The NASA research program on propulsion for supersonic cruise aircraft

NASA

TECHNICAL

NASA TM X-71666

MEMORANDUM

Ir-

X (NASA-TM- R) THE NASA 6 66 RESEARCH PROGRAM N75-18238 (A ON PROPULSION FOR SUPERSONIC CRUISE AIRCRAFT (NASA) 24 p HC $3.25 CSCL 21A Unclas G3/07 12456

THE NASA RESEARCH PROGRAM

ON PROPULSION

FOR SUPERSONIC

CRUISE AIRCRAFT

by Richard J. Weber Lewis Research Center Cleveland, Ohio 44135 TECHNICAL PAPER to be presented

at a

National Transportation Meeting sponsored by the Society of Automotive Engineers Hartford, Connecticut, May 6-9, 1975 ON PROPULSION RESEARCH PROGRAM THE NASA AIRCRAFT SUPERSONIC CRUISE FOR Weber by Richard J.

Administration and Space National Aeronautics Center Research Lewis Ohio Cleveland, ABSTRACT at advancing the pursued a program aimed Since 1972 NASA has the possible appropriate for a data base and establishing technology This paper brief- aircraft.

supersonic cruise development of future of propulsion portion of the and status the objectives ly reviews of propulsion series upon a continuing Building the program.

noise and pol- underway in activities are research system studies, and materials.

inlet stability, lution reduction, INTRODUCTION initiated a program aimed at the development In 1963 the U.S.

(SST). In 1971 of a commercial supersonic transport and production technical abandoned as a result of concerns about the project was federal financing, and environ- readiness, economic feasibility, is now called the Super- mental impact. In 1972 NASA started what In contrast to the Cruise Airplane Research (SCAR) program.

sonic a production project, the SCAR work is not aimed toward earlier SST a data base of but rather, it is intended to establish airplane, air- to be available for the design of future advanced technology nation determines it is desirable to build craft if and when the are relevent in varying them. The various elements of the program applications.

degrees to both potential civil and military rate of program has been funded at an annual The total SCAR about 9 million dollars per year. It involves work in propulsion, stability and control. However, this aerodynamics, structures, and a survey of the SCAR propulsion activities. In paper is limited to recognized that there are many other this discussion, it should be program that are appli- projects within the general NASA research The intent of the cable to both subsonic and supersonic flight.

addition- SCAR program is to supplement the general activities with al work that is focussed on those unique problems of supersonic otherwise not receive adequate attention.

aircraft that would RESEARCH ELEMENTS the SCAR program has been to perform the The philosophy of great majority of the work through contracts with industry. Table I lists the propulsion contracts that have been let since the into the general work can be divided inception. The program's of: categories studies Engine Noise reduction Pollution reduction dynamics Propulsion Unique components described in will be briefly of these categories work in each The effort indication of the relative sections. As an the following how the propulsion table II shows expended in each category, year. The total pro- in each fiscal has been distributed budget of the available one-quarter represent about pulsion expenditures funds.

SCAR work had been invested STUDIES - Considerable PROPULSION SYSTEM with the SST project, culminating during the original in propulsion GE/4, an after- engine - the and testing of a preprototype building when the SCAR program was begun, burning turbojet. Nevertheless, all the a very broad study of to start anew with it was decided broad from this concepts. Starting competing propulsion plausible systems, it was planned to progressively move base of parametric greater each time focussing in of later studies, through a series approach candidates. This smaller number of promising detail on a 1. The results of the by the triangle of figure is represented serve several purposes: studies were to (s) the favored propulsion concept • to determine needs in order to guide the associated technology • to identify in the that are described research activities the supporting this paper later sections of air- to be used in overall engine performance data to generate the other parts of contractors in by airframe plane studies SCAR program the engine program, if an experimental ultimately, to define if funds were unusual and concept were sufficiently selected available with such a broad- reasons for starting There were several based study program: no specific one, having program is a long-term The entire SCAR analysis a new, open-minded allowing time for target date, thus in technology.

could incorporate advances that to a greater are recognized Environmental considerations * greater a correspondingly project, with in the SST degree than on engine design.

impact extensive been proposed which require engine concepts have * New be established.

merits can their true study before with involved major contracts was set up has The program that Company.

Company and Pratt and Whitney Aircraft the General Electric concepts the conventional engine have addressed These contracts after- turbofan, turbojet, duct-burning afterburning (dry turbojet, unconventional, variable-cycle plus a number of burning turbofan) studied by have also been types of VCE's engines (VCE). Other and the Rockwell International, Laboratories, Advanced Technology Boeing Company.

commercial that an advanced in these studies It was presumed same environmental to meet the would have transport supersonic the case of noise, transports. In as new subsonic regulations type of each engine to determine the ability the studies sought the penalties and also to find FAR-36 limits to satisfy the present might be in force limits, which meeting more stringent involved in (perhaps is placed into service a future airplane at the time years from now).

10-20 faced by a supersonic flight conditions The widely varying make it difficult by the noise constraint, aggravated transport, engine. For conventional a light-weight, efficient, to design sub- noise, and efficient thrust, low jet good takeoff example, turbofan.

by a high-bypass-ratio are best provided sonic operation obtained with a cruising is hand, best supersonic On the other engine The variable-cycle turbofan or a turbojet.

low-bypass-ratio internal changes requirements through both of these tries to satisfy have been proposed Many techniques of airflows and jet velocities.

do it without problem is how to this; the real for accomplishing penalties.

weight and drag incurring excessive by means been made progress has that definite 2 shows Figure was avail- from what advances and technology optimization of cycle primarily The improvements are SST program.

able in the original - to the lower noise levels the ability to achieve reflected in a modern that of area approaches noise footprint point where the transport. However, continued engine wide-body subsonic jet airplane performance to better the are still desired improvements economics.

and by the about the noise generated NOISE REDUCTION - Concern have a major impact has been found to engines powerful supersonic sub- performance. Unlike airplane engine design and resulting on ex- to have very high engines tend engines, the supersonic sonic jet major problem is excessive velocities, and so their haust how attempts were being The preceding section mentioned noise.

section design. This problem through engine to alleviate this made seek to better under- that the SCAR technology programs describes find ways to reduce and hopefully of jet noise stand the character research major national supplements other (This work its effect.

suppressor with industry on DOT/FAA. contracts engine noise, e.g.

on technology.)

was to system studies results of the propulsion One of the of a in the form engines, of dual-stream out the potential point speeds.

a turbofan at low that behaved like or of a VCE turbofan such the jet noise of in the past on work has been done Little of coannular in the area has been started so a program engines, aero- acoustic and to study the of the work is objective jets. The and without both with nozzles, of coannular dynamic performance and of exhaust pressures wide range ejectors. A and suppressors tested streams are being and duct in both the primary temperatures treatment is of acoustical facilities. The potential in static work was begun in August 1973, also being investigated. This in 1975.

GE, and will be completed contracts to P&W and through the type being of suppressed nozzle 3 shows a typical Figure diameter, which is cm (5 inches) in is about 13 The model tested.

in are shown acoustic test results Some of the 1/10 scale.

about and full scale to been adjusted the data have in which figure 4, the Perhaps measuring distance.

FAR-36 sideline the standard to nozzle that the coannular to observe is interesting fact most in the region noise suppression 8dB of inherent possesses up to velocity. A higher than the core the duct velocity is where measured for the has been suppression amount of additional similar with acousti- an ejector suppressor and of a multitube combination about was obtained with of 15dB suppression The total cal lining.

thrust loss.

7 percent con- under static been obtained results have preceding The past that in-flight has been observed in the ditions. However, it Figure than static.

to be worse tends performance suppressor the flight account for important it is to properly illustrates how to adjust static it was common Until fairly recently effects.

through a "relative flight conditions of noise to measurements SAE document.

by a standard specified velocity" correction is as suppressor assumed that a noise it was usually Furthermore, in the However, as shown it is statically.

in flight as effective these approaches both of indicate that flight data recent figure, with in future work it is planned optimistic. Hence, are overly the flight to simulations of to extend the tests coannular nozzles environment.

initiated by studies have been meantime, fundamental In the the will investigate These studies and Lockheed.

both Boeing with acoustical pro- problems associated theoretical and practical plus jet- a stationary observer, a moving source to.

pagation from surrounding air, and due to motion of the noise source alteration these effects.

techniques to verify soon will is planned to start basic study that An additional noise as a absorption of data on atmospheric obtain experimental up to 100,000 and humidity for frequencies function of temperature to interpret information is necessary hertz. The high frequency with very on suppressed configurations model scale data, especially elements.

small in has been evidenced - Growing concern POLLUTION REDUCTION pollution of the atmosphere.

about the problem of recent years small contributors to this problem, Although aircraft are relatively air- the vicinity of polluters in be significant are felt to they has estab- Protection Agency the Environmental ports. Accordingly unburned hydro- reduction of carbon monoxide, lished goals for the by subsonic transports during nitrogen oxides emitted carbons, and add a new Supersonic aircraft and landing process.

the takeoff into at altitudes well They will cruise dimension to the problem.

ad- aroused fears of possible ( 20km), which has the stratosphere that the formation of SO verse climatic effects. One concern is surface temperatures.

and thus change atmospheric opacity may affect process can eliminate the fuel refining Removal of sulphur during is that nitrogen-oxide remaining worry this problem. The principal concentration; will cause a gradual reduction in ozone emissions reach the surface, more ultra-violet radiation to this would permit and the incidence of skin adverse effects on plants with possible Impact Assessment The recent conclusions of the Climatic cancer.

show that this problem the Department of Transportation Program of originally suggested. Nevertheless, is not as great as some had nitrogen need to reduce, over the long run, there is an apparent conventional the levels generated by current oxide emissions below this need, even though there are no combustors. Anticipating high-altitude emissions, NASA has applicable EPA regulations for NO reductions.

aimed at achieving substantial initiated a program x is to reduce that is being explored The principal technique combined with premixing/ temperature by fuel-lean combustion, flame mixture. An indication of the prevaporizing to achieve a uniform 6. Very low values approach is shown in figure potential of this per kg of fuel burned) of emission index (grams of NO produced penalty to combustion efficiency.

are seen to be achievable without 15-20 g/kg typical of index values are in contrast to the These 6 were obtained in idealized combustors. The data of figure current not achievable experiments; these low values are probably combustion engines.

in actual date, using various combustor Figure 7 summarizes progress to con- experimental combustors to idealized techniques ranging from and of the premix, lean combustion, ceptual tests. The results years promising, but several more catalytic approaches are extremely demonstration by combustor development and of laboratory work followed is known what value is realistically will be needed before it achievable.

com- been in terms of primary discussion has The preceding con- concepts now being turbofans and variable-cycle bustors. The burners, either afterburners or duct sidered usually incorporate both takeoff and cruise. The typically which may be used during tend to make in an augmentor and high velocities low pressures to achieve. It is emissions difficult efficiency and low high this area in the research program in start an extensive hoped to near future.

airplane performance of a supersonic PROPULSION DYNAMICS - The diffuser, which of the inlet sensitive to the performance is quite air, slow it to low streamtube of rapidly-moving must capture the energy to high convert its kinetic velocity, and efficiently type In the mixed-compression before entering the engine.

pressure transport, of present interest for a supersonic of inlet that is is decelerated to is obtained when the air maximum performance located at the a terminal shock that is velocity through subsonic the point) within the inlet. If (i.e. minimum-flow-area throat the the pressure recovery of allowed to move downstream, shock is of the airflow. However, and there is high distortion inlet suffers in engine flow or near the throat, small changes with the shock An unstart is when flow can create an inlet unstart.

inlet capture is an unstable upstream of the throat, which the shock moves entirely, which rapidly pops out of the inlet location, and then for the airplane to yaw a large thrust loss, a tendency results in un- causes of such Typical passenger discomfort.

and roll, and changes, augmentor light-up, are: engine throttle starts waves from variation, shock or temperature atmospheric turbulence other aircraft.

to minimize this device of inlet stabilization A new type that has being investigated unstart is presently occurrence of The previous techniques.

than faster response and lower losses principle ones, operates on the approach, like many previous new too the shock moves of the inlet whenever bleeding air out of the inlet the engine until airflow bypasses upstream. Excess far throat to its desired the shock can open, returning by-pass doors a by means of this principle device mechanizes The new position.

of the inlet, spaced about the circumference series of poppet valves parts is shown of the valve in figure 8. A photograph as sketched 9.

in figure to Lockheed Aircraft Company feasibility study contracted A they Under a later contract suitable valve design.

resulted in a the inlet of system'for a complete valve and fabricated designed is capable of U.S. airplane that airplane, the only the YF-12 were successfully Prototype valves supersonic flight.

long-range An actual facility at NASA/Lewis.

in a special dynamic tested is now under- of the valves, to contain 50 inlet, modified YF-12 Tunnel. De- Supersonic Wind Lewis 10 x 10-Foot going tests in the be a flight that there will it is possible pending on the results, on the YF-12 airplane.

test UNIQUE COMPONENTS - The preceding sections have described research related to exhaust nozzles, combustors, and inlets that is covered by the noise, pollution, and dynamics programs. It was felt that the propulsion systems studies would identify other supersonic engine components that deserved attention. These com- ponents are covered under the final catch-all category of "Unique Components." The primary subject that has so far been addressed in this category is the general one of materials. Improved mater- ials are recognized to be beneficial in any type of engine; however, the unique design and operating conditions of a supersonic engine has led to work in two particular areas.

Fan blades - Some of the most promising supersonic propulsion systems are turbofans or variable cycles that contain fans. These fans would use thin, sharp-edged blades similar to, although larger than, the one pictured in figure 10. Such a blade is normally made of solid titanium. Much effort has been invested in the past toward the use of lighter-weight composite materials instead of metal. The usual composites are not applicable to the hotter engine. The current program is aimed environment of a supersonic blades, which can tolerate at the development of boron-aluminum the higher temperatures. Successful development of such blades would eliminate the part-span shrouds, reduce blade weight by 35 percent, and permit additional reductions of disk and containment weight. For a typical supersonic transport these improvements would result in a decrease in takeoff gross weight of 3.5 percent.

has been obstacle facing the use of B/Al composites The major good impact resistance. Prior studies have demonstrated poor foreign object damage such as from bird static properties, but failure. The approaches selected strikes has caused catastrophic to improve B/Al impact strength are: a in the present program promoting energy absorption more ductile aluminum alloy matrix, larger diameter boron filaments, through plastic deformation; to permit the matrix to increasing the spacing between filaments processes, selected to deform in a ductile manner; fabrication to increase filament reduce reaction at the fiber-matrix interface is optimized for failure; and filament ply lay-up that strain to the more ductile behavior.

Notched Charpy The potential of these approaches in terms of figure 11. The original pendulum impact strength is pictured in foot-pounds and very B-Al technology provided Charpy values of 3-8 brittle failures. Use of a slightly more ductile matrix, 5052 Al, left). Use of the still raised this value to 13 ft-lb (upper more ductile 1100 Al matrix raised the strength to 47 ft-lb, with a significant amount of plastic deformation present at failure filament (upper right). Substituting the larger 8-mil-diameter amount of raised the strength to 68 ft--lb, with an even greater plastic behavior.

These results offer hope for the successful completion of the current B-Al program, which includes obtaining design data, fabri- cating and testing blades in whirling arm impact tests, and demonstration of performance gains in ground engine tests.

- A supersonic propulsion system Exhaust system components to hot exhaust gases has many more complex and heavy parts exposed engine (e.g. variable-geometry convergent- than does a subsonic noise suppressor, and augmentor).

divergent exhaust nozzle, is benefit of using lighter-weight materials Consequently, the The objective of the present program is to investigate marked.

the capabilities of SiC-fiber-reinforced superalloy and demonstrate reducing the weight of supersonic propulsion systems.

sheet for of each engine typically The nozzle/suppressor/reverser portion Because of its lower density, the com- weighs about 3000 pounds.

posite sheet could reduce this weight by 30 percent. This in reduce airplane gross weight by 5 percent. This does turn would for the additional weight savings from the following not account properties, measured at 1250K improvements in projected mechanical (18000F): four times greater strength, two times greater modulus, 1000-hour rupture strength.

and five times greater program is underway To verify this potential, an experimental fabrication techni- that will screen candidate matrixes, develop shapes.

ques, and test panels and actual component CONCLUDING REMARKS research program is being conducted by NASA to A long-term establish a data base to be available for possible development of The effort does not compare in magni- future supersonic aircraft.

tude or cost to the activities that pertained to the early SST progress has since project. However, considerable development fields. It seems clear the various propulsion-related been made in will be of great value to the design that the advances being made supersonic airplanes.

of tomorrow's I. - SCAR Propulsion Contracts (through January 1975) Table Contractor Title Start Engine Studies Variable Cycle Sept. 1972 Advanced Technology Labs. Study of an Unconventional (NAS3-17559) with a Supersonic Inflow Fan Whitney Aircraft Advanced Supersonic Propulsion Technology Sept. 1972 Pratt & Studies (NAS3-16948) Extension I Jan. 1974 April 1975 Extension II Electric Company Advanced Supersonic Propulsion Technology Oct. 1972 General (NAS3-16950) Studies Extension I Jan. 1974 Extension II April 1975 Pan American World Airways. Airline Appraisal of AST Engines Jan. 1973 (NAS3-17216) Rockwell International Corp. Study of a Multimode Integrated Propulsion April 1973 (NASl-12245) System in an Advanced Supersonic Transport Noise Reduction Jet Aug. 1973 Pratt & Whitney Aircraft Acoustic Tests of Duct-Burning Turbofan (NAS3-17866) Noise Simulation General Electric Company Acoustic Tests of Duct-Burning Turbofan Jet Aug. 1973 (NAS3-18008) Noise Simulation The Boeing Company Effects of Motion on Jet Exhaust Noise from July 1974 (NAS3-18539) Aircraft Lockheed Effects of Motion on Jet Exhaust Noise from July 1974 (NAS3-18540) Aircraft Table I. - SCAR Propulsion Contracts (through January 1975) continued Contractor Title Start Pollution Reduction Pratt & Whitney Aircraft Experimental Clean Combustor Program, Phase I June 1973 (NAS3-16829) (AST Addendum) General Electric Company Experimental Clean Combustor Program, Phase I Aug. 1973 (NAS3-16830) (AST Addendum) Solar Div. - Int'l. Harvester Experimental Study of Advanced Combustor March 1974 (NAS3-18023) Concepts to Reduce Formation of Oxides of Nitrogen in Gas Turbine Engines for High- Altitude Aircraft Advanced Technology Labs. Development of Concept for Low NO - Oct. 1974 x (NAS3-18563) Premixed, Prevaporizing Combustor Propulsion Dynamics Lockheed Feasibility Study of Inlet Shock Stability April 1972 System of YF-12 Lockheed YF-12 Inlet Shock Stability System for May 1973 Wind Tunnel Tests Unique Components General Electric Company Boron-Aluminum Fan Blades for AST Engine June 1974 (NAS3-18910) Westinghouse Electric Co. Fabrication Process Development of SiC/ June 1974 Superalloy Composite Sheet for Exhaust System Components Authority (thousands New Obligational II. - SCAR Propulsion Table of dollars).

. 1974 1975 Fiscal year studies Engine Noise reduction reduction Pollution dynamics Propulsion Unique components 2375 2220 Total L-.- 25,2 BYPASS . 1.2 - -DOUBLE I VCE c- AFTERBURNING TURBOJET TECHNOLOGY A (GE4) B 19751.1 PROGRAMS GREATER REFINEMENT C BASELINE OF FEWER ENGINES 0 1.0 irSUBSONIC ' MIXED-FLOW TURBOFAN DTJBPT VSCE WIDE-BODY WIDE-BODY DBP DUAL-CYCLE 1974 I AIRPLANE AIV-IRV AIV-2V .9I 0 25 50 75 STUDIES DTJ ABTIJ DBTF MFABTJ 90 DB FOOTPRINT AREA, SQ N. MI.

Figure 2. - Propulsion system comparison, 292 pax, 4000 n. mi.

MOAFP-1V AV-2V TACE FLEX73 = 762 000 lb.

range, Mcr 2.32, ref. TOGW MMIPS TFRJ AE SS-FAN Figure 1. - Progress of propulsion system studies.

MULTI-TUBE NOZZLE SUPPRESSOR PRATT & WHITNEY CONTRACT NAS3-17866 A EJECTOR 44 TUBES END VIEW A-A Figure 3. - Duct burning turbofan acoustic tests.

STATIC EQUIVALENCE MEASUREMENT---, \ RATIO C;FLIGHT COMBUSTION .6 MEASUREMENT-COMBUSTION S-10 EFFICIENCY, C) p -20- ! 5 - "OLD" FLIGHT PREDICTION o

4b -30 1 I

40 60 80 100 120 140 160 x99.70 ACOUSTIC ANGLE FROM INLET, DEG z2 Figure 4. - Flight effects on jet noise. Suppressed conical 99.50 nozzle. 9. .5 z 1- UJ X 9.25 CALCULATED SUM OF CORE PLUS DUCT .

o SUNOISE-, UNSUPPRESSED S= 0 COANNULAR S100 - - MULTITUBE SUPPRESSOR S90 a. "- .- AND TREATED EJECTOR .2 w I I .5 1.0 1.5 2.0 2.5 3.0 80 I TIME, MSEC RESIDENCE 1500 2000 FAN JET VELOCITY, FTISEC Figure 6. - Effect of residence time on nitrogen oxides emissions. Inlet mixture temperature, 800 K; inlet Figure 5. - Acoustic performance of coannular nozzles, pressure, 5. 5 atm; reference velocity, 25 and 30 m/s.

core velocity, 1320 ft/sec.

E-,252 DAMPING I-- CONVENTIONAL . .jp ORIFICE .

o 0 , CLEAN COMBUSTOR (P & W, GE) 407 POROUS --------------- --- TRAP SWIRL CAN (NASA) COWL BLEED- ] LEAN COMBUSTOR (SOLAR) CENTERBODY BLEED PRE-MIX RIG (NASA, ATL) CATALYTIC (NASA, SOLAR) LOUVERS- rVALVES

i I I I

0 5 10 15 EMISSION INDEX, gNOxlKG FUEL Figure 7. - Status of cruise NO, emission ex- periments, M = 2.7, 60 000 ft.

'-FORWARD -AFT DOORS DOORS bleed system in YF-12 inlet Figure 8. - Shock stability C-74-2574 stability system relief valve.

Figure 9. - Disassembled ! ,, iCip IAMMI

ir

a lde.

Figure 0. - Tiale supersoic-,, enief 13 FT-LB; 50 VIO 5.6 MIL B IN 5052 47 FT-LB; 50 VIO 5.6 MIL B IN 1100

V

68 FT-LB; 50 V/O 8 MIL B IN 1100 Figure 11. - Improved B/AI impact resistance.

NASA-Lewis