Study on Simplified Alternative Method for Downstream Boundary of Centrifugal Compressor

The casing-wall static pressure of the compressor in this paper has a very interesting phenomenon under a small mass flow rate. Four static pressure bands with high/low alternating distribution are formed in the circumferential direction, which is called the static pressure circumferential double-peak distribution. In order to study the formation mechanism of static pressure circumferential double-peak distribution, a simplified alternative method of downstream boundary is proposed. The complicated downstream boundary is simplified into a form with only local high static pressure and circumferential pressure gradient. The compressor volute and outlet pipe are removed, and the simplified boundary conditions are directly imposed to the diffuser outlet. The results show that under the simplified boundary condition, the casing-wall static pressure of the compressor can still show a circumferential double-peak distribution, which is very similar to that with volute. Furthermore, the circumferential pressure gradient is removed and only the local high static pressure region is retained. The static pressure circumferential distribution is also very similar to that with volute, which proves that the static pressure circumferential distribution is mainly affected by the downstream high static pressure region induced by volute. © 2022, Science Press. All right reserved.