The MOSIAC Model And Numerical Simulation Of Contact Electrification By Collision Of Homogenous Particles

It widely exists particle systems consisting of the same materials in nature or industrial systems, such as ash, sand How. And it’s found moving particles are charged due to the frequent occurrence of inter-particle friction, collision, which will affect the movement of the particles. But the contact electrification mechanism of homogenous particles is not yet clear. Thus the thesis focuses on the research of contact electrification of the same materials; the main work is as follows:Since the impact angle could affect contact electrification, we carried out experiment study on the charge carried by ball obliquey impacting with plate, the ball and the plate have the same materials. The ball and plate after impact would be charged, while the polarity depends on the materials. And the magnitude of charge is related to angle of inclination of plate, which first increases and then decreases with the increase of angle. When the angle is45degree the charge maximizes, which is6-8times as much as that of direct impact. By analysis of ball-plate oblique impact dynamics, it is found the charge and friction area are perfect correlation.Based on the charged surface Mosaic distribution observed by Baytekin and the hypothesis proposed by Apodaca. a statistical model to compute the net charge of electrified particle after a single collision and multiple collisions are established, respectively. The model shows the net charge carried by the electrified particles depends on the difference between the two surfaces’ areas involved in collision contact and gives results in good agreement with experiment results. The charge arrived at maximum when the ratio of radius is about0.7. We introduce ball-plate oblique impact equivalent to multiple collisions and find the calculation is qualitatively consistent with experimental phenomena. With increasing of the number of collisions the charge reaches saturation gradually, magnitude of which depends on ratio of particles, particle sizes and the relative collision velocity.The thesis simulates the charge of multi-particle collisions including systems of two particle sizes and multiple sizes. The results show the charge gradually reaches saturation with the increase of the number of collisions; and it is found impact angle can reduce the saturation number of collisions effectively. The polarity of charge depends on the particle sizes and the distribution of size, in addition, the magnitude of charge has a certain distribution.In summan, the impact angle significantly affects the charge through the experiment:and the mosaic model is established to explain the contact electrification due to collisions of particles: then the electrification due to multi-particle collisions is simulated. Therefore. the study will be conducive to understand and explore the contact electrification by collision of homogenous particles.