Gas/liquid ratio measurements by rf resonance capacitance sensor

摘要

A radio-frequency resonance sensor with variable capacitance for gas/liquid volume ratio measurements is presented. The variable capacitor is made in the form of two semi-cylindrical electrodes, mounted on the outer side of the wall of a dielectric pipeline through which a liquid with gaseous bubbles flows. The variation in the percentage of the gas and liquid causes the capacitance of the electrodes to be changed. Because the electrodes are connected to a resonant circuit of an oscillator tuned to high frequency of 80 MHz, the capacitance variations change the frequency of this oscillator. The changes of frequency generated by the oscillator are the measure of the gas and liquid volume ratio of a two-phase flow in the pipe. In the experiments, two half-cylinder electrodes of height of 10 mm were mounted on the outside wall of a pipe of diameter of 40 mm. The frequency deviations were up to 4 MHz when the pipe was empty or filled with water. (C) 2004 Elsevier B.V. All rights reserved.