粉体颗粒摩擦碰撞荷电过程的数值模拟

Discrete Element Numerical Simulation of Powder Particles Triboelectric Charging

为揭示粉体颗粒摩擦碰撞荷电过程机理及其变化规律,建立了摩擦带电器三维模型,运用离散元素法建立了颗粒的几何模型,通过研究颗粒及其相互之间的作用力关系确定了求解的力学模型,对摩擦带电器内粉体颗粒的摩擦碰撞荷电过程进行了数值模拟,获得了颗粒运动速度和荷质比的变化特征。结果表明,颗粒在摩擦带电器的三个区域内带电效果存在差异:喷嘴区域的颗粒荷质比最小;摩擦棒区域因存在摩擦棒实现了强化带电,获得了颗粒的最大荷质比,但因颗粒团聚与电性中和现象影响了颗粒荷电,该区域荷电不稳定;无摩擦棒区域颗粒荷质比最稳定。摩擦带电器内颗粒带电后运动速度逐渐降低,并在无摩擦棒区域达到稳定值,为进入高压静电场高效分选创造了有利条件。本研究可为粉体颗粒强化荷电和摩擦带电器优化设计提供技术参考。

Particles are charged owing to contact,friction and impact in the process of industrial powder material treatment.Electrostatic separation is based on the process of friction charging to achieve physical separation of different particles,and the enhancement of particle frictional electrification is the main way to improve separation efficiency.In this paper,three-dimensional model of tribocharger and geometric model of particles were established.The mechanical model of the solution is determined by studying the interaction among particles.The numerical simulation of the friction collision of powder particles in tribocharger was carried out.The particle motion velocity and the ratio of charge to mass were obtained from the motion behavior and electrification law of the powder particles in the same area.The results show that the charge effect of the particles in the three regions of tribocharger is different,the particle charge ratio in nozzle region is the smallest,electrification is strengthened by the existence of friction rod in friction rod region,and the maximum charge ratio of the particles is obtained,but particle agglomeration and electrical neutralization affect particle charging,which leads to unstable charging in the region.The charge density ratio of particles in friction rod-free region is the most stable.The motion velocity of particles in tribocharger decreases gradually and reaches the stable value in friction rod-free area,which creates favorable conditions for the high efficient separation in high voltage electrostatic field.This research provides a technical reference for the optimization of powder particle charging and friction device.