Optimization and analysis of inverse design method of maximum thrust scramjet nozzles

Abstract

With the development of scramjet engines and hypersonic vehicles, the importance of the scramjet nozzle has become increasingly prominent. Many studies have attempted to increase the aerodynamic performance of nozzles. Under this circumstance, an inverse design method on the scramjet nozzle has been proposed on the basis of maximum thrust theory. The effectiveness and flexibility of the proposed method have been verified. As an inverse method, the target (i.e., the flow conditions on the key point) is a primary factor in the design process that significantly affects the performance and geometry of the nozzle. The present study investigates the influence of the key point on the shapes and performance of the nozzles. It aims to obtain a relative universal design principle in the inverse design process. First, the inverse design method is introduced briefly to facilitate understanding of the background. Second, the design of experiment (DOE) technique is presented, which can be used to study the effect of factors on the responses. Third, the effects of flow conditions, including Mach number, flow deflection angle, and ratio of mass flow rate, are investigated. The major factors on the thrust, lift, and nozzle length are distinguished successively. The thrust is mainly affected by the Mach number and flow deflection angle. The lift and nozzle length are dominated by the Mach number and ratio of mass flow rate. The influence of the flow deflection angle on the lift and length is negligible. Finally, the conclusion obtained from the DOE study is utilized to optimize an actual nozzle design process. The aerodynamic performance and geometrical configuration of the nozzles can be adjusted quickly. Combined with the inverse design concept, a fast and comparatively accurate design method on scramjet nozzle is formed.