| Pumps are widely used in many fields of national production,applied to water conservancy,mining,chemical,electric power,civil engineering,environmental protection and other industrial sectors.In the fie ld of pump related research,the study on the stability of the pump has been the most important.The rotor/ stator cascade is the basic unit of work,pressure and diversion for the high pressure fluid machinery such as mult istage pump and so on,due to the double effects of the "jet wake" flow of the impeller outlet and the static and dynamic interference between the rotor and the stator,the vortex structure is very complicated 。With the development of multistage pump to high lift and wide working area,higher demands are put forward for the fluid dynamics response of vibration,noise and so on.However,under the condition o f sediment laden water and running at off-design operation conditions,the whole system will have higher load and higher operating cost,therefore,it is necessary to study the flow problem of centrifuga l pump under the condition of off-design condition,which can provide some reference for improving the stability and efficiency of fluid machinery.In this paper,the large eddy simulation and Mixture mixed phase model are used as the calculat ion model,and the two-dimensional numerical calculation and the three-dimensional numerical calculation of the model pump are carried out.The centrifugal pump with guide vane which the design flow is 22.85m3/h is chosen as the model,and performance calculation of model pump with different flow rates.Get the performance curves of a centrifuga l pump,and on this basis,the static cascades in different working conditions and particle size under the condition of unsteady flow of solid-liquid two-phase flow and rotor stator interaction,and the vorticity for reference combining streamlines and pressure pulsation of hydraulic machinery to describe the internal flow process.The main conclusions are as follow:(1)Using the commercial modeling software Pro/E as the tool to model the vane type centrifugal pump,the professional C AE pre-processing software AN SYS IC EM is used to carry on the topology of the whole flow field of the vane type centrifugal pump and is divided into the structured grid.Besides,the basic parameters of the vane centrifugal pump are defined,the finite volume method is used to discretize the flow control equation,and some control condit ions of numerical calculation w ith ANSYS Fluent are described.(2)Based on the two-dimensional and three-dimens ional numerical calculation,it is found that the concentra tion distribut ion of the two and three-dimens ional vortex is similar.In the clear water,two dimensional numerical results can be used as a reference for the results of three-dimensional numerical calculat ion,two dimensional numerical results can be used as a reference for the results of three-dimensional numerical calculation.It is possible to find out the most turbulent flow field by means of two-dimensional numerical results,and then by modifying the three-dimensional computational grid which can more realist ic simulat ion of the internal flow field.The numerical simulation results of the two-dimensional vane centrifugal pump are similar to the results of three-dimensional numerical simulation.The particles distribution is mainly concentrated in the pressure surface of the impeller blade,the large vorticity region is mainly concentrated on the back of the impeller blade,and the flow is unstable at the junction between the stator and rotor.However,the results of two-dimensional numerical calculatio n are more unstable than that of the three-dimensional numerical results,under the influence of the model,the distribution of the vorticity the particles in the two-dimensional numerical s imulation are more disordered,and in some small place will appear different results which calculated in three-dimension.(3)According to the analysis of the internal flow in the rotor and stator cascades under the off-design condit ion,It is found that under the design condition,the internal pressure pulsation periodic of the dynamic cascade is the best,and the pulsation is the most regular.Under the 1.0Q flow,the distribution of pressure coefficient Cp is narrow and it is the widest in the 1.3Q flow.Compared the distribution of pressure fluctuation in the stator cascade with different flow rate and rotating speed,found that the pressure fluctuation is the most unstable at 750 rpm speed,compared with the distribution of pressure fluctuation under different flow rate,the pressure fluctuation is more severe than the pressure fluctuation under the low flow rate.Under the off-design condit ions and speeds,the internal flow of rotor-stator cascade appeared different degrees of deterioration,especially in the case of off-design speed,the flow in the cascade is the most unstable.In addit ion,due to the interaction of dynamic and static interference,the phenomenon of flow surge occurs at the junction of the stator and rotor.The main function of the guide vane is to make the fluid within the impeller more stable into the volute.But under the off-design conditions and speed,the guide vane cannot fully play its role in drainage.Therefore,in the off-design conditions,especially under the high rotation rate conditions,the flow in the guide blades should be more disorder than that in the impeller.Under the off-design condit ion,especially in the condition of high rotating speed,the vortex region in the dynamic cascade is obviously higher than that in the other rotating speed,especially at the junction of the rotor and stator cascade.Under the condition of different flow rate at the same speed,the large vorticity current in the stator and rotor cascade under the condition of small flow rate is obviously higher than that in other flow conditions.(4)Based on the analysis of the pressure and the vorticity distribution,the volume fraction of particles and the pressure fluctuation in the dynamic cascade,found that the particle size has a great influence on the flow in the rotor and stator cascade.In order to improve the effic iency of vane type centrifugal pump,the structure optimization of vane and impeller is carried out for different particle sizes... |
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