Influence of Compressor Exit Conditions on Diffuser Performance

Results are presented of an experimental investigation into the way in which compressor exit conditions influence the performance of two optimum combustor-dump diffusers. In an optimum system nearly all of the pressure rise occurs in a relatively long prediffuser which is designed to produce a symmetrical outlet velocity profile at the design flow split. One diffuser was tested downstream of a seven-stage axial flow compressor and, for comparative purposes, retested with fully developed flow at inlet. The second diffuser was tested downstream of an annular tandem cascade which could be sited at a number of positions relative to diffuser inlet. The overall performance, measured when the wakes from the outlet guide vanes had decayed considerably, was the same as that achieved with fully developed inflow.