Numerical simulation on cavitating characteristic in impeller of axial-flow pump

In order to study the internal cavitation characteristic of axial flow pump, the steady turbulent flow field of an axial flow pump(ns=1033) at different conditions was simulated by using standard κ-ε turbulence model, RNG κ-ε turbulence model，κ-ω turbulence model, SST κ-ω turbulence model and homogeneous multiphase model based on ANSYS CFX software. The numerical results were compared with the experiment values to verify the adaptability of the different turbulent models and multiphase model, and to study the cavitation characteristics of the impeller region. The results showed that the κ-ε turbulence model has better accuracy than the other three turbulent models in simulation, predictive errors of critical NPSHc is 6.32%,which can reflect the internal cavitation characteristic of the axial flow pump well. With the decrease of the NPSH, along the flow direction, vapor first occurred on the leading edge of the blade close to the tip, and then developed to the middle area of the blades until to the whole passage. On the critical cavitation condition, the vapor area of the middle side along the radical direction of the blade is large. When the cavitation is serious, the streamline at the back of the blade's suction side is disorder and generate the vortex micro group, which will flow from the hub to the shroud of the impeller, cause the distribution of axial flow velocity at the outlet of the impeller inhomogeneous, and increase the disturbulence of the flow field in impeller region. These phenomena reveal the cavitation characteristics of the axial-flow pump.