Optimization of Hybrid Wingbody Aircraft

1. National Aeronautics and Space Administration Spring Progress in Mathematican and Computational Studies on Science and Engineering Problems May 3-5, 2014, National Taiwan University Optimization of Hybrid Wingbody Aircraft Meng-Sing Liou NASA Glenn Research Center

2. A Tribute A cumulative effort, by postdocs and students under various NASA programs, developing and piecing together a set of necessary elements for performing MDAO. • SFW, SUP • NASA Postdocs Program • NASA USRP • Akira Oyama • Hyoungjin Kim • Byung Joon Lee • Justin Lamb • Angelo Scandaliato • Nick Stowe • Weigang Yao • Mattia Padulo • May-Fun Liou Knowledge Capabilities Applications

3. NASA’s Technology Development Goals

4. Current Commercial Aircraft

5. Hybrid Wingbody vs Current Aircraft • Pros: lighter weight, higher lift to drag ratio, and lower fuel burn, reduced community noise • Cons: aerodynamic interferences may reduce aerodynamic performance, propulsive efficiency and structural tolerance to distortion • A complex system requires simultaneous consideration of of multiple disciplines and design objectives Tube and wing Hybrid (blended) wingbody N2-B

6. Historical Development of HWB Vehicles Northrop Gruman B-2, 1989 Northrop YB-49, 1947 Northrop YB-35, 1946 • Airfoil:NACA 65-019 root, NACA 65-018 tip

7. Historical Development of HWB Vehicles Boeing UAV X-48, 2007 Boeing UCAV X-45C, 2002 Burnelli CBY-3, 1955 DassaultnEUROn, 2012 Commercial Transport ???

8. Hybrid Wingbody Aircraft – N3-X • HWB (hybrid wing body) configuration for N+3 requirements • Turboelectric Distributed Propulsion • Embedded fans driven by electric motors in a mail-slot nacelle • Wingtip mounted superconducting turbo-generators • Decoupling of generator and motor speeds • Ingestion of upper surface boundary layer • Expected to reduce fuel burn by more than 70% relative to Boeing 777-200LR Kim, H. and Liou, M.-S., AIAA-2013-0221.

9. Fuel Efficiency and Noise Data Expected improvement by 26% But …

10. Challenges • Integration of propulsion and airframe • Inlet ingesting thick boundary layer, resulting in a considerably distorted flow with total pressure loss at the compressor face • Significant loss in aerodynamic performance resulting from their mutual interferences

11. HWB Configurations Studied by NASA Boeing UAV X-48, 2007 N2-A N2-B N3-X

12. Outline of Presentation • Integrated Configuration • Mitigation of inlet flow distortion and loss of propulsive efficiency • Aerodynamic analysis and optimization for N2-B and N3-X

13. Flow Features in Embedded Boundary Layer Ingestion (BLI) Inlet Hybrid Wing Body Aircraft: N2B • Advantages: • Reduced ram drag • Reduced structural weight • Reduced wetted area • Reduced noise • Increased propulsive efficiency Hybrid wing-body • Forces: • Viscous stresses • Streamwise adverse pressure gradient • Centrifugal force Boundary-Layer Ingestion N2-B S-bend separation, Secondary flow • Impact on Propulsion System: • Thick low-momentum layer ingested into inlet, • Significant distortion and • Total pressure loss at AIP Non-uniform flow at AIP Horseshoe vortex, Lip flow separation

14. BLI Inlet Allen et al. Vortex generator Wall bleeding

15. Taming Distortion and Losses in BLI Inlets • Alternative way to conventional flow control, without incurring system losses. • Shape optimization: properly conditioning the flow before it entering the inlet. Yu the Great – Xia Dynasty

16. Design Optimization: Problem Statement • Design Formulation • Minimize : • Subject to : • zi : z coordinate of ith control point • zL : limit of design variable (10% of Inlet Height) • Design Condition • M0=0.85, Re0=3.8mil., A0/Ac=0.533 • BL thickness : 35% of Inlet Height • Design Variables • Control Points on the NURBS Patch, -1.8 x/D 0.5 Liou, M.-S. and Lee, B. J., “Minimizing Inlet Distortion for Hybrid Wing Body Aircraft,” ASME J. Turbomachinery, Vol. 134, #3, 2012. Lee, B. J. and Liou, M.-S., “Optimizing Shape of Boundary-Layer-Ingestion Offset Inlet Using Discrete Adjoint Method,” AIAA J. Vol. 48, No 9, 2008-2016, 2010.

18. Detailed Flow Structures: Near Inlet Throat Y/D=0.5 Plane flow separation at lip • Establishing a global pressure field, resulting in flow acceleration • Eliminated lip flow separation

19. Performance at Off-design Conditions • Simultaneous improvements in total pressure recovery and distortion • Superior performance is maintained by the optimized design at all off-design conditions

20. Oil Flow Patterns at Off-Design Conditions Baseline Model A0/Ac=0.533 A0/Ac=0.506 A0/Ac=0.401 Optimized Model A0/Ac=0.557 A0/Ac=0. 423 A0/Ac=0. 523

21. Inlet-fan Coupling • Mitigate deficiency in traditional specification of outflow pressure condition for assessing the inlet performance • Direct coupling of, hence specification by the fan operating condition • Need for fan flow analysis • Full-scale simulation • Reduced-order modeling

22. Reduced-order Model for Fan Flow • R4 Fan—1/5-scaled model tested in NASA Glenn Research Center, 22 in. diameter and 22 blades • Reduced-order model built based on the CFD solutions

23. The Need for Analyzing Integrated Configuration

24. Propulsion Model for N2-B

25. Effects of Propulsion System Installation

26. Impacts on Flowfield and Aerodynamic Performance

27. Inlet Performance

28. Design Optimization • Nacelle geometry • Minimize drag, and • Minimize distortion

29. Drag Minimization

30. Distortion Minimization

31. N3-X • Turbo-electric distributed propulsion (TeDP) • Targeted benefits: fuel burn savings by 70% relative to Boeing 777-200LR, M=0.84

32. Why Electric Propulsion • Exhaust of current airplanes, CO2, NOx, particulates, … contributes climate changes • Noise mitigation • Allowing solar energy as power source Solar Impulse II

33. Fan Model

34. Flowfield near and inside the propulsion system Symmetry place Centerplane of Outermost passage

35. Propulsion Performance

36. Design by Drag Minimization Baseline Optimized

37. Concluding Remarks & Outlook • Using high fidelity analysis and optimization in early design phase can reveal areas of importance and shed insight on technological challenges. • Have discovered an effective way to improve inlet performance, without sacrificing system efficiency. • Geometry, geometry, geometry … • MDAO has received considerable emphasis, developed fast, and its future for prime time is very promising.

38. Leonardo di ser Piero da Vinci April 15, 1452~May 2, 1519, Florence, Italy

39. http://www.solar-impulse.com/ http://www.youtube.com/watch?feature=player_embedded&v=FWvgpngKIW4 Thank you for your attention and Best wishes! Keep up your dream, Look up to those pioneering dreamers, and Follow their spirits.