Void Fraction Measurement of Gas-Liquid Two-Phase Flow Based on Capacitance Sensor

In this study, two-phase flows comprising vacuum and water were used to simulate the two-phase flow of oil and gas in industrial applications. Accordingly, a theoretical model was established for the capacitance sensor to measure the void fraction of ring-type flows in vertical pipelines. Subsequently, the calculation formula of the void fraction was determined. Furthermore, ring- and plate-type electrodes were considered in the sensor simulation experiment. Numerical results showed that the sensitivity of ring electrodes is better than that of plate electrodes, while the linearity of plate electrodes is better than that of ring electrodes. For the plate electrode, the gap angle and electrode length were set to 20 degrees and 80 mm, respectively, to achieve the optimal sensor. Meanwhile, for the ring electrode, the electrode distance and width were set to 40 and 20 mm, respectively, to achieve the optimal sensor. The results of simulation experiments were verified through void fraction measurement experiments. The relative error was calculated using four sets of actual measurement values. The results showed a large deviation between the measured and theoretical void fractions near the empty tube, and the closer the measurements were to the full tube, the smaller the measurement error. In addition, the eccentric annular flow was found to have a significant influence on void fraction measurement.