Unsteady wall pressure measurement in a one-and-a-half stage axial transonic compressor during stall inception

Abstract

This paper presents the experimental investigation of the stall inception of a state-of-the-art transonic compressor that resembles a typical front stage of a commercial jet engine. The compressor was designed and manufactured in cooperation with Rolls-Royce Deutschland and assembled in the Darmstadt Transonic Compressor test facility at Technische Universität Darmstadt, Germany. Utilising the 1.5-stage design it is possible to investigate stall inception for different rotor inflow conditions. The aerodynamic features prior and during stall inception are investigated by means of unsteady pressure probes in the casing above the rotor. All stall inception events have a spike-type stall character. However, in some cases the spikes are preceded by modal-type activities. In addition to the unsteady wall pressure, speed lines are presented. The combination of the data shows a clear effect of measurement position and averaging process on the shapes of the speed lines but did not allow to predict the type of stall inception.