Local Particle Mean Velocity Measurement in Pneumatic Conveying Pipelines Using Electrostatic Sensor Arrays

In this paper, a measurement system for the local mean velocity of pneumatically conveyed particles is proposed and developed. It mainly consists of electrostatic sensor arrays, signal conditioning circuits, and a digital signal processor (DSP)-based data acquisition and processing unit. Electrostatic sensor arrays are used to detect the charge on particles in its sensing zone and further make the local particle mean velocity measurement in conjunction with cross-correlation method. The sampling frequency is determined from theoretical analysis of the bandwidth of electrostatic signal and accuracy of correlation velocity calculation. Experiments are carried out on a belt conveyor and a gravity-fed particle rig to determine the optimized sampling number of the electrostatic signal through analyzing the measurement error of the transit time. The results showed that the more sampling numbers, the higher stability of measurement results. The repeatability of the measurement system is less than ±2.2% and the linearity is better than ±4.9% over the velocity range of 5.50–21.98 m/s. Experiments are also performed on a high-pressure dense-phase pneumatic conveying system of pulverized coal, indicating that the measurement system is capable of achieving local mean velocity measurement of pneumatically conveyed particles with the relative standard deviation less than 5.5%.