Analysis On The Spike-type Rotating Stall For Axial Compressor By Dynamic Mode Decomposition

In this paper, the spike-type rotating stall for axial compressor have been studied by dynamic mode decomposition. The full-wheel model with unsteady Navier-Stokes simulation is established and the atmospheric boundary condition is applied in order to obtain the detailed unsteady flowfield. The Omega-criterion is applied for better visualization of vortex. The stall process, including stall inception and stable stall, has been captured and studied. It is found the fluctuation in the compressor flow is dominated by blade passing in the stall inception stage, while it is dominated by stall cell in the stable stall stage. The stall onset is triggered by the increasing of the momentum ratio between tip leakage flow and main flow, developed by the adverse pressure gradient between the downstream and upstream, and finally sustained in a stable manner. The stall cell consists of a pair of high-low pressure cells. The unsteady results with high nonlinearity were then decomposed by the dynamic mode decomposition (DMD). By analyzing the modes and the reconstruction results, the leading characteristics during the stall inception and the fully-development are dug out. The stage of the stall inception and steady stall can be easily recognized by the mode frequency and energy. The frequency and the strength of the flow structure can be reflected by the corresponding mode shape.