Aerodynamic Analysis of a Blended-Wing-Body Aircraft Configuration A thesis submitted in fulfilment of the requirement for the degree of Master of Engineering by Research. Toshihiro Ikeda Bachelor of Engineering School of Aerospace, Mechanical and Manufacturing Engineering Science, Engineering and Technology Portfolio RMIT University March 2006 Toshihiro Ikeda RMIT University, Melbourne, Australia Contents RMIT University, Australia Declaration The author certifies that except where due acknowledgement has been made, the work is that of the author alone, the work has not been submitted previously, in whole or in part, to qualify for any other academic award; the content of this thesis is the result of research which has been carried out since the official commencement date of the approved research program, and any editorial works, paid or unpaid, carried out a third party are acknowledged. Signed: Toshihiro Ikeda March 2006 Toshihiro Ikeda ii Contents RMIT University, Australia Acknowledgements There are so many who have helped both directly and indirectly in assisting with this research that it is difficult to thank everyone. The author’s sincere thanks and appreciation are extended to: Associate Professor Cees Bil of RMIT University and Mr. Robert Hood of GKN Aerospace Engineering Services for their unceasing positive guidance and sage advices, and RMIT IT staff for their support. Mr. Hawk Lee of Fluvius Pty Ltd for his professional advice regarding CFD simulation, and maintaining engineering workstations, as well as to the staff of Fluent Asia Pacific Co., Ltd. for their services. Mr. Tony Gray of Altair Engineering Inc. for his assistance and useful guidance of computational methodologies of HyperWorks applications. Mr. Adrian Baker of one of author’s friends and Associate Professor Cees Bil of RMIT University for taking the time to read, advise and make constructive comments on the document at various stages of its production. Finally, the author would like to thank his parents for their encouragement and support for his studies in Australia. Toshihiro Ikeda iii Contents RMIT University, Australia Abstract In recent years unconventional aircraft configurations, such as Blended-Wing-Body (BWB) aircraft, are being investigated and researched with the aim to develop more efficient aircraft configurations, in particular for very large transport aircraft that are more efficient and environmentally-friendly. The BWB configuration designates an alternative aircraft configuration where the wing and fuselage are integrated which results essentially in a hybrid flying wing shape. The first example of a BWB design was researched at the Loughead Company in the United States of America in 1917. The Junkers G. 38, the largest land plane in the world at the time, was produced in 1929 for Luft Hansa (present day; Lufthansa). Since 1939 Northrop Aircraft Inc. (USA), currently Northrop Grumman Corporation and the Horten brothers (Germany) investigated and developed BWB aircraft for military purposes. At present, the major aircraft industries and several universities has been researching the BWB concept aircraft for civil and military activities, although the BWB design concept has not been adapted for civil transport yet. The B-2 Spirit, (produced by the Northrop Corporation) has been used in military service since the late 1980s. The BWB design seems to show greater potential for very large passenger transport aircraft. A NASA BWB research team found an 800 passenger BWB concept consumed 27 percent less fuel per passenger per flight operation than an equivalent conventional configuration (Leiebeck 2005). The purpose of this research is to assess the aerodynamic efficiency of a BWB aircraft with respect to a conventional configuration, and to identify design issues that determine the effectiveness of BWB performance as a function of aircraft payload capacity. The approach was undertaken to develop a new conceptual design of a BWB aircraft using Computational Aided Design (CAD) tools and Computational Fluid Dynamics (CFD) software. An existing high-capacity aircraft, the Airbus A380 Toshihiro Ikeda iv Contents RMIT University, Australia was modelled, and its aerodynamic characteristics assessed using CFD to enable comparison with the BWB design. The BWB design had to be compatible with airports that took conventional aircraft, meaning a wingspan of not more than 80 meters for what the International Civil Aviation Organisation (ICAO) regulation calls class 7 airports (Amano 2001). From the literature review, five contentions were addressed; i. Is a BWB aircraft design more aerodynamically efficient than a conventional aircraft configuration? ii. How does the BWB compare overall with a conventional design configuration? iii. What is the trade-off between conventional designs and a BWB arrangement? iv. What mission requirements, such as payload and endurance, will a BWB design concept become attractive for? v. What are the practical issues associated with the BWB design that need to be addressed? In an aircraft multidisciplinary design environment, there are two major branches of engineering science; CFD analysis and structural analysis; which is required to commence producing an aircraft. In this research, conceptual BWB designs and CFD simulations were iterated to evaluate the aerodynamic performance of an optimal BWB design, and a theoretical calculation of structural analysis was done based on the CFD results. The following hypothesis was prompted; A BWB configuration has superior in flight performance due to a higher Lift-to-Drag (L/D) ratio, and could improve upon existing conventional aircraft, in the areas of noise emission, fuel consumption Toshihiro Ikeda v Contents RMIT University, Australia and Direct Operation Cost (DOC) on service. However, a BWB configuration needs to employ a new structural system for passenger safety procedures, such as passenger ingress/egress. The research confirmed that the BWB configuration achieves higher aerodynamic performance with an achievement of the current airport compatibility issue. The beneficial results of the BWB design were that the parasite drag was decreased and the spanwise body as a whole can generate lift. In a BWB design environment, several advanced computational techniques were required to compute a CFD simulation with the CAD model using pre-processing and CFD software. Toshihiro Ikeda vi Contents RMIT University, Australia Nomenclature A Statistical Empty Weight Fraction KVS Variable Sweep Constant a Speed of Sound Ks Scale Factor of Cabin Area AR Aspect Ratio k Turbulent Kinetic Energy B Fuselage Width of Aircraft L Lift b Wing Span L/D Lift to Drag Ratio bvert Tail Length M Mach number C Negative Exponent of Relationship Nult Ultimate Load Factor between Empty Weight and TOGW Nseat Number of Passenger Seat c Specific Fuel Consumption (SFC) P Maximum Pressure Differential C.G. Centre of Gravity R Range CL Lift Coefficient R Universal Gas Constant CD Drag Coefficient (287.05 J/Kg/K for Air) CDtotal Total Drag Coefficient Re Reynolds number CDpressure Pressure Drag Coefficient S Reference Area CDfriction Friction Drag Coefficient Scabin Cabin Area CDwave Wave Drag Coefficient Sfuse Gross Wetted Area of Fuselage CM Momentum Coefficient Sgw Gross Wing Area CDp Parasite Drag Coefficient Sref Reference Area of Aircraft CDI Induced Drag Coefficient Svert Vertical Tail Area D Drag T Absolute Temperature (Kelvin) d Mission Segment Range T Engine Thrust e Aircraft Efficiency TOGW Take-Off Gross Weight g Gravity (= 9.8 m/s2) T/W Thrust-to-Weight Ratio Toshihiro Ikeda vii Contents RMIT University, Australia (t/c)avg Average Airfoil Thickness W/S Weight Loading Ratio u Velocity of Fluid Wwing Wing Weight V Velocity WZFW Zero Fuel Weight V/c Propulsion Capacity Efficiency F Density Wair con Air Conditioner and Anti-Icing G Aircraft Shape Factor System Weight H Parameter of Wing Shape Wapu Auxiliary Power Unit Weight I Taper Ratio of Wing Wcabin Cabin Weight Jea Swept Angle of Structural Axis Wcrew Crew Weight µ Dynamic Viscosity Wdeng Dry Engine Weight µt Turbulent Kinetic Viscosity Welecp Electrical Equipment Weight Hij Kroenecker Delta Wempty Empty Weight Gb Generation of Turbulent Kinetic Energy Wfuel Fuel Weight due to Bouyancy Wfurni Furnishing Weight Gk Generation of Turbulent Kinetic Energy Wfuse Fuselage Weight due to Mean Velocity Gradient Wgear Landing Gear Weight Gv Production of Turbulent Viscosity Whp Hydraulics and Pneumatics Weight YM Contribution of Fluctuating Dilation Wsc Surface Control Weight Yv Destruction of Turbulent Viscosity Wtakeoff Take-Off Weight M Adiabatic Index (1.402 for Air) Wpayload Payload Weight O Kinetic Viscosity Wpro Propulsion Weight P 3.14159 Wvert Vertical Tail Weight Toshihiro Ikeda viii Contents RMIT University, Australia Table of Contents Declaration ii Acknowledgements iii Abstract v Nomenclature vii Table of Contents ix List of Figures xiii List of Tables xviii Chapter 1 Introduction 1 1.1 Definition of Blended-Wing-Body Aircraft Configuration ……………………… 1 1.2 Historical Background …………………………………………………………….. 1 1.3 Multidisciplinary Design Study of a BWB Aircraft Configuration …………….. 7 1.3.1 Specification of Airbus A380-800 …………………………………………... 7 1.3.2 Current BWB Configuration Designs …………………………….……… 10 1.3.3 BWB Design of NASA and the Boeing Company, USA ………………….. 11 1.3.4 Conceptual Flying Wing Configuration of Airbus, France ……………… 13 1.3.5 Feasible studies of BWB Aircraft by Cranfield College of Aeronautics, UK ………………………………………………………………………….