Effect of Axial Casing Groove Geometry on Rotor-Groove Interactions in the Tip Region of a Compressor

Abstract This experimental study characterizes the interactions of axial casing grooves (ACGs) with flow in tip region an turbomachine. The tests involve same inlet overlapping rotor blade leading edge, but different exit directions located upstream. Among them, U grooves, whose circumferential outflow opposes motion, achieve a 60% reduction stall flowrate, degrade efficiency around best point (BEP) by 2%. S outlets are parallel to rotation, improve flowrate only 36%, do not BEP performance. To elucidate mechanisms involved, stereo-PIV measurements covering and interior performed refractive index-matched facility. At low flowrates, inflow into both which peaks when they aligned pressure side (PS), rolls up large vortex that lingers within groove. By design, from is circumferentially positive. For fast negative at base each groove, causing substantial periodic variations angle near edge. BEP, become milder, most leakage (TLV) remains passage. Interactions limited; hence, efficiency. In contrast, reverses direction, entrainment secondary flows, likely contribute reduced