Study Of Method For Liquid Volume Fraction Measurement With Capacitance Sensor Based On Hydrocyclone Technology

With the rapid development of science and technology,the measurement of multiphase flow is becoming more and more important in the fields of natural gas,nuclear power and so on.This research aims to develop a set of measuring technology by means of theoretical analysis,mechanical design and laboratory real flow experiment using capacitive sensor and venturi tube.This technique can overcome the influence of flow pattern on the measurement of capacitance sensor as far as possible,so that it can be applied to a wider measurement range of liquid volume fraction.At the same time,a combination technique based on the liquid volume fraction method is explored to provide more accurate and convenient measurement for multiphase flow parameters.Firstly,the gas-liquid hydrocyclone is added to the measuring section of the capacitance sensor.Combining the kinetic theory of gas-liquid two-phase flow,the structure of gas-liquid hydrocyclone has been optimized.And the measuring principle of the capacitive sensor is designed based on the unit.The laboratory data show that the absolute error of the measured liquid volume fraction and the true value is less than 2% in the experimental condition of volume fraction of 0~20%.Secondly,the new sensor structure is designed by using CFD numerical simulation software,and the measurement characteristics of the sensor under this structure are studied by the real flow experiment in laboratory.The absolute error of volume fraction is less than 0.5% in the experiment.The slug flow was formed during the experiment because of the influence of the length of the pipe and the connection mode.The test results of gas water two phase flow in the range of volume fraction of 0-88% show that the sensor has the ability to distinguish in the experimental range.Thirdly,in the oil-water two-phase flow experiment,when the WLR is within 0-21.98%,the capacitance measurement value increases gradually.When WLR is 24.05% and 24.29%,the value of capacitance increases sharply and fluctuates violently.It is considered that the transition point between oil in water and oil in water state appears in the oil water two phase flow under this condition.When WLR is greater than 27.11%,the capacitance measurement value remains basically unchanged.This phenomenon verifies the correctness that water is considered as a conductor in the design.Finally,based on the De Leeuw virtual height model,the application of the model under the experimental conditions of this research is explored for the vertical upward Venturi measurement model;Because the conditions of this experiment are not completely applicable to De Leeuw model,When Frg>1.5,the relative error of gas phase is less than 5%;when 0.5<Frg <1.5,the relative error reaches 28.8%.Therefore,the characteristics of parameter n in this study are analyzed,and the L-M parameter is introduced to reconstruct the model of parameter n,and the relative error of gas phase is kept within + 5%.