Study on nonuniform tip clearance in mixed flow compressor

Abstract

In compressed air energy storage system, the inevitable axial vibration during the frequent start-stop of compressor leads to circumferential nonuniform tip clearance formation, which significantly impacts compressor performance. This paper utilizes numerical simulation to study the overall performance and internal unsteady flow field of a mixed flow compressor with 4 different eccentricities and compares them with the original model. The results indicate that the eccentricity of blade tip clearance has little effect on pressure ratio and isentropic efficiency of the mixed flow compressor, but has an important impact on its stall margin. Specifically, when the eccentricity is 70 % of the blade tip clearance, the compressor stall margin is reduced by 5.96 %. The circumferential distribution of tip relative leakage aligns with the circumferential variation of tip clearance height. The average tip relative leakage increases gradually with the increase of eccentricity, and its growth rate also increases gradually with the increase of eccentricity. There are two peaks and valleys in the radial force distribution of a single blade, while the axial force of a single blade is consistent with the change in circumferential tip clearance height. These findings can provide valuable guidance for subsequent compressor design and operation.