Investigation of unsteady flow in a centrifugal pump at low flow rate

Abstract

Due to the characteristics of unsteady flow in the centrifugal pump at low flow rate is not revealed well, a simulation of the internal flow at different flow rates is carried out with renormalization group k–ε turbulence model and multiple reference frame. For analyzing the influence of flow rate, ratios of flow rate ( Q/ Qd) are set to 0.1, 0.3, 0.6, and 1.0 at this study. The hydraulic performance of the centrifugal pump obtained by numerical calculation has matched well with the corresponding experimental result. From the characteristics of the internal flow captured by the numerical simulation, it can be seen that backflow occurs in the inlet of impeller at low flow rate, which prevents fluid discharging into impeller passages and leads to vortical structures in suction region. With further decrease in flow rate, the strength of backflow has been intensified, and the number of vortex has significantly increased. A visualization experiment of the backflow evolution in suction pipe is carried out to validate the unsteady simulated results. Results show that the prerotation is an important factor for the deterioration of centrifugal pump performance.