Numerical Simulation of Aerodynamic Instability Mechanisms in the Diffuser of a Multistage Centrifugal Compressor
The main reason for limiting the working flow range of the compressor is the unstable flow phenomenon of the compressor working at a small flow rate, including stall, surge, and rotational instability. Among them, the rotating stall phenomenon is particularly prone to occur during the operation of centrifugal compressors. In this paper, a three-stage nitrogen centrifugal compressor is taken as the research object, and the dynamic development process of rotating stall in the diffuser is captured by full-channel numerical calculation. After research, the leading-edge vortex at the diffuser inlet is the cause of rotating stall. In the throttling process, the backflow in the diffuser causes the channel blockage and the stall phenomenon triggered by the leading-edge overflow. There are six stall channels in the first-stage diffuser and nine stall channels in the second-stage diffuser. The propagation direction is the same as the rotation direction of the blade, and the propagation speeds are 4.348% and 5.26%, respectively.