Analysis of a Channeled Centerbody Supersonic Inlet for F-15B Flight Research

Abstract

The Propulsion Flight Test Fixture at the NASA Dryden Flight Research Center is a unique test platform available for use on the NASA F-15B airplane, tail number 836, as a modular host for a variety of aerodynamics and propulsion research. The first experiment that is to be flown on the test fixture is the Channeled Centerbody Inlet Experiment. The objectives of this project at Dryden are twofold: 1) flight evaluation of an innovative new approach to variable geometry for high-speed inlets, and 2) flight validation of channeled inlet performance prediction by complex computational fluid dynamics codes. The inlet itself is a fixed-geometry version of a mixed-compression, variable-geometry, supersonic inlet developed by TechLand Research, Inc. (North Olmsted, Ohio) to improve the efficiency of supersonic flight at off-nominal conditions. The concept utilizes variable channels in the centerbody section to vary the mass flow of the inlet, enabling efficient operation at a range of flight conditions. This study is particularly concerned with the starting characteristics of the inlet. Computational fluid dynamics studies were shown to align well with analytical predictions, showing the inlet to remain unstarted as designed at the primary test point of Mach 1.5 at an equivalent pressure altitude of 29,500 ft local conditions. Mass-flow-related concerns such as the inlet start problem, as well as inlet efficiency in terms of total pressure loss, are assessed using the flight test geometry.

Research on the Design Methods of Channeled Centerbody Supersonic Inlet

“…To estimate the entrance Mach number, the bicone of the centerbody was simplified to a single, average right-circular cone. And we assumed that the average Mach number for the inlet entrance was equal to the surface Mach number on this average cone [2]. Once the throat area was determined, we could choose a proper area distribution along the x axis to determine the contour of the centerbody.…”

“…The translating channeled centerbody inlet is complex than translating centerbody inlet, but simpler and lighter than the variable diameter inlet. Since the phenomenon of inlet unstart is primarily dependent on area distribution, Ratnayake, N. A [2] studied the starting characteristics of the Equivalent Centerbody inlet (ECB),a smoothed centerbody that provides the same area distribution as the Channeled Centerbody(CCB) inlet.…”