| Fluid is widely present in the industrial field of Chemical, petroleum, metallurgy, power and atomic energy, etc., the parameters measurement has a great significance for both process control and parameter adjustment. Conductivity is a basic physical parameter and process control means, fluid parameter detection method based on the conductivity measurement is a kind of effective fluid parameter detection method. But the current conductivity measurement methods are mainly contact measurement method, which have the disadvantages of polarization effect and the electrochemical reactions. Capacitively coupled contactless conductivity detection (C4D) technology is a new detection technology with advantages of non-contact and easy to achieve. But, C4D technology application is mainly focus on laboratory environment, the scene of the industrial application has few literature reports, and C4D technology in millimeter pipeline fluid parameters detection is little. So this paper aims to do some research on a C D measuring system suitable for the conductivity measurement in industrial fields. Meanwhile, propose a new flow measurement method in millimeter pipe. The main work of this paper is summarized as follows:1. By analyzing and summarizing the problems of industrial application of C4D technology. Find out the problems which have not solved. Then Design the corresponding strategies to solve these problems, and put forward a kind of industrial application of C4D system design.2. A C4D system applied to online measurement of fluid conductivity is developed. The inductive module effectively eliminates the effects of coupling capacitance. Specially designed shielding structure can suppress an adverse effect of the coupling capacitance on the measurement, effectively isolate disturbances on the worksite and the adverse effect of the floating voltage on the measurement, and achieve a successful connection with the industrial metal pipe. Respectively in four cases of insulated pipes, the maximum relative difference of conductivity measurement experiments is less than4.2%. Also, the experiments of anti-jamming performance are conducted. The results show that the anti-jamming performance of this conductivity measurement method is satisfied and able to be applied to the conductivity detection in industrial field, which provide an effective reference for conductivity detection in industrial field based on C4D technology.3. Based on C4D technology a new flow measurement method in millimeter pipes is proposed. Use four pairs of electronic switches to obtain two fluid conductivity signals. Then the flow and velocity of the fluid will be calculated by conducting cross-correlation operations on the obtained signals. The pairwise interaction of the two pairs of switches eliminates coupling relations of the upstream and downstream C4D sensors, making sure of the independence of them. Meanwhile, separately connecting a inductance module which can be independently adjusted in series to the three electrodes can offset the coupling capacitor produced by the conductive fluid in pipes, insulation measuring pipes and metal electrodes, so as to effectively improve the accuracy and adjustability of the system.4. Based on C4D technology a millimeter pipeline flow measurement system is developed, which is made up of a three-electrode C4D sensor, signal processing module, data acquisition system and the associated flow measurement module. As a preliminary study, this paper carried out two flow measurement experiments in the inner diameter of3.2mm and5.4mm pipes. Both the relative deviation of the experimental results is less than10%, proving that the proposed millimeter pipeline flow measurement method based on C4D technology is feasible and effective.This study confirms the C4D technology can provide an effective solution to the difficulties of the current fluid conductivity and flow measurement, and also provide a useful reference to the further applications of C4D in the field of engineering. |
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