Influence of lightweight material on tip flow of a transonic centrifugal impeller based on bidirectional fluid-structure coupling

The energy consumption and stability of centrifugal impellers can be effectively improved by using a lightweight material. Tip flow is the main factor affecting energy consumption and operational stability of centrifugal impellers. In this study, the mechanism underlying the influence of material weight on the flow in the tip region of a centrifugal impeller was explored. First, a numerical model of a bidirectional fluid-structure coupling was established and validated. Then, a comparative analysis was conducted on the vibration deformation of 17-4PH, titanium alloy, aluminum alloy, and epoxy carbon UD (CFP) impellers under extreme stall conditions. Finally, the changing trends of shock wave structure, leakage flow, and secondary flow in the tip region of these four kinds of impellers were compared and analyzed. The results show that tip clearance decreases gradually with decreasing impeller material density. By comparing with a stainless-steel impeller, the tip clearance of a CFP impeller decreased by 53% at most, and the total displacement decreased by nearly 100% (except in the case of resonance). The shock wave of the CFP impeller can be characterized by fast detachment, fast dissipation, and minimal countercurrent. The leakage flow of the CFP impeller was uniform, the leakage vortex moved forward slowly, the volume of the vortex was small, and the flow velocity on the blade surface was also small. With decreasing impeller density, the influence of the secondary flow on the main flow gradually weakened. These results lay a theoretical foundation for optimizing the structural and aerodynamic design of centrifugal impellers.