Effect of end-wall roughness on performance of transonic axial compressor

The influence of end-wall roughness on the performance of the axial compressor stage was investigated with different values of roughness added to the hub and shroud surfaces of transonic compressor stage, NASA Stage 35. Firstly, the numerical code was validated against the experimental data, which were available from the open literature. Afterwards the model was applied to simulate the effect of end-wall roughness with different amplitudes of dimensionless sand-grain roughness height. Numerical results indicated that the increment of end-wall roughness caused the deterioration of compressor stage performance. To understand the mechanism behind, the distributions of loadings, losses and the detail flow situations near end-wall region were analyzed and discussed. The results show that the overall performance drop is mainly due to the thickened end-wall boundary layer. Near the hub region, the rough hub surface induces larger corner stall and the shock wave moves upstream. Meanwhile, the casing roughness leads to the slight increment of tip leakage mass flow and extension of blockage in the circumferential direction.