Initial selection of groove location combination for multi-groove casing treatments

Abstract

Stall margin improvement (SMI) curve is a function of a single groove location for a low-speed axial compressor and is investigated numerically and experimentally in this paper. SMI curve illustrates that good grooves are located in a fairly wide region approximately from 30% Cax to 80% Cax aft of the rotor leading edge. The narrow region that contains bad grooves is near 20% Cax aft of the rotor leading edge. The initial selection of groove location combination for multi-groove casing treatments is proposed based on the SMI and efficiency improvement data generated by a series of single-groove and multi-groove casing treatments. The grooves should be set in the “wide region” of the SMI curve. The grooves located near the “narrow region” and the rotor trailing edge should be avoided. The “narrow region” can be identified by the axial momentum distribution of the tip leakage flow or the circumferentially averaged axial shear stress on the casing using the simulation results of the smooth casing at the near-stall point.