Analysis on the effect of variable guide vane numbers on the performance of pump as turbine

Abstract

To study the effects of different guide vane numbers on the unsteady performance of pump as turbine based on the Navier–Stokes equation and standard k-epsilon turbulence model, computation fluid dynamics technology was used to simulate the flow field in pump as turbine. The turbulent kinetic energy, unsteady radial forces, and power losses were also clarified. The results show that for turbines with a guide vane, the distribution of turbulent kinetic energy is more uniform than before, and the radial force vector distribution is more symmetrical within four quadrants. The time-domain distribution of radial force is more periodic, the number of fluctuation periods is equal to the guide vane numbers, and the dominant frequency of the radial force is equal to the blade frequency. For different guide vane numbers, the effects on the unsteady performance of pump as turbine are different. When the guide vane number is equal to 9, the distribution of turbulence kinetic energy is optimal. In addition, at an optimal flow rate, both the time domains of the radial force and the power losses of the impeller are minimal, so to the geometric parameters of the hydraulic turbine are definite, the optimal guide vane number exists.