Oscillation Frequency $LC$ -Based Sensor for Characterizing Two-Phase Flows in Energy Systems

The need for two-phase flow measurement in the power generation industry has been significantly increased over the last few years. This is mainly because the reliable measurements of the two-phase flow parameters, such as void fraction, phase velocity, and flow pattern identification, are important for accurate modeling and/or in the operation of energy systems. Although many two-phase flow sensors were recently developed, challenges in measuring two-phase flow characteristics using a simple and inexpensive sensor remain unresolved. Therefore, extensive research efforts that were spent in designing accurate two-phase flow sensor that does not require complex software solving an inverse problem are currently under development worldwide. In this paper, a multichannel, high-resolution capacitance sensor system for two-phase flow void fraction measurements was developed for slightly conductive and non-conductive fluids. Inductance-capacitance (LC) metering circuit is designed to relate the change in the measured resonance frequency to the change in capacitance registered by the sensor. The narrow band filtering effect of the LC circuit allows for the system to be more resistant to background noise. Three sensor electrode configurations were designed in order to provide more information on the flow behavior in the piping system, including the bubble velocity, flow distribution, and time signal of void fraction for different flow patterns. Both static and dynamic measurements were carried out, and the sensor operation was validated using a high-speed imaging system.