Numerical Simulation And Characteristics Investigation Of Dynamic Stall Vortices In A Centrifugal Pump

It always require centrifugal pump to operate at off-design operations because of some special requirements.However,there will be a lot of unsteady phenomenon inside the impeller under the condition of part-load,which challenges the safety and stability of the centrifugal pump.Rotating stall is a common phenomenon that always leads to positive slope,efficiency decreases,and even results in noise,vibration and fracture in fatigue points.Therefore,it is significant to study the mechanism and characteristics of rotating stall in centrifugal pump,try to suppress or even eliminate the stall in the passage,which is very important for optimizing the hydraulic performance and improving the operation stability of the centrifugal pump.Based on the 3D modeling and mesh generation of the model pump,the proper numerical calculation method is adopted in this paper to analyze the stall phenomenon inside the centrifugal pump.Mainly about:(1)The unsteady numerical simulation of the stall phenomenon under different operating conditions is carried out,to analyze the difference of the stall characteristics under different conditions.The type of stall at slight stall conditions is “stationary stall”,and the “rotating stall” phenomenon appears at deep stall conditions.Under the condition of rotating stall,the unsteady flow phenomenon inside impeller is obviously aggravated,the pressure pulsation is enhanced,the radial force direction of impeller increases,and the efficiency of centrifugal pump decreases.These phenomena will cause serious harm to the safe and stable operation of centrifugal pump.(2)The effect of inlet non-uniform flow on stall is investigated by setting up two non-uniform flow in radial and circumferential directions at inlet pipe of the pump.The results show that the influence of non-uniform flow on the stall phenomenon in centrifugal pump is very significant : under the influence of two kinds of non-uniform flow,the type of stall in the centrifugal pump are converted to rotating stall.With the influence of radial non-uniform inflow,some back flows aroused locally at inlet of the impeller and interact with mainstream,so that reducing the inlet pre-whirl and improving the internal flow of the impeller,therefore,the number of stall cells in the impeller is less than that in other two kinds of inflows.(3)Notching grooves at inlet pipe to suppress and eliminate stall cells in the impeller.Compare and analyze the stall cells distribution in the impeller in three shapes(rectangular,triangular and arc)and different numbers of the grooves.For the model in this passage,with the number of 40,the triangular groove has the best effect on stall in the model pump,in this case the appearance of the stall is postponed effectively.