Design Method of a Modular Shape-Transition Nozzle for an Axisymmetric Scramjet-Powered Vehicle

For a hypersonic vehicle powered by modular scramjet, integration of the airframe with the engine is critical to generating positive net thrust. In this study, a design method that combines the ideas of streamline tracing and trimming is generalized to design the modular shape-transition nozzle for integrating with the axisymmetric vehicle after-body. As an example, the design of a modular shape-transition nozzle with three modules for an axisymmetric vehicle is presented, and the computational fluid dynamics (CFD) approach is adopted to obtain the detailed flowfield and performance of the modular nozzle. Smooth expansion of the burner-exits gas along the flow direction is involved in the modular nozzle. The flow interactions between any two module exhausts, as well as the flow interaction of the modular jet with the external freestream, are all appearing at the trailing edge of the modular nozzle. Moreover, the modular nozzle produces a net thrust coefficient of 0.8536 and an integrated thrust coefficient of 0.7896 for the vehicle. The mixing of the modular nozzle jet with the freestream is enhanced with the trimming of the separate nozzle module, an approach which can reduce the infrared radiation signal.