Stall inception and control in a transonic fan, part A: Rotating stall inception

Half-annulus numerical simulations of rotating stall inception have been carried out on a transonic axial compressor rotor. In order to initiate stall, the tip gap of one of the blades in the half-annulus computational domain was increased, and computations were conducted from choke to near-stall and in-stall conditions. Spike-type stall inception was observed by throttling behind the near-stall point. The large-tip blade was found to be responsible for stall initiation (i.e., stall is initiated from its upper neighbor). The stall cell then rotated at an initial speed of about 70 percent of the rotor speed. Results reveal a vortical structure within the stall cell upstream of the rotor, starting from the cell rear and moving radially inward as approaching the blade. The growth of a low-velocity region near the pressure-surface and the blade tip leading-edge (causing leading-edge vortex spillage) was found to be responsible for stall initiation. The effect of back plenum chamber on the rotor in-stall behavior is further investigated in the current study.