Optimization design for scramjet flowpath considering hypersonic vehicle trim effects

Due to the highly integrated engine and airframe, scramjet as high speed propulsion system of airbreathing hypersonic vehicle can not be designed as an independent component. Design process of scramjet must consider effects on whole hypersonic vehicle integrated performance. Flowpath of scramjet includes forebody and afterbody of vehicle. In vehicle flight process, high pressure of pre-compress coming air on forebody surface will produce pitch up moment, and high pressure of expanded gas on afterbody surface will produce pitch down moment In addition, internal surface of scramjet will produce pitch up or down moment more or less, such as dissymmetrical wall of combustor. For an operational hypersonic vehicle, approach of stability and control is deflection of tails. Too much degree deflection of tail will increase trim drag of vehicle and therefore design of scramjet flowpath should decrease effect on vehicle trim moment. This paper presents some further research work based on our previous research work that scramjet optimization design aimed at optimum propulsion performance (IAC-04-S.5.11). Effects of scramjet operation on hypersonic trim moment have been analyzed. In design process of multi-lever optimization aimed at trim drag keep minimum, optimization object of scramjet flowpath is determined and new design object consider propulsion performance and effect on vehicle trim moment. Results show new scramjet flowpath design has little effect on hypersonic vehicle trim moment than design just aimed at propulsion performance, and meanwhile overall trim drag of vehicle will be reduced. This research also show design strategy of multi-lever decompose optimization for hypersonic vehicle can efficaciously deal with component optimization and overall system optimization.