Effects of Compound Sweep and Lean on the Aerodynamic Performances of Transonic Centrifugal Impellers

Abstract

The blade lean and sweep has a significant effect on the centrifugal compressors performance. This paper modifies the blade leading edges of two transonic centrifugal impellers with two compound sweep and lean (CSL) methods: the blade tip forward sweep with a negative lean (SFB), the blade tip backward sweep with a positive lean (SBB), and the CSL effects are numerically studied. For the unshrouded impeller, the SFB improves the highest isentropic efficiency and total pressure ratio. The SBB decreases the total pressure ratio and almost has no effect on the isentropic efficiency. The SFB expands the stall margin. Conversely, the SBB decreases the stall margin. The CSL effects on the shrouded impeller are less obvious compared with the unshrouded impeller. By analyzing the flow field, it is found that, the CSL has important effects on the shock, the accumulation of low momentum fluid and the blade loading near the blade leading edge for unshrouded impeller and shrouded impeller. Since the CSL effects on the stall margin of the unshrouded impeller are associated with the blade tip loading and tip clearance leakage flow, the CSL does not influence the stall margin of the shrouded impeller without a tip clearance.