Study on vortex flow and pressure fluctuation in dustpan-shaped conduit of a low head axial-flow pump as turbine

Abstract

In the plain river network area, the constructed axial-flow pumping station is used to generate electricity by reversing as turbine when the upstream water is abundant, which can reduce the environmental pollution caused by coal-fired power generation while making full use of water resources. When the axial-flow pump as turbine (PAT) operates, there are severe flow instability and obvious pressure pulsation in the dustpan-shaped conduit. In this paper, the transient numerical simulation method is used to study the evolution characteristics and pressure pulsation of the vortex in the dustpan-shaped conduit when the axial-flow PAT runs, and the pressure pulsation signal of simulation is compared with the pressure pulsation result of model test. The formation of the spiral vortex rope in the dustpan-shaped conduit is related to the velocity circulation at the impeller outlet and the axial velocity of the fluid. The axial velocity and tangential velocity near the vortex center are close to zero. The inlet of the dustpan-shaped conduit is subjected to the dynamic and static interaction effect of impeller domain and conduit domain. Further downstream, rotor and static interaction effect weakens gradually. As the distance from the impeller increases, the dominant frequency of pressure pulsation changes from 3 times the rotational frequency to 0.5 times the rotational frequency. The dominant frequency of pressure pulsation at the monitoring points near the vortex rope are 0.5 times the rotational frequency, and massive low frequency near the vortex rope are generated by the vortex rope rotation.