Measurement Of Gas Holdup Using Distributed Differential Pressure Coupled With Conductance Sensors

Gas-liquid two-phase flow widely exists in petroleum industry,nuclear energy engineering,thermal energy engineering and other industrial production processes.In order to realize the optimization of industrial production process,it is necessary to accurately identify and master the flow characteristics of gas-liquid two-phase flow.Compared with single-phase flow,gas-liquid two-phase flow has more characteristics of diversity,randomness,instability and complexity,and fluid flow patterns are complex and diverse.These unstable factors bring great challenges to the accurate measurement of gas holdup in gas-liquid two-phase flow.Accurate prediction of gas holdup of gas-liquid two-phase flow is of great practical significance to the design of dynamic monitoring and sensing measurement system of oil wells in the production process of oil and gas fields.Based on the differential pressure sensor has the advantages of strong stability,high reliability,easy realization in mine,fast response and high accuracy.In this paper,a measuring system for gas holdup parameters of gas-liquid two-phase flow is proposed,which combines distributed differential pressure sensor and conductivity sensor.Distributed differential pressure sensors are designed to obtain pressure fluctuation information at different locations in the same section.In this dissertation,a dynamic experiment of gas-liquid two-phase flow in a vertical upward small diameter pipe is designed.The measurement signals of distributed differential pressure sensor,eight-electrode rotating electric field conductivity sensor and inserting cross-correlation conductivity sensor are analyzed experimentally.Recurrence plot is used to identify the flow pattern of two-phase flow.On this basis,five typical pressure drop models were tested in order to optimize the model selection.According to the relationship between the mixed Reynolds number of gas-liquid two-phase flow obtained by the combined measurement system and the friction factor,the gas holdup predicted by the five pressure drop models was evaluated.The results show that the gas holdup predicted by Ansari model is better in the range of gas apparent velocity 0.0552m/s?0.6256m/s and liquid apparent velocity0.0368m/s?1.1776m/s,and the average absolute relative error is 5.947%.On the basis of extracting gas holdup,the drift model of gas-liquid two-phase flow was established,and the Separate-phase flow rate under different flow patterns was predicted,and a high precision Separate-phase flow rate prediction effect was achieved.In addition,the timefrequency analysis of the measured signal of the distributed differential pressure sensor is carried out to investigate the energy distribution of different flow patterns.Based on the traditional recursive graph,the cross recurrence plot method is introduced to identify the flow pattern.Finally,the distributed pressure sensor signals in upstream and downstream is analyzed by using Cross-Sample Entropy(CSE)algorithm.The flow pattern instability is analyzed,and the non-linear dynamic characteristics of gas-liquid two-phase flow pattern are further understood.