N84-24581 NASA Technical Memorandum 83641 9 Supersonic STOVL Ejector Aircraft from a Propulsion Point of View R. Luidens, R. Plencner, W. Haller, and A. blassman Lewis Research Center Cleveland, Ohio Prepared for the Twentieth Joint Propulsion Coiiference cosponsored by the AIAA, SAE, and ASME i Cincinnati, Ohio, June 11-13, 1984 I 1 1 SUPERSONIC STOVL EJECTOR AIRCRAFT FROH A PROPULSION POINT OF VIEW R hidens,* R. Plencner,** W. Hailer.** and A Glassman+ National Aeronautics and Space Administration Lewis Research Center Cleveland, Ohio Abstract 1 Higher propulsion system thrust for greater lift-off acceleration. The paper first describes a baseline super- sonic STOVL ejector aircraft, including its 2 Cooler footprint, for safer, more propulsion and typical operating modes, and convenient handllng, and lower observability identiftes Important propulsion parameters Then a number of propulsion system changes are 3. Alternattve basic propulsion cycles evaluated in terms of improving the lift-off performance; namely, aft deflection of the ejec- The approach of this paper is to use the tor jet and heating of the ejector primary air aircraft of reference 5 as a baseline. and then either by burning or using the hot englne core to consider some candidate propulsion system flow The possibility for cooling the footprint growth options The vehicle described in refe- is illustrated for the cases of mixing or lnter- rence 5 was selected on the basis of detailed changlng the fan and core flows, and uslng a alrcraft design and performance analyses The core flow ejector Flnally, the appllcation of present paper analyses the propulsion system a new englne concept ls presented, the turblne options from a fundamental point of view and bypass engine plus a turbocompressor to supply does not Involve detailed design or the evalua- the ejector primary air, and thrust during take- tion of such factors as weights, aircraft- off and combat propulsion integration, and costs Any selec- tlon from the candidate growth options will depend on further detailed studies Introduction It is generally accepted that short takeoff Baseline Ejector Aircraft and vertical landlng (STDVL) aircraft have an important place in the mllltary The Brltlsh The baseline ejector aircraft and propulsion built Harrler, a subsonic aircraft. is used by system Is descrlbed first Brltaln, Spain, Indla, and the U S Marines The Russlans also have a subsonic VTOL aircraft, Elector Types the Forger, for use on small aircraft carrlers Even having plcked an ejector type aircraft, The next generation of STOVL aircraft Is there are five types of ejectors listed on the expected to have at least supersonlc dash capa- left side of ftgure 3 that could be considered bllity There are many candldate configurations They fall into two categories- those wlth modest for a follow-on aircraft, but four of the leadlng prlmary pressure ratios and subsonic secondary 1 contenders are shown in figures 1 and 2 They flow, and those wtth a hlgh prlmary pressure are- (1) the Remote Augmented Llft System (RALS) ratio Those with the modest prlmary pressure (which is taken to Include the turblne bypass ratlo are: (1) those wlth steady flow and flxed englne with turbocompressor unit),2' (2) the prlmary nozzles, (2) those with low speed Tandem or Hybrid Fan,4 (3) the Ejector, and (4) rotatlng prlmary nozzles, and (3) those with the Deflected Thrust System, such as, an pulsed flow primarles Those with the hlgh advanced Harrier wlth fan air burning primary pressure ratio are: (4) those having supersonlc secondary flow, and (5) two stage The present paper deals with the Ejector ejectors Diffuser blowlng for greater dlffu- c~nflguratlon,~and in particular its propul- slon ratlo or rate and acoustic enhancement of sion system. The configuration to be discussed, mixing might be used with any of these The shown in figure 2, has a delta wing with foldable present study deals with only the first type ejectors through the wing adjacent to the fuselage Based on detailed analyses and experiments for thts type of ejector, the geometric charac- In considering the propulsion system for an teristics shown on the rlght of figure 3 were advanced STOVL alrcraft. there are several selected as glving good ejector performance or a important characteristlcs to be considered which high augmentatlon ratio: (a) a 1 8.1 ejector form the outline for the paper exit to throat area ratio, and (b) a dlffuser -- wall half angle of 8 degrees This yields a *Deputy Chief, Advanced Programs and Planning secondary to primary mass flow ratio, ms/mp. of Office, Associate Fellow AIAA about 10 for equal primary and secondary flow **Aerospace Engineer densities, and an augmentatlon ratio, cp of eJ ' 'Head, Subsonic Mlssions Analysts Sectlon. about 1 7. 1 1 Even with a high subsonic throat Mach num- ejector thrust per unit fan plus ejector ducting ber, the thrust per volume of the ejector is low frontal area, and (3) the thrust per unit volume and the drag associated with its volume Is of the propulsion system. Each of these will be generally inconsistent with supersonic flight discussed This problem is overcome by assuming the ejector walls are foldable to eliminate the diffuser Thrust Per Ejector Throat Area volume A key performance parameter of the ejector then becomes the thrust per throat area Figure 5 shows a typical ejector layout in a For the case of the ejector in the wing, a large delta wing The purpose of this ejector is two value reduces the hole size that must be cut fold. (1) to augment the basic fan thrust (the through the wing fan flow is the ejector primary flow) to provide lift, and (2) to provide an airplane nose.-up Aircraft Operation pitching moment about the aircraft center of gravity (c.g ) for aircraft trim Because the purpose of the paper is to dls- cuss the propulsion system, it is important to The ejector throat area to wing area ratlo. review how it operates during a typical flight At/&, is related to other ajrcraft and This is illustrated in figure 4 engine characteristics by the relation STO Ground Run, sketch 1; For the short (At/Sw) = (&I%) (FtotlWG) take-off, e g , 400'. the core air is directed (FfnlFtot) 'PO rearward, and the fan air is burned in the fan (l/Fej/At) air aft duct and also directed rearward This, of course, is to achieve maximum axial accelera- The terms in this relation are defined below tion The aircraft is at near zero angle of and typical values are listed attack, and the ejector is deployed ready for operati on Term: Typical Value- STO Lift Off. sketch 2. At lift off the WG/& = aircraft wing 60 fuel to the fan air burner is shut off, but a loading. lbs/ft2 small quantity of fan air may be still exhausted rearward to keep the aft duct clear of residual Ftot/WG = aircraft thrust 08 fuel The main quantity of fan air Is directed loading forward, by a valve, to the ejectors The ejec- tor force must pitch the aircraft nose up to Ffn/Ftot = fan to total thrust 0 31 18O to ZOO angle of attack to generate wing split lift in addition to the ejector lift The core nozzle is deflected downward about 45O to 'po E Fej/Ffn = overall ejector 15 provide lift and thrust to overcome the aircraft augmentation ratio and ejector drags This is discussed in more detail later Fej/At = ejector thrust to throat 300 area ratio, lbs/ft2 Subsonic Crutse. sketch 3: For subsonic cruise, both the fan flow and core flow are At/& = ejector throat to wing 07 directed rearward The fan air is not after- area ratio burned and the engine is at part throttle The ejector is now folded in contrast to the case at This relation shows that a high ejector takeoff thrust per unit of ejector throat area, Fej/At, will reduce the area cut through the Supersonic Cruise and Combat, sketch 4: The wing structure At/%, A reduced ejector fan and core jets are directed rearward, and the throat area will also permit the moment arm to fan air is afterburned for supersonic cruise and the center of the ejector thrust, Xc , to combat increase, thus Increasing the ejector pifching moment capability Vertical Landing, sketch 5; The fan is ducted to the ejector whose jet is 90° to the Figure 6 shows the results of a simple anal aircraft longitudinal axis, and the core air is ysls of a steady flow ejector Figure 6a shows also deflected down 90° A higher deflection that higher thrusts per unit throat area are may be needed during approach to aid in aircraft achieved by high, subsonic, secondary flow deceleration. The ejector ram drag is helpful throat Mach numbers in this case Figure 6b relates the secondary flow throat Mach number to the ejector primary pressure Basic Ejector Propulsion Parameters ratio and temperature Increasing the primary pressure ratio, especially up to values of about We begin with a discussion of some basic 4 is important, but increasing primary flow tem- ejector propulsion system parameters relevant to perature is also important The increase in the baseline ejector aircraft and ejector air- secondary throat Mach number with primary gas craft In general before dlscussing some poten- temperature assumes the primary nozzle size tial growth system options Increases with temperature, and that the secondary flow geometry remains constant (A Three propulsion system parameters of impor- later discussion considers the case of no pri- tance to a supersonic ejector aircraft arec (1) mary or secondary geometry change) The dotted the ejector thrust per unit throat area, (2) the line, for example, shows a primary nozzle i 2 pressure ratio of 3, a primary gas temperature Figure 9b presents the corresponding ejector of about 80O0R yielding a secondary flow Mach thrust divlded by the fan shaft energy tnput.