不同粒径比的双组份粗颗粒垂直管道提升堵塞过程和机理

Blocking Process and Mechanism of Vertical Pipe Lifting of Two-Component Coarse Particles with Different Particle Size Ratios Based on Immersed Boundary Method

该文针对深海多金属结核在垂直输矿管道内的输运、堵塞和疏堵过程,建立了二维简化模型,使用CFD-DEM方法,开展了初始分选条件下,不同粒径比双组份颗粒群在垂直管道内输运的数值模拟。通过控制粒径比和给料浓度,研究固液两相流流态的变化、堵塞体中力链的演变和堵塞体与管壁间摩擦力的变化。提出较高的局部体积分数是引发管道堵塞的必要条件,但不是充分条件,配位数超过临界值2.25并保持稳定标志着堵塞状态的形成;浓度越高,粒径比越大,越容易引发堵塞,但浓度与粒径比无法单独确定输运状态。提高泵的功率可以使堵塞转变为段塞流状态,但无法使堵塞体分散为游离的颗粒。

In this paper,a two-dimensional simplified model is established for the blocking and restarting processes of deep-sea polymetallic nodules in a vertical pipeline.The transport of two-component particles with different particle-size ratios in a vertical pipeline under initial sorting conditions is numerical simulated using the CFD-DEM method.By controlling the particle-size ratio and particle feed concentration,the changes of the solid-liquid two-phase flow pattern,the evolution of the force chain in the blockage body and the changes of the friction between the blockage body and the pipe wall are investigated.It is stated that a higher local volume fraction is a necessary but insufficient condition for triggering pipe blockage,and that a coordination number exceeding a critical value of 2.25 and remaining stable marks the formation of a blockage state.Moreover,a higher volume concentration and a larger particle-size ratio are more likely to trigger blockage,but they cannot determine the flow state individually.Increasing the pump power can change the blocked flow to the plugged flow,but cannot disperse the blockage body into free particles.