Study On Measurement Method Of Gas-solid Two Phase Flow Parameters With Electrostatic Sensors

The accurate and on-line measurement of flow parameters is of great importance to gas-solid two phase flow widespread existing in lives and industries. Due to collision and friction of solid phase particles during being conveyed into the pipe, they will create charge on their superficies, and so electrostatic sensor may measure and obtain flow parameters of gas-solid two phase flow by electrostatic induction principle, such as solid phase charge quantity and velocity. Electrostatic sensors have better application prospect to measure flow parameters of gas-solid two phase flow with its simple structure and low cost.There lie two types of studied electrostatic sensors that include the inserted and ring probe, and based on the predecessor work this thesis mainly studies the physical model of electrostatic induction, electrostatic sensor characteristic and the measurement method of gas-solid two phase flow parameters. The main work is as following:(1). The mathematical models of the inserted electrostatic sensor are debated which include the mathematical model of the single particle and the mathematical model of the homogenous flow dispersed by electrostatic induction principle in this paper; With the same idea, three mathematical models of ring electrostatic sensor are obtained:the mathematical model of continuous mass point at the pipe central axial, the mathematical model of the homogeneous flow dispersed and the mathematical model of the roping flow; The sensitivity characteristics of ring and inserted probe researched have better actions guide electrostatic sensor design.(2). The velocity measuring method of the inserted electrostatic sensor using spatial filtering effects is obtained with the point charge mathematical model established in this paper and transfer function inalterability of measurement system. With experiments it is obtained that "3dB" method of the inserted probe spatial filter velocity measures particles velocity of gas-solid two phase flow. (3). When velocity of thin sand(0.1mm) seemed as measured object is within2-7m/s, the velocity is measured with cross correlation principle. With stationary velocity of thin sand, the repeatability error that measured velocity result deviates the mean value of cross correlation velocity sample is in range of±2%; Because cross correlation measurement method belongs to an absolutely measuring velocity method, adopting cross-correlation velocity of ring electrostatic sensor adjusts spatial filter velocity of electrostatic sensor inserted into pipe.(4). Measurement experiments about velocity parameter of gas-solid two phase flow are realized with made-up experiment equipment, and the velocity value may be adjusted from1m/s to25m/s. Some influent factors of inserted probe are debated with made-up experiment equipment:With the change of thin line position on cross section of pipe the sensitivity plot of inserted probe is obtained; With the change of thin line velocity on the same position of pipe cross section, experiments proof the spatial filter characteristic of the inserted probe. When measurement system obtains cross correlation velocity and spatial filter velocity, employing hall element obtains the true velocity of thin line, and with the’true’thin line velocity cross correlation velocity of ring probe is corrected, with which the spatial filter velocity of inserted probe is adjusted.