High-accuracy water cut measurement for two-phase flow based on microwave resonant cavity sensor

Measurement of water cut in two-phase flows (especially oil–water, gas–water, and wet steam) is crucial for industrial process control in fields such as petroleum, chemical engineering, and energy. Aiming at the problems of insufficient accuracy and poor robustness of traditional measurement methods under complex conditions, a high-precision measurement method using a microwave resonant cavity sensor is proposed. Combining electromagnetic simulation and multiple experimental setups, we systematically analyze the resonant frequency response characteristics of the sensor under three typical two-phase flow conditions (oil–water, gas–water, and wet steam). Experimental results show that in wet steam measurement, changes in the pressure inside the pipeline cause significant drift in the resonant frequency. This pressure effect is considered a key factor limiting high-precision measurement. To address this issue, we conduct an in-depth study on the relationship between the dielectric constant of the mixture and pressure, and innovatively propose a compensation model that uses pressure as a calibration parameter. Accurate conversion from resonant frequency to water cut is achieved through a pressure-dependent function. The introduction of pressure compensation greatly improves the measurement accuracy of wet steam and gas–water two-phase flows. The calibrated model exhibits excellent accuracy and environmental robustness over the entire range of operating conditions, with measurement errors effectively controlled within the range required for industrial applications.