Formation mechanism of static pressure circumferential double-peak distribution in a centrifugal compressor under the action of downstream boundary

Abstract

In the centrifugal compressor applied in the automobile turbochargers, the asymmetric structure of volute causes the non-uniform flow field in the impeller and compressor stall. The non-uniformity of the flow field in the compressor can be reflected by the casing-wall static pressure distribution. In this study, by removing the volute and directly imposing different simplified static pressure boundary conditions at the diffuser outlet, the formation mechanism of casing-wall static pressure circumferential double-peak distribution of the compressor is explored. It is found that the mass flow rate is redistributed at the impeller outlet due to local high static pressure induced by the volute tongue, which results in the formation of two airflow regions with high velocity in the diffuser, ultimately leading to the static pressure circumferential double-peak distribution in the diffuser and the impeller. Noted that because of the existence of the blades, the airflow regions with high and low velocity formed in the diffuser are locked within a limited range of one or more widths of the blade passage. When the number of blades in the compressor is large, the static pressure can appear as multi-peak distribution in the circumferential direction. Moreover, the result of the mass flow rate redistribution at the impeller outlet is determined by the static pressure distribution characteristics at the diffuser outlet.

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

“…The stall cell is first produced at the impeller inlet circumferential region, corresponding to the first high static pressure strip induced by the VT. With a further decrease in the flow rate, the LE spillage also appears at the impeller inlet circumferential position corresponding to another high static pressure strip. PD-DP was also displayed in the studies of Tamaki et al, 24 Harley et al, 25 and Zheng et al 26 Moreover, Su et al 29,30 further elaborated that the PD-DP is caused by the redistribution of the impeller outlet flow rate, and the static pressure strips are gradually created from the downstream to the upstream of the compressor.…”

Effect of bend-induced inlet distortion on a centrifugal compressor performance and stall inception

“…Zheng et al investigated the volute-induced non-axisymmetrical flow in a centrifugal compressor, 10,11 and developed non-axisymmetrical self-recirculation casing treatment 12 and a volute design method. 13 The study of Yang et al 14 and Su et al 15 showed that the volute could determine both the static pressure distribution on the casing wall and the circumferential position of stall inception. Moreover, Fu et al 16 investigated the same centrifugal compressor with vaned/vaneless diffuser and found that the vaned diffuser reduces the potential effect of volute but could not eliminate the “locking effect” of stall inception.…”