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New instrument based on electrostatic sensor array for measuring tribo-electrification charging due to single particle impacts.

In the processing of particulate solids, particle-particle and particle-wall collisions can generate electrostatics. This is called contact/impact/frictional electrification and can lead to many problems such as affecting powder flow and explosion hazards. It is necessary to research the tribo-electrification charging due to single particle impacts on a target as the fundamental understanding of tribo-electrification. A new impact charging test rig based on an electrostatic sensor array that can measure charge transfer caused by a single impact between a particle and a target plane has been designed and established. Combined with the electrostatic sensor array, the compressed sensing algorithm is used to estimate not only the spatial position but also the charge amount of particle. The cross-correlation algorithm is used to determine particle's velocity instead of using other devices such as a photodetector. The new instrument allows single particles impacting target planes at different angles with a velocity exceeding 100 m/s. An oil calibration test rig has been constructed to verify the proposed methods. The estimation errors of the spatial position and charge amount are both within 5% when the particle is located at the central area of the pipeline and the estimation errors of velocities are within 2%. The impact charging experiments show a special initial charge prior to impact for which no net charge transfer would occur for polymer particles, but the charge would completely transfer for metal particles.