Research And Design Of Discrete Phase Concentration Capacitance Sensor For Gas/Solid Two-Phase Flow

With the development of science and technology, gas/solid two-phaseflow system is widely used in modern industrial and agricultural production,such as Power plant, Steel metallurgy and food such as pneumaticconveying, they are related to the gas/solid two phase flow system.Because of gas/solid two-phase flow belong to complex flow system, so itsparameter detection is a difficult problem.When the two phase flow through the capacitance sensor, the flowingdifferent dielectric constant will change the Capacitance. Capacitancedetection concentration is use of this theory to measure gas/solid two-phaseflow discrete phase concentration. This method with non-radioactive,non-invasive, rapid response speed, simple structure, low cost, wideapplication range and other advantages, in the industrial process has goodapplication prospects. But in the system design and application also have alot of problems and difficulty need to be resolution.Gas/solid two-phase flow in pipelines and distribution in complexchanges as the soft field characteristics of capacitance detection fieldcaused larger output error. And the dilute phase concentration caused thecapacitance change is very small and it difficult to identify. So this paper will try to solve these two problems.First of all, in order to make the change of capacitance is only relatedto solid-phase concentration of gas/solid two-phase flow through sensormodel changes, trying to find a sensitivity to uniform capacitance sensormodel. Building the spiral electrode capacitance sensor modelmathematical and parameter optimization, and use ANSYS to analysis andsimulation the detection field of this model.Secondly, because the capacitance change caused by dilute phaseconcentration is very tiny, and combining with the correlation theory, Iused capacitance readout chip MS3110as the base, design a minimumresolution of0.02pF, the sampling frequency is2KHz capacitive readoutcircuit, and transmitted the data through the S serial port to the hostcomputer, the LabVIEW display interface is to receive the data and storage.Finally, test the static performance of capacitor acquisition circuit,analysis the results of sampling error, and suggestions for furtherimprovement.