Regulation Effects of Asymmetric Impeller on Flow Distribution Characteristics of Double-Sided Centrifugal Compressor

For the applications of the double-sided centrifugal compressor in the turbocharger, due to the inlet flow field differences at the front and rear impellers, the imbalanced flow distribution between the front and rear impeller are produced with the flow decrease, resulting in the single front impeller working mode. In order to further broaden the stable working range of the double-sided centrifugal compressor, the method of increasing the rear impeller radius in present paper is proposed to achieve the flow regulation between the front and rear impellers. The numerical simulation has been carried out on the two double-sided centrifugal compressor models to comparatively analyze the working mode of the compressor. The results show that the increase of the rear impeller radius, can effectively regulate the flow distribution between the two impellers at medium flow and small flow conditions, thus improve the flow balanced condition of two impellers. It also changes the working mode conversion process of the double-sided centrifugal compressor. The flow distribution of each blade channel of the front impeller is mainly decided by the distribution of the static pressure distribution in the volute, but the blade channel flow of the rear impeller is also influenced by the outlet flow field of the rear bending pipe. The air-flow intersection area is formed at the bending pipe outlet, which caused the mass flow of the downstream blade channel obviously smaller than the other blade channels. The intersection strength of the two air-flow in the area of the bent duct outlet is affected by the flow-rate of the rear impeller and the interaction strength weakens with the flow rate decrease. The working capacity of the rear impeller will be enhanced by increasing the rear impeller radius, which delays the double-sided impellers converting from the parallel working mode to single-sided impeller working mode. The pressure ratio increased by 4% under design flow, and the stable working range of the double-sided centrifugal compressor can be broadened by 12.5%.