Multi-Fuel Rotary Engine for General Aviation Aircraft

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m T 1 - F U E L ROTARY'ENG~NE FOR GENERAL AVIATION AIRCRMT

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Z i Authors: Charles Jones Director of Research, Rotary Combustion Engine Facility, Curtiss-Wright Corporatiofi David R. Ellis Advance Design and Systems Research, Pawnee Division, Cessna Aircraft Company Phillip R. Meng Project Snager, Lewis Research Center National Aeronautics 6 Space Administration ABSTRACT

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m o Design studies, conducted for NASA, of Advanced Multi-fuel w t w pra a w se

2: General Aviation and Commuter Aircraft Rotary Stratified

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i Charge Engines are summarized. Conceptual design studies - - b - were performed of an advanced and highly advanced engine sized \ m t3 to provide 186/250 shaft W/HP m d e r cruise conditions at 7 6 2 0 / W C : n t u 25,000 m/ft. altitude. Relevant engine development background W = a 4 u m u covering both prior and recent engine test resulzs of the direct a v1 u

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injected unthrottled Rotary engine technology, including the a : br V) k 4 IC Z capability to interchangeably operate on gasoline, diesel fuel, w - 8, kerosene, or aviation jet fuel, are presented and related to br I d a : W ffi

= 9 -growth predictions. Aircraft studies, using these resultant

r4 0; f H n 4 growth engines, define anticipated system effects of the per- E-l 4 2 3 0 fomance and power density inprovements for both single engine S : H w -14 and twin engine airplanes. The calculated results indicate cD P N 4 - S 0 superior system performance and 30-35% fuel econoiny improvement o d d a2 lC !

for the Rotary-engine airplanes as compared to equivalent airframe E W E & a s \ c w m d u o concept designs with current baseline engines.

The Research m d i i w - . . . . . .

and ~ e c h n o l o ~ ~ activities required to attain the projected en-

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gine performance levels are also discussed.

This paper is organized into three basic sections, The Introduction presents the NASA perspective and briefly covers how the Lewis Research Center interest in the Rotary first developed and then describes the initial steps which led to advanced aircraft design studies. The second major section discusses the Rotary stratified charge engine background and related developments from the Curtiss-Wright viewpoint and the third describes Cessna's application studies. The closure, presents an overview from the NASA co-author.

INTRODUCTION The Lewis Research Center of the National Aeronautics and Space Administration began working on intermittent-combus-

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tion (IC) propulsion systems f~ - qeneral aviation aircraft in

At that time, the prirnar:? :oncern was with the reduction 1973.

of exhaust emissions from these engines. The Environmental Protection Agency (EPA) had proposed exhaust emissions standards for hydrocarbon (HC), carbon monoxide (CC) and nitric The initial oxides ( N O , ) which were to take effect in 1979, NASA, FAA and Contractor efforts were directed toward the .

measurement and characterization of these emissions, Based o n the results, it soon became apparent that nearly all of the then-current gasoline recips would be in trouble if the standards were to be enforced. The next order of business, therefore, was to find methods to reduce the emissions and meet the proposed standards, This included consideration of alternative, completely-different engine types (such as

i . f rotaries) as well as trying t o improve the current-production recips.

As part of this effort, the Curtiss-Wright RC2-75 aircraft rotary engine (Figure 1) was tested to determine .

the exhaust emission levels characteristic of this type of engine. This low-compression, non-turbocharged engine was originally designed to operate on 8 0 / 8 7 octane aviation gasoline. The test results showed that the HC emissions ex- ceeded the emissions standard only by 39 percent, while both [ E the CO and NOx were within the proposed lcmits. The brake i specific fuel consumption (BSFC) at cruise conditions of 7 7

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percent power was 0 . 5 4 lb/BHP-hr (328g/Kw-hr). This BSFC was 15 to 20 percent higher than typical, then-current air- craft gasoline piston engines of comparable power. However, I .

the rotary's specific weight was 1 . 2 6 lb/HP ( 0 . 7 6 6 Kg/Kw), which was about 15 percent lower than typical, non-turbccharged aircraft piston engines.

The program emphasis was later redirected from emissions reduction to improved fuel economy, when it was learned that the proposed exhaust emisslons standards for light aircraft were to be withdrawn. A follow-on contract with Curtiss- Wright which incorporated a higher compression ratio and other minor modifications to thio engine reduced the cruise BSFC to 0 . 4 5 lb/BHP-hr (274g/Kw-hr), while meeting the former aircraft exhaust emission standards.

Encouraged by these favorable results, NASA has established a parallel, in-house rotary engine test program at the Lewis Research Center. Early results include the development of specialized diagnostic instrumentation for ' rotary combustion processes ( 1 ) and initial tests of a turbo- charged rotary engine ( 2 ) . In the latter tests, the measured minimum BSFC of an automotive-type rotary engine was improved from 0 . 5 3 lbs/BHP-hr (in stock form) to 0 . 4 5 lbs/BHP-hr (after minor modifications to accept turbocharging and a leaner fuel schedule). Thus, the NASA and C-W results tend to confirm one another while showing that the rotary can definitely be competitive, economy wise, with otherwise comparable reciprocating gasoline engines.

Meanwhile, parallel advances in stratified-charge rotary engine technology have been made by Curtiss-Wright in the design and development of a large (350 in /rotor) multi-fuel engine under contracts with t:12 United States NavyIMarine Corps. One-, two-, and four-rotor versions of this multi- fuel engine (Figures 2 and 3 ) have been successfully tested and have achieved the requi;ed design The minimum .BSFC in this program to date has been measured as 0 . 4 2 6 lbs/ BHP-hr. Its multi-fuel combustion system and several other features were used as baseline data for the Advanced Stratified Charge Rotary Atrcraft Engine Design Study, which was performed under a NASA contract with Curtiss-Wright, ( ) = Numbers in parentheses designate references at end of paper.

THE STRATIFIED CHARGE ROTARY ENGINE Over t h e l a s t s e v e r a l years a l l Rotary (Wankel-type) engine technology research a t Curtiss-;.lri,t,ht has been d i - rected a t s t r a t i f i e d charge d i r e c t chamber i n j e c t i o n . During t h i s period, successive improvements (3, 4) have r e s u l t e d Zn an e f f i c i e n t multi-fuel combustion configuration which i s incorporated i n t h e m i l i t a r y vehicle powerplant being de- veloped f o r t h e USMC.

The same basic technology, which was defined i n t h e smaller RC1-60 displacement (one r o t o r of 6 0 " ~ displacement) s i n g l e r o t o r research r i g , is applicable t o a wide range of engine s i z e s and engine applications, As a r e s u l t of t h e aforementioned design study contract f o r General Aviation and a subsequent Conanuter A i r c r a f t applications study sponsored by N A S A ( 5 ) , which were supplemented by C-W research t e s t i n g using both t h e RCl-60 and RC1-350, growth d i r e c t i o n s The key have been confirmed and concept engines defined.

elements f o r reduced f u e l consumption and higher power density of the advanced a i r c r a f t engines a r e increased BMEP a and operation a t very lean mixtures by turbocha~ging t o high engine airflow r a t e s .

ROTARY AIRCRAFT ENGINE BACKGROUND Briefly summarizing Curtiss-blright's a i r c r a f t Rotary engine background, i n i t i a l i n t e r e s t was directed t o propeller driven or h e l i c o p t e r m i l i t a r y applications where it was f e l t t h a t the RC Engine could compete with small gas turbines. I n . .

early studies conducted for NASA (6) the RC Engine plus fuel weight usually proved lighter 5-n all but very short missions.

In 1966 the RC2-90 was built and tested. This Stratified Charge air-cooled 300HP drone helicopter engine showed technical promise for fts designed application but was not developed beyond test stand operational status as a result of changes in military planning.

Acoustic measurements made on the test stand during the RC2-90 testing indicated a potential for extremely low noise level aircraft powerplants and led to a U.S. Navy sponsored tesc series with a carbureted RC2-60 engine in the Lockheed Q-Star aircraft. This aircraft (the first to be wholly dependent upon a Rotary Combustion Engine for flight) demonstrated hitherto unattained levels of quiet flight, in part due to the absence of valve and . : a l v e t-ain noise. A second quiet-airplane research contract followed in which the RC2-60 engine was installed in a Cessna Cardinal (Model 177) This test series also met the sound level goals airplane.

established by the U.S. Navy. A flight test in a Hughes . .

model TH-55 helicopter was also completed demowtrating im- provement in auto-rotation entry, reduced airframe vibrations, and maintenance accessibility.

The RC2-60 used in the flights mentioned had been d e ~ signed as an automotive-carbureted Rotary Engine with low overlap side inlet ports to achieve good fuel economy at low power road loads. Peripheral ports are preferred for high . .

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output a p p l i c a t i o n s such as a i r c r a f t engines, and the perfor- mance data achieved i n t h e f l i g h t t e s t s r e f l e c t e d the high end breathing l i m i t a t i o n s of t h e automotive s i d e ports. In addition, t h e b e l t e d p r o p e l l e r speed reductions were heaby and ine!:'ficient. The t e s t nevertheless, demonstratt: Potary .

inai?,s r e l i a b i l i t y , smoothness, l o w noise l e v e l s , and f l e x i b l e , e f f i c i e n t l i q u i d cooling. Rich f u e l l a i r r a t i o s were not required f o r cooling, and t h e r e w a s no speed o r descent l i m i t a t i o n f o r thermal s t r e s s e s from over-cooling.

The RC2-75 Engine (Figure 1) w a s designed a s a car- bureted General Aviation prototype, r e f l e c t i n g t h i s experience.

The configuration and approaches were reviewed with Piper, Cessna, Beech, the FAA, accessory s u p p l i e r s , foundries, and machining vendors, and t h e i r inputs r e f l e c t e d i n the design.

Significant f a c t o r s i n t h e choice of l i q u i d cooling over the l i g h t e r weight air-coo1ir.g were t h a t air-cooling did not give growth margin t o accommodate f u t u r e power output increases and it r e s u l t s i n higher p a r a s i t i c drag losses.

inches o v e r a l l and The RC2-75 i s 21.5 x 23.7 x 31.4 weighs 280 l b s . dry, 358 l b s . wet ready t o fly,.with heat exchangers. This model has completed 1500 t e s t hours, in- cluding 100 hours WOT and speeds t o 7000RPM, with a l l indica- t i o n s t h a t t h e basic configuration is sound, The engine was i n i t i a l l y designed f o r a 7 , 5 : 1 compression r a t i o with 80187 octane f u e l . Subsequent limited t e s t i n g with an 8 . 5 : l r a t i o ( 4 ) , with extrapolation t o higher BMEP's and s t i l l higher compression r a t i o fo; 100/130 f u e l , shows

e s s e n t i a l l y the same f u e l consumption as current General Aviation engines, although there is an advantage in t h a t liquid cooling does not require r i c h e r than optixnum mixture strengths i n c r i t i c a l cooling regimes as high power climb.

X n the e a r l y 70's. a t the point where it was clear t o Curtis.-Wright t h a t t h i 8 engine enjoyed several advantages over e x i s t i n g General Aviation engines, the f i r s t tremors of the energy crunch were beginning t o be f e l t .

As a r e s u l t , and as a response, our S t r a t i f i e d Charge rescdrch e f f o r t s were i n t e n s i f i e d and, i n 1973, our f i r s t breakthrough resulted i n s p e c i f i c f u e l consumption, on a range of fuels with diverse o c t m e r a t i n g s , b e t t e r than the gasoline engine. Faced with t h i s combination of events, it was decided t o defer f u l l de- velopment and FAA C e r t i f i c a t i o n of t h e RC2-75.

THE DIRECT INJECTErj STRATIFIED CKARGE ENGINE The d i r e c t injected S t r a t i f i e d Charge Rotary competes with the advanced d i e s e l and the s h a f t gas turbine as future The future of the small gas General Aviation powerplants.

turbine which s u f f e r s a BSFC penalty by scaling t o t h e . .

smaller s i z e s , w i l l be strongly influenced by breakthroughs i n ceramic technology, which w i l l have t o include significant s t r u c t u r a l gains t o insure a i r c r a f t l e v e l r e l i a b i l i t y . None- t h e l e s s , t h e s h a f t gas turbine may provide a viable General Aviation contender i n the long-range picture.

STRATIFIED CHARGE ROTARY RATIONALE - -- - The gasoline homogeneous charge Rotary engine advantages

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include: reduced size and weight; low vibration with as few as one or two rotors; higher speed capability by virtue of complete balance; high volumetric efficiency through porting w4 thout the limitations of valve dynamics ; non-reversibility of seal paths; sizing flexibility; mechanical simplicity; and moderate NSx emissions.

The direct injected Stratified Charge Rotary compared to the diesel reciprocating engine has the same advantages of the gasoline Rotary and, in addition, the advantages of lower NOx emissions, better cold-starting, capa~ility for operation on a wide range of fuels, and lower particulate emissions. The naturally-aspirated stratified Rotary state-of-the-art is competitive with the indirect-injected automotive diesel now and the turbocharged advanced version will challenge the ad- vanced direct-injected diesel.

The Rotary Stratified Charge Engine can provide signi- ficantly higher power density than either the current Diesel or the Stratified Charge Reciprocating Engine, Advantage over the latter results from a unique suitability of the Wankel ' engine geometry to direct injected stratified charge.

Briefly stated, stratified charge engines burn leaner (overall) fuel- air mixes, and achieve automotive diesel level fuel efficiencies as a function of the degree to which this lean- burning is realized. The direct i r jected unthrottled confi- guration is the only stratified charge engine variation which can operate as lean as a diesel. To do this throughout the

complete range a varying air velocity field must be induced to allow the injected fuel to be effectively "layered" (or, atratified) so that a combustible mixture of fuel and air is consistently developed at the spark plug, where the "triggering" combustion is initiated, and a significantly leaner mixture , ratio is maintained at all other points in the combustion chamber.

This essential flow/velocity gradient has to be generated in the incoming air charge of a reciprocating engine by some combination of swirl inlets or shrouded intake valves, special cylinder heads and piston shapes, etc,, all of which introduce pumping work which limit the possible fuel economy gain and also reduce the volumetric efficiency, which, in turn, In addition these recip- increases engine size and weight.

rocating engine "modifications" often show significant change with engine speed.

The moving rotor in a Rotary engine, regardless of the type of combustion employed, always moves the charge (air in stratified charge engines) past the stationary location of the spark plug and nozzles, as an inherent function of its .

geometry, and this develops the necessary flow distribution for stratification without flow friction losses or'reduced breathing capacity. Multi-fuel capability is retained by spark ignition and injection at the approximate combustion rate, again facilitated by the manner which the combustion chamber form varies with shaft rotation. The transfer velocity o£. O R "squish" past the trochoid "waist" can be determined by shape

of t h e r o t o r combustion pocket - a powerful development t o o l .

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The t r a i l i n g quench of t h e homogeneous charge engine i s hmdled by designing t h e pocket and nozzle spray t o avoid depositing f u e l a t t h e extreme t r a i l i n g s e c t i o n of t h e r o t o r combustion face. I n a d d i t i o n , flame propagation and h e a t re- ' l e a s e r a t e respond strongly t o these design parameters.

I n a d d i t i o n t o t h e general advantages of t h e Rotary l i s t e d e a r l i e r , t h e s t r a t i f i e d charge version o f f e r s another s i g n i f i c a n t p l u s with i t s broad f u e l tolerance over t h e f u l l speed and load range. This engine has shown e s s e n t i a l l y the same combustion performance on gasoline, jet engine f u e l (JP4 and JP5), d i e s e l f u e l , and methyl alcohol without a configura- t i o n change. Furthermore, while optimized s e t t i n g s may d i f f e r f o r the various f u e l s , t h e changes a r e minor and the engine runs well without change cf timings.

BACKGROUND

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Although C~irtiss-Wright designed t h e i r first Wankel-type Rotary Engine i n 1958 and ran t h i s engine i n e a r l y 1959, t h a t engine was s i g n i f i c a n t l y d i f f e r e n t from any other experimental versions i n existence a t t h a t time and deve1oprn;nts continued i n t o 1962 befnre a r e l i a b l e , durable and e f f i c i e n t baseline conventionally carbureted engine could be demonstrated.

The f i r s t S t r a t i f i e d Charge t r i a l s were made t h a t sirme year, d i r e c t e d towards a multi-fuel m i l i t a r y engine. During t h e mid-60's period, two prototype S t r a t i f i e d Charge Rotary Engines were designed, b u i l t and developed through the

operational test stand stage (19). The RC2-60U10 (Figure 5) C is a liquid-cooled two rotor vehicular engine in the 160 -200HP c l a m and the RC2-90 (Figure 4) an air cooled 310HP helicopter drone engine. 'Rae trochoid of these engine8 was the name size as the 1958-designed 60 cutic inch single rotor engine (the RC1-60), but the rotor width was hcreased SO percent for the RC2-90. Both engines proved their multi-fuel capabilities, but neither could match the fuel economy of our carbureted RC2-60U5 automat ive prototype engine of the same era, which was comparable to existing automotive engines (8).

Furthermore, the RC2-60U10 performed well (including cold- starting on JP-4, without aids, down co - 3 5 ' ~ ) only within any specific narrow speed band, wnereas the 90 cubic inch c m - bustion configuration which was subsequently developed to meet high power goals, showed low load deficiencies. In both cases, however, the engine showed sufficient technical promise for their specific applications, but as a result of changes in military planning, the fntended uses did not materialize and development was shelved, Although t h e m 1 efficiency equal to our homogeneous charge (gasoline) Rotaries was never demonstrated with these engines, the inherent compatibility of the Rotary geometry with unthrottled and direct chamber injected Stratified Charge combustion led Curtiss-Wright to believe that the potential for superior performance had to be there.

Following the fuel crises of 1973, R&D efforts were

resumed in an attempt to resolve whether or not this qerceived potential was real and, if so, if it c~ttld be realized with a practical machine. This time, feasibility trials were directed towards automotive application8 which meant not only wide range power and speed flexibility with goo* fuel economy,, Since hydro- but low and/or controllable missions as well.

carbon emissions at the very low speeds and powers typical of an automotive operating regime had proved the most difficult area for the homogeneous charge Rotary, new configurations were screened on the basis of road-load brake specific fuel con- sumption (BSFC) and raw brake specific hydrocarbons (BSHC).

The 1973 attempt to combine the best features cf RC2-6OU10 and final RC2-90 inf ection/ignition designs into a single con- figuration which could run well throughout the full range was successful and, for the' first time, achieved better fuel cons;unption, on a varie;y of fuels, than the gasoline car- bureted engine. This desigu improvement (3) led, in 1974, to a more flexible arrangement vhereby a separate pilot nozz;e, with relatively small fuel flow, is used to trigger cornbus- tion. This two-nozzle design, shown in Figure .6, uses a multi-hole main nozzle, located close to the trochoid sur- face to modulate fuel flow in response to power demand.

RC1-60 TESTING All of the basic stratified charge technology develop- ments were carried out with a single rotor rig engine of 60 cubic inches displacement. Since one "swept vo!umel' moves

through the engine with every shaft revol.ution, the engine size is comparable in output to an approximately two liter (2 x 60 in. ) four stroke reciprocating engine. This RC1-60 test engine (8) has served for a number of developments over the past 23 years.

The R6D activity through 1976 included test of a number of geometric variations of the basic dual injection canfigura- tion, primarily location of the main nozzles, spray pattern of the main nozzle in relation to rotor combustion pocket form, and basic rotor modifications. The design arrangement shown in Figure 6 proved best on an overall basis, but the reversed sense (effectively changing the sense of the rotor direction arrow) of this arrangement (ATC Pilot) showed promise because it could result in less direct spray impingement of the pilot jet on the rotor; however, the required rotor pocketjnozzle combinations compatible with this change were not sufficiently explored at that time to determine if the potential was realizable.

As of the completion of the 1976 Research Program, it had been demonstrated, using an RC1-60 rig engine, that an automotive sized module could provide: 1, specific fuel con- sumption equal to or better than an automotive Diesel, 2, pro- capability to burn a mising HC, CO and WOx emission levels, 3, wide range of fuels w i ~ h equal effectiveness, and 4, package size and weight competitive with the regenerated shaft turbine.

In addxtion, based on work done with a similar combustion

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process on the Texaco stratified charge engine ( 9 ) . the prognosis for low particulate emission levels (10) was favorable.

The fuel consumption of this engine in the part-load automotive engine operating regime is compared to current diesel autwaotive (pre-chamber) engines, including points for the normally aspirated and turbocharged Volkswagen Rabbit en- The "cast iron rotor housing" curve gine ( 7 ) , in Figure 7.

illustrates the SFC improvement attained with a moderate in- crease of trochoid temperature but the temperatures that were actually tested with a cast iron housing do not preclude the use of aluminum. The size comparison of a complete RC1-60 zrngine with accessories, against the comparable output six cylinder VW Diesel version is shown in Figure 8.

To compare advanced versus advanced, it has to be stated that these comparisons against automotive indirect injection in BSFC diesels do not s h o ~ the additional 10-15% improvement that a direct injected diesel could provide. As of this point, noise, power density, wide range and emission factors have favored the pre and swirl chamber fqr autqmotive, but future direct injected automotive diesels are a distinct possi- bility.

ALCOHOL FEASIBILITY Using a non-optimized (rotor pocket/main spray pattern) configuration that was tested at 10:l compression ratio (Figure 9) in 1979, the same engine build was briefly run on . .

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methanol.

The test was run a t power l e v e l s tesced on gasoline and d i e s e l f u e l . N o attempt w a s made t o change t h e configura- t i a n f o r alcohol and, accordingly, t h e i n j e c t i o n durations were s i g n i f i c a n t l y longer t o rur t h e same power points using nozzles sized f o r gasoline, d i e s e l , and j e t engine f u e l .

Nonetheless, t h e engine f i r e d c o n s i s t e n t l y and ran very smoothly.

The petroleum-derived f u e l s have close t o t h e same heating value on a mass b a s i s and roughly twice the heat con- t e n t of t h e alcohol on a volume b a s i s . Therefore, t h e r e s u l t s a r e presented (Figure 10) i n terms of s p e c i f i c heat input.

RC1-350 TESTING

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I n e a r l y 1977 t h e RC1-60 t e s t i n g program was deferred f o r Engineering a c t i v i t y on a l a r g e r 350 cubic inch module.

The 350 cubic inches per r o t o r was achieved by enlarging t h e trochoid by approximately two-thirds and widening r o t o r pro- The b a s i c configuration and system portions by 25 percent.

evaluation work conducted on the RC1-350 r i g engine, which l i k e t h e RC1-60 r i g engine has t e s t stand driven o i l and coolant The r i g test program, which has c o n e l a i e d very well pumps.

with complete multi-rotor d a t a , i s e s s e n t i a l l y independent of t h e number of r o t o r s i n t h e f i n a l machine and was i n i t i a l l y The RC4-350 i n support of a 4 r o t o r 1500HP engine (Figure 2 ) .

was subsequently r e d i r e c t e d i n 1980 t o a 2 r o t o r version (Figure 3 ) , a l s o under Advanced Development contract t o t h e USMC. The two r o t o r engine can produce 750HP n a t u r a l l y

a s p i r a t e d , with s i g n i f i c a n t growth c a p a b i l i t y when turbo- charged.

The same technoloay and b a s i c configurations developed i n t h e RC1-60 were used f o r the 350 cubic inch engine. The output t a r g e t s f o r t h e l a r g e r engine were established from t h e RC1-60 t e s t r e s u l t s .

A comparison of excerpted b a s i c performance r e s u l t s is of i n t e r e s t f o r d i r e c t l y applicable technology and because of t h e i l l u s t r a t i o n of s c a l i n g e f f e c t s t h a t it affords.

The l a r g e r module s i z e has t h e advantages o f : more a v a i l a b l e space t o accormnodate nozzle and spark plug v a r i a t i o n s within a given r o t o r housing; reduced r a t i o s of s e a l i n g l i n e , leakage a r e a , and heat t r a n s f e r surface t o charge volume; and a reduction of FMEP with s i z e . While carbureted "similar" engines over a displacement range of 500:l have shown t h a t both thermodynamic and mechanical performance can be predicted, t h i s was t h e first s i g n i f i c a n t s t r a t i f i e d charge s c a l i n g exercise.

Therefore, t h e key technical question at t h e o u t s e t of the l a r g e r s t r a t i f i e d charge engine program was-whether o r n o t s t r a t i f i e d charge would s c a l e thermodynamically. To f a c i l i t a t e a d i r e c t comparison, t h e c u r r e n t a v a i l a b l e data f o r t h e two engine s i z e s , both having t h e design configuration shown i n Figure 6 (BTC P i l o t ) and t h e same 8.5:l compression r a t i o , a r e compared on an Indicated b a s i s and equivelent (same s e a l s l i d i n g speed) RPM i n Figure 11. It can be seen t h a t . .

the RC1-350 and RC1-60 are very close at the lower IMEPs, whereas the 1-60 data shows lower ISFC (or better thermal f efficiency) at the higher loads, indicating further probable

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improvements for the l.?rger engine.

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Figure 12 shows both curves on a BSFC basis, reflecting the differences in friction, This plot shows that the RC1-350 enjoys a brake basis advantage over the RC1-60 because of the lower specific friction. The ATC pilot ("reversed") configuration curve additionally reflects a combustion The improved thermal efficiency of the ATC pilot advantage.

design is one of the potential gains over the automotive pro- totype data previously shown, which would obviously be included in an "updated" engine. In addition to lower friction, the 350 cubic inch engine enjoys the advantage of considerably L more development effort, particularly with support injection and ignition systems. Further, brake values for multi-rotor engines are slightly better than the single rotor rigs, even though the rig enjoys the benefit of slave accessories, since the FMEP of the multi-rotor engines are generally somewhat lower. The conclusion of these and several other comparisons, .however, is that performance of the engine scales well, al- though demonstrated to date only in the larger direction.

It should be added, however, that while scaling to smaller sizes has not been demonstrated by test of the same exact full-range configuration, feasibility of applying a direct injected stratified charge basic approach to engines in the 30 -45" 3 category has been proven elsewhere.

_IMPROVED COMBUSTION EFTICIEIJCY THROUGH TURBOCHARGING

1. Rationale - The s t r a t i f i e d charge engine a i r

u t i l i z a t i o n i s closer t o a d i e s e l than a conventional c a r - bureted engine because it can run well on t h e very lean mix- t u r e s which g.-ve b e s t combustion and thermal e f f i c i e n c y .

Predictions based on d a t a obtained from t e s t s of n a t u r a l l y a s p i r a t e d s t r a t i f i e d charge r o t a r y engines indicated t h a t turbocharging was not only a means of obtaining a higher power d e n s i t y , but offered p o t e n t i a l f o r f u r t h e r improvements i n f u e l economy.

The theory t h a t turbocharging could permit broader operation a t optimum combustion efficiency p o i n t s was pre- dicated on t h e c h a r a c t e r i s t i c ISFC vs. F/A curve shapes shown i n Figure 13, which is representative f o r both t h e RC1-60 and RC-350 engines. The bulk of t h e data is f o r t h e BTC p i l o t The preferred A T C p i l o t i s spotted i n f o r one configuration.

t e s t a t 1200RPM t o show t h e comparison. Since ISFC is in- versely proportional t o t h e r n a l efficiency, it can be seen t h a t t h e engine not only can run a t the extreme l e a n mixture r a t i o s of t h e d i e s e l , but does s o more e f f i c i e n t l y than a t higher F/A r a t i o s . Accordingly, based on analyses, t h e q u a l i t a t i v e e f f e c t s of turbocharging a r e shown on Figure 14.

A s output i s increased (higher BMCP), the mechanical e f f i c i e n c y a l s o improves and t h i s gain is a d d i t i v e t o t h e improvements i n thermal e f f i c i e n c y through leaner mixture s t r e n g t h s .

Based on t h i s trend it was predicted t h a t higher power BSFC could be reduced approximately 17% by d r i v i n g t h e BSFC

curve "hook1* out beyond the "normal" naturally aspirated range. "Normal" i s an a r b i t r a r y high l i m i t mixture strength (generally about ,055 F / A ) where increased fueling provides l i t t l e additional power increase. Like t h e d i e s e l , the rotary s t r a t i f i e d charge engine can a l s o "make smoke" f o r extreme over-fueling, but t h e smoke levels throughout the operating range appear t o be substantially lower, which is conceptually a t t r i b u t e d t o the absence of compression ignition combustion lag. Although both N A S A study General Aviation and Conamtter Aircraft engines (13) were based on t h i s approach, there was no t e s t data on s t r a t i f i e d charge Rotary engines The t o support the predictions a t the t i m e they were made.

succeeding sections describe how, since t h a t point, the bases f o r these predictions haw been confirmed,

F e a s i b i l i t y Testing Results 60 Cubic Inch Module -

2 .

Turbocharging t e s t s on the RC1-60 were conducted during l a t e 1980 with peripheral and side a i r intakes, both with the standard 8 . 5 : l compression r a t i o r o t o r s , I n addition, a re- duced compression r a t i o r o t o r was run t o explore wider range operation without exceeding the n a t u r a l l y aspirated engine peak combustion pressure and r o t o r housing temperature levels.

A basic turbocharger (Schwitzer S6) was selected to- gether with extra turbine casings (3LM) of different area r a t i o s , and an additional compressor (3LM). A l l engine builds u t i l i z e d t h e BTC p i l o t configuration r o t o r housing ( ~ i g u r e 3) with an available i n t e g r a l pocket (non-inserted) r o t o r from another engine which, while s u i t a b l e f o r a

generalized trend evaluation, did not represent an "optLsZted" system match of r o t o r combustion pocket, main nozzle clpray pattern and r o t o r housing. I n addition, the BTC p i l o t de- sign has since been shown, on t h e RC1-350 program, t o be less e f f i c i e n t than the ATC p i l o t variation. The t e s t s were run nonetheless because performance trends were expected t o be applicable t o l a t e r configurations. The tests, it should be added, were biased towards t h e higher speed regimes of i n t e r e s t f o r m i l i t a r y and a i r c r a f t applications.

Figure 15 shows t h a t , as additional a i r is supplied by turbocharging, bringing the F/A r a t i o a t 50HP from ,044 t o .025, ) remains a t t h e same minimum the ISFC (@ Thermal Efficiency value t h a t it had obtained a t 20HP. Accordingly, the 4000RPM BSFC curve, instead of "hooking up" i n t h e customary curve shape, continues t o decrease, showing an improvement of 19% a t an assumed limiting ,055 F/A n a t u r a l l y aspirated, both t e s t curves extrapolated t o t h i s point. The BSFC improvement re- lated t o b e s t BSFC n a t u r a l l y aspirated, a t approximately 314 .:N.S. power, i s 11% on t h e same basis.

.

This improvement i s consistent with t h e growth engine predictions.

Although t h e absolute BSFC values shown on Figure 15 do not represent current c a p a b i l i t i e s , there was good confidence t h a t t h e same general trends would hold f o r more developed configurations as well. Therefore, t h e basic theoretical contention t h a t t h e Indicated Specific Fuel Con- sumption (ISFC) would remain e s s e n t i a l l y a t i t s optimum value

for higher inputs, if the corresponding F/A ratio was main- tained, is considered to have been confirmed by the RCI-60 tests, The obvious next steps are to run state-of-the-art combustion configurations and to test at higher powers.

.

The comparable data for dual side ports indicated that the airflow restriction of the inherently late-opening side ports wae more detrimental than excess air through-flow with the higher overlap of the peripheral intake ports. From these specific tests, the peripheral port configurations per- formed better but one cannot conclude that this trend will hold with higher pressure ratio co~rpressors and/or later side port closing angles.

The testing at 6 . 0 : l compression ratio, shown compared to the 8.5:l C.R.

results in Figure 16, is particularly in- structive because, despite anticipated poorer performance when naturally aspirated, the data shows: 1. The improvement by turbocharging is relatively large, bringing the BSFC close turbocharged results for the higher compression ratios, The reduction in peak pressures and thermal loading 2.

is significant as can be inferred by the higher HP reached for the same monitored pressure levels.

Figure 17 shows these effects more clearly, plotted here for 5000RPM.

The test results clearly indicate that a lower compression ratio is desirable when turbocharging and further work is in order to establish reduction degree as a function of engine . , . - . . - parer rat ing and operat ing regime.

As would be expected for the mixture strengths tested, the large quantity of excess airflow keeps turbine entry temperatures in the same general moderate range as turbo- charged diesel8 .

W i l e all' of the structural and thermal loading inputs to evaluate durability of baeic engine com- ponents have not yet been thoroughly mapped, one positive indi- cation noted thus far is that the specific engine heat rejec- tion appears to reduce with the leaner operation.

This will further increase the current total heat rejection advantage over diesel engines. The implication of smaller heat exchanger volume is particularly important for military applications, where total system l a w specific volume is a key advantage.

Second Phase, Turbocharging Feasibility Testing,

3 5 0 " ~ Module - The 60"' sized hardware. of circa 1974-5

origins, did not reflect the performance refinements made dur- ing the early (1978-9) phases of the 350 cubic inch program.

Therefore, since the RC1-350 engine rig hardware incorporates more advanced state-of-the-art combustion technology than the RC1-60, a brief exploration with the RC1-350 hardware was run in late 1981.

RC-350 test hardware reflects hitgal program emphasis on demonstrating the interim power and fuel consumption per- formance targets. Improvements were generally the result of a number of cumulative evolutionary gains in better optimiza- tion of rotor pocket form and matching spray pattern, injection system and technique, configuration detail, ignition, structure, . .

etc. The one more "radical" change bas th; 'interchange of

- .

- - - ------ pilot and main nozzle locations to the ATC pilot design, first noted as a p~omising trend on the RC1-60 in 1976.

While the test did include these performince gain features, there was inrufficient lapsed ti- to procure a lower campreesion ratio rotor, as suggested by the earlier RC1-60 test series, and the tests were run with the rtandard 8 . 5 : l compression ratio. Accordingly, the first euntey was run to a peak combustion preseure limit approximately 25% higher than our maximum for naturally aspirated operation.

This resulted in reduced output, for the same pressure limits, than would have been the case with reduced compression ratio.

Figure 18 shows that the improvement of BSFC with out- put, as the lean mixture strength is maintained by turbo- charging, applies in the game manner to this engine as well.

However, this initial turbocharger match (modified Schwitzer 5 ~ ) provided nore induction air than desired, pimarily be- cause of higher than expected exhaust energy, including pulse recovery. The large gain in BSFC when run without intercool- ing is partiallydueto a liore optimum mixture strength, in this case slightly richer, as well as irnpro7red combustion efficiency as a function of the higher temperatures.

Nan-intercooled data was not run for the full load and speed range. Figure 19 shows intercooled BSFC vs BMEP at various speeds. The slope of the curves indicates that further BSFC improvements can be anticipated at higher loads,

I While f u r t h e r work i s c l e a r l y i n order, thr r e r u l t r a r e supportive of t h e advanced engine growth predictions.

ADVANCED STRATIFIED CHARGE ROTARY ENGINES

1. Technology - Based on t h e described current Rotary

S t r a t i f i e d Charge technology, c o n ~ i d e r i n g additional technology judged t o be r e a l i z a b l e by mid-decade t o allow production in- clusion e a r l y next decade, several scaled engines have been defined and analyzed.

The supporting p a r a l l e l technology gains arsmed for the a i r c r a f t engine are covered i n more d e t a i l i n Reference 11, but t h e most important of these a r e high rpeed electronic d i e s e l l e v e l f u e l i n j e c t i o n , seal/coating materials, and im- p r ~ v e d strength aluminlrm alloys. Further gains i n turbocharging technology w i l l prove rewarding f o r a i r c r a f t a l t i t u d e perfor- mance.

High Speed Injection - The developing f i e l d of small

high speed d i e s e l automotive engines has provided the re- quired impetus f o r a c t i v e electronic f u e l injection develop- ment by a number of major manufacturers i n t h e f i e l d , Experi- mental and limited production <for a m i l i t a r y (IOOORPM) applica- tion) high speed u n i t s a r e already operational and there a r e many indications t o believe t h a t additional developments t o reduce cost and improve r e l i a b i l i t y w i l l be forthcoming.

Seal Durability - Developments of durable apex s e a l

materials and compatible coatings f o r higher outputs a l s o ehow a favorable prognosis, but v e r i f i c a t i o n s and f i n a l choices

can only be established on the basis of engine testing.

The early (pre-1974) problems of Rotary production automotive engines, resolved by the successful experience of Toyo Kogyo (12, 131, were driven by a different act of requirements: The need to have an apex seal of material rtrong enough to incorporate an "adjustable" triangular corner for city driving cycle fuel economy, and, with a compatible coating, provide engine life comparable i.c piston automotive engines at an acceptable production cost. This was a difficult task, taken in total, even with consideration ;hat the automotive service regime is relatively light duty.

As early as 1961 Curtiss-Wright had tested a tungsten carbidelcobalt detonation gun applied trochoid coatirrg cornpati- ble with cast iron e>ex reals that met a11 of the technical requirements but was prohibitively expencive for automotive use. However, this same system could be used in the aircraft and military engine market place. Versions of the same coat- ing, applied by the lower cost plasma spray process, have . since been successfully used in small air-cooled snowmobile engines produced by OMC (14) and in initial pr6-production runs of an air-cooled multi-purpose engine by S W A R O (15j, both tested at relatively high outputs and speeds. I n addi- tion, plasma-sprayed Ferro-Tic, tested experimentally at Curtiss-Wright (16) had shown promise. of even lower wear rates, with both materials and application method attractive economically.

Carbide-based coatings, in combination with a promiring apex s u l material now being teeted the military engine progrua may p r w e ratisfactory at the higher BMEP level8 anticipated for growth military/aircraft engines. If this does not prove to be the case there are a qtmrber of other cam-' bination8 which have shown screening rig indication# of lower wear rates, not needed at current power levels, which caa be tested ar well as a nunber of newly developed promistng c m d i - dates which await screening. Therefore, the probability o f a satisfactory solution i~ judged to be high.

Finally, the material cmpat.ibility search for apex seals and trochotd wear surfaces that have growth cepacity and good economics may receive help from another direction: automobile racing.

Toyo Kogyo , having developed m eminently

successful seal/coating configuration for the engine of their production RX-7, also support a racing vtrsion which develops close to 300 horsepower (naturally arpivated) at speeds in ?he 10,000RPK range.

A t t h e s ~ high speeds a one piece seal is acceptable, as demonstrated by the excellent high speed fuel consumption of this engine, which uses a relatively strong reinforced graphite single piece seal compatible with tkie cSromium plated trochoid bore. Other licensees have run at BMEPs considerably in exceed of our growth engine ratings, admittedly withovt demonstrating the required long-term durability at there peak outputs, but the directions provide relevant inputs.

. .

Thermal Insulation f o r Reduced Coolant and O i l Heat

Rejection - The use of cermets a s trochoid coatings may pro-

vide improved wear r e s i s t a n c e p l u s thermal i n s u l a t i o n . The l a t t e r could prove p a r t i c u l a r l y s i w i f i c a n t for ultra-high speed engines where t h e apex seals can be supported by a hydrodynamic gas f i l m o r e l s e be r e t r a c t e d s l i g h t l y from t h e t r o c i o i d surface (17). Thus, without a need t o provide o i l lubrication, t h e allowable surface temperature l i m i t s could be increased t o whatever limits t h e material could withstand.

The reciprocating p i s t o n engine, with a r e v e r s a l of a p i s t o n d i r e c t i o n a t TDC and BDC p o s i t i o n s , is l e s s amenable t o a non-

- lubricated, r i n g l e s s design or hydrody~..amic f i l m gas sealing

and is thus more dependent on t h e material choice, such a s ceramic r i n g s on ceramic bores, f o r "adiabatict' o r extreme iow heat r e j ection engines.

The t o t a l (water plus o i l ) heat r e j e c t i o n of t h e d i r e c t injected s t r a t i f i e d charge engine when n a t u r a l l y aspirated is roughly t h e same as a gasoline engine, which makes it l e s s than t h e d i e s e l . When turbocharged, calculations and l i m i t e d t e s t data i 3 d i c a t e t h a t t h e s p e c i f i c heat r e j e c t i o n w i l l drop s i g n i f i c a n t l y even without use of techniques t o i-nsulate coolant walls and/or run a t higher temperatures, This i s r a t i o n a l since the improved thermal efficiency removes more of the input f u e l energy as s h a f t work while t h e heat r e j e c t e d t o the coolant does not change appreciably s i n c e i n t e r n a l ( ~ ~ g i n e casing) pressures and temperatures remain c l o s e r t o spark i g n i t i o n ranges than t o compression-ignition engine l e v e l s .

Nigher Strength Alloys - The improved aluminum alloys

that would be preferred choices for aircraft engine housing use, such as AMS-4229 (17), are progressing along the com- mercial development path and is now being col~lercially cast for aircraft quality components. In fact, C-W has recently poured AMS 4229 rotor housings for the 350'" engines end the While high speed engines demand castings look promising.

light strong rotors, modular iron rotors are acceptable for speeds proposed and there are a number of promising alterna- tives (such as advances in materials. powder metal and sinter- for ultra-high speed ing technology, welded constructions) engines.

Turbochargers - The turbocharger assumptions used to

predict aircraft engine performance were relatively cons, arva- tive. However, the fuel economy gains were limited by the turbocharger pressure ratios expected to obtain over the next several years. For 25,300 feet cruise performance, the maximum practical (i.e., good efficiency and wide range surge-free ratio was assumed to be between five and .. operation) pressure . .

six, which limits jea level pressure ratios to *around 2:1.

If anticipated turbocharging improvements do not materialize, an obvious alternative is to series turbocharge for high al- titude performance,

2. Specific Engine Choices for General Aviation -

The NASA Advanced Rotary Combustion Aircraft Engine Design Study objectives included a 75% cruise BSFC of . 3 8 lb/HP-hr, or better, at 250HP and 25,000 feet minimum altitude. Two

I liquid-cooled engines were selected (11) to meet the program I

I i objectives. Both were twin rotor machines, representing a

i

compromise between minimum weight, favored by more rotors, f and low cost, generally pointing to lees rotors. The larger of the two, an RC2-47, represents a less ambitious technology projection, noted as "Advanced", while the smaller machine, the RC2-32, would require a larger development effort to meet the same timing goals and is designated "Highly Advanced".

The key difference between the two is that the "Highly Ad- vanced" engines include a further increase in BMEP and speeds, the latter possibly requiring reduced contact force or retract- ing apex seals, and moLe emphasis on advanced weight reduction materials and manufacturing techniques, The "Highly Advanced" engine assumes use of a variable area turbine in the turbo- charger system but there is some question of whether this will be necessary to achieve predicted performance levels, The specific fuel consumption prediction for the RC2-32 is shown in Figure 20, The RC2-32 BMEP is 2llpsi at the 320HP take-off power and 198psi at 250HP cruise. The engine RPM is 9420 which, on an equal RC-60 apex seal sliding velocity basis, is equivalent to 7050WM, which has been run in the RC-60 trochoid sizea en- gines (RC-60, 75 and 90). The cruise RPM is 7850 which is equivalent to 5875 fox the RC-60 and derivative geometries.

Corresponding values for the RC2-47 are 19lpsi BMEP at 320HP take-off, 179psi at cruise, 7030 T.O. RPM (6000 "equivalent") and 5860RPM cruise RPM (5000 "equivalent"). The rotor width

I . .

proportions for both engines (width/eccentricity ratio) are i the same as the RC2-75 aircraft engine prototype and the i 350" military engines.

The comparison of cruise SFC and overall dimensions with the selected current reciprocating baseline engine, the RSIO-550 is shown in Table 1.

The RC2-32 installation longitudinal layout is shown in Figure 21. To achieve a small frontal area (a 16 inch square), most of the accessories are mounted at the anti- propeller end and the turbocharger spaced even farther aft.

For improved packaging and to minimize the number of drives and associated gearing, the coolant and oil pumps (scavenge and pressure) are coaxial mounted on the same shaft. Drives are included for an air-conditioning compressor, vacuum pump and hydraulic pump, but the weights given include only the accessories needed to start and run the engine, While only one engine size is shown for each of the two levels of technology, a ntrmber of other engine possibilities, all representing the same degree of "advancement" were defined . .

and tested via the Cessna Aircraft Company analytical model before the choices shown were made, Tn either category, im- proved BSFC can be realized, for the same IMEP level, by either reducing the engine speed, going to a larger displace- ment single rotor engine, or both. In all cases analyzed, however, the Cessna aircraft analysis programs indicated more sensitivity to weight and size than to the degree of SFC . .

change which had been calculated.

To put the projections in perspective, while the BMEP's aas\mtcd are not high relative to turbocharged diesel engines and are on the order of only about a third higher than Curtise-Wright has run in developed Rotary homogeneous - charge engines which have demonstrated durability at sus- I tained high output, they have not been demonstrated in a stratified charge Rotary e n ~ i n e as of this point. Turbo- charged homogeneous charge Rotary engines have been perfor- i mance tested to these levels and, separately, at the projected f i engine speeds, but long-term durability testing at high out- i puts has been limited. Therefore, it is recognized that the resulting best compromise to attain projected goals may not be exactly those shown even though the direction is believed correct. The "best compromises" cannot be evaluated on paper but requires testing to successively increasing BMEP and speed levels, with each new plateau yielding both new inputs

and new solutions - this of course, is the normal engine

technology advancement process, ENGINEIAIRFRAME IFIZGRATION STUDIED PERFORMED BY CESSNA AIRCRAFT This section deals with the integration of the advanced Perfox- Rotary Combustion Engines with typical airframes, mance, cost, and installation factors are compared with those for a conventional aircraft engine, An outline of the design mission and performance constraints is given, followed by a discussion of the method of comparison and the results obtained.

MISSIONS AND PERFORMANCE CONSTRAIAWS The design mis~ion is transportation oriented and con- sists of a maximum rate climb to 7620 m/25,000 ft. followed by a constant altitude cruise segment at rated cruise power over a prescribed distance. Fuel for 45 minutes of operation .

at cruise power is reserved. In addition to basic payload and range requirements, minirnum levels of performance must be met in other areas as indicated in the following listing: SINGLE-ENGIm TWIN-ENGINE 635 kg11400 lb

PAYLOAD - occupants 544 kg11200 Ib

and baggage

STAGE LENGTH - with IFR

1296 km/700 rm fuel reserves

CRUISE SPEED - minimum

3700 hn/hr/200 kt 417 km/hr/225 kt CRUISE ALTITUIIE 7620 m/25,000 ft 7620 m/25,000 ft

TIME TO CLIMB - maximum 30 min 30 min

RATE OF CLIMB at 152 m/min/ 25,000 ft., minimum 500 ft/min SINGLE ENGINE RATE OF CLIMB at 5000 ft ., min.

. TAKEOFF DISTANCE AT SEA 762 m/250Q ft

: . LEVEL - max- mum

STALL SPEED, maximum 113 km/hr/61 kt I i I Ths missions chosen are demanding ones which cannot be accomplished in total by presently available airplanes; the other performance constraints assure that contemporary standards of utility are attained.

THE SIZING PROCESS With mission and performance constraints defined, a com- puterized sizing program is used to determine the "best" air- frame for each engine. In the context of this study, "best" is equated with lowest mission fuel, direct operating cost, and acquisition cost.

The sizing program is covered in detail in Reference 18, For the purposes of this discussion, it is sufficient to know that the program performs two basic calculations, the first determining the weight required to meet the payload/range re- quirement, the second giving pc?rformance at a given weight.

A carpet plot format conveniently displays the computed per- formance as a function of weight and any two design variables such as wing area and aspect ratio; performance constraints are overlaid on the carpet, defining areas where all require- ments are met as shown in Figure 22, If the solution space defined by the constraints is well defined, the normal choice will be the smallest, lightest airframe since that will be the lowest cost case, Sometimes few constraints appear on the carpet, and engineering judge- ment concerning such things as practical aspect ratios and efficiency at off-design operating points must enter into the choise.

The above process was used to define "baseline" single- and twin-engine airplanes powered by a conventional piston engine, and resized versions taking advantage of the smaller . .

size and weight and lower fuel consumption of the Rotary Corn- bustion Engines.

BASELINE AIRPLANES In general, the baseline airplanes may be considered to be refined versions of typical 1981 technology products, using conventional light metal structure joined by riveting and bonding. This approach was taken in preference to one calling for advanced composite materials or unconventional aerodynamic layouts, for example, in order to take advantage of well documented design procedures and weight drag, and cost data bases, and to focus attention on powerplane advances rather than airframe features.

The single engine baseline airplane is a high wing tractor monoplane seating six, with a cabin pressurized to 31 kpa/4.5psi differential so as to obtain a cabin altitude of 3048 m/10,000 ft, when flying at 7620 m/25,000 ft. The wing features a long-span single-slotted flap to meet the current FAR requirement that stalling speed be less than 113 km/hr/dl kt; a combination of small "feeler aileronst' and slot-lip spoilers are employed for roll control. Takeoff gross weight (arrived at by the sizing process described earlier) is 2023 kg/4600 lb, while empty weight is 1241 kg/ 2736 lb.

Similarly, the twin-engine baseline airplane features a conventional low-win2 tractor layout and eight-place seating in a pressurized callin (same 31 kpa/4,5psi differential), Empty weight is 2008 kg/4428 lb. and takeoff gross weight is 3107 lg/6850 lb.

The powerplant for both baseline airplanes is the

Teledyne Continental Motors TSIO-550, a conventional six- cylinder. horizontally-opposed, aircooled engine developing i 254 kw/340BHP at 2700RPM for takeoff.

A cruise rating of [ - I 186 kw/250BHP at 2300RPN is used for this study; specific i * ' fuel consumption at cruise power is 271 g/kw-hr/0.446 lb/HP- hr. Installed powerplant weight is 320 kg/706 lb for a single engine.

. Three view drawings of the baseline airplanes are shown in Figures 23 and 24.

ROTARY-POWERED AIRPLANES i The single-engine design with the rotary-combustion en-

!

i i gine is shown in Figure 25, For considerations of passenger I ; comfort, the size of the cabin cannot be appreciably altered I t from that of the baseline. For structural and aerodynamic reasons, the wing cannot be moved very far fore or aft, so the f lighter rotary must be located well forward compared to the 'i i baseline engine in order to keep the center of gravity in a -i the right position. This has the advantage of allowing a . baggage compartment to be located ahead of the cabin, increas- I f ing allowable baggage volume and loading flexibility .

The

i

.wing is significantly smaller than that of the baseline due to the reduction in gross weight brought about by the favor- able interaction of lower engine weight and less fuel required to accomplish the specified mission, The engine installation concept is shown in Figure 26 for the RC2-32 version (the RC2-47 would be essentially the same). The small size sf the powerplant allows it to fit

easily into the engine compartment since. the cross-oection is set mainly by cabin dimensions, Accessibility should be very good relative to the bareline. The radiator, which - is large and thin for minimum cooling drag, fits comfortably f I alongside the engine. Induction and cooling air are brought .

f in thtough NACA flush ecoops on the sides of the cowling.

Installed powerplant weight is 221 kg/487 lb for the RC2-47 and 178 kg/393 lb for the RC2-32, The twin-engine configuration using the rotary engines is shown in Figure 27. Radiators are housed in leading edge extensions on the inboard wing panels similar to the scheme i

- !

used on the British DeHavilland Mosquito of World War 11.

, As indicated also in the installation concept in Figure 28, j i i the nacelles are much smaller in cross-section than those of i f the baseline, thereby reducing both drag and destabilizing

f

pitching moments, As with the single, substantial reductions in wing size and gross weight are achieved,

' f

1 COMPARATIVE RESILTS i A detailed comparison of the baseline and rotary-powered . .

t airplanes is possible by rdference to Table 2 which lists t weights, dimensions, and performance parameters. The rotary-engined machines are clearly superior to t t . e baseline airplanes in every respect, with the following items being especially noteworthy:

-

27% to 33% reduction in required mission fuel

-

12% to 17% reduction in direct operating cost&* L .

* Calculations based upon methods and data of Refertnce 18,

-

9% to 16% reduction in acquiritim costa*

- Subrtmtial gain8 in cruirirrg rpeed, cl- perfor-

mance and takeoff dirtance Paramtric studier reported in Referaice 18 rhaj that the above finding8 are relatively lnrenritive to mirrion de- finition. In addition, the arsurnption of zero cooling drag for the rotary-powered airplanes has little influence on any of the results except cruise speed, which would decrease about 10 kt if the drag were increased to the level of the air-cooled baseline.

Other areas in which the rotary-engined airplanes would be expected to show advantages over the baseline are:

- Multi-fuel capability

- Inherently low vibration levels

-

Better control of engine temperature, particul.ar1y for low power descents

- Effective, carbon-monoxide free cabin heating

-

Possible use o f engine coolant for heating of inlets

-

Lower flyover noise due to lower oropeller speed at maxi~mrm power (2400 vs 2700RPM) .

COIJCLUDING REMARKS In this study, single-and twin-engine airplanes were de- signed to suit the features of two aircraft rotary combustion

engines - the "advanced technology" RC2-47 and the "highly

advanced technology" RC2-32 - and the results were compared

*Calculations based upon methods and data of Reference 18.

with rimilar baseline airplanes u i n g a conventional horizontally oppo~ed air cooled engine, the TCM TSIO-550.

The baseline airplanes are very capable machines in their own right, meeting or exceeding a11 mission require- .

ments, and offering transportation capability not prermtly available fn production piston-engine aircraft. However, the rotary-engined airplanes are clearly superior in every performance and cost category due to lower weight and fuel consumption. Other factors, including multi-fuel capability, noise vibration, and installation factors also favor the rotary combustion powerplant.

From an airframe manufacturer's standpoint, the rotary engines offer an attractive alternative to presently available powerplants.

COMMUTER AIRCRAFT ENGINE Under a separate subsequent NASA contract (PAS3-22140).

Curtiss-Wright was requested to apply the Rotary Engine "Highly Advanced" technology approach to the Conmuter Aircraft , .: requirements at 800 to 2500HP. The engine needs.for future commuter aircraft are expected to emphasize reduced operating costs that can accrue to engines of small size, lighr weight While aircraft system and with better f u e l c:onsumption.

studies were not part .-rf this contract effort, NASA has data for turboprop azii diesel powerplants to complete trade-off and comparative studies.

In view of the larger power class, turbo-compounding

--- -- war conridered, without bmafit of ~ ~ ~ p o r t i n g rtudier to evaluate cart-rffectivmers, and more emphauia war placed on multi-rotor nyinea for p a t e r weight saving.

The 800 and 2500HP exaapler, again each war one of a a&+ of porribilitier, a m dercribed geomettica~ly in Tabla S I X aad t h ~ operating rang8 data rramrrrized in Tables I V and V.

Aa C M be reen from Table8 IV and V, the power 8ai.n for turbo-compounding ir relatively small, shown a8 a function of puwer and speed in Figure 29. The turbo-compounding fuel i eonsumption (calculated to mrealiotic precirion to ohw !

camparisoar) gain, however, ir more rignif icant and can be

i

i areeoord, with some indirect manipulattonu against the w e Q h t i This is ba- penalty, by use of weight chart8 which follow.

I

% c a w e the turbocharging (particularly with the excesr air used for *roved t h e m 1 efficiency) has used most of the

1 i

available exhaust energy. The recent RCl-350 turbocharging tests, which rhawed very high exhaust energy, m y challenge these assumptione.

Similar to earlier mention relative to the General . : Aviation engines, these engines would also gain. in BSFC for a lower F/A ratio a8 a function of Lmprwed turbochargers.

In the case of the Canmutor Aircraft, where the cruise al- titude is 15,000 instead of 25,000 feet, the justification Jor not assuming more boost was only by reason of direct com- parison with General Aviation engines rather than the limiting assumption of 1990 turbocharger status technology.

. .

. . . .

The 800HP RC4-41 i n r t a l l a t i a n l q f t u d l n a l vim i r ohown in Figure 30 and the 2500HP RC6-122 i n Figuro 31.

The d i a p l a c ~ t vr T.0, power i r rhown i n Figure 32 and t h e engine dimenrionr, lesr gearbox, i n Figure 33 with correrponding weigirtr plotted i n Figure 34. E r t h a t e d ad- vanced gearbox weigntr and length are rhown an Figure 35.

CLOSURE

--

The two engine General Aviation derignr of different technology levels rhaw very promiring potential as advanced a i r c r a f t enginee. NASA is i n the proceos of negotiating a contract with Curtiss-Wright Corporation t o produce and demon- r t r a t e the keg technologies required f o r advanced rotary en- giner which could be comercially introduced i n the 1990'r t i m e frame. The contract w i l l result i n the design and fabrication of a single rotor technology crtablanent t e a t mgine which w i l l be used t o determine the basic engine pcr- fonaance and t o evaluate the varioue :ethnologies needed f o r the advanced engine design. After i n i t i a l tesrtng of the .. f i r s t engine, a second engine w i l l , be b u i l t fc,e additional testing in-house a t NASA Lewis Research Center. l'ha research and technology program w i l l take approximately three and one- half years and hopefully w i l l reeult i n technology for a hi.gh1y advancad stratified-charge engine which w i l l operate efficiently on a l l available aviation fuels and w i l l be smaller, lighter and/or more econolrical than currently-avail- able choices,

REFERENCES 1. Shoek, H.J. Rice, W.J. and lieng, P.R.: "Experi- mental Analysis of IMEP in a Rotary Combustion Engine", Paper 810150 presented at the SAE Automotive Engineering Con- gress, Cobo Hall, Detroit, February 1981.

2. Meng, P.R., R;.ce, W.J., Shock, H.J. and Pringle, D.P.: "Preliminary Results on Perfornrance Testing of a Turbocharged Rotary Combustion Engine", Paper 820352 presented at the SAE International Congress & Exposition, Detroit, February 1982 .

3. Charles Joaes, Harold D. Lamping, David M. Myers, Robert W. Loyd, "An Update of the Direct Injected Stratified Charge Rotary Combustion Engine Developments at Curtiss- Wright". SAE Transactions 1977, Vol. 86, Paper No. 770044.

4. Charles Jones, "An Update of Applicable Automotive Engine Rotary Stratified Charge Developments", SAE Paper No.

820347, February 1982.

5. NASA Contracts, Nos. NAS3-21285 and NAS3-22140.

6. C.H. Hurkamp, W.H. Johnston, and J.H. Wilson, "Technology Assessment of Advanced General Aviation Aircraft1', Report Nos. NAS CR-114338 and NASA CR-114339, prepared under Contract No, NASA2-5972 by Lockheed-Georgia Company for NASA, June 1971, 7. B. Wiedemann and P. Hofbauer, "Data Base for Light- weight Automotive Diesel Power Plants", SAE Paper No, 780634, June 1978.

-- - - - - - - - - - - * - - - 8. Charles Jones, "A Survey of Curtiss-Wright's 1958-1971 Rotating Combustion Engine Technological Deve-

t

i lopments". Paper No. 720468, presented at the National Automobile Engineering Meeting, Detro:.t, Michigan, b y 1972.

9. J .M. Lewis, W .T. Tierney, "United Parcel Service Applies Texaco Stratified Charge Engine Technology to Power Parcel Delivery Pans-Progress Report", SAE Paper No. 801429.

10. Richard N. Wares, "Performance Evaluation of a Stratified Charge Engine Powered Automobile", U.S. Department t of Energy, September 23, 1980.

11. P. Badgley, M. Berkowitz, C. Jones, D, Myers, E.

i E Nomood, and W.B. Pratt, "Advanced Stratified Charge Rotary i Aircraft Engine Design Study", Final Report, NASA CR-165398, t 1981.

b

12. K. Shinamamura and T, Tadokoro, "Fuel Economy

I

Improvement: of Rotary Engine by Using Catalyst System".

Paper No. 810277, presented at SAE Congress and Exposition,

1 f

i Detroit, February 1981.

13. K. Yamamoto and T. firoki, "Development on Exhaust Emissions and Fuel Economy 'of the Rotary Engine at Toyo Kogyo". Paper No. 780417 presented at SAE Car-gress and Exposition, Detroit, February 1978.

14. H.M. Ward, M.J. Griffith, G.E. Miller, and D.K, Stephenson, "Outboard Marine Corp's Production Rotary Combus- tion Snowmobile Engine", SAE Paper 110. 7301.19, presented at the international Automotive Engineering Congress, Detroit, Michigan, 1973.

Andrei Adam, "Syvaro's SP-440 Air Cooled, Rotary- 15.

Trochoidal Engine", SAE Paper No. 800974, September 1980.

16. H.D. Lamping, M.W. Galliers, and S.W. Wolosin, "Rotary Combustion Engine Trochoid Coatings and Seals", SAE Paper No. 741043, presented at SAE Automobile Engineering Meeting, October 1974.

17. C. Jones and M. Berkowitz, "Multi-fuel Rotary Air- craft Engine", Paper No. AIAA-80-1237, presented at AIAAISAEI ASME Joint Propulsion Conference, June 1980.

18. Huggins, G.L. and Ellis, D , R , , "Advanced General Aviation Comparative Engine/Airframe Integration Study", NASA CR-165565, 1981.

"Curtiss-Wright's 19. Charles Jones and Harold Lamping, Development Status of the Stratified Charge Rotating Combus- tion Engine". SAE Transactions 1971, Vol. 80, Paper No.

710582.

RC2-75 AIRCRAFT ENGqNE PROTOTYPE

RC4-350 Engine Ficure 2

CURTISS-%'RIGHT ROTARY COMBUSTION ENGINE Gtratlfied Charge Model RC2-350 F i p u r e 3

o . p , - . - # r - . -

C.. ! ' ... . 'S OF ~ 0 9 ~ QUALITY

WEIGHT . . . . 285 LB.*

WIDTH . . . . 25 IN.

LENGTH . . . . 34 I N .

HEIGHT . . .19-1/2 I N .

* LESS STARTER, SF?ARATE 01 L C03LER/SUMP A Figure 4 i t

RC2-60U 10 LIQUID-COOLED STRATIFIED ENGINE (1 965) WEIGHT. . . . 2 9 4 L B .

WIDTH . . . . 2 4 I N .

LENGTH . . . . 2 4 I N .

HEIGHT . . . . 2 4 I N .

160-200 HP

DUAL INJECTOR ROTOR HOUSING CONFIGURATION

--

r e ' , rOtrria

COMPARISON DATA - RSFC vn BMEP

N/A R C l - 6 0 . 8 . 5 ; I C.R.

l.SOk - J

a

I COMPARISON DATA -COMET MK V DIESEL I Q. ALUMINUM ROTOR HOUSING, 1979 A N/A-VW DIESEL 0 T/C VW DIESEL V

w CAST IRON R O ~ A

L HOUSING, 1976 . -

u .so

- lL

-

2Q00 RPM

-

.40 W x q a PROJECTED S.C.

m (N/A) 3'7 J I I I D l 1 0 20 30 40 5 0 6 0 70 8090lOd BRAKE MEAN EFF€CT!V~ PRESSURE- PSI Figure 7 - - - - - -

ORIGINT.,I- ! ? . ; : f~ OF POOR QL'ALIW

S( K 1 - 6 0 YW b CYL DIESEL

kw (BHP; 'PPM a a (so: lsooo 56 1 7 5 j . G C D .

109 (210) (405) kg (La) Comparison of SCRCI-60 v i t h Volkswagen 6 C y l i n d e r D i c e e l Figure 8

I S F C vs IMEP, PC1 - 60 BTC PILOT

10: 1 COMPRESSlON RATIO vs 8.5 :I NATURALLY ASPI RATED, 2000 RPM BASELINE ( 8 . 5 : 1 C.R) .38 IND. SPEC.

FUEL CONS.

LB/I HP- HR 0 C ) - ? ?

2 -: I C.R.

C Y J -- Q - - a . .

-

.30 -

-

-.

I 1 I > I I I I I 20 30 4 0 5 0 6 0 70 80 90 I)

INbICATED MEAN EFFECTIVE PRESS - PSI

Figure 9

RCI-6Q 2000 RPM PERFORMANCE, BTC PILOT 10: 1 COMPRESSION RATIO NATURALLY ASPIRATED BSFC

BTU/BHP - HR

0 92 OCTANE UNLEADED GASOLINE + 99.85% METHANOL 8 , 0 0 0 ~ REF: GASOLINE LHV 18607 BTU/LB MFTHANOL LH',V' 9750 BTU/LB

BMEP - P S I

\ \ ;PC: -350 BTC PILOT \ i200 R P M

+

RCI-60 BTC PILOT

%- +- - - + +*

IMEP - PSI !

I n d i c a t e d S p e c i f i c F u e l Cc - l m p t i o n (ISPC) * : s Indicated Mean

E f f e c t i v e P r e ~ e u r e (IHEP) Comparison o t RC1-60 and RC1-150 Data, b r C P i l o t , O . 5 : l Compression Ratio Figure 11

.80 -

RC I - 60 BTC PI LOT

-

BSFC -70 LBIBHP-HR RC 1- 350 BTC PILOT

-60 -

.so -

/*

RCI -350 CITC PILOT 1200 RPM I I I I I I 1 I I I I I I l I 1 . I I

~b

20 30 40 5 0 60 70 80 90 100

BMEP - PSI

BSFC vs RMEP, kc1-GO and Rcl-350, 8 , 5 : 1 Compre$sion flat40 Figure 12

B F C rt F/A SATIO FOR 5 SEPARATE IC1-350 EH6lNE BUILDS.

SANE CORFIEURATIOW, 8.51 COMPRESSION R A T I O 3600 RPM f BTC s # M * / PLOT .

a .40 , J a/ I a H < e

\

+ AH

tl \

%--+3-'C

!

3 0

THEORETICAL TURBOCHARGING EFFECTS ON BSFC BSFC

ORlGlflXL t" - " -1 : ' ; OF POOR QLlfiLl7-f RCI -60 STRATIFIED CHARGE -- - - 4000 RPM PERIPHERAL INTAKE PORTS EMG. NO. 7C2-60 8.5:1 C.R.

/

NATURALLY ASPIRP.TED - - @ e-

/ F I B

,+'@-

/"

- *+--

+b/O

4 qeoe+-

\ eee+*i& TURBOCHARGED

BSFC \ +. N.A.

.b

\ o / f

\ - 0 - 0 79% ..

. + ,T.C.

RED.

-I

-+- -

-- 1

" BRAKE HORSEPOWER Figure 1 5

'NO. 2 DIESEL FUEL COMP. RAT10 o---- 0 N.A. 8.5:1 +-----+ T I C 8 m 5 : I 0 - 0 N.A 6,,0:1 / o X - x T/C 6.0:1

)

RC 1-60

STRATIFIED CHARGE

4080 RPM

PERiPHERAL INTAKES

BSFC x - x /*

A lX

I I I J . 3 0 U t a .

ur '10 2 0 30 40 50, 68 70 80

BRAKE HORSEPOWER Figure 1 6

-.

.

MEASURED REDUCTION IN THERMAL AND PRESSURE LOADS FROM LOWER COMPRESS) ON RATIO AND HIGHER AIR/FUEL RATIO SCRI -SOT ENGINE 5000 R PM OT..:~, O F P C C l i C . ,--' I

SMEP - Kpo

20 30 40 50 60 70 80 90 400 PSI

, -

OU!G!n!n.7- 7.. .- .

OF PO32 '7 I,,-; -.'

CURTISS-WRIGHT

RC 1-350 TURBOCHARGED STRATIFIED CHARGE

ROTARY COMBUSTION ENGINE

8.5"' TURBINE INLET AREA SCWITZER 5MF-863 TURBOCHARGER I NON- INTERCOOLED BRAKE HORSEPOWER I F i g u r e 18

RC 1-350 TURBOCHARGED STRATIFIED CHARGE

ROTARY COMBUSTION ENGINE

INTERCOOLED

-

-26

+

0.5"2 TURBINE INLET AREA

-

.60 SCHWITZER 5MF-863 TURBOCHARGER

-

.58

-

.56

-

.54

-

.52 a I

-

L.50 I m \

-

5-48

I

-

2.46 m m

-

.44

-

.42

-

-40

-38 -

X X t I I I I

.36 i

I 20 40 60 80 1 0 0 120 140

BMEP - PSI

Figure 1 9 .

RC2- 32 H IGHLY ADVANCED ROTARY AIRCRAFT ENGINE

ESTIMATED PERFORMANCE

TURBOCHARGED STRATIFIED CHARGE

BSFC LB/BHP- )MAXIMUM CRUISE - ~ BRAKE HORSEPOWER

YOU(T CAD - - f

.. . 2 CLEAR- A T 'A' -8

' STARTER RYWU

, . i * L-

. 4 , .A.

~.

i * ! , , , .

1 , , . , . I - I i - - ~. L ~ . L r la 4 2 1 a I - / ' I ' 7 i - -- -1; I - / - - I

PERFORMANCE CONSTRAINTS ON CARPET PLOT OF CONSTANT P A Y L O A D RANGE

Z F I X E D E N G I N E SIZE, VARIABLE AIRFRAME, N X E D PAYLOAD-RANGE GR0S.S wl; LB 4460 SPAM, FT 4 0 2 ASPECT RATIO 9.5

Z F I X E D ENGIAIE SUE, VAR/ABL& AIRFRAME, FIXED PAYLOAD-RANGE t R 0 S S W ; S L B 6850 SPAN, F T 4 4.5 ASPECT RATIO f l a 0

ROTARY S I N G L E

n F I X E D EhfGINE SIZE, V A R I A B L E AIRFRAME, FIXED P A Y L O A D - R A N G E

GROSS W 7 ; L B 388r 369/ SPAN', F T 34.9 32.6 ASPECT RATIO 8.3 7 . 73 v P- OI, C ri r?

ROTARY T W I N

n FIXED E N G I N E SIZE, VARIABLE AIRFRAME, F I X E D PAYLOAD-RANGE

RC 2-47 RCZ-32 5788 5454 GROSS W7, LB 38.1 35.0 SPAN, F T 9.8 B . 4 5 ASPEC7 R A T I O 0 0 - z w n 0 ; : 0 ; : I ' arc c J l 1 0 - --I , -c; t$'

AND F t L T H

e a m ~ P R ~ ? P I / R ~ Z ~ ~ ~ A ~ ~

HEAT EXCHAAI66RS

W R I G H T AIRCRAFT E N G I N E PERFORMANCE

I ,-CLEARANCE AT ' A ' PERMITS STARTER REMOVAL

i

I

I ' ,- TURBOCHAAOER AND

, , i

, ~ U R B O C O U P O U N D I N G TURBINE I !

I

i

I

- - - .-- ---- - - - _ _ -

I - -- 5 . - ? !

- '-COOLAMT IN R C I - 4 1 INSTALLATION DRAWING nlOnLY A D V A N C E D I ROTARY COMBUSTION 9 CENTER OF GRAVITY AIRCRAFT ENOlllE - 800 HP

E N 0 VIEW A ClACLC O f 10 ' OIAUETER -----.--.--- -- -.-.-- -. -.-

T -

FOR O l M E M I I O ~ ' a ' SEE OLAR REDUCTION CURVE ~GS--- --

- -- ---

-.

CONCICJUAATIOC( snoww FOR 1 8 0 0 PROP RPU . - - -.. .a,- . < a d

- - - - - - -- - - - - 4 5 - - - w - . *

r

- AOLDCUT F ~ ~ n l e L

0RICIKP.L Pf,S;7 '2 OF POOR Q U A L l N . . . . . . . . , - - - - .- - .-- I ! . - - ,

*.-..- - - . - I .-. , --. . 1 .--

- . . - . r - . . , , .I , . . , . - , . - . - .

. . . . .

-. .-A -- - 1 . . . . - - . - ' - - - .

- . . - - . . . .- 1 -, .. .Ti.,. . :- , . . . . . . I !

. . . .

... .... -- .- -- -&-- --4- -* : . . . . . ! ....-. - . . - . , . , , lr-: - .

---- ---

:I.--.- . - 10 I L L COOLANT COOLERS NOT INCLUDED - _ _ -- . _ _ _ - _ -- ___

, . . - - . ! '' I .. - . . : C ---. .... ..- -- .-- L..-' - - - ....

. I..... I : L .......... ..--,

DISPLACEMENT PER ROTOR - CUBIC INCHES

Figure 33

ORlGI!VAL PAGE fS Oc FQOR QUALITY I " I I *- Figure 34

INTEGRAL PROP REDUCTION GEAR BOX LENGTH b WEIGHT vs .-OfflPUf TORQUE

-

BASIC ENGINE DATA 250 CRUISE HP AT 25,000 FT.

Highly Advanced Advanced TSIO-550 RC2-47 RC2-32 Length (") 5 9 . 2 5 Width 3 3 . 4 Height 1 9 . 2 5

Weight -Flyable ( l b . ) 585

S p e c i f i c Fuel Con- sumption at Cruise , 4 4 6 (Lb/HP-hr. ) Table I

A 1 R P I A N E COY P A R I S O N S

- - . - - -

TWIN ENCINE SINGLE ENGINE T S I O - 5 5 0 FC2-4? Ht2-32 - - ( - .

TAKEOFF kW PWER . 8 HP CRUISE d W P3VJER BHP E!4PTY REIGST kg lb

I

GR3SS W E I Z H R k g I l b I W I N S AREA

' 9 "

sq t

- WING SPAN m

f t ASPECT RATIO ROC m/m i n A T 2 5 0 0 0 ' f ~ m CLI>¶S rIME m i n SEROC m/min t a t 5000 it fpm T A K E 3 F F n D I STANCE f t ST A L L km/hr S P E E D R TS C R U I S E km/hr 1 SPEED K TS PAYL3AD k 9 l b RhYSE: k m N ;*I ! I ISSIOg FJEL k g l b C R U I S E km/I, M I LEhGE iJYPC I Pi?? CE $1000 I D3C S / h r Table I1

GEOMETRIC DATA ~ - - - - p~ ~ (In Inches) HORSEPOWER v S I Z E S P E E D , RPM ECCENTRICITY E ROTOR WIDTH W TROCHOID MAYOR A X I S TROCHOID MINOR A X I S NUMBER O F RGTORS DISPLACEPENT PER ROTOR Table I11

1200 BHP OPERATING DATA SUMMARY 70% Cruise Take Off 15,000 Ft.

Sea Level - Altitude

WITHOUT TURBOCONPOUNDING BHP 1,200 RPM (Crankshaft) 6,904 IMEP, PSI 244.11 IHP 1,381.43 FMEP, PSI 32.06 FHP 181.43 BMEP, PSI 212. r e .

Fuel/Air Ratio . C 4 BSFC, Lb/BHP-Hr. .3536 Airflow, LblHr. 10,757 Compressor Press. Ratio* 2.17 Eng. Inlet Temperacure, OF 149.8 Eng. 1-let Pressure, PSI 31.2 WITH FJRBOCOMPOUNDING BHP (RC4-75) BHP (RCi-81) BSFC, LbIBHP-Kr.

*

Before 2% intercooler pressure drop.

Assumes Intercooler effectiveness of 50% and compressor efficiency of 70%.

Table XV .

2000 BHP RC6-95 ( 9 4 . 8 7 ) OPERATING DATA SUMMARY Standard Day -No Ram 70% Cruise Take-Of f 15,000 Ft.

Sea Level Altitude WITHOUT TURBOCOMPOUNDING BHP R P M (Crankshaft) IMEP, PSI IHP F I ' E P , PSI FHP BMEP, PSI Fuel Air Ratio BSFC, Lb/BHP-Hr.

Airflow, Lb/Hr.

Compressor Press. Ratio* Eng. Inlet Temperature, OF Eng. Inlet Pressure, PSI WITH TURBOCOMPOUNDING BHP (RC6-87) BHP (RC6-95) BSFC * Before 2% intercooler pressure drop.

Assumes inte-cooler effectiveness of 50% and compressor efficiency of 70%.