Measurement Of Gas-liquid Two-phase Flow Parameters With Coaxial Phase Sensor

Petrochemical industry has always been a hot topic in today's society,so experts and scholars have never stopped their exploration of petrochemical research.Due to its importance and complexity,more and more attention has been paid to the detection of multiphase flow in many researches.Void fraction is one of the most important flow parameters in gas-liquid two-phase flow.Due to the nonlinear characteristics among the parameters of gas-liquid two-phase flow and the unknown flow mechanism,it is difficult to establish an organic model to solve the information of void fraction of two-phase flow based on macroscopic measurement parameters in a short time,and the existing prediction models are limited by their own conditions.Therefore,the measurement of void fraction is a difficult problem in scientific research and industrial application.In this paper,a new coaxial phase sensor is designed to study the flow parameters of vertical gas-liquid two-phase flow.On the basis of theoretical analysis and previous work experience,the structure parameters of the sensor are calculated and analyzed.A new coaxial phase sensor measurement system is built,including the design of hardware circuit,signal acquisition module and measurement system.On this basis,the static calibration experiment of vertical tube was carried out in the laboratory,and the response characteristics of the new coaxial phase sensor in full gas-bearing range in different frequency bands were studied and analyzed.It is found that the phase difference output of the coaxial sensor response at each frequency point has a linear relationship with the variation of void fraction.According to the phase characteristic of electromagnetic wave and the change rule of gas-liquid two-phase medium,the void fraction measurement model of coaxial section is established.The dynamic experimental scheme of vertical gas-liquid two-phase flow was developed and the signal frequency and experimental conditions were determined.Based on the bubble and slug flow patterns,a dynamic experiment of gas-water two-phase flow in the flow condition of 1m~3/h-11m~3/h and 0.3m~3/h-0.8m~3/h in the flow condition of vertical tube was carried out.In terms of the time and frequency of the signal,the response characteristics of the sensor at each operating point are investigated and analyzed.It is found that the response of the new sensor varies obviously in each operating point,and the gas-liquid two-phase flow pattern can be identified by time-frequency domain analysis.At the same time,the void fraction of gas-liquid two-phase flow was measured by the sensor.Because of the difficulty of experimental measurement and the susceptibility to environmental factors.Based on the theory of dimensional analysis,the inlet parameters of the new coaxial phase sensor are analyzed.Based on dimensional analysis,a prediction model of void fraction is proposed,which is dependent only on inlet parameters and not on experimental testing technique.Through literature comparison and prediction analysis,the applicability and extrapolation of prediction model of void fraction is evaluated.From the perspective of flow pattern,the results show that considering the inlet parameters such as gas-liquid density,pressure,pipe diameter and velocity,the prediction model of void fraction can not only predict the void fraction of slug flow,but also be applicable to other flow patterns,such as:emulsion flow,annular flow and bubble flow.In addition,it is also suitable for pipe sections with different diameters,shapes and placement angles.From the perspective of the prediction effect of void fraction,the average absolute error of the derived void fraction model to the prediction result of its own data is 1.24%.The 194 sets of data from the cited literature were substituted into the prediction model of void fraction,and the average absolute error of the prediction results was 8.00%,which indicated that the results of dimensional analysis method were effective in the measurement of void fraction.A new coaxial phase sensor is used to measure the void fraction and analyze the flow pattern.And based on the theory of dimensional analysis,a void fraction model is proposed which is independent of the existing detection techniques of multiphase flow.It provides an effective method for measuring gas-liquid two-phase flow without separation.