A New Design Concept for Supersonic Axisymmetric Inlets

Abstract

Inlets designed for high-speed flight require a wide variation in throat area to provide proper airflow to the engine for efficient operation at all Mach numbers. The inlet concept of this study consists of a design proven through prior research to offer high performance and excellent operability at cruise conditions (an axisymmetric inlet with a moderate amount of internal compression). It is made viable at off-design conditions with the application of an innovative variable geometry concept. This variable geometry system opens up longitudinal channels in the centerbody with forward centerbody translation at offdesign Mach numbers. The translating channeled centerbody inlet is slightly more complex than a traditional translating centerbody inlet, but significantly simpler and lighter than the variable diameter centerbody inlet. A VDC configuration was previously considered to be required to make axisymmetric inlet configurations without excessively large amounts of internal compression capable of meeting transonic engine airflow requirements. A flight research program utilizing the F-15B aircraft at NASA Dryden Flight Research Center has been initiated to demonstrate the inlet’s off-design masscapture capabilities and assess its impact on performance and distortion due to application of the variable geometry. This paper discusses the concept and the development of the aerodynamic designs of the configurations to be tested. * Chief Executive Officer, Senior Member AIAA. † President. ‡ Aerospace Engineer, Member AIAA. Nomenclature A Area Ac Cowl lip projected area At Throat area At,untran Throat area with zero centerbody translation m Mass flow mo Theoretical capture mass flow M Mach number Mo Freestream Mach number M2 Engine face Mach number Ml Local Mach number Mt Throat Mach number p Static pressure Po Freestream total pressure r Radial dimension r2 Engine face radius Rc Cowl lip radius rcb Centerbody radius at engine face x Axial dimension xt Throat station xtran Centerbody translation distance Wg Groove width θc Cowl lip initial angle θt Throat exit angle σ1 First centerbody cone angle σ2 Second centerbody cone angle