Investigation of the diffusion characteristics of supersonic streamscomposed mainly of boundary layers.

Abstract

The diffusion characteristics of a supersonic stream composed primarily of boundary-layer flow were investigated using an annular supersonic wind tunnel discharging into an annular diffusion system representative of the surfaces near the throat region of an axisymmetric hypersonic inlet. Tests were conducted over a range of freestream Mach numbers of 2 to 5. At each test Mach number, the boundary layer approaching the diffuser was varied by changing the length of the constant area section upstream of the models. Data for diffusion system pressure recovery, static pressure distributions, and velocity profiles were obtained at each test Mach number for a range of area contraction ratios, convergence angles, and Reynolds numbers. An analytical method for predicting the performance of the supersonic boundarylayer diffusion system was developed on the basis of an experimental correlation of the minimum throat Mach number with an average flow distortion parameter. Both the analytical and experimental results indicate that the maximum pressure recovery of a supersonic boundary-layer diffusion system is obtained with a convergent section having a low convergence angle, between 3° and 6°. This analysis, which was developed for duct flows composed entirely of boundary layers, can also be employed to analyze duct flows having an inviscid core. The application of this method in calculating the performance of a hypersonic inlet is illustrated by means of examples.