The effect of inlet conditions on the flow in annular diffusers

Abstract : Tests were carried out on annular diffusers (plain and split) having a common area ratio of 3.19 and varying in divergence angle from 6.5 to 15. The performance of each diffuser was measured for a variety of inlet velocity distributions, and the effect of axially splitting the flow in the diffusers was investigated. Diffuser efficiency deteriorated as inlet conditions became nonuniform; this tendency increased with diffuser angle. Splitting of the higher angle diffusers improved efficiency for nonuniform profiles, but these increases in efficiency were accompanied by pronounced static pressure gradients across the diffuser throat which in certain applications might prove undesirable.