Blended Wing Body Optimization Design And Aerodynamic Performance Analysis With Nacelle

The BWB is an airplane with a wing blended to the body that still maintains distinct wing and body structures.With the increasing demand for economy and environmental protection of civil transport,BWB has attracted more and more attention from all countries due to its characteristics of high lift-to-drag ratio,low fuel cost and low noise,and has become the research hotspot of the next generation of civil transport.Many countries such as the United States,the European Union(EU)countries,and Russia have done a lot of research on BWB.However,wing body blended also brings many technical challenges.Such as the problems of fuselage volume,cabin ground angle and trim,landing speed and attitude,buffeting and stall,static stability margin,etc.In order to solve the above technical problems,researchers all over the world regard multidisciplinary optimization design as the main technical approach.But this would also need to solve many difficult problems in optimization design,such as the problems of the coupling of multiple disciplines,the large number of design variables and constraints,etc.In addition,conventional airplane engines often located beneath and in front of the wing,but the engine of the BWB is located over the wing and behind the body.In order to do the engine/airframe integration design well,many factors need to be carefully figured out first.For example,how to design the BWB engine nacelle,what are the influences of nacelle position on the aerodynamic characteristics of the BWB body,what are the interference characteristics between the BWB engine and body,and whether the engine reverser technology can be used in BWB,etc.In the key technical problems of BWB civil aircraft technology research,two of them are focused on in this paper.One is how to do the layout optimization with high efficiency in the conceptual design stage;the other is the interaction influences of airframe/engine on aerodynamics for the unconventional layout,especially the BWB with podded engine.In this paper,using VB and CATIA software,combined with CFD calculation and adjoint optimization and other related programs,the aerodynamic optimization design platform of BWB based on CAD and adjoint method is constructed,and the shape of BWB at high-speed cruise state is optimized by using this platform;the design method of engine flow_through nacelle(FTN)is studied,and then the nacelle position influence on the aerodynamic characteristics of BWB is studied;the simplified method of the engine powered nacelle model is studied and verified,and then the engine/airframe interaction influence on BWB is analyzed through comparing the high and low speed aerodynamic performances of the BWB WPN(With Powered Nacelle)configuration,FTN configuration and Clean Configuration;the engine’s power influence on the aerodynamic characteristics of BWB airframe is studied by comparing the high and low speed aerodynamic characteristics of the BWB WPN and Clean landing configuration;the engine cascade thrust reverser is taken as an example to study if there is any problem of appling it on BWB.Through the above research,in the aspect of layout optimization,this paper independently develops a BWB aerodynamic optimization design platform,and achieves the optimization design of BWB at cruise speed;in the aspect of airframe/engine integration research,the influence of nacelle position along chord,vertical and longitudinal on the aerodynamic characteristics of BWB airframe is obtained,the influence of engine on the aerodynamic characteristics of BWB cruise configuration and the influence of the engine’s power on the aerodynamic characteristics of BWB take-off state are also obtained.It provides the basis and direction for the BWB optimization design and airframe/engine integration design.In addition,a reasonable design of cascade thrust reverser for BWB is given in this paper.The application of cascade thrust reverser in BWB is preliminarily realized.