Some Operating Characteristics of the Supersonic Axi-Symmetric Parallel Diffuser

Abstract

This paper extends the investigation of the supersonic parallel diffuser previously reported by Martin and Baker (I)‡ and Baker (2) to cover the case of the axi-symmetric cross-section. The flow patterns and the wall static pressure distributions appear broadly to correspond to those which occur in the parallel diffuser of rectangular cross-section. But the axi-symmetric diffuser is found to have a wider operating range (in terms of overall blowing pressure ratio) before the single shock gives way to an oblique shock system, and this permits higher optimum recovery of static pressure. In the axi-symmetric configuration, only very short lengths of duct are necessary to achieve full static pressure recovery in both the single shock and the oblique shock regimes. The use of short diffusers would lessen the cooling problems of large-scale jet engine test facilities, in which exhaust jets must be recompressed at elevated temperatures.