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Wear mechanism in the impeller was investigated numerically and experimentally. The solid slip velocity is one of the key factors to identify the wear location. The wear location predicted by the simulations agreed well with experimental observations.
Centrifugal slurry pumps are widely used in ore mining, metal smelting, petrochemical and other industries. They are mainly used to transport muddy fluids containing a large number of solid particles. The impellers in slurry pumps always experience serious wear with damages the equipment. This study analyzed the flow in a slurry pump to identify the key sources of the wear. A centrifugal slurry pump was analyzed using the particle Eulerian-Eulerian multiphase flow model to study the impeller wear. The results show that increasing the flow rate causes the high solid volume fraction area to gradually move along the suction surface from the inlet to the outlet. At over-load flow rate, the high volume fraction area moves to the junction of the blade and the rear shroud. For the same conditions, increasing the concentration reduces the pump lift and efficiency, gradually increases the solid slip velocity at the blade outlet, and creates higher solid volume fractions on the suction surface of the blade than that on the pressure surface. The wear location predicted by the simulations agreed well with experimental observations. This study provides guidance on how to optimize slurry pump impeller designs to reduce the wear.
Slurry pumps are used to convey slurries containing solid particles and are widely used in the mineral processing and power generation industries. Slurry pumps contain high concentrations of solid particles in the flow, which causes wear and corrosion during operation. The conditions leading to wear in slurry pumps need to be better understood to develop more effective anti-wear designs. Veselin experimentally studied the wear in slurry pumps for various inlet conditions. Walker et al. also studied wear in slurry pumps and developed an empirical wear relationship for a centrifugal slurry pump. Various measures have been developed to reduce the wear of slurry pump impellers. Batalovic developed a wear model for slurry pump impellers which predicted the impeller service life. Zhao experimentally studied the effect of solid materials on centrifugal pump efficiencies to show that increasing the solid particle concentration gradually reduced the flow rate for the same head with the pump efficiency curve decreasing exponentially. Peter and Shem, and Wang and Peter developed an effective prediction method to evaluate the impeller performance degradation which gave better predictions than earlier methods. Pagalthivarthi et al. simulated the abrasion in a slurry pump with solid–liquid two-phase flow for various working conditions and design parameters for low solid particle concentrations. Tarodiya et al. used another method to determine the maximum local wear area and methods to reduce wear. Khalil et al. studied the head and efficiency decreases of a slurry pump when conveying soft slurries with solid concentrations below 18% and gave a head prediction correlation as a function of the solid concentration and density which had prediction errors less than 10%. Duarte et al. studied solid–liquid two-phase flows in an elbow which showed that for particle concentrations higher than 20%, the wear increased slowly with increasing particle concentration, which was called the buffer effect. Madadnia et al. studied the wear in a slurry pump body and impeller using an electron microscope with the results showing serious wear on the impeller inlet, inside and outside the impeller shroud, inside the pump body cover and along the impeller outlet. They also presented multiphase flow calculations that were consistent with the observed wear. Eulerian multiphase flow models have also been used to simulate solid–liquid two-phase flows in centrifugal slurry pumps with similar wear patterns. Sugiyama et al. combined numerical simulations with test data to predict the wear depth on the impeller. Liao et al. used a two-phase particle flow model to analyze the effect of various sand particle sizes on the blade surface wear. There have been various other studies on slurry pump wear. Thus, most research on wear in slurry pumps has been based on two-phase flow models to simulate the flow fields in the pumps. However, there are few analyses of the cause of the wear based on the results of two-phase flow simulations and wear tests. In this study, the particle Eulerian multiphase flow model supplied by numerical simulation software was used to determine the positions where wear easily occurs. Then, rapid slurry pump wear tests were used to experimentally study the wear on an impeller to verify the simulation accuracy. The results can be used to help optimize slurry pump impeller designs to reduce the wear.
This study analyzed a 100SHL centrifugal slurry pump with the flow conditions at Q BEP (best efficiency point, BEP) representing the rated conditions. The main model parameters are listed in Table 1.
The flow field in the slurry pump was modeled by simplifying the domain into the inlet pipe, impeller, volute and outlet pipe. The geometry model was simulated under a frozen potion, where the cutwater face to the middle of one of impeller blade, as shown in Fig. 1. ANSYS-ICEM was used for the mesh
In the test, the flow rate of the pump is measured by a turbine flowmeter (with an accuracy of ±0.1%). The inlet and outlet pressure of the pump is measured by a pressure sensor with an accuracy of ±0.1%. The shaft torque is measured by a torque speed sensor (accuracy ±0.5%). Fig. 3 shows that the numerical simulation results are generally greater than the experimental data, because some losses in the pump test (leakage loss, disc friction loss and friction loss of bearings and sealing devices)
The slurry pump wear test bench design is shown in Fig. 17. The ratio of the original pump size to the model pump size is 1:0.408 with the design based on the pump geometry similarity law. The pump flow rate was 1.0Q BEP, the particle concentration was 30%, the particle diameter was 0.165 mm, and the test was run for 50 h. The impeller material is aviation aluminum 2A60.The wear test measured the impeller weight loss to study the impeller wear. A speed sensor was attached to the motor housing to
In this study, the wear of a slurry pump impeller was studied numerically and experimentally for various solid particle volume fractions and flow rates.
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