Study of the mechanism governing the stability expansion of the self-circulating casing treatment of a centrifugal impeller at a low rotating speed

To explore the mechanism governing the stability enhancement of the self circulation casing treatment, the authors have conducted a detailed study of a low speed centrifugal compressor (LSCC) in which a casing treatment was applied by using a full-three-dimensional numerical simulation.It has been found that the self circulation casing treatment can effectively delay the occurrence of a stall and slightly enhance the efficiency of the compressor and total pressure ratio in zones nearing the stall region.The casing treatment can efficiently lower the blade tip loads, thus decreasing the relative speed of the leakage flow, prohibiting the development of the leakage flow vortices in the clearances of the blade tip passages, reducing the jam of the low speed flow in the passages, enhancing the flow capacity of the passages of the rotor and achieving the aim to enlarge the stable operation range.The comprehensive stability margin can increase by 12.57%.