Design Optimization and Experimental Study of Tandem Impeller for Centrifugal Compressor

Although significant advances have been made in tandem-blade technology for axial compressors, few efforts were devoted to its application in centrifugal compressors. Based on detailed computational fluid dynamics simulations and sensitivity analysis, multiobjective design optimization is conducted for a tandem impeller. An optimized tandem impeller, for which the objectives are all better than those of the baseline, is fabricated and tested on a high-speed centrifugal compressor rig. The numerical results show that the baseline tandem impeller has more uniform discharge flow but lower efficiency than the corresponding splitter impeller. The geometries of the inducer blade profile and inducer-exducer gap are found to have the greatest impact on the tandem impeller efficiencies. By optimization, the tandem impeller efficiency can be increased through reduced curvature of the blade profile at the inducer hub, S-shaped blade angle distribution at the inducer tip, and increased blade angle at the exducer tip near the leading edge. The measured performance of the centrifugal compressor with the optimized tandem impeller agrees well with the computational fluid dynamics calculations, and the compressor peak efficiency is 0.796 at the design speed (45,000 rpm).