Research On Dense Phase Gas-Solid Two-phase Flow Parameters Measurement Method Based On Segmented Excitation Capacitive Sensor

Real-time detection of dense phase pneumatic conveying corresponding parameters is essential for industrial applications. The characteristics of dense phase pneumatic conveying include complex flow pattern and parameters distribution, and in the process of dense phase pneumatic conveying, the slug flow is the typical pattern of dense phase flow in the horizontal pipeline.In this thesis, considering the characteristics of dense phase pneumatic conveying, a novel capacitance sensor array with eight excitation electrodes and one detection electrode was proposed. On the basis of optimal designing the capacitive sensors, the methods of obtaining the flow pattern, velocity, concentration and mass flow were researched. The signal detection circuit was designed and made, and the dense phase gas-solid flow detection system based on horizontal pipeline was built. By using this system, the experiments of obtaining the flow pattern, velocity, concentration and mass flow were done. The main works of this thesis are as follows:(1) The characteristics of dense phase pneumatic conveying in the horizontal pipeline and the parameters measurement method were investigated. The goal of this system was determined and the design scheme to obtain the dense phase gas-solid flow parameters based on novel capacitance sensor array in horizontal pipeline was also proposed;(2) The output characteristics of proposed capacitance sensor were studied, considering the design requirement, a novel capacitance sensor array with eight excitation electrodes and one detection electrode was proposed, the capacitance sensors were optimized and made;(3) The detection principle of segmented excitation capacitance sensor was investigated, and the dense phase gas-solid flow parameters measurement hardware circuit was designed which include the C/V conversion circuit, phase shift circuit, phase-sensitive demodulation circuit, data selection circuit, analog switch circuit, and so on. The circuit boards were made and debugged which based on the output characteristics of the capacitance sensor;(4) The flow pattern recognition algorithm was proposed, under the slug flow conditions, the methods of measuring the length of slug flow and measuring the start and end of the slug flow based on FFT was proposed, in order to improve the sampling rates and the resolution of the delay time, interpolation technique was proposed, a new cross-correlation peak search method based on Hilbert transform of cross-correlation function and combination interpolation were also researched, and the slug flow concentration measurement method was also proposed, by using these methods, the length of slug flow, velocity and concentration could be obtained on the same time. Considering the information of the flow pattern, velocity and concentration, the model of solid phase mass flow was established;(5) Under the Lab VIEW development environment, switching 16 incentive plates was finished, the programs of data acquisition, digital filtering, FFT, Hilbert transform, increasing sampling rates by interpolation, cross-correlation velocity measurement, concentration determination and mass flow determination were finished by using LabVIEW;(6) The dense phase gas-solid two-phase flow parameters detection system based on horizontal pipeline was developed, under the laboratory environment, the experiments of detecting the dense phase pneumatic conveying solid phase mass flow and other corresponding parameters were done;(7) The results of experiment show that this system can accurately identify the flow pattern(slug flow、laminar flow), the relative error of mass flow measurement was less than 8%.