Development And Application Of The Capacitively Coupled Electrical Resistance Tomography System Based On Digital Phase-Sensitive Demodulation Method

As a way to acquire conductivity spatial-distribution of detected medium, electrical resistance tomography (ERT) technique has been considered to be of vital prosperity as well as potential value. However, traditional ERT technique has met its limit of promotion due to the contact between electrodes and liquid, which may cause electrode corrosion and polarization effect. Recently, a novel non-contact capacitively coupled ERT(CCERT) system has been reported by combining capacitively coupled contactless conductivity detection (C4D) technique and traditional ERT technique. The new system can avoid electrode corrosion and polarization effect, however, there still exists some drawbacks:the existing system adopted analog phase-sensitive demodulation method in which the demodulating ability is hard to meet the high requirement of the CCERT system.To solve the above-mentioned problems, this work is to apply the digital phase-sensitive demodulation method to CCERT system design. Also, a novel gas velocity measurement method in gas-liquid two-phase flow is proposed based on this combined technique and thus expanding its application area.The main works of this dissertation are listed as follows:(1)Apply digital phase-sensitive demodulation method to CCERT system design. A new CCERT data-aquicisiton system based on digital phase-sensitive demodulation method is designed to meet the high requirement of measurement performance. To ensure correct functionality of the whole system, every key module is tested and verified, which establish the foundation of system-level on-line running. Compared with the previous CCERT system based on analog phase-sensitive demodulation method, this new system achieves a higher performance on measurement resolution and velocity.(2)A novel gas velocity measurement method is proposed based on C4D technique and phase-sensitive demodulations method, which is applied to the gas-liquid two-phase flow in millimeter-scale pipes. (3)To verify the feasibility of above-proposed gas velocity measurement method, a new four-electrode C4D sensor is designed and a gas velocity measurement experimental system based on this sensor is developed. The experimental results verified the effectiveness of the proposed method as well as the proposed sensor, which demonstrated a maximum relative error less than5%.