Numerical and experimental investigations have been conducted on a self-recirculating casing treatment for a centrifugal compressor.Stall margin improved due to redirecting the low-momentum fluid to increase the mass flow in the impeller passage and decreasing the positive attack angle in the tip region with preswirl blowing.Based on the working mechanism

parametric studies were conducted to design the casing treatment geometry.It was found that the angle of the grooves

the position and the length of overlap were three key parameters for the “best casing configuration” in terms of larger stall margin improvement and smaller lowering of efficiency according to the given range of rotating speeds.The effectiveness of this casing treatment was verified by the single stage centrifugal compressor experiments

and it was observed that the stall margin and efficiency can be improved simultaneously at lower rotating speed.