Toward Zero Sonic-Boom and High Efficiency. Supersonic Bi-Directional Flying Wing

Transcription

1 AIAA Paper Toward Zero Sonic-Boom and High Efficiency Supersonic Flight: A Novel Concept of Supersonic Bi-Directional Flying Wing Gecheng Zha, Hongsik Im, Daniel Espinal University of Miami Dept. of Mechanical and Aerospace Engineering Coral Gables, FL GZha@miami.edu

2 Future Supersonic Flight Fast global travel, Mach= High Aero efficiency i for low fuel consumption and pollution Quiet for environmental friendliness and stealth Extremely short takeoff/landing (ESTOL) Long endurance subsonic loitering i at destination Intermediate vehicles between subsonic and hypersonic

3 Problems of Current Supersonic Airplanes Sonic Boom, No flight above land High Wave Drag, high fuel consumption/cost Low Subsonic performance, long takeoff/landing distance Conventional tube-wing configuration difficult to break through technology barriers

4 SR71, Mach=3, A Noisy Military Pride

5 Concord: Noisy, High Sonic Boom Good Aerodynamic Efficiency High operating cost Cease to fly in 2003

6 Recent Efforts DARPA Quiet Supersonic Program ($35M) Q p g ($ ) Sonic boom reduced by shaping fuselage nose No wave drag reduction addressed No subsonic performance improvement addressed

7 Gulfstream Quiet Spike TM

8 Gulfstream Quiet Spike TM Multi-steps spike to split a strong shock to multiple weaker shocks Long spike required Structure stability a challenge Movable wing to improve subsonic performance, bring weight penalty No significant wave drag improvement Configuration conventional

9 Oblique Flying Wings(OFW) Variable sweep at different Mach number Supersonic high sweep and low aspect ratio Subsonic low sweep and high aspect ratio Aimed at reducing wave drag

10 Difficulties of Oblique Wings Asymmetric configuration in cruise direction Induce instability problems Large size required for head room space and mission volume Thick airfoil undesirable for low wave drag No obvious advantage for sonic boom Wing rotation difficult

11 Strategies to Reduce Sonic Boom 1) Nose Bluntness based on Area Rule Strong shock near aircraft, weakened to ground due to interaction with expansion waves High wave drag due to entropy increase 2) Sharp Nose Using Isentropic Compression Weak or no shock near aircraft May generate strong shock in mid- and far field Possible to have both high efficiency & low boom High Aero Efficiency has no Warranty on Low Boom

12 Novel concept: Supersonic Bi-Directional Flying Wing (SBiDir-FW) Aimed at 1) Near zero sonic boom 2) Low wave drag 3) High subsonic performance Revolutionary performance improvement Provisional patent filed to USPTO, No , 27 Apr

13 Feature 1: Low Wave Drag Feature 2: High Subsonic Performance Supersonic and subsonic performance conflict for conventional configuration High sweep and low aspect ratio desirable for supersonic Opposite favorable for subsonic performance SBiDir-FW rotate 90deg to achieve high efficiency for both subsonic and supersonic

14 Bi-Direction Planform Take Care of Both Supersonic and subsonic Aero Performance δ M<1 = 90 - δ M>1 AR M<1 = (L/b) 2 (AR) M>1 Performance conflict removed

15 Dual Symmetry y Facilitate Rotation o Supersonic thin airfoil Subsonic thick airfoil Similar to flying Frisbee Rotate by Aerodynamic force, no power system needed d

16 SbiDir-FW-UM (AIAA Paper ) M=1.6, passenger 70, R=2000nm, takeoff 2471ft, fuel efficiency: 5.93pmpp M>1 M<1

17

18 Wing tips unfold Wing tips unfold Wing rotates while engines locked in position p

19 Wing tips unfold Wing tips unfold Wing rotates while engines locked in position

20 Feature e 3: Very Low Sonic Boom How Sonic Boom is generated? V Conventional fuselage Sonic Boom Signature on Sonic Boom Signature on ground

21 Zero or near zero sonic boom Concept Isentropic compression pressure surface to avoid or minimize downward shock waves At zero AoA, a flat surface is an isentropic compression surface (roughly, based on 2D theory) At AoA>0, an isentropic compression surface may be designed using characteristic method. A flying wing without tube fuselage provide maximum flexibility to design optimal shape for aero efficiency and sonic boom This paper demonstrate t the concept at flight condition of AoA=0 for simplicity

22 Sonic Boom Validation NASA Cone Model 1, M=2.01, β=3.24deg 181x141x61 H/L=2

23 Sonic Boom Validation NASA Cone Model 1, M=2.01, β=3.24deg H/L=10 Mesh refinement

24 Sonic Boom Validation NASA Cone Model 1, Mach contours

25 Sonic Boom Simulation of SbiDir-FW AoA=0, Sweep=80, 60, AR M>1 = , AR M<1 = , M= % airfoil Surface mesh

26 Upper surface Mach number contours AoA=0 A

27 Mach number contours AoA=2 A Upper surface Upper surface

28 CL/CDp, CL and CDp

29 Over-pressure signature isentropic compression pressure surface generate smooth over pressure wave, low boom 0.3psf H/L=2 ground

30 H/L=2.5 Over-pressure signature mesh refinement test

31 Spanwise Section Mach number Contours AoA=0degA

32 Spanwise Section Mach number Contours AoA=2degA

33 Spanwise Section Surface Mach Number Distribution

34 Spanwise Section Surface Mach number Distribution

35 Sreamwise Section Mach number Contours AoA=0degA

36 Sreamwise Section Mach number Contours AoA=2 A

37 Increase Sharp Leading Edge Stall Margin 1) Conventional means using slats to increase stall margin Bring weight penalty and system complication

38 2) LE Radial a Injection, Create Virtual LE Radius CFD simulation Theoretical fundation

39 3) Use delta wing detached ed vortices Image from An album of fluid motion by M. Van Dyke

40 M>1

41 M<1

42 Conclusions cuso s A novel supersonic bi-directional flying wing suggested SBiDir-FW rotate 90deg between subsonic and supersonic mode, performance conflict for M<1 and M>1 removed Mode transition challenging, expected to be stable due to dual symmetric planform similar to flying Frisbee M>1: high sweep, low aspect ratio, low wave drag, low sonic boom M<1: low sweep, high aspect ratio, high L/D, long loitering, ESTOL. No fuselage provide maximum flexibility for aerodynamic configuration design

43 Conclusions (continued) CFD show low boom, 0.3psf, smooth ground boom signature Zero or near zero sonic boom possible with isentropic compression pressure surface Aerodynamic and Sonic Boom performance vary with: sweep, aspect ratio, airfoil thickness, Spanwise airfoil twist, planform shape The geometry studied is rough, has no optimization Large room for further improvement on aerodynamic and sonic boom performance

44 Future Work Optimize supersonic and subsonic performance CFD Simulation proof of stable unsteady supersonic-subsonic mode transition Wind tunnel testing for supersonic, subsonic, mode transition performance Mission i design optimization i for long range supersonic flight at Mach 2-4 and possible long endurance loitering ote Prototype design/manufacturing, wind tunnel testing, flight tests

45 Acknowledgement Florida Center for Advanced Aero-Propulsion for funding support L. Cattafesta at UF, F. Alvi at FSU H. Welge & A. Shmilovich at Boeing, J. Padin at Aerospace Corp. Don Durston from NASA Ames M. Wintzer at Stanford, M. Aftosmis at NASA Ames Bertrand Dano at UM