Effects of blade leading edge lean and sweep on the aerodynamic performance of centrifugal impellers

To study the effects of blade leading edge lean and sweep on the aerodynamic performance and stable operating range of centrifugal impellers, this paper presents four different blade leading edge lean and sweep by sweeping blade tip forward and backward, and sweeping blade root forward and backward along the meridional chord line. Firstly, the effects of blade leading edge sweep on the overall performance and flow field of a transonic centrifugal impeller are studied, and the results show that the blade tip forward sweep or blade root forward sweep can improve the highest isentropic efficiency and total pressure ratio of the centrifugal impeller; the blade tip backward sweep almost has no effect on the isentropic efficiency, but can decrease the total pressure ratio; the blade root backward sweep decreases both the isentropic efficiency and total pressure ratio. Additionally, the stall margin is increased by the blade tip forward sweep or blade root backward sweep, and reduced by the blade tip backward sweep or blade root forward sweep. Finally, the effect of blade leading edge sweep on a subsonic centrifugal impeller is investigated, and it indicates that, compared with transonic centrifugal impeller, the blade leading edge sweep has less effect on the isentropic efficiency and total pressure ratio in a subsonic centrifugal impeller. However, the effects on stall margin are almost the same for both transonic and subsonic centrifugal impellers. For an unshrouded transonic impeller, blade tip forward sweep is an effective way to increase its isentropic efficiency, pressure ratio and stall margin.