Sectional water fraction measurement for gas-water two-phase flow containing a conductive water phase utilizing capacitance sensor

Abstract

By applying an electrical capacitance sensor to sectional water fraction measurement for gas–water (salinity) two-phase flow, this paper investigates the effect of a medium’s conductivity on the measurement of capacitance sensors and its elimination. Firstly, the mechanism of how a medium’s conductivity influences the capacitance measurement of a capacitance sensor is analyzed by combining a physical model of the sensor with its conditioning circuit. The theoretical analysis indicates that the applied exciting frequency is a key factor influencing the conductivity effect; the effect can be restrained by increasing the excitation frequency. Then, an exciting frequency optimization rule is proposed accordingly. In addition, sensor configuration and geometry optimization (based on finite element method simulations) are discussed to achieve better performance. Dynamic and static calibration experiments are carried out for stratified gas–liquid (salinity) two-phase flow for the purpose of validating the proposed method. The experimental results confirm the effectiveness of the proposed method. This work is constructive to the design of capacitive sensing technologies applied to conductive objects, and offers insights into the structural design and optimization of capacitance sensors.