Electrostatic charging of single granules by repeated sliding along inclined metal plates

Abstract

In this work, repeated sliding tests for single granules were investigated for their electrostatics generation. Several factors were considered including granule length-ratio, sliding face shape, sliding times, sliding area, sliding velocity, front-facing edge, plate inclined angle and humidity. Generally, it is found that electrostatics increases with granule length-ratio. Two kinds of granular sliding face shapes were used in this work, half circle and rectangle. Under the same working conditions, a granule with the sliding face shape of half-circle tends to produce more electrostatics than that of rectangle. In addition, the efficiency of granule charge generation increases with sliding times although the amount of impact charge is decreased by the initial charge. Electrostatics increases with sliding area, which is independent of granule sliding-face shape and sliding times. Electrostatics also increases with granule sliding velocity. Front-facing sliding with a short edge tends to generate more electrostatics than that with a long edge. In this work, three sliding-plate angles were chosen as 30°,54°,70°, where granules sliding along the inclined plate at 54° acquired the highest electrostatics in comparison with other two angles. Humidity has significant effect on electrostatics as that electrostatics decreases with humidity. At lower relative humidity, the granule length-ratio is found to have more effect on electrostatics.

Eulerian models and kinetic theory closures for triboelectric charging in dense granular and gas-particle flows

“…Another parameter that is currently not considered in charging models is the surface roughness of the colliding surfaces, which was proven to be a relevant material property for charge generation in experimental studies (Yao et al 2017;Karner et al 2014;Angus and Greber 2018). Specifically, Yao et al (2017) found that there exists a critical roughness value that maximizes the charge generated upon contact (Zhao et al 2017). Given that the surface roughness primarily affects the contact area between the two surfaces, one option to incorporate its effect on charge transfer would be to multiply the computed contact area with a surface roughness factor (may not be a constant).…”