Numerical and experimental investigations of the flow in a compressor with circumferential grooves

Numerical and Experimental investigations were conducted to study the effect of circumferential grooves on the performance and flowfield of an axial-flow compressor rotor. A single-stage compressor rotor with no inlet guide vanes was tested under subsonic condition. Circumferential grooves as well as the original smooth wall configuration were analyzed to investigate the effects of circumferential grooves on compressor performance. The result shows that circumferential grooves are able to effectively extend the stall margin of the compressor with little influence on efficiency throughout the mass flow range tested. Steady-state Navier-Stokes analysis were performed to analyze flow structures associated with each casing treatment. The overall effects of circumferential grooves were correctly calculated with the numerical procedure. Detailed investigation of the calculated flow fields indicates that the key mechanism lay to the interaction with the tip leakage. Taking advantage of the existing pressure difference in the rotor blade row, circumferential grooves remove tip leakage flow in the high pressure zone and weaken or even destroy the structure of tip leakage vortex. At the same time the tip leakage reenters the main flow in the low pressure zones again and mixes with the main flow of the compressor, thus circumferential grooves influence the efficiency and stall margin of the compressor.