Aerodynamic design and experimental validation of centrifugal compressor impellers with small flow rate

With the centrifugal compressor's flow rate reduced, the compressor's anti-surge system often has to be opened for providing enough cycle flow rate, and this inevitably wastes lots of energy. This paper reports the efforts in redesigning the compressor's impeller with the design flow coefficient of 0.0076 to satisfy the needs of flow rate reduction for a CO₂ centrifugal compressor. Two inverse design methods: the all-over-controlled vortex distribution method and the S2 inverse stream function method, are respectively used to the impeller's design. The experimental validation is carried out on the closed loop compressor stage test rig with the designed two impellers respectively. The experiment results show that the operating flow range is largely extended to the small flow rate region with the S2 inverse stream function method, but the improvement on efficiency is not well demonstrated. In order to understand the flow mechanism, the flow fields inside the impellers and the stationary components are also analyzed in detail.