shaft compression ratio, R increases with R but T4.1 is constant. In turn this results in a small pressure rise across the wave rotor, so that little benefit results Figure4.--Ratio of turbine inlet temperature to compressor exit temperature (i.e., temperature ratio across wave rotor) from its use. The opposite is true for low values of R. The results as function of shaft compression ratio.
of calculations to determine the effect of adding a wave-rotor topping cycle to a jet engine for turbine inlet temperatures of 2900, 3100, 3300, and 3500 °R are given in figures 5 and 6 as a function rotor pressure ratios less than 1. A wave-rotor temperature ratio of of shaft compression ratio.
1.6 occurs forR = 80 and a turbine inlet temperature of 2900 °R.
At a turbine inlet temperature of 2900 °R the advanced wave- At first sight the performance improvements to be gained by rotor performance was lower than the simple jet engine perform- adding a wave-rotor topping cycle seem relatively small, and ance for shaft compression ratios above about 80. In other words, indeed, the efficiency gains are not spectacular. However, the if the jet engine has a shaft compression ratio of 80 or greater, efficiency gains are accompanied by increases in specific power, adding an advancedwaverotorwouldresultinlowerperformance!
which is not the case if one were simply to increase the compres- Reference to the advanced wave-rotor characteristic in figure 2 sion ratio. For example, if one takes as a base case a simple jet shows that it has a threshold slightly above a temperature ratio of engine with a compression ratio of 33.3, which is typical of some 1.6. Wave-rotor temperature ratios below 1.6 will generate wave- of today's large engines, and a turbine inlet temperature of 3300 °R, then from figures 5 and 6 the efficiency is 51.3 percent and the specific power is 510 hp/lb-sec. If, in an effort to improve Turbine inlet temperature, efficiency, one were to increase the conventional compression .6 m oR ratio by 1.8 (i.e., to 60), the efficiency would increase to 54.2 per- cent but the specific power would drop to 480 hp/lb-sec. Alterna- tively, ifa wave-rotor topping cycle were used to achieve the same overall compression ratio of 60, the efficiency would increase to 54.3 percent, and the specific power would also increase to .5 537 hp/lb-sec (i.e., 12 percent more than the jet engine with an t- overall pressure ratio of 60).
._o In order to see more clearly the comparison between a jet 0.)
engine and a jet-engine/wave-rotor combination of the same overall compression ratio, the thermal efficiency and specific49ower are II) ¢..
plotted against overall compression ratio (i.e., PRxR) in figures 7 I--- .4 and 8. For the whole range of compression ratios considered, the 0 This calculation jet-engine/wave-rotor combination has about the same or slightly ONX higher efficiency and significantly higher specific power than the jet engine alone, particularly at high compression ratios.
These numerical results assumed only the wave-rotorperform-
.3 I I I I I
ance demonstratedby General Electric and not the advanced wave- 0 20 40 60 80 100 rotor performance. Obviously, if better wave-rotor performance Compression ratio were available, the jet-engine/wave-rotor combination would be Figure 3.--Thermal efficiency of simple jet engine as func- even more promising. Of course, the increase in specific power tion of compression ratio calculated with present model with a wave rotor is not obtained without a price--the price being and also with computer code ONX of reference 14 for an increase in combustion temperature. This is shown in figure 9, turbine inlet temperatures of 2900 and 3500 °R.
Jet engine plus advanced wave rotor
F
- Jet engine plus wave rotor .......... Simple jet engine
I/......-."
__ /-_° .5 / : /,,, !
/il l i J i
,,' I I I I
O (a) Turbine inlet temperature, 2900 °R.
(c) Turbine inlet temperature, 3300 °R.
I---
'r
/f .......................
// ......-" ........
.5 / .,,,
//
t
!/ I i /I i i I i I
I I I
0 20 40 60 80 100 0 20 40 60 80 100 Shaft compression ratio, R (b) Turbine inlet temperature, 3100 °R.
(d) Turbine inlet temperature, 3500 °R.
Figure 5.--Thermal efficiency of jet engine with and without wave-rotor topping cycle for engines with same shaft compres- sion ratio.
m Jet engine plus advanced wave rotor Jet engine plus wave rotor ........... Simple jet engine i
I I I I I I I I I
? (a) Turbine inlet temperature, 2900 °R. (c) Turbine inlet temperature, 3300 °R.
O.
c- O O.
O om i I ..................
/ !" ......
50O I I I
t
300 I I I I I I I I I I
0 20 40 60 80 100 0 20 40 60 80 100 Shaft compression ratio, R (b)Turbine inlet temperature, 3100 °R. (d)Turbine inlet temperature, 3500 °R.
Figure 6.---Specific power of jet engine with and without wave-rotor topping cycle for engines with same shaft compression ratio.
in which the combustion temperature is plotted again st shaft com- that is within the materials capabilities expected to be available by pression ratio with turbine inlet temperature as a parameter. the turn of the century. If advanced wave-rotor performance could A different view of the advantage of a wave-rotor topping be achieved, the same efficiency goal could be reached at a shaft cycle can be seen by considering the design of an engine to meet compression ratio of 35 and a turbine inlet temperature of a specific thermal efficiency goal, say 54 percent. To do this with 2900 °R. This is within the range of current technology and so a simple jet engine would require a compression ratio of 60 at a would require no new material development, Because the wave turbine inlet temperature of 3300 °R. This would require major rotor itself is alternately heated and cooled by the gases flowing advances in materials to achieve both the turbine inlet tempera- through it, it attains a temperature between the turbine inlet ture and the high temperatures of the final compressor stages temperature and the compressor exit temperature. Its construction (T3 = 1630 °R). A jet engine plus a wave-rotor topping cycle is relatively simple and is not likely to require advanced materials.
could achieve the same efficiency at a shaft compression ratio of The specific power is approximately identical for the three cases considered here.
40 and a turbine inlet temperature of 3100 °R, a more modest goal Jet engine plus advanced wave rotor Jet engine plus wave rotor .......... Simple jet engine D_====== ====== .5--
i I I I I I I I I I I
._ .4 O (c) Turbine inlet temperature, 3300 °R.
(a) Turbine inlet temperature, 2900 °R.
_E E .6 m I- =._w==== ====" =5 --
/ I I I I -I
! I I I I I
.4 0 20 40 60 80 100 20 40 60 80 100 Overall compression ratio, P3.2/Po (b) Turbine inlet temperature, 3100 °R. (d) Turbine inlet temperature, 3500 °R.
Figure 7.mThermal efficiency of jet engine with and without wave-rotor topping cycle for engines with same overall com- pression ratio.
m Jet engine plus advanced wave rotor Jet engine plus wave rotor .......... Simple jet engine w
t
40O m f
I I I I I
I I I I ..... J
3O0 (c) Turbine inlet temperature, 3300 °R.
(a) Turbine inlet temperature, 2900 °R.
.Q
%
J= 7O0 °m .m 6OO IA ....................
li,." .........
5OO t _'"==_.m 40O
I I I I I
I I I I I
30O 0 20 40 60 80 1 O0 20 40 60 80 1O0 Overall compression ratio, P3.2/Po (b) Turbine inlet temperature, 3100 °R. (d) Turbine inlet temperature, 3500 °R.
Figure 8.--Specific power of jet engine with and without wave-rotor topping cycle for engines with same overall compres- sion ratio.
Turbine inlet
Conclusions
temperature, oR Using a wave-rotor topping cycle on a jet engine will give improved performance over a simple jet engine of the same 330O overall compression ratio. Adding a wave rotor to an existing engine while maintaining the same turbine inlet temperature but increasing the combustion temperature will increase both effi- 38OO r_ ciency and specific power.
o This conclusion was based on a comparison of the wave-rotor- topped cycle with a simple jet engine at constant component efficiencies. In fact, as compression ratios get higher, the blades of the high-pressure stages of conventional turbomachinery get e-- smaller, resulting in increased losses and lower component effi-
o 340o
ciencies.An engine with a wave-rotor-topped cycle may therefore e-s have an even greater advantage over a simple jet engine than is E indicated by these calculations.
32OO In addition, wave rotors can deliver improved performance without requiring the development of new materials.
aooo I I I I I
0 20 40 60 80 100
References
Shaft compression ratio, R 1. Meyer, A.: Recent Developments in Gas Turbines. Mech. Eng., vol.
Figure 9._Combustion temperature as function of shaft com- 69, no. 4, Apr. 1947, p. 273-277.
pression ratio for jet engine plus wave rotor having charac- teristic of equation (15) (PR = 1.8). 2. Kollbrunner, T.A.: Comprex R Supercharging for Passenger Diesel Car Engines. SAE Paper 800884, 1981.
3. Jenny, E.; and Zumstein, B.: Pressure Wave Supercharging of Passen- ger Car Diesel Engines. Institution of Mechanical Engineers, Confer- ence Publication C-44, 1982, pp. 129-141.
4. Croes, N.: The Principle of the Pressure-Wave Machine as Used for Charging Diesel Engines. Shock Tube and Shock Wave Research: Proceedings of the 1lth International Symposium on Shock Tubes and Waves, B. Ahlborn, A. Hertzberg, and D. Russell, eds., Univer- As is well known, increasing the pressure ratio of an engine sity of Washington, Seattle, WA, 1978, pp. 36-55.
requires an appropriate increase in turbine inlet temperature if 5. Keller, J.J.: Some Fundamentals of the Supercharger Comprex R. Pre- optimum efficiency is to be achieved. This is true whether the sented at the ASME Winter Meeting, New Orleans, LA, Dec. 1984.
higher pressure ratio is obtained by mechanical compressors or 6. Hitomi, M.; Yuzuriha, Y.; and Tanaka, K.: The Characteristics of Pres- wave rotors. For example, if the turbine inlet temperature is sure Wave Supercharged Small Diesel Engine. SAE Paper 890454, 1989.
2900 °R, a simple jet engine with a compression ratio of 85 has 7. Peacock, N.J.; and Sadler, J.H.R.: Advanced Propulsion Systems for lower efficiency and lower specific power than a simple jet engine Large Subsonic Transports. J. Propul. Power, vol. 8, no. 3, May-June with a compression ratio of 55. Adding a wave rotor to the engine 1992, pp. 703-708.
with the compression ratio of 85 only gives the same efficiency as 8. Taussig, R.T.: Wave Rotor Turbofan Engines for Aircraft. Mech. Eng., the simple jet with the compression ratio of 55 but with lower vol. 106, Nov. 1984, pp. 60-66.
9. Roberts, J.W.: Further Calculations of the Performance of Turbofan specific power and added complexity. Obviously, the simple jet Engines Incorporating a Wave Rotor. M.S. Thesis, Naval Postgradu- with the compression ratio of 55 is to be preferred to the other two ate School, Monterey, CA, 1992.
examples. Still, for shaft compression ratios between 22 and 80, 10. Kentfield, J.A.C.: The Performance of Pressure-Exchanger Diviclers the wave-rotor-topped cycle will have higher efficiency than a and Equalizers. J. Basic Eng., vol. 91, Sept. 1969, pp. 361-369.
simple jet engine of any compression ratio, and for overall com- 11. Mathur, A.: A Brief Review of the G.E. Wave Engine Program (1958- 1963). Proceedings of the 1985 ONR/NAVAIR Wave Rotor Research pression ratios less than 60 the specific power will also be higher.
and Technology Workshop, Report NPS-67-85-008, Naval Post- As the turbine inlet temperature is increased to 3500 °R, the graduate School, May 1985.
wave-rotor-topped cycle has higher efficiency than any simple jet 12. Paxson, D.: A General Numerical Model for Wave Rotor Analysis.
of lower shaft or overall compression ratio up to, and beyond, the NASA TM-105740, 1992.
maximum compression ratio calculated here (i.e., 100). More- 13. Moritz, R.: Rolls-Royce Study of Wave Rotors 1965-1970. Proceed- ings of the 1985 ONR/NAVAIR Wave Rotor Research and Technol- over, for overall compression ratios less than 100 (shaft compres- ogy Workshop, Report NPS-67-85-008, Naval Postgraduate School, sion ratio of 55), the specific power is greater with the May 1985.
wave-rotor-topped cycle than the maximum achievable with a 14. Mattingly, J.D.; Heiser, W.H.; and Daley, D.H.. Aircraft Engine simple jet (at a compression ratio of 30).
Design. AIAA, New York, 1987.
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1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED October 1993 Technical Memorandum 4. TITLE AND SUBTITLE 5. FUNDING NUMBERS Jet Engine Performance Enhancement Through Use of a Wave-Rotor Topping Cycle WU-505-62-10 6. AUTHOR(S) Jack Wilson and Daniel E. Paxson 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NUMBER National Aeronautics and Space Administration Lewis Research Center E-7836 Cleveland, Ohio 44135-3191 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORING/MONITORING AGENCY REPORTNUMBER National Aeronautics and Space Administration Washington, D.C. 20546-0001 NASA TM-4486 11. SUPPLEMENTARY NOTES Jack Wilson, Sverdrup Technology, Inc., Lewis Research Center Group, 2001 Aerospace Parkway, Brook Park, Ohio 44142; Daniel E. Paxson, NASA Lewis Research Center. Responsible person, Daniel E. Paxson, (216) 433--8334.
12a. DISTRIBUTION/AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE Unclassified- Unlimited Subject Categories 07 and 44 13. ABSTRACT (Maximum 200 words) A simple model is used to calculate the thermal efficiency and specific power of simple jet engines and jet engines with a wave-rotor topping cycle. The performance of the wave rotor is based on measurements from a previous experiment. Applied to the case of an aircraft flying at Mach 0.8, the calculations show that an engine with a wave- rotor topping cycle may have gains in thermal efficiency of approximately 1 to 2 percent and gains in specific power of approximately 10 to 16 percent over a simple jet engine with the same overall compression ratio. Even greater gains are possible if the wave rotor's performance can be improved.
14. SUBJECT/I=HMS 15. NUMBER OF PAGES Wave rotor; Topping cycle; Jet engine 16. PRICE CODE A03 17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION 20. LIMITATION OF ABSTRACT OF REPORT OF THIS PAGE OF ABSTRACT Unclassified Unclassified Unclassified NSN 7540-01-280-5500 Standard Form 298 (Rev. 2-89) Prescribed by ANSI Std. Z39-18 298-102