Detailed measurements of the static pressure characteristics around the centrifugal compressor casing wall

The non-axisymmetric geometry structure of the volute leads to the uneven circumferential distribution of the flow field inside centrifugal compressors. It is difficult to describe the whole flow field for few measuring points installed around the centrifugal compressor casing wall. In this paper, seventy-two static pressure measuring probes including the six circumferential position and the twelve meridional position were installed around the casing wall, and the circumferential distribution of the static pressure was compared under the different speeds at the full flow rate. Some especial circumferential distributions of the static pressure were founded through analyzing the experimental results. At the small flow rate, the circumferential distribution of the static pressure not only has the peak static pressure point induced by the volute tongue but also has the bulge phenomenon, which also appears near the design flow rate. The stall inception most likely occurs at the static pressure peak or the static pressure bulge region. In each speed, there is a flow rate corresponding to the lowest circumferential variation of the static pressure and the peak efficiency. The amplitude of the circumferential static pressure variation does not decrease with the reducing flow rate, on the contrary, the amplitude has the increasing tendency along the meridional direction. The circumferential static pressure distribution at the leading edge of the splitter blade is almost the same at different small flow rates. Meanwhile, the circumferential static pressure distribution has the two peaks phenomenon, which has the approximately 180 degrees circumferential difference between the two peaks points.