Compressible Cavitation Flow Simulation in Prototype Pump Turbines During Transitions
In the simulation study of cavitation two-phase flow in a model pump turbine,the influence of water flow compressibility on pressure pulsation is usually not considered,but in the calculation of the transition process of the prototype pump turbine,this influence is significant.Therefore,a compressible simulation method for cavitation two-phase flow was proposed to simultaneously consider the compressibility of the mixture medium between liquid water and gas-liquid two-phase.In this simulation method,a computational model was obtained by combining the weakly compressible model of liquid water and the state equation of gas-liquid two-phase intermediate medium,which corrected the fluid density based on the pressure distribution of the flow field.The density correction model was used to simulate the load rejection process of a prototype pump turbine,and the cavitation phenomenon was first captured in the high-pressure inlet return vortex of the turbine during the load rejection process of the unit.In addition,research has found that the coupling effect of cavitation and inflow vortex at the impeller inlet induces high amplitude pressure pulsation below 5 times the rated rotational frequency near the no-load condition.
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