Compound cycle engine program

NASA

USAAVSCOM

Technical Memorandum 88879

Technical Report 86-C-37

Compound Cycle Engine Program

lMASB-TB-88879) C C f l P C U N I ) C Y C L E E N G I N E N87-I 17’30 PEOGHAei { N A S A ) 2 3 p C S C L 2 1 E U n c l a s G3/07 44804

G.A. Bobula

Propulsion Directorate

U. S. Army Aviation Research and Technology Activity-A VSCOM

Lewis Research Center

Cleveland, Ohio

W. T . Wintucky

Lewis Research Center

Cleveland, Ohio

and

J.G. Castor

Garrett Turbine Engine Company

Phoenix, Arizona

Prepared for the

Rotary Wing Propulsion System Specialist Meeting

sponsored by the American Helicopter Society

Williamsburg, Virginia, November 12- 14, 1986

COMPOUND CYCLE E N G I N E PROGRAM G.A. Bobula Propulslon D i r e c t o r a t e

U.S. Army A v i a t i o n Research and Technology A c t i v i t y - AVSCOM

Leu1 s Research Center Cleveland, Ohio 44135 W. T. W i n t u c ky N a t i o n a l Aeronautics and Space A d m i n i s t r a t i o n Lewi s Research Center Cleveland, Ohio 44135 and 3 . 6 . Castor G a r r e t t Turbine Engine Company Phoenix, Arizona 85010 SUMMARY The Compound Cycle Engine (CCE) i s a h i g h l y turbocharged, power compounded ower p l a n t which combines t h e l i g h t w e i g h t pressure r i s e c a p a b i l i t y o f a gas t u r b i n e w i t h t h e h i g h ' e f f i c i e n c y o f a d i e s e l .

When o p t i m i z e d f o r a r o t o r - c r a f t , t h e C C E w i l l reduce f u e l burned f o r a t y p i c a l 2 hr ( p l u s 30 min reserve) m i s s i o n by 30 t o 40 p e r c e n t when compared t o a conventional advanced technology M gas t u r b i n e . . T h e CCE can p r o v i d e a 50 p e r c e n t I n c r e a s e i n range-payload p r o - I W d u c t on t h i s m i s s i o n .

A program t o e s t a b l i s h t h e technology base f o r a Compound Cycle Engine i s presented. The g o a l o f t h i s program i s t o research and develop those t e c h n o l - ogies which a r e b a r r i e r s t o demonstrating a m u l t i c y l i n d e r d i e s e l c o r e i n t h e i s a three-phased c o n t r a c t w i t h t h e e a r l y 1990's. The major a c t i v i t y underway G a r r e t t Turbine Engine Company t o perform: ( 1 ) d l i g h t h e l i c o p t e r f e a s i b i l i t y study, ( 2 ) component technology development, and ( 3 ) l u b r i c a n t and m a t e r i a l research and development. Other r e l a t e d a c t i v i t i e s a r e a l s o presented.

INTRODUCTION A program i s b e i n g conducted t o e s t a b l i s h t h e technology base f o r a com- pound c y c l e engine (CCE). The program g o a l i s t o develop those t e c h n o l o g i e s which a r e b a r r i e r s t o demonstrating a m u l t i c y l i n d e r gas generator, o r core engine, d u r i n g t h e e a r l y 1990's. A m a j o r p a r t o f t h e technology program i s a t h r e e phase c o n t r a c t u a l e f f o r t being conducted by t h e G a r r e t t Turbine Engine Company, under t h e sponsorship of t h e U.S. Army A v i a t i o n Systems Command: t h e f i r s t phase i s an a n a l y t i c a l f e a s i b i l i t y study o f a compound c y c l e engine f o r a l i g h t h e l i c o p t e r a p p l i c a t i o n ; t h e second i s a component technology develop- ment program; and the t h i r d i s a l u b r i c a n t and m a t e r i a l s research and develop- Other r e l a t e d program elements a r e a l s o underway i n an e f f o r t ment program.

t o accomplish t h e 1990's demonstration o f a m u l t i c y l i n d e r d i e s e l core.

Recent s t u d i e s have shown t h a t f u e l i s 70 percent o f t h e tonnage shipped Another by t h e Army f o r supply and support under b a t t l e f i e l d c o n d i t i o n s .

study, r e f e r e n c e 1, showed t h a t a compound c y c l e engine, w i t h i t s s u p e r i o r f u e l e f f i c i e n c y , when i n s t a l l e d i n a Blackhawk h e l i c o p t e r and operated over a t y p i c a l 2-hr mission, c o u l d have a s p e c i f i c weight as h i g h as 0.76 pounds per horsepower ( l b / h p ) and s t i l l be c o m p e t i t i v e w i t h a gas t u r b i n e engine i n terms o f range-payload p r o d u c t . T h i s r e s u l t assumed t h e same t a k e - o f f gross w e i g h t , and balanced t h e CCE's increased engine w e i g h t a g a i n s t i t s lower f u e l consumed p l u s tankage weight.

T h i s paper summarizes t h e s t a t u s o f t h e c u r r e n t C C E a c t i v i t i e s . The f e a s i b i l i t y study p r e d i c t e d t h a t t h e 1000 horsepower (hp) h e l i c o p t e r engine would have a s p e c i f j c w e i g h t of 0.432 l b / h p and a s p e c i f i c f u e l consumption The s t a t e o f t h e s i n g l e (SFC) o f 0.33 pounds p e r horsepower-hour ( l b / h p - h r ) .

research c y l i n d e r component development program and o f t h e l u b r i c a n t / m a t e r i a l s w i l l a l s o be presented. The paper w i l l conclude w i t h . o t h e r r e l a t e d a c t i v i t i e s o u t s i d e t h e scope of t h e i n i t i a l three-phase c o n t r a c t . A l l these elements t a k e n t o g e t h e r comprise t h e l o n g range p l a n t o meet t h e 1990's d i e s e l core, m u l t i c y 4 i n d e r demonstration date.

BACKGROUND A compound c y c l e engine, shown s c h e m a t i c a l l y I n f i g u r e 1, combines t h e a i r f l o w c a p a c i t y and ' l i g h t - w e i g h t pressure r i s e f e a t u r e s o f a gas t u r b i n e w i t h t h e h i g h l y e f f i c i e n t , a l t h o u g h h e a v i e r , d i e s e l . The compressor o f t h e t u r b o - a h i g h l y p r e s s u r i z e d charge o f a i r t o t h e d i e s e l machinery module d e l i v e r s c y l i n d e r s . W i t h i n t h e c y l i n d e r s , f u r t h e r compression, f u e l i n j e c t i o n , combus- t i o n , and expansion takes place, as i n any c o n v e n t i o n a l r e c i p r o c a t i n g engine, b u t a t s u b s t a n t i a l l y h i g h e r pressures and temperatures. Power i s e x t r a c t e d d u r i n g t h e expansion s t r o k e and t h e exhaust gases a r e then r e t u r n e d t o t h e turbomachinery module. The exhaust energy a v a i l a b l e i s i n excess o f what i s r e q u i r e d t o d r i v e t h e compressor, and t h a t excess power i s e x t r a c t e d i n a f r e e t u r b i n e and combined w i t h t h e d i e s e l o u t p u t through a gear t r a i n . T h i s com- b i n e d o u t p u t comprises t h e t o t a l c y c l e o u t p u t , hence t h e name compound c y c l e engine.

A s o u t l i n e d i n r e f e r e n c e 2, t h e 1940's and e a r l y 1950's saw c o n s i d e r a b l e i n t e r e s t i n compound c y c l e engines b e i n g a p p l i e d t o a i r c r a f t . D u r i n g t h e e a r l y 1950's, t h e most f u e l e f f i c i e n t i n t e r n a l combustion engine ever flown, t h e Napier Nomad, demonstrated an SFC o f l e s s t h a n 0.35 lb/hp-hr i n f l i g h t , r e f e r e n c e 3. The engine used a h i g h l y turbocharged, power compounded c y c l e t o reach t h i s l e v e l o f performance. It d e l i v e r e d 3050 hp o u t p u t a t a w e i g h t o f 3580 l b . The advent o f t h e gas t u r b i n e , however, coupled w i t h t h e low c o s t o f f u e l a t t h e t i m e and t h e d r i v e toward f a s t e r speeds, brought an end t o t h e Nomad. T h i s technology stagnated w h i l e gas t u r b i n e s f l o u r i s h e d i n t h e 30-plus i n t e r v e n i n g years.

The Army/NASA S m a l l Engine Technology program, r e f e r e n c e 4 i n d i c a t e d t h a t performance increases o f s i g n i f i c a n t magnitude f o r t h e year 2000 turbomachine w i l l r e q u i r e improved c y c l e s i n c o r p o r a t i n g t h e r e s u l t s o f i n t e n s i v e research and development e f f o r t s , m a i n l y i n m a t e r i a l s , t h a t i s ceramics, and secondly i n component aerodynamic design. E f f o r t s i n o t h e r areas w i l l p r o v i d e p a y o f f s o f a s m a l l e r magnitude. The r e d u c t i o n i n f u e l burned p r e d i c t e d f o r t h e year 2000 r o t o r c r a f t a p p l i c a t i o n was dependent on a l l t h e key t e c h n o l o g i e s r e a c h i n g t h e a p p l i c a t i o n s phase, references 5 and 6.

Economic and l o g i s t i c pressures have f o r c e d us t o r e c o n s i d e r more e f f i - c i e n t power p l a n t s such as t h e compound c y c l e . The a l r e a d y mentioned tonnage which t h e Army must supply and support under b a t t l e f i e l d c o n d i t i o n s , and t h e need f o r a deep p e n e t r a t i o n c a p a b i l i t y , a r e examples o f t h e d r i v e r s toward b e t t e r f u e l e f f i c i e n c y . It i s estimated t h a t by a d a p t i n g t h e Napier Nomad t o a h e l l c o p t e r m i s s i o n and i n c o r p o r a t i n g modern technologies I n t o i t s 35 year o l d SFC i n t h e range design, t h i s compound c y c l e engine could be made t o r u n a t an The weight r e d u c t i o n would be o f 0.35 lb/hp-hr and weigh 0.6 lb/hp o r l e s s .

accomplished by removing t h e r e d u c t i o n gearbox which had been needed f o r a p r o p e l l e r d r i v e ; d e l e t i n g t h e variable-speed transmission, which had been needed f o r turbomachinery and d i e s e l speed matching, and i n s t e a d i n c o r p o r a t i n g a f r e e t u r b i n e stage f o r power e x t r a c t i o n ; r e d u c i n g t h e number o f t u r b o - machinery stages s u b s t a n t i a l l y f r o m t h e o r i g i n a l Nomad design; and t h e n by u t i l i z i n g modern m a t e r i a l s and s t r u c t u r a l a n a l y s i s techniques.

U n t i l r e c e n t l y , few major advances have occurred i n r e c i p r o c a t i n g engines.

I n 1977, however, a j o i n t Defense Advanced Research P r o j e c t Agency ( D A R P A ) , A i r Force, and G a r r e t t program, reference 7, i n v e s t i g a t e d a h i g h l y turbocharged, power compounded t u r b o f a n / d i e s e l engine f o r a c r u i s e m i s s i l e a p p l i c a t i o n .

Power d e n s l t i e s g r e a t e r t h a n seven times t h a t o f t h e b e s t c u r r e n t p r o d u c t i o n d i e s e l s were demonstrhted i n a s i n g l e c y l i n d e r r i g . A m i s s i o n r e d i r e c t i o n t e r m l n a t e d t h a t e f f o r t , however, t h a t program formed t h e b a s i s f o r t h e p r e s e n t 1 v i t y .

a c t COMPOUND CYCLE ENGINE PROGRAY The l o n g t e r m goal o f t h e compound c y c l e engine program i s a 30 t o 40 p e r c e n t r e d u c t i o n i n m i s s i o n f u e l w e i g h t w i t h a r e s u l t a n t 50 p e r c e n t improvement i n payload-range product f o r a l i g h t h e l i c o p t e r . I n t h e near t e r m , t h e s p e c i f i c o b j e c t i v e i s t o a t t a c k t h e h i g h r i s k , b a r r i e r t e c h n o l o g i e s i n p r e p a r a t i o n f o r a r n u l t i c y l i n d e r core demonstrator program i n t h e e a r l y 1990's.

Toward t h i s end, t h r e e p a r a l l e l phased c o n t r a c t u a l e f f o r t s w i t h t h e G a r r e t t T u r b i n e Engine Company a r e underway. I n t h e f i r s t phase, a f e a s i b l l l t y study was conducted t o determine t h e m e r i t o f u s i n g a compound c y c l e engine i n a l i g h t h e l i c o p t e r . I n t h e second phase, component research i s b e i n g conducted on a s i n g l e c y l i n d e r t e s t r i g . L u b r i c a n t and m a t e r i a l research i s b e i n g con- ducted i n phase t h r e e .

L i g h t R o t o r c r a f t F e a s i b i l i t y Study Phase I : F i g u r e 2 d e p i c t s t h e numerous options whlch were considered i n t h e engine f e a s i b i l i t y study. I t should be noted t h a t t h e engine looks very s i m i l a r t o a normal t u r b o s h a f t c o n f i g u r a t i o n , but w i t h t h e combustor replaced by a power p r o d u c i n g d i e s e l core. The turbomachinery maps were e s s e n t i a l l y l i f t e d f r o m e x i s t i n g t u r b i n e engines, w i t h t h e study e f f o r t p r i m a r i l y r e v o l v l n g around t h e d i e s e l core c o n f i g u r a t i o n .

T h e study options include: 2-stroke versus 4-stroke cycle, compressor discharge aftercooling, scavenging method (loop versus uniflow versus 4-stroke), turbocompounding versus turbocharging, method of compounding, and cylinder geometry. T h e engine design point conditions w e r e a l s o considered 3 presents a summary plot of BSFC and weight trends a s they options. Figure w e r e affected by scavenging option, and b y turbocompounding versus turbo- chosen due t o its substantially lower charging option. Turbocompounding was T h e 2-stroke cycle, with t w o times a s many engine weight and fuel burned.

power strokes a s a 4-stroke, provide a lighter power plant than t h e 4-stroke cycle. T o achieve t h e lowest possible predicted weight, a uniflow scavenged design was chosen. Finally, for more stable off-design operation, a one-and- one-half spool turbocompounding scheme was selected. T h e half spool refers t o t h e use of a mechanically disconnected, or free, power turbine.

T h e decision on aftercooling was driven by life considerations. A t w o point SFC penalty w a s predicted with aftercooling, d u e t o pressure losses and power extracted for a blower. However, an effectiveness of 0.4 produced a reduction in cylinder inlet temperature of 3 0 0 O F at maximum power, which should result i n a significant improvement in life. T h e weight added d u e t o t h e aftercooler was balanced by a cylinder size and weight reduction, since t h e cooler, more dense intake a i r charge now required less displaced volume for t h e same mass flow.

T h e trends which led t o t h e final design are shown in f i g u r e 4. These plots assumed that f d r t h e life goal of t h e helicopter CCE, a mean piston speed of 3000 ft/min should not be exceeded. Having previously selected a uniflow scavenged cylinder, a minimum bore size of 3.0 in. was required t o a l l o w room f o r exhaust valves and an injector, and this drove the design t o six cylinders.

T h e six cylinder configuration accepted a small weight penalty compared t o I eight or t e n cylinders, however, t h e weight w a s somewhat reduced b y selecting a n over-square bore t o stroke ratio of 1.05 t o reduce cylinder height. A s life and wear a r e t h e major concerns in this engine, the selection of t h e six cylinder design d l d a l l o w a substantially lower engine speed than either the eight or t h e ten. S F C was nearly independent of both bore t o stroke ratio and numbers of cylinders, and although the maximum firing pressure is independent of t h e ’ n u m b e r of cylinders, t h e pressure was slightly reduced by choosing the 1.05 bore t o stroke ratio. Thus, the final design configuration, presented in t a b l e I, is seen to be a t r a d e among life, performance, and weight considera- tions. A schematic of t h e final design is presented in figure 5.

A simple analysis, using figures 6 t o 8, may be performed t o examine the benefits of a compound cycle. In figure 6, a composite mission profile is presented for comparison purposes. It can be seen that 80 percent of the mission is spent at 50 percent power or less. Using t h e performance shown in f i g u r e 7, a n advanced technology 1000 h p turboshaft engine would weigh about 240 lb and operate a t an S F C of 0.55 lb/hp-hr at t h e 50 percent power condi- tion. A compound cycle engine, under the same conditions, weighs about 4 3 0 lb and has an S F C of 0.36 lb/hp-hr.

Looking now at t h e fan plot of f i g u r e 8, it is obvious that the SFC difference 0.f 0.19 lb/hp-hr begins t o outweigh t h e CCE weight deficit o f 190 lb in less than an hour. T h e fan plot is a simple representation o f t h e dependence of breakeven t i m e on t h e differences in specific weight a n d i n fuel consumption between two engines, and includes an allowance for tankage. The advanced technology turboshaft engine used in t h e I .

comparison represented T 8 0 0 technology, but a t 1000 hp. T h e performance levels presented are, therefore, representative o f what might be expected in t h e near term.

T h e mission used in t h e preliminary design, which was shown in figure 6, w a s 2 hr, with a 30-min fuel reserve.

The engine was designed t o produce 1000 h p f r o m sea level on a standard day t o 4000 ft on a 95 O F , hot day. This flat rating of t h e CCE is achieved b y upspeeding t h e compressor by 4 percent w h i l e increasing t h e trapped equivalence ratio from 0.68 t o 0.80. T h e gas turbine, however, when designed t o produce 1000 hp at t h e 4000 ft/95 OF condi- tion, is actually In t h e 1400 hp range a t sea level/standard day, and the aircraft must be designed t o carry this heavier engine. In addition, t h e performance of t h e gas turbine is penalized in that a t 5 0 percent of rated power, 1000 hp, it actually uses less than 40 percent of t h e maximum available power, and thus t h e gas t u r b i n e cruises at an even lower efficiency.

It should be pointed out that considerable effort i n t h e study phase of this program was directed a t formulating a weight prediction method. This method i:s discussed in some detail in reference 2. Based on this prediction, t h e C C E will weigh 0.432 lb/hp. This w a s nearly 3 0 percent lower than the initial weight prediction which was based on t h e CCTE of reference 7. T h e trend from t h e CCTE design, t o the present CCE all-metal design, t o a highly advanced design incorporating n e w technologies such a s advanced materials and improved energy recovery methods, should continue as shown in f i g u r e 9. An example of such desigrl improvements would be t h e development of lubricants which can be operated at high enough temperatures t o permit t h e removal of the aftercooler. As indicated above, this could result in essentially n o weight c h a n g e but should subtract t w o points f r o m the SFC.

Phase 11: Component Technology Development This phase of t h e CCE program began b y using hardware f r o m t h e DARPA-Air Force CCTE program which had already been run at more than seven times t h e power density o f t h e best current production dlesels, reaching 7.2 hp/cu-in.

This hardware, w h i l e loop scavenged, provided an early opportunity t o concen- trated on thermal characterization a n d piston ring/liner wear w h i l e operating a t t h e specific power level of the CCE. T h e thermal characterization work was directed toward measuring cylinder and piston temperatures t o validate analy- tical, thermal models. T h e piston rlng/liner wear activity dealt mainly with t h e development of a method f o r making in-situ measurement of wear.

These measurements make use of a SPIRE-WEAR radionuclides measurement system which has evolved t o a point of utility for t h e CCE program, reference 8. The results w e r e used t o establish baseline wear rate measurements.

Typical trends a r e shown in f i g u r e 10. It should be noted that during t h e single cylinder e n g i n e tests, power densities o f nearly 5 hp/cu-in w e r e consistently run i n over 100 h r of testing.

Development of t h e wear measurement system required identification of an appropriate material/isotope combination t o provide a reasonable energy level and half life t o accomplish wear rate test objectives. Location of t h e radla- tion detector f o r optimum data acquisition, and maintenance of a constant detector temperature w e r e key t o achieving consistent results. Software a c t i v i t i e s Included changing t h e energy i n t e g r a t i o n technique t o an area i n t e - g r a t i o n scheme o v e r a w i d e r bandwidth t h a n o r i g i n a l l y proposed. This a l l o w e d f a s t e r , more accurate a c q u i s i t i o n o f data. A s a r e s u l t s , t h e SPIRE-WEAR system and t e s t setup I s now ready t o be a p p l i e d on t h e n e x t t e s t sequence, which w i l l employ a u n i f l o w scavenged engine.

Since t h e p r e l i m i n a r y C C E design had u n i f l o w scavenged c y l i n d e r s , a u n i - flow, s i n g l e c y l i n d e r t e s t r i g a c t i v i t y has been undertaken. D e t r o i t D i e s e l A l l i s o n has provided GTEC, under a subcontract, m o d i f i e d s e r i e s 53 hardware which i s b e i n g operated as a s i n g l e c y l i n d e r engine t e s t bed. The DDA hard- ware support i s t h r e e phased. An I n i t i a l s e t o f hardware i s b e i n g i n s t a l l e d t o b e g i n b a s e l i n e u n i f l o w t e s t i n g , producing 50 hp (about 1 hp/cu-in) i n i t s s l n g l e 53 c u - i n c y l i n d e r , w h i l e o p e r a t i n g a t 2500 rpm and a BMEP o f 140 p s i a .

A second s e t o f upgraded hardware, w i l l p e r m i t 100 hp (about 2 hp/cu-in) by o p e r a t i n g a t 3500 rpm and a BMEP o f 213 p s i a . The t h i r d phase, an upgrade of t h e second s e t o f hardware w i l l a l l o w 150 hp ( n e a r l y .3 hp/cu-in) by o p e r a t i n g a t 4000 rpm and a BMEP o f 280 p s i a .

T h e . p r e d i c t e d o p e r a t i n g c o n d i t i o n s f o r t h e t h r e e r i g b u i l d s a r e shown i n t a b l e 11. A s i n d i c a t e d above, t h e main f a c t o r s i n a c h i e v i n g t h e h i g h e r power d e n s i t i e s a r e increased m a n i f o l d pressure, t o more c l o s e l y s i m u l a t e CCE l e v e l s o f boosting, and increased engine speed. The maximum p i s t o n speed i s 3000 f t / m i n . This s i n g l e c y l i n d e r t e s t r i g w i l l thus p r o v i d e t h e c a p a b i l i t y t o s y s t e m a t i c a l l y make wear measurements i n a u n i f l o w scavenged c o n f i g u r a t i o n , w h i l e o p e r a t i n g a t c o r l d i t l o n s which approach those o f t h e C C E .

Phase 111: L u b r i c a n t and M a t e r l a l s R&D The l u b r i c a n t and m a t e r i a l research and development a c t i v i t i e s have centered around t w o e f f o r t s ; t h e f i r s t i s a l u b r i c a n t s p e c i f i c a t i o n f o r com- pound c y c l e engines, and t h e second i s a Hohman wear r i g . A d r a f t o f t h e C C E l u b r i c a n t s p e c i f i c a t i o n has been w r i t t e n and was c i r c u l a t e d t o government, i n d u s t r y , and u n i v e r s i t y e x p e r t s f o r comment. The Hohman wear r i g , I s b e i n g used t o screen l u b r i c a n t / a d d i t i v e combinations and l u b r i c a n t / m a t e r i a l couples f o r t h e C C E program. I n c o n j u n c t i o n w i t h t h i s a c t i v i t y , I n d u s t r y sources have been p r o v i d i n g l u b r i c a n t and a d d i t i v e samples f o r e v a l u a t i o n . F i g u r e 11 shows a schematic o f t h e Hohman wear r i g and p r e l i m i n a r y t e s t r e s u l t s . The S t a u f f e r STL p l u s 10 percent TAP i s t h e b a s e l i n e , o r c o n t r o l , l u b r i c a n t f o r t h i s a c t l v - i t y . The Montsanto MCS 2189 w i t h i t s 85 p e r c e n t r e d u c t i o n i n wear and i t s 30 percent lower f r i c t i o n c o e f f i c i e n t has produced t h e m o s t p r o m i s i n g bench t e s t r e s u l t s t o date. Combining t h e b a s e l i n e s i n g l e c y l i n d e r wear d a t a w i t h t h e improvements b e l i e v e d p o s s i b l e u s i n g Montsanto 2189, l i f e f o r t h e C C E should be near 1400 h r . While l i f e and wear c o n t i n u e t o be t h e major b a r r i e r s t o t h e development o f a CCE, t h e p o t e n t i a l o f 1400 h r o f l i f e a t such an e a r l y stage i n t h i s program I s s i g n i f i c a n t progress toward b r e a k i n g down those b a r r i e r s .

OTHER A C T I V I T I E S RELATED TO ACCOMPLISHING C C E LONG TERM GOALS Beyond the C C E c o n t r a c t u a l e f f o r t s , t h e r e a r e s e v e r a l o t h e r r e l a t e d a c t i v i t i e s . Because t h e h i g h e s t r i s k t e c h n o l o g i e s o f t h i s program a r e l i f e and wear, m o s t o f the r e l a t e d a c t i v i t y I s i n t h e area o f t r i b o l o g y . A s i g n i f i c a n t technology advancement i s hoped f o r through a r e c e n t l y i n i t i a t e d c o n s o l l d a t i o n o f e f f o r t s i n t h e government's d i e s e l research community. The g o a l o f t h i s c o n s o l i d a t i o n , i n which t h e e f f o r t s o f a l l p a r t i c i p a n t s a r e b e i n g coordinated, i s t o a t t a c k common problems and a l l i g n p a r a l l e l e f f o r t s . The US Army AVSCOM a t t h e P r o p u l s i o n D i r e c t o r a t e , t h e Tank-Automotive Command, and t h e B e l v o i r Research and Development Center; Southwest Research I n s t i t u t e ; t h e N a t i o n a l Aeronautics and Space A d m i n i s t r a t i o n ; and t h e Department of Energy a r e con- t r i b u t i n g t h e i r i n d i v i d u a l i n p u t s i n t o a combined program p l a n , a s i g n i f i c a n t accomplishment f o r an a c t i v i t y of t h i s magnitude.

Another r e l a t e d a c t i v i t y i s an e f f o r t t o a l l i g n t h e research a c t i v i t i e s i n t h e u n i v e r s i t y community more d i r e c t l y w i t h t h e needs o f t h e Compound Cycle Engine Program. W e a r e working w i t h t h e Army Research O f f i c e and a l s o w i t h t h e European Research O f f i c e t o t a r g e t more research toward our program needs.

Beyond these b a s i c research t h r u s t s , we have been a d v o c a t i n g t h e C C E pro- gram throughout t h e engine I n d u s t r y . There has been. an ongoing e f f o r t t o spark t h e i n t e r e s t o f i n d u s t r y i n our program, and a l s o t o e x p l o r e and extend t h e i r i n t e r e s t i n a t t a c k i n g s e v e r a l o t h e r b a r r i e r technologies, such as h i g h speed, h i g h pressure combustion; b r e a t h i n g and scavenging; h i g h pressure f u e l i n j e c - t i o n ; as w e l l as t h e t e c h n o l o g i e s a f f e c t i n g engine l i f e .

SUMMARY OF RESULTS The C C E program'goals a r e t o prepare t h e way f o r a 1990's c o r e engine demonstration o f t h e compound c y c l e by a t t a c k i n g t h e b a r r i e r t e c h n o l o g i e s . A major c o n t r a c t e d a c t i v i t y i s being conducted by t h e G a r r e t t T u r b i n e Engine Company. Other r e l a t e d e f f o r t s a r e b e i n g conducted w i t h i n t h e government, w i t h i n i n d u s t r y , and i n u n j v e r s i t i e s . C o l l e c t i v e l y , these a c t i v i t i e s w i l l p u t t h e A v i a t i o n Systems Command i n t h e b e s t p o s i t i o n p o s s i b l e t o s u c c e s s f u l l y accomplish t h e C C E demonstrator program.

The implementation o f a compound c y c l e engine i n a l i g h t h e l i c o p t e r can i n a 30 t o 40 percent r e d u c t i o n of m i s s i o n f u e l w e i g h t as compared t o a r e s u l t c o n v e n t i o n a l advanced technology gas t u r b i n e . I n a d d i t i o n , an i n c r e a s e i n range-payload p r o d u c t o f about 50 percent i s p r e d i c t e d . These enormous sav- i n g s , on one o f i t s most d i f f i c u l t a p p l i c a t i o n s , presents a p r o m i s i n g f u t u r e p r o p u l s i o n system a l t e r n a t i v e , n o t only f o r Army a v i a t i o n systems, b u t a l s o f o r numerous o t h e r a p p l i c a t i o n s .

REFERENCES 1. W i l s t e d , H.D., tlPreliminary Survey of P o s s i b l e Use o f t h e Compound A d i a b a t i c D i e s e l Engine f o r H e l i c o p t e r s , " SAE Paper 820432, Feb. 1982.

2. Castar, J.G., "Compound Cycle Engine f o r H e l i c o p t e r A p p l i c a t i o n - Executive Summary," NASA CR-175110, 1986.

3. Sammons, H. and C h a t t e r t o n , E., "Napier Nomad A i r c r a f t D i e s e l Engine," SAE Transactions, 63, 1955.

4. Vanco, M., Wintucky, W., and Niedzwiecki, R., "An Overview o f t h e Small Engine Component Technology (SECT) Studies," A I A A Paper 86-1542, June 1986.

5. Turk, M. and Zeiner, P., "Advanced Technology Payoffs f o r Future Rotorcraft, Commuter Aircraft, Cruise Missile, and APU Propulsion Systems," A I A A Paper 86-1545, J u n e 1986.

6. Larkin, T . , Staton, D . , and Mongia, H . , "Rotorcraft Propulsion f o r Year 2000 P1 us, I' AIAA Paper 86-1 543, J u n e 1986.

7.

Castor, J.G., "Compound Cycle Turbofan Engine," A I A A Paper 83-1338, J u n e ., 1983.

8. Blatchley, C.C. a n d Sioshansi, P., 'Surface Layer Activation Technique f o r Monitoring and I n Situ Wear Measurement o f Turbine Components," Journal o f Propulsion and Power, 2, (3) May-June, 1986.

TABLE I. - FINAL DESIGN C O N F I G U R A T I O N - 1000 HP E N G I N E 1-1 /2 SPOOL TURBOCOMPOUNDED C SHAFT POWER DIESEL

-

4 + C

M AIRFLOW Y ~~~

Diesel 1 Turbomachinery

V-6 Rad1a1/Ax) a1 C o n f i g u r a t i o n 7 6 24 Power o u t p u t , p e r c e n t 61 00 66 000/19 000 Speed, rpm a 0 . 3 3 BSFC, o v e r a l l lb/hp-hr - ------------ BMEP, p s i 7.5 10.6 Cornpresslon/pressure r a t i o 2 . 4 4 A i r f l o w , l b / s e c

_____---__---

5.7 S p e c i f i c power, hp/cu-in 0.43 S p e c i f i c weight, l b / h p (Wet i n s t a l l e d ) 0 . 4 A f t e r c o o l e r E f f e c t i v e n e s s a I n c l u d e s 5 p e r c e n t o l l c o o l e r / a f t e r c o o l e r f a n power p e n a l t y , b u t n o t a c c e s s o r i e s .

TABLE 11. - UNIFLOW SINGLE CYLINDER RIG OPERATING CONDITIONS Bui Id 1 2 3 Horsepower 50 100 1 5 0 Speed, rpm 2500 3250-3500 4000 Inlet air temp, O F 200 300 300 Manifold press, psia 36 60 90 Coolant temp, O F 200 200 200 Bulk oil temp, O F 200 200 200 BMEP, p s i 140 213 280 Max pressure, psi 1 5 5 0 2300 3000 Equivalence ratio .5 .5 .5 Compression ratio 14 12-10 10-8 TURBOMACH I NERY 0 LOW WEIGHT 0 HIGH POWER DENSITY DIESEL LOW FUEL CONSUMPTION '-COMB I N I NG GEARBOX U FIGURE 1.- SCHEMATIC OF COMPOUND CYCLE ENGINE.

AFTERCOOL I NG CRANK ANGLE COMPOUNDING COMPRESSOR TURBINE MAPS MAPS FIGURE 2.- FEASIBILITY STUDY OPTIONS.

ENGINE TYPE

-

4 STROKE

---

2 STROKE UNIFLOW

---

2 STROKE LOOP

/ ~ TURBOCOMPOUNDED

.25 .4 .5 .6 .7 .8 SPECIFIC WEIGHT. LB/HP FIGURE 3.- VARIATION OF BRAKE S P E C I F I C FUEL CONSUMP- T I O N (BSFC) WITH S P E C I F I C WEIGHT FOR VARIOUS SCAVENG- ING AND COMPOUNDING OPTIONS.

NUMBER O F CYLINDERS

----

--- l o

-

cr ALL I I I 5nnn

5 3.0

I a - f 2.5 Y e m 2.0 .90 .95 1.00 1.05 1.10 BORE TO STROKE R A T I O F I G U R E 4.- TRENDS LEADING TO F I N A L CCE DESIGN CONFIGURATION.

cLLaR-2rnS F I G U R E 5.- COMPOUND CYCLE ENGINE-CUTAWAY DRAWING OF FINAL DESIGN.

- c I n % ?

zc U CL W L 60 80 100 20 40 PERCENT RATED POWER FIGURE 6.- COMPOSITE PROFILE OF TYPICAL LIGHT ( 2 HOUR + 30 MINUTE FUEL HELICOPTER MISSION R E S E R V E ) .

u

---------_-

k CCE u W n

I I

v) 40 60 80 100 PERCENT RATED POWER FIGURE 7.- SPECIFIC FUEL CONSUMPTION VARIATION WITH PERCENT RATED POWER FOR 1000 HP ENGINES, DIFFERENCE

1 I N SFC

oc W g 2 v, 0 CL V 0 .1 .2 . 3 .4 .5 .6 DIFFERENCE I N SPECIFIC WEIGHT. LB/HP SPECIFIC WEIGHT DIFFERENCE SWCCE - SWGT = .19 LB/HP SPECIFIC FUEL CONSUMPTION S W ~ ~ ~ - SWGT DIFFERENCE = 1.15 (SFCGT - SFCCCE) SFC6-r - SFCCCE = .19 LB/HP-HR I N F I G U R E 8.- CROSSOVER TIME AS A FUNCTION OF DIFFERENCES CONSUMPTION.

ENGINE SPECIFIC WEIGHT AND SPECIFIC FUEL OR I G I NAL GOALS *BASED ON CCTE CYCLE TRADE STUDIES *TURBOMACHINERY - HIGHER PR *DIESEL - UNIFLOW. LOWER CR

B

0 TODAY *ALL METAL ENGINE NEW TECHNOLOGIES ADVANCED MATERIALS

2000 ,” IMPROVED ENERGY RECOVERY

. 2 . 2 . 3 .4 BSFC, LB/HP-HR FIGURE 9.- COMPOUND CYCLE ENGINE - PERFORMANCE TRENDS.

CYLINDER ENDURANCE CYCLE LINER 7, \ \

I

PI STON \ DOME 7 \% I \ CL I Y I J I

s I - I

R I N G I L SLIDING SURFACE TIME, HR FIGURE 10.- TYPICAL RING WEAR TRENDS BASED ON RADIONUCLIDES MEASUREMENT SYSTEM.

365 F n

I

MOOlFltP HOHMAY A d

&LNL TOTAL

STAUFFER STL MONSANTO PLUS 10 PERCENT TAP MCS 2189 FIGURE 11.- LUBRICANT AND MATERIALS R AND D RESULTS.

3. Recipient's Catalog No.

2. Government Accession No.

1. Report No. NASA TM-88879 USAAVSCOM-TR-86-C-37 5. Report Date 4. Title and Subtitle Compound Cycle Engine Program 1 L162209AH76 8. Performing Organization Report No.

7. Author(s) G.A. Bobula, W.T. Wintucky, and J.G. Castor E-3286 10. Work Unit No.

9. Performing Organization Name and Address 11. Contract or Grant No.

P r o p u l s i o n D i r e c t o r a t e , U.S. Army A v i a t i o n Research

and Technology A c t i v i t y - AVSCOM, Cleveland, Ohio

and NASA Lewis Research Center, Cleveland, Ohio 13. Type of Report and Period Covered 2. Sponsoring Agency Name and Address Technical Memorandum U.S. Army A v i a t i o n Systems Command, S t . Louis, 14. Sponsoring Agency Code Mo. 63120 and N a t i o n a l Aeronautics and Space A d m i n i s t r a t i o n , Washington, D.C. 20546 The Compound Cycle Engine (CCE) i s a h i g h l y turbocharged, power compounded power p l a n t which combines t h e l i g h t w e i g h t pressure r i s e c a p a b i l i t y o f a gas t u r b i n e w i t h t h e h i g h e f f i c i e n c y o f a d i e s e l . When o p t i m i z e d f o r a r o t o r c r a f t , t h e C C E w i l l reduce f u e l burned f o r a t y p i c a l 2 h r ( p l u s 30 min reserve) m i s s i o n by 30 t o 40 p e r c e n t when compared t o a conventional advanced technology gas t u r b i n e . The C C E can p r o v i d e a 50 percent increase i n range-payload product on t h i s m l s s i o n .

A program t o e s t a b l i s h t h e technology base f o r a Compound Cycle Engine i s presented. The goal o f t h i s program i s t o research and develop those t e c h n o l o - g i e s which a r e b a r r i e r s t o demonstrating a m u l t i c y l i n d e r d i e s e l core i n t h e e a r l y The major a c t i v i t y underway i s a three-phased c o n t r a c t w i t h t h e G a r r e t t 1990's.

Turbine Engine Company t o perform: (1) a l i g h t h e l i c o p t e r f e a s i b i l i t y study, ( 2 ) component technology development, and ( 3 ) l u b r i c a n t and m a t e r i a l research and development. Other r e l a t e d a c t i v i t i e s a r e a l s o presented.

7. Key Words (Suggested by Author@)) 18. Distribution Statement

Compound Cycle Engine; Diesel; U n c l a s s i f i e d - u n l i m i t e d

T u r b i n e / d i e s e l ; High performance STAR Category 07 d i e s e l ; L i g h t w e i g h t d i e s e l ; H e l i c o p t e r engine 20. Security Classif. (of this 22. Price' 9. Security Ciassif. (of this report) 'age) 21. No. of pages U n c l a s s i f i e d U n c l a s s i f i e d