Numerical Simulation of Three Dimensional Flow in Large Mixed-Flow Pump System

The three-dimensional flow inside a mixed-flow pump system was simulated by using CFX software. The Shear Stress Transport turbulent equation which combined k-ε and k-ω turbulent model was applied. The flow field in volute and discharge passage of the pump system was obtained and the hydraulic performances of the pump system were predicted. The velocity and pressure distribution in pump system were analyzed. From the calculation results it is evident that the flow in the double helix volute passage is a spiral movement combining axial and rotary flow; the static pressure distribution in the volute is symmetric; the uniformity of axial velocity distribution and velocity-weighted average swirl angle at the outlet section are relatively low; and static pressure distribution on pump blade surface is regular with higher static pressure on pressure side and lower one on the suction side. The axial forces decrease gradually with the decrease of lifting head and the radial forces decrease first and then increase. A model test of the pump system was conducted to verify the calculation results. The pressure fluctuation at certain sections of the pump system was measured from the model test. A good agreement was found for lifting head between calculated and measured results. While the deviation of the efficiency between calculated and measured results does exist in non design points which need to be improved.