Twin Rectangular Fork-Like Capacitance Sensor to Flow Regime Identification in Horizontal Co-Current Gas–Liquid Two-Phase Flow

In this paper, a twin rectangular fork-like capacitance (TRFLC) sensor to recognize the flow regime of gas-oil two-phase flow in a horizontal pipe is proposed. Two phase flow experiment is carried out in a 26.6-mm ID horizontal pipe to determine the response of TRFLC sensor on different flow regimes. Both measuring and exciting electrodes consist of a base and double rectangle blades, which are placed alternately. The finite-element method (FEM) is used to calculate the sensitivity field of the sensor. The effect of sensor geometry on the distribution of sensitivity field and the optimal sensor structure is presented. Based on FEM and experimental results, the sensitivity of TRFLC was higher than the previous concave electrode (overall sensitivity of TRFLC 3.27 pF and concave 2.19 pF). Simulation results show that two blades for each electrode have more sensitivity than three or four blades in the regions near to the center of the pipeline and more uniform sensitivity in whole section of the pipe. The flow variations especially in the center of the pipeline were traced with higher sensitivity than concave type. As a result, the flow regimes such as slug can be identified with more accuracy. The flow regimes were classified using wavelet transforms and power spectral density (PSD). The wavelet variance is not sufficient to flow regime assignment due to some flow regimes overlapping. The wavelet variance in conjunction with the cumulative PSD solves this problem and presents a very useful tool to flow regime classification.