Transient Characteristics of a Centrifugal Pump at Rapid Startup

An experimental and CFD(Computational Fluid Dynamics) study was conducted on the transient behavior of a rapidly starting centrifugal pump. The transient characteristics of the centrifugal pump in the transient period were examined from experimental results. Instantaneous flow rate and pressure were measured at suction and discharge ports of the pump with rotational speed and pump shaft torque when the pump is in transient operation. The suction and discharge pressures of the pump were measured by pressure sensors of the strain gauge type. The unsteady flow rate was calculated based on the pressure difference between two pressure measurement points in the straight suction pipe of the pump. The unsteady pump rotational speed and shaft torque were measured using the highly responsive torque meter. The true pump total head because of the pumping action at the unsteady operation of the pump was able to be calculated by subtracting the apparent pump total head cause by the fluid inertia effect from the measured pump total head. According to the present study, the transient characteristics of the rapid starting pump can be measured using the experimental setup. And it was shown that the dynamic operating point and shaft torque during the pump startup period deviate from the quasi-steady change. Comparing the experimental results with CFD, the reason for the deviation of transient characteristics from quasi-steady change was considered to be due to that the formation of the flow field in the pump during the transient period is delayed relative to the flow field of the steady-state. (paper)