Investigation on the power loss and radial force characteristics of pump as turbine under gas–liquid two

To study the power loss and radial force characteristics of pump as hydraulic turbine (PAT) under gas–liquid two-phase condition, a single-stage centrifugal pump in reverse mode as turbine was adopted. Based on the Navier–Stokes equation and standard k-epsilon turbulence model, CFD (computational fluid dynamics) technology was used to simulate the flow field in hydraulic turbine. The results show that the gas content has a serious effect on the hydraulic turbine performance. Under the gas–liquid two-phase condition, the fluid velocity distribution in turbine is uneven, and the power loss is not uniform enough when the gas content is less than 0.1. The radial force vector distribution all closed to ellipse shape for different gas content and flow rates, but near the volume tongue an obvious wave appeared. The more the flow rate is, the larger the radial force is. The radial force does not change as regular as that of pure liquid condition, serious fluctuation appeared. For different gas contents, the dominant frequency always equals the rotating frequency of impeller, and subordinate dominant frequency does not appear. Under low gas content and high flow rate, both the fluctuation amplitude and dominant frequency are the maximal