Design Of Gas-Solid Two-Phase Flow Velocity Measurement System Based On Electrostatic Sensor

The flow parameters of gas-solid two-phase flow include velocity, concentration, mass flow and so on. Velocity is an important parameter which reflects the flow conditions of gas-solid flow. Detection of gas-solid flow rate for two-phase flow is of great significance for industrial safety, economic and efficient operation.At present, using electrostatic sensing to measure the velocity of solid particles is a new technology in the field of international multi-phase flow measurement. However, the electrostatic sensing technique still has many problems and difficulties in theory and practice because of the complexities and randomness of gas-solid two-phase flow.In this dissertation, FEM simulation for the electrostatic sensor is discussed based on the analysis of the basic electrostatic sensing principles; The electrodesatic output signals are analyzed by multi-scale resolution in the terms of the characteristics of the electrodestatic sensor. The improved cross-correlation algorithm is also discussed int this dissertation. The velocity measurement system of gas-solid two-phase based on electrostatic sensor are built. In the laboratory environment, the velocity of particles is measured, and the experimental results are also analyzed. The main works are as follows:(1) The electrostatic sensing principle has been derived, then it has been discussed about the influences of the electrostatic sensor plate width, the dielectric pipe thickness, the dielectric pipe relative permittivities, the metal screen lengths and the metal screen radiuses on the sensor sensitivity and sensitive field uniformity;(2) The electrostatic sensor is designed and produced, multi-scale analysing have been done to the electrostatic fluctuations signals from the sensor with FFT and HHT; and the relationships of the signal time-frequency-energy have been drawn according to the analysis of the non-linear, non-stationary nature of the static signal;(3) A sensing circuit of eletrodynamic sensor was designed. Experimental results from the simulation show that the circuit can relize the measurement of electrostatic signal without distortion;(4) The cross-correlation velocity measurement algorithm based on electrostatic sensors is investigated. An improvement algorithm based on the FFT interpolation and Hilbert transformation in order to locate accurately the peak point of the correlation function is also introduced;(5) The whole system design is completed; the software for the ARM development board is also done by the ADS kit. The real-time measurement system display of gas-solid velocity can be realized by HMI. Furthemore, RS-485 bus interface is provided to communicate and to send data. The host system is programmed with Labview which is a kind of virtual instrument SDK;(6) The experiment plahtform is set up. Testing the system equipment, analyzing the experiment results and correcting the system error also have been done. The experiments include observing the correlation characteristics of signal, determination of sample rate and sample number and test of the precision and long-term stability of the velocity measurement system.