Numerical Considerations on Design Parameters of Diffuser Vane Slit

In this study, CFD simulations were conducted to investigate the optimal design parameters for the diffuser vane slit, which is one of the means to suppress diffuser rotating stall (DRS), in terms of slit width, height, and position, to maximize the DRS suppression effect while maintaining diffuser performance. The investigated pump is a centrifugal pump with a specific speed of Ns = 138 m 3 /min, m, rpm and the diffuser is an axial-flow type. The simple prediction method of DRS by CFD simulation used in the previous study was applied and evaluated in terms of the coefficient of variation C . V ., static pressure recovery coefficient C P , and total pressure loss coefficient C T in the diffuser flow channel. As a result, it was found that the slit position was the best at 18% of the vane axial chord length regardless of the slit width, and that the slit height from the hub to the tip provided the best DRS suppression. A wider slit width increases the flow rate through the slit and enhances the DRS suppression effect, but it causes lower diffuser performance and results in a trade-off relationship. Therefore, the slit width should be set to an appropriate value depending on the required operating range.