Flow Measurements inside a Heated Multiple Rotating Cavity with Axial Throughflow

This paper discusses experimental results from a number of different build configurations of the Sussex Multiple Cavity Rig. Measurements of the axial, tangential and radial velocity components are presented. These measurements were made using a two component, Laser Doppler Anemometry (LDA) system. The test rig is a 70 % of full scale version of a high pressure compressor stack from a gas turbine aero engine. Of particular interest are the internal cylindrical cavities formed by adjacent discs and the interaction of the flow in these with a central axial throughflow of cooling air. Tests were carried out for a range of non-dimensional parameters representative of H.P. compressor internal air system flows (ReO up to 4 x 106 and Rez up to 1.8 x 105). Two different builds have been tested and the difference between these is the size of the annular gap between the (non-rotating) drive shaft and the bores of the discs. There are significant differences between the radial distributions of tangential velocity in the two builds of the test rig. For a smaller annular gap between the drive shaft and the disc bore, there is an increase of non-dimensional tangential velocity VO / N)r with radial location to solid body rotation VO / N)r = 1. For the larger annular gap, there is a decrease with radial location to solid body rotation. An analysis of the frequency spectrum obtained from the tangential velocity measurements is consistent with a flow structure consisting of pairs of contra rotating vortices.