Characterization Of Particle Flow In A Square-Shaped Pneumatic Conveying Pipe Using Electrostatic Sensor Arrays

Rapid and refined characterization of pulverized coal flow in pneumatic conveying pipelines is of great importance to improve the operation flexibility of a coal-fired boiler.However,little research has been conducted on characterization of the complex gas-solid two-phase flow in square-shaped pneumatic conveying pipelines.In this study,an electrostatic sensor arrays measurement system with distributed strip-shaped electrodes is designed to characterize the particle flow in square-shaped pipelines under various flow conditions.The main research includes the following aspects:(1)The electric field distribution of charged particles and the dynamic characteristics of gas-solid two-phase flow in square-shaped pipelines are studied.Novel electrostatic sensor arrays with distributed strip-shaped electrodes are proposed and implemented to characterize the particle flow parameters,such as the velocity profile,concentration profile,flow stability and flow pattern of particles,in a square-shaped pipe for the first time.(2)A mathematical model of the electrostatic sensor arrays is established based on the theory of electrostatic induction and the method of images.Meanwhile,a finite element model(FEM)is also developed using the multiphysics modeling software COMSOL.Theoretical analysis and experimental results demonstrate the validity of the mathematical model.(3)Characteristics of induced output signals and spatial sensitivity for strip-shaped electrodes with various dimensions are studied based on the established mathematical model and finite element model.A differential measurement method is proposed to homogenize the spatial sensitivity and optimize the design of the electrostatic sensor arrays.(4)A weak-signal conditioning circuit is designed according to the time and frequency domain characteristics of the outputs from electrostatic sensor arrays.Multi-channel signal cross-correlation and data fusion algorithms for the electrostatic sensor arrays are also proposed.A piece of host computer software for the electrostatic sensor arrays measurement system is developed based on the virtual instrument development software LabVIEW.(5)An experimental platform with square-shaped pneumatic conveying pipeline is designed and built.The performance of the electrostatic sensor arrays measurement system was evaluated under a range of conditions.The characteristics of the particles were further studied using non-intrusive,intrusive distributed strip-shaped electrodes and square-ring shaped electrodes.Test results demonstrate that the particle flow profile in square-shaped pipe is non-uniform,and the electrostatic sensor arrays consisted of distributed strip-shaped electrodes are able to characterize the profile informations of particle velocity,concentration,flow stability and flow pattern.