Numerical investigation of unsteady flow field in multi-stage compressor

The detailed unsteady flow field in a multi-stage compressor has been obtained by dual time step. The investigation of unsteady flow field structure could help to understand the unsteady traits of turbomachinery under reversed pressure grads and give some hints for multi-stage compressor performance improvement. The results show that: (a) The interaction effect between rotor and stator to the pressure distribution on downstream stator surface is stronger as the radius of stream surface is larger. (b) As the wake upstream transfer to the passage downstream larger loss is produced because of mixture of lower energy wake with and main flow. On the other hand, wake upstream hits the leading edge of blade downstream, the region with low Mach number is smaller; (c) Stator downstream has great potential effect on flow structure at trailing edge of rotor upstream, and the effect is stronger when radius of stream surface is larger. In fact, the separation structure of flow at trailing edge of blade upstream is different greatly from hub to tip.