A Contribution to the Theoretical and Experimental Examination of the Flow Through Plane Supersonic Deceleration Cascades and Supersonic Compressor Rotors

Abstract

The results of the experimental investigations of plane supersonic deceleration cascades (tandem cascades) conducted in recent years at the Institut fu¨r Strahlantriebe und Turboarbeitsmaschinen der Technischen Hochschule Aachen (Institute for Jet Propulsion and Turbine Machines of the Aachen Technical University) are summarized. The flow through a supersonic compressor rotor is determined by means of a suitably enlarged method of characteristics. A division of the blade channel into two sets of stream surfaces permits an iterative calculation of the three-dimensional flow. To determine the flow values in the subsonic range, 5-hole-probes featuring a semi-spherical head are used in front of the rotor. The supersonic flow is determined by means of 5-hole-probes of the conical type arranged at varying distances behind the rotor. To determine the efficiencies, all probes were equipped with two NTC-elements each, for temperature measurement. These measurements were carried out at different rotational speeds and throttle positions and supplied rotor characteristics as well as information on the course of the flow behind the rotor. With unthrottled flow, a total pressure ratio of 3.9 resulted, with a total isentropic efficiency of 89 percent. The measurement of wall pressures on hub and tip furnishes additional information on the course of flow. The test values measured show a satisfactory agreement with the calculated design values.