Numerical study on the stall process of a low speed axial compressor rotor

To explore the flow characteristics of the compressor stall process, a multi-passage three-dimensional unsteady numerical simulation of the first stage rotor of a two-stage large-scale low-speed axial compressor was carried out. Results show that the flow instability of the rotor is caused by the separated flow from the hub corner and the tip leakage vortex. The separated flow from the hub corner migrates radially to the tip of the blade, forms a backflow under the entrainment of the tip leakage vortex and blockes the mainflow. Under the near-stall condition, there is a number of circumferentially propagating flow structures in the tip region, and their circumferential propagation speeds are consistent. During the stall inception process, the number of circumferentially propagating flow structure is gradually reduced, and the propagating structures merge into a stall sell which occupies 2-3 blade passages. In addition, the calculation results show that the spike-type stall inception is detected by the numerical probe arranged on the casing, and the circumferential propagation speed of the inception is about 66.77% of the rotor speed in the absolute coordinate system. Furthermore, during the stall inception process, the influence of the backflow from trailing edge at the tip region is further enhanced. Under the interaction of the backflow, the mainflow and the tip leakage flow, the flow structures such as the wall vortex, the secondary vortex and the leading edge separation vortex are gradually formed on the suction surface of the blade.