Three-dimensional flow field downstream of an embedded stator in a multistage axial flow compressor: Part 1: Steady and unsteady flow fields

Abstract

A comprehensive investigation of the three-dimensional unsteady flow and thermal field downstream of an embedded stator in a multistage compressor, acquired with a high-response hot-film probe and aspirating probe, is presented and analysed. Some of the earlier data (from a five-hole probe and a high-response Kulite probe) from the same compressor is used with the present data to provide an integrated interpretation of the flow and thermal fields. Part 1 includes a brief description of the facility, the development of the hot-film technique for the multistage flow field measurement and an interpretation of the various flow field features, such as the hub clearance flow and the suction surface-casing end-wall corner region. Part 2 covers velocity-velocity and velocity-temperature correlations and the assessment of their magnitudes in the average-passage equations. The results presented in this part of the paper (Part 1) indicate that major blockage in the stator hub end wall is caused by leakage flow and its possible subsequent roll-up into a vortex. Similar features exist in the suction surface casing end-wall corner due to secondary flow and its interaction with the upstream rotor end-wall flow. These are also the regions with the highest levels of unsteadiness. The transport of rotor wake towards the pressure side of the stator is confirmed. Both the revolution and the blade periodic velocity fluctuations are found to be significantly greater than the aperiodic fluctuations.