Investigations into sensing characteristics of electrostatic sensor arrays through computational modelling and practical experimentation

Abstract

Abstract Recently, great advance has been made on electrostatic sensing techniques for gas–solid flow measurement. However, reports on research studies of the sensing mechanism and characteristics of the electrostatic sensor arrays (ESA) are scarce. The ESA is a key element of the Electrostatic Tomography system (EST) and multi-channel electrostatic sensors for the local characteristic measurement of gas–solid flow. The geometric sizes of the ESA and the velocity and distribution of particles in the pipeline have important effects on the spatial sensitivity, spatial filtering effect and temporal frequency response of the ESA. In this paper, the charge induced on the electrodes of an ESA with different geometric sizes from a single particle having a unity charge is modelled mathematically, and the 3-dimensional electrostatic field due to the charged particle in the sensing zone of the ESA is solved by using a Finite Element Method. The effects of geometric and material parameters of the ESA, including the width and angel of the electrode, the thickness, length and permittivity of the dielectric pipe, the radius of metal screening on the sensing field of the electrodes are investigated numerically. Furthermore a computational model of the sensitivity of the ESA is proposed based on a fitted Gaussian function to the finite element results and its spatial filtering characteristics are also theoretically analyzed. The temporal frequency response of the ESA is also derived. Experimental work is performed on a purpose-built particle flow test rig to verify the modelling results. The theoretical and experimental results obtained demonstrate that the ESA acts as a low-pass filter in the spatial frequency domain. The measurement system, including the ESA and an interface circuit, acts as a band-pass filter. And the space position of charged particle, the electrode width and particle velocity affect the temporal frequency responses of the ESA. These results provide the basis for the performance improvement and optimized design of the ESA.