Inhibition mechanism of static pressure circumferential double-peak distribution using a recirculation device for a centrifugal compressor

The asymmetric volute structure in the turbocharger centrifugal compressor causes a static pressure circumferential double-peak distribution (PD-DP) at small flow rates and affects the circumferential stall position near the impeller inlet. In this study, a recirculation device was added to a prototype compressor, and the effect of the recirculation flow on the PD-DP was studied to reveal the difference in the PD-DP formation mechanism with and without the device. In addition, the influence of the PD-DP difference on the compressor flow stability was investigated. The results show that the PD-DP generated various pressure gradients between the front and rear slots of the recirculation device at different circumferential positions, resulting in a double-peak distribution in the recirculation flow rate. When the recirculation airflow flowed back into the impeller inlet, the two recirculation flow rate peaks were near the circumferential positions occupied by the two static pressure peaks in the prototype compressor. Therefore, the pressure distortion degree near the impeller inlet could be inhibited, weakening the difference in the deflection degree of the tip leakage flow (TLF) in each compressor passage. It should be noted that the circumferential positions with more prominent variation in the TLF corresponded to the passages with more serious flow deterioration in the prototype compressor, and the blockage of these passages near the inlet was reduced to a greater extent, which could better improve the flow stability of the compressor.