Abstract
Along with the pressing demand for the long-distance transportation of coarse particles in the deep-sea mining industry, evaluating the slurry pump’s passing through and erosive wear by studying the particle motion characteristics and the slurry behavior is becoming increasingly important. Research on the influence of leakage flow through the clearance and balancing devices on the motion characteristic of granular grain flow is of great significance but has been seldom studied. This study coupled the discrete element method with the CFD method to investigate the comprehensive effect of a double-stage slurry pump’s main flow and leakage flow on the motion characteristics of particles with a 10 mm diameter. Results show that the leakage flow occupation in main flow falls from 26%–27% to 8%–9% for the two stages, with the flow rate increasing from 80 m3/h to 200 m3/h. In the first stage with leakage, accumulation of coarse particles was observed at the impeller eye, which should be paid much attention to slurry pumps’ operation to eliminate the chance of blockage. In the nonleak situation, although the increment of the average kinetic energy of particles through the impeller is more significant than in the leak case, most of them dissipate primarily by more than 10% collision in the bowl diffuser. In the leak or nonleak case, the average kinetic energy of particles was more than twice through the first stage but only 1.1 times through the second stage. The selection of stages in the slurry pump design should consider the limitation of particle velocity improvement.
Highlights
IntroductionIn the deep-ocean mining of polymetallic nodules, which are up to 50 mm in size and deposited at depths as great as 5000 m [6, 7], the slurry pump is the only power of hydraulic hoisting, and the core parts of flow passage should have an optimized structure with resistance to blockage and wear
Introduction e hydraulic transportation of solids by the slurry pump has been widely used in situations where a practical approach is needed to convey granular solids, such as dredging industry, mining industry, and ash transportation in power plants [1, 2]. e useful life of most slurry transport pumps is limited by the block and erosive wear of the flow passages [3]. erefore, the conventional design of centrifugal pump has been generally modified to develop a slurry pump, including the enlargement of the wetted passage to eliminate the chance of blockage, use of a robust impeller with a smaller number of vanes, and special sealing arrangements to ensure longer life [4]
In the first stage’s impeller, given the squeeze of the leakage from the balance hole, the streamline deviates to the shroud, and a vortex is at the hub side of the impeller exit. e effect of the balance chamber leakage to the main flow at the second stage is less than that in the first stage, and the vortex is not observed at the impeller’s exit. erefore, the axial clearance has an important effect on the internal flow structures in the slurry pump
Summary
In the deep-ocean mining of polymetallic nodules, which are up to 50 mm in size and deposited at depths as great as 5000 m [6, 7], the slurry pump is the only power of hydraulic hoisting, and the core parts of flow passage should have an optimized structure with resistance to blockage and wear. Engin and Gur [15] studied the effect of impeller tip clearance on the performance of a shrouded pump transporting slurry. Park [16] studied the impact of the back clearance size and the balance holes on the backflow of the centrifugal pump with a semiopen impeller and produced empirical equations for the leakage loss through the balance holes using the CFD predictions
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