Research On Flow Rate Measurement Method In Millimeter-scale Pipes Based On Capacitively Coupled Contactless Conductivity Detection Technique

Flow rate is one of the most important parameter both in academic research and industrial process. With the trend of miniaturization of industrial devices, the flow rate measurement in millimeter-scale pipes is of increasing importance. Capacitively Coupled Contactless Conductivity Detection (C4D) is a new conductivity detection technique. The advantages of C4D technique include non-contact, simple construction and so on. However, C4D is mainly used in the research field of analytical chemistry for ion concentration detection in capillaries. Few researches have been reported in the field of flow rate measurement in millimeter-scale pipes so far. The aim of this work is to propose a new method for flow rate measurement in millimeter-scale pipes based on C4D technique, and design a new C4D sensor and measurement system. The research work expands the application area and establishes the foundation of C4D technique in the area of flow rate measurement. The main works are listed as follows:(1) Propose a new method for flow rate measurement in millimeter-scale pipes based on C4D technique. This work combines C4D technique and the cross-correlation measurement technique, and proposes a new method for flow rate measurement in millimeter-scale pipes based on C4D technique.(2) Design a three-electrode C4D sensor. The sensor is mainly composed of an insulation pipe and three electrodes, and has series resonance and shield configuration. The series resonance configuration not only can eliminate the unfavorable influence of the coupling capacitances and expand the application pipes’ scale of C4D technique, but also can form the upstream sensor and downstream sensor independently. The shield configuration can solve the unfavorable influence of the capacitances coupled by the electrodes through the air.(3) Develop a flow rate measurement system in millimeter-scale pipes based on C4D technique. The system includes the three-electrode C4D sensor, the signal processing module, data acquisition module and flow measurement module. The three-electrode C4D sensors have different pipes with inner diameters of3.00mm,4.00mm,5.50mm,6.00mm and7.60mm respectively. In order to prove the proposed method, the conductivity detection experiments and the flow rate measurement experiments have been carried out. The maximum relative deviation of the results of experiments mentioned above is less than5%. The experimental results have proved the feasibility and effectiveness of the proposed method.