Research on the influence mechanism of operating characteristics of an 11-stage pump as turbine under turbine mode

Under the background of sustainable development of renewable energy, it is more and more important to recover the energy of high-pressure medium produced in the petrochemical process. In the field of petrochemicals, the multi-stage pump as turbine (PAT) has a strong economy. PAT can not only generate the high-pressure medium required in the petrochemical process but also recover the high-pressure medium energy that has been completed. When the multi-stage PAT is operated under the turbine condition, the internal flow state is more complicated than that under the pump condition. The hydraulic performance often has problems such as a narrow high-efficiency zone, low efficiency, and flow instability. The hydraulic performance will decrease, but the reason for the decrease in hydraulic performance is still unclear. In this paper, the mechanism of PAT internal flow loss and evolution of pressure pulsation is studied. The hydraulic performance and internal flow characteristics of the multi-stage PAT are studied by comparing the experimental and numerical simulation results. The influence of inflow conditions on the internal loss and internal flow characteristics of the PAT stage is found, and the relationship between inflow low-frequency signals 0.2 f BPF and internal loss and the cumulative effect of inflow pressure pulsation is revealed.