Research On Stall Characteristics And Stall Suppression In A Centrifugal Compressor

Centrifugal compressor is widely used in various fields, because of its large treatment capacity, high pressure ratio, simple structure and convenience in maintenance. However, rotating stall occurs when centrifugal compressor runs under low flow rate. Therefore, research of rotating stall and increasing stable working range of centrifugal compressor are of great significance.Key factors contributed to rotating stall were analyzed. Based on these conclusions, the effects of circumferential groove treatment on performance and stall suppression were studied. The main work of this thesis can be described as follows:The numerical calculation model of centrifugal compressor with vaneless diffuser was established. The numerical models are verified by comparing with literature data.The key factors of vortices formation in the impeller, which are separated from blade suction side, secondary flow and tip leakage flow, were found out by numerical analysis. The vortices blocking flow channel develop into stall cell, which propagates circumferentially. The flow distortion at diffuser inlet and reversal flow on shroud side are the key factors of stall in the diffuser. The disturbance from impeller outlet and decrease of stability lead to stall in the diffuser.Circumferential grooves can improve stability of compressor by reducing interaction between tip leakage flow and main flow, weaken secondary flow, and suppress the separation from blade suction side. The section size, position and number of circumferential groove can affect performance and stability of compressor, and stability increase lead to performance reduction.The geometry of vanless diffuser has obvious effects on performance and stability. The stability can be improved by reducing distortion of flow angle at diffuser inlet and reversal flow on shroud side.Detailed research on stall and stability enhancement was carried out. The conclusion has deepened the understanding of rotating stall, and provide a reference for the optimal design for the stable operating range of centrifugal compressor.