Electrostatic Coupled Capacitance Sensor For Gas-Solid Two-Phase Flow Parameters Measurement

Gas-solid two-phase flow refers to the pneumatic conveyance widely used in industrial production processes such as electricity,chemical industry and grain processing.It is very important to realize the accurate measurement of its particle velocity,concentration and mass flow rate for the study of the flow mechanism,the system control and optimization.Electrical method has great application potential in the measurement of gas-solid two-phase flow parameters because of its simple measurement principle,noninvasiveness,low-cost,high adaptability,and rapid response.This paper mainly studies and develops a novel electrostatic coupled capacitive sensor for the gas-solid two-phase flow parameter measurement.Experiments are conducted to verify and evaluate the performance of the electrostatic coupled capacitive sensor.The feasibility of coupling the electrostatic sensor and the capacitive sensor into one sensor is firstly theoretically analyzed and experimentally verified by a single particle experiment.A new sensor structure is proposed to solve the temperature drift issue of the traditional capacitance sensor.The sensitivity characteristics of the proposed sensor are analyzed by finite element method.Results show that the proposed electrostatic coupled capacitance sensor can simultaneously act as the electrostatic sensor and capacitance sensor.The dielectric constant of the insulating ring has little effect on the sensor capacitance when the pipe is empty,indicating that the proposed sensor structure can effectively suppress the temperature drift of the traditional capacitance sensor.A electrostatic coupled capacitance sensor for gas-solid two-phase flow parameter measurement is further designed and developed,which is composed of hardware and software.The hardware part mainly includes a sensor probe,a signal conversion circuit,and a data acquisition module.The software is developed for data processing,which can realize the real-time signal acquisition,result calculation,display and storage.Finally,the performance of the developed measurement system is experimentally evaluated.The experimental results show that the temperature drift of the sensor is extremely small,confirming that the proposed sensor structure can effectively solve the temperature drift problem.Besides,the temperature drift of the measurement circuit is less than 1.4m V/?,which fully meets the measurement requirement.The single particle experiment results show that the electrostatic coupled capacitance sensor can simultaneously obtain two electrostatic signals and two capacitance signals with good correlation,which can be used to calculate the particle velocity.The experimental results on a pulley demonstrate that the measurement system can accurately measure the belt velocity and the relative deviation of the measurement results is within the range of-5.6%? 2%.Experiments are also carried out on a gravity-fed particles flow rig.When the particle velocity is within the range of 2.48?4.23m/s,the relative standard deviation of the velocity measurement is less than2.2%.When the mass concentration is in the range of 0?120kg/m~3,the particle concentration and voltage are in a quadratic function relationship.The particle mass flow rate measured by the measurement system after calibration is basically consistent with the result of the load cell.