Effect of blade thickness on performance of small flow rate centrifugal compressor impellers

The last stage of a thirteen-stage centrifugal compressor used for petrochemical production, in which the exit relative width of the impeller was only 0.0092, was studied. The blades of the centrifugal impellers were generated with constant thickness, zero thickness and C4 profile respectively and the performance of the structured impellers was computed with a computational fluid dynamics (CFD) code. The analysis results indicate that the performance of the C4 impeller is best in small flow rate range, and in large flow rate range the efficiency of zero thickness impeller is the highest one. In the design point the efficiency of C4 impeller is 1% higher than that of constant thickness impeller. Considering both the machining capability and strength requirement, the blade thickness distribution is proposed as the design variable to be optimized with the response surface method. The overall performance of the optimized impeller is higher than that of the original impeller, and in the large flow rate range it is also higher than that of C4 impeller.