The Research On Numerical Simulation And Abrasion Property Of Solid-liquid Two-phase-flow Centrifugal Pump

The solid-liquid two-phase flow transportation by centrifugal pump has been more andmore widely. As the existence of solid phase and its abrasion, there were two key problems: poorefficiency and poor reliability. These two problems restrict the research and application of thesolid-liquid two-phase pump.In this dissertation, hydraulic performance and wear property of channel-type centrifugalpump were studied through numerical simulation and experimental research. The forces actingon particle in the solid-liquid two-phase flow were classified. Based on analyzing the order offorce magnitude, the solid-liquid two-phase flow model and erosion model were proposed. Aimat different particle diameters, the Mixture model and the DPM model were used to simulate thetwo-phase flow respectively on the condition of different volume fraction. The influence ofinternal flow characteristic on pump performance was analyzed. The test rig for solid-liquidtwo-phase flow transportation was constructed. And characteristic tests of the channel-typecentrifugal pump were carried out. Based on theoretical analysis, the prediction formula of headdescent ratio was derived at best efficiency point when pumping solid-liquid two-phase mixture.The main contents and conclusions of this dissertation are showed as the follows:1. Solid-liquid two-phase flow model and abrasion model for the centrifugal pump aredetermined.Firstly, acting forcesare classified according to the relationship between the particle and theliquid phase. The magnitude of each force is compared with that of resistance force to confirmthe relation between the particle diameter and the acting force. Accordingly, different two-phaseflow models are proposed. Consideringthe influence of turbulence on particle, the kinetic modelof particle motion is established based on random walk method. The model of particle abrasionfor simulation is got by the Taylor expansion of suitable abrasion model for single particle.2. The numerical simulation and results validation are carried out for the solid-liquidtwo-phase flow in the centrifugal pump.Mixture model and DPM model are used to simulate the solid-liquid two-phase internalflow field separately. Compared the simulated results with the test results in a publisheddissertation, it can be found that these two models differentiated by particle diameter are properly used in computation.3. The relationship of the solid-liquid two-phase flow characteristic, hydraulic performanceand abrasion property is revealed.On the conditions of different particle diameter and different volume fraction, the pressureand streamline of liquid phase in whole flow channel, the velocity difference between the solidphase and the liquid phase in volute channel are analyzed. It is concluded that pressuredistributions are almost the same on different working conditions. The values of pressure in flowchannel decrease with the increasing of the particle diameter and the volume fraction.On the conditions of different particle diameter and different volume fraction, the erosionvelocity ratio, shear stress and particle concentration are analyzed. It can be found that theerosion velocity ratio on the flow channel wall increases along with the increasing of the volumefraction. But along with the increasing of the particle diameter, the erosion velocity ratio on thevolute wall decreases. And the variation trend of erosion velocity ratio on the impeller channelwall changes according to the wear position.4. The performance experiments of the centrifugal pump transporting solid-liquid two-phasemixture are carried out.Compared with head and efficiency values of the water transportation, values of solid-liquidtwo-phase transportation decrease slowly as the increasing of particle diameter and volumefraction. The decreasing values of efficiency are totally smaller than the decreasing values ofhead. The comparing results indicate that the change trend of experimental values is the same asthat of simulated values basically. But experimental values are smaller than simulated values.5. The prediction formula of head descent ratio is derived and validated when pumping thesolid-liquid two-phase mixture.Assumping that two phases’velocities of pump outlet are equal, the head prediction formulaof two-phase mixture transportation is derived based on the theory analysis. The influence ofsolid phase is introduced in pump performance by local volume fraction in this formula. So theformula can be conveniently applied to compute the head at the best efficiency point. But thepredicted values are smaller than the test values.