CFD-DEM Simulation and Experimental Study of Two-phase Flow in Vortex Pump

Abstract

【Objective】 Vortex pumps are widely used in many hydraulic engineering projects and water flow in them often involves sediments. The aim of this paper is to propose and validate a numeral model to simulate two-phase flow in the pumps. 【Method】 The numerical model is based on a combination of computational fluid dynamics (CFD) and discrete element method (DEM). Rapeseeds are used as a proxy of the sediment particles in the experiment. Water flow and sediment transport under different flow conditions and sediment concentrations in the pump were simulated. 【Results】 At low flow rate, the vortex characteristics of the circulating flow in the lateral cavity are more noticeable, the length of the inlet rotation and return flow are both longer, and the disturbance to the inlet flow is large. As the flow rate increases, the radius of the circulating flow and the range of influence decrease. The particles in the pump are subject to a combined effect of the through-flow and the circulating-flow, while particles in the central tube wall are greatly affected by the through-flow. The particles pass through the lateral cavity priori to directly entering the impeller. The particles near the pipe wall are greatly affected by the circulating flow, and distribution of the particles in the three sections along the axial direction in the impeller differ noticeably, with the number of particles gradually increasing from the front end of the impeller to its rear cover. For the vortices with opposite rotation directions, the front vortex beam gradually dissipates after the V section, and the rear vortex beam rotates all the way to the eighth section. Influenced by both the through-flow and the circulating flow, the particles are brought into the inlet area along the pipe wall by the rotating backflow. 【Conclusion】 The existence of the circulating flow reduces the efficiency of the vortex pump, despite the great role it plays in conveying particles, which increases the conveying performance of the pump. Numerical simulation results are consistent with the experimental data, indicating that the model correctly captures water flow and sediment transport in the pump.

Keywords

• vortex solid-liquid two-phase flow pump
• cfd-dem coupling calculation
• circulating flow
• high-speed photograph
• inlet rotating backflow