Response Characteristics of Coaxial Capacitance Sensor for Horizontal Segregated and Non-Uniform Oil-Water Two-Phase Flows

In this paper, the response characteristics of a coaxial capacitance sensor for horizontal oil-water two-phase flows with segregated and non-uniform phase distribution are investigated. First, the experiment of horizontal oil-water two-phase flow is carried out in a 20-mm inner diameter pipe with a flow concentration device. The response signals of the coaxial capacitance sensor under different flow patterns are collected by a data acquisition device. Meanwhile, the liquid holdup is measured using three pairs of parallel-wire capacitance probes and quick closing valve technology to uncover the complex slippage behaviors between phases. Then, the effects of the flow slippage and non-uniform phase distribution on the sensor response characteristics are investigated based on the equivalent impedance circuit analysis and adaptive optimal kernel time-frequency representation. In general, the results show that the coaxial capacitance sensor presents preferable response resolution for selected horizontal oil-water two-phase flow patterns, such as stratified flow and stratified flow with mixing at interface. However, as the flow pattern evolves to dispersed oil-in-water and water flow with high water-cut, the response resolution of the coaxial capacitance sensor is lower.