Research on Modification of the Recirculation Groove for Widening the Operating Range of a Centrifugal Compressor

Using CFD method, a centrifugal compressor with inlet recirculation casing treatment was investigated, and according to the compressor performance test, the simulation results are validated. In order to enhance the stable operating range of the compressor, the geometry of the recirculation groove was adjusted according to the original flow field. The simulation results showed that the modified design could effectively broaden the operating range of the centrifugal compressor, and no obvious change of efficiency and pressure ratio occurred. The flow field analysis showed that the guide function of the diversion section added by the modification affected the airow direction, and enhanced the axial velocity of the air near the tip of the blade, which could make the relative flow angle near the front edge of the impeller decrease, the meridional velocity increase in the impeller channel tip, air blockage in the channel relief and airow be more smooth, was an important reason for the stable operating range widening. The flow field changes showed that the recirculation ow rate increased at 80 kr•min^-1, resulting in the axial backow region expansion at the downstream of the recirculation groove, making the separation flow at impeller suction increase slightly was the reason for the slight failure to widen the operating range at 80 kr•min^-1. The whole compressor changed little after the modification, so this scheme for widening operating range is an easy and effective one.