Research On The Flow Mechanism And Effect On Cavitation Of Impeller And Volute Interaction In Single Stage Centrifugal Pump

As a general-purpose machine,centrifugal pumps are widely used in various sectors of the national economy,and improving their performance has always been the focus of research.This paper uses Fluent numerically simulates the instantaneous turbulent flow of the centrifugal pump under different working conditions and different volute structures under non-design conditions.So,it is descript the cavitation phenomenon under non-design conditions of the centrifugal pump.Combining with the numerical simulation results and the basic flow theory of centrifugal pump,this paper analyzes the interaction mechanism and the effect on cavitation of the flow between the impeller and the volute,and obtains the following basic conclusions.(1)Steady state numerical analysis of the effect of the angle between the blade and the volute of the centrifugal pump on its performance.It is found that the angle between the blade and the tongue has a great influence on the flow of the centrifugal pump.That were compared the pump characteristics between the steady simulation,the unsteady simulation,and experimental results.It is found that the unsteady simulation is closer to the experimental result.(2)The tongue clearance flow is the superposition of the differential pressure flow on both sides of the tongue and the drag flow of the impeller.The strength of the drag flow and differential pressure flow and the influence on the volute and impeller flow are related to working conditions.Under design conditions,the flow of the gap between the both sides tongue is only the impeller drag flow.Under the small flow conditions,the differential pressure flow is enhanced,the drag flow is weakened due to the decrease of the impeller flow,and the flow of the gap between the tongue has a significant effect on the flow of the volute and the impeller.Under the large flow conditions,although the differential pressure flow of the gap between the tongue is enhanced,the impact is weaker than the drag flow of the high flow impeller,and the impact on the flow of the impeller and the volute is also weak.Considering the tongue-gap flow and assuming that the impeller flows evenly under different working conditions,and using a one-dimensional flow theory of the centrifugal pump to derive the expression of the flow velocity in the volute.This formula is in good agreement with the numerical simulation results when Q>0.8Qd.(3)The performance of the impeller matched with the different volute diffusion tube were compared and analyzed of the centrifugal pump.The results show that the straight cone volute pump can improve the performance of the pump under large flow conditions,but has little effect on the flow of the small flow conditions.(4)When the rotating cavitation occurs,there is a slow decline before the pump Head-NPSH curve drops rapidly.Therefore,new requirements have been put forward for judging the initial cavitation in the project.