CFD-DEM investigation of vortex characteristics within the hydraulic jet pumps in the vertical hydraulic conveying process

Using a hydraulic jet pump (HJP) for coarse particle transport is a promising method for hydraulic conveying in deep coal mining. In this work, a semi-resolved CFD-DEM model was developed to simulate the hydraulic conveying of coarse particles by the HJP. The diffusion averaging method was applied to determine the distributions of solid volume fraction and momentum sources in the fluid domain. The study identifies four types of vortices in the HJP: the fluid entraining vortex, fluid rotating vortex, fluid attacking vortex, and fluid mixing vortex. Among these, the fluid mixing vortex and fluid attacking vortex are influenced by the mixer-nozzle width. Moreover, the fluid attacking vortex plays a vital role in the regime transition of the HJP jet, leading to variations in its hydraulic performance, including primary and secondary fluxes, particle conveying rate, and pressure distributions. Finally, an empirical width coefficient representing the mixer-nozzle width was proposed based on the findings. These new insights will guide the application of the HJP in the coarse particle hydraulic conveying.