Performance and wall static pressure measurements on centrifugal compressor diffusers

Abstract

The results of experimental studies on performance and wall static pressure distribution in the diffuser passage of a low specific speed centrifugal compressor are given. The performance tests were carried out with vaneless, vane and low-solidity vane diffusers at speeds of 2500, 3000 and 3500r/min. Diffuser wall static pressures measured at 3000r/min for four flow coefficients on the shroud and hub walls are reported. The peak energy coefficient is maximum for the vane diffuser. The operating range of the low-solidity vane diffuser is wider than that of the vane diffuser. At high flow coefficients, the static pressure rise is substantially lower for the vane diffuser, as the incidence on the vane leading edge is very high. The low-solidity vane diffuser did not suffer a large drop in static pressure near the leading edge. The most probable reason may be the large area available in the low-solidity vane diffuser for flow adjustment and weaker flow separation zones on account of the lower number of vanes.