Study On The Applications Of Capacitively Coupled Contactless Conductivity Detection Technique To Two-phase Flow Measurement

The conductivity detection method is widely used in the measurement of two-phase flow parameters, which is of great importance for academic research and engineering applications. However, the conventional contact conductivity detection method would cause electrode corrosion and electrode polarization. Capacitively coupled contactless conductivity detection (C4D) technique is a non-contact conductivity detection method which can solve these problems effectively. In this thesis, based on series resonance C4D technique, a mini-pipe two-phase flow measurement system and a capacitively coupled non-contact ERT system are studied. Main works and innovative points are listed as follows:1. A signal generation method is proposed for C4D system based on series resonance with the quartz crystal. This method greatly simplifies the system construction. Experiments are carried out and the results show that the proposed method is effective.2. A mini-pipe two-phase flow measurement system is developed based on quartz crystal series resonance C4D. Gas-liquid flow experiments are carried out in the pipe with inner diameter of 3.0mm and the conductivity signals of four typical flow patterns are obtained. Features in time-domain and frequency-domain are extracted from the obtained signals. The experiment results show that the features extracted can effectively reflect the characteristics of different flow patterns of gas-liquid two-phase flow.3. Based on quartz crystal series resonance C4D, a new resistance measurement method of capacitively coupled non-contact ERT is proposed, a prototype system is developed and two detection modes (the serial detection mode and the parallel detection mode) are proposed for this system. The hardware design and the software programming are done. Then static simulation experiments are carried out in both detection modes and the reconstructed images of the simulated two-phase flow are obtained. Experimental results show that the developed system can obtain the conductivity distribution images of two-phase flow.