Study On Parameter Measurement Methods For Bubble Flow And Slug Flow Of Gas-liquid Two-phase Flow In Small Channel Based On Photodiode Array

In recent years, with the rapid development of the miniature industrial equipment, gas-liquid two-phase flow system in small channel has become an attractive research focus. However, the present study on the two-phase flow in small channel is still immature theoretically and practically, and needs to be further investigated. Study on parameter measurement technique is always an important research area in small-channel gas-liquid two-phase flow field. However, the existing measurement methods are still difficult to meet the requirements of mechanism studies and industrial applications of small-channel gas-liquid two-phase flow. Therefore, research on parameter measurement of gas-liquid two-phase flow in small channel is of great important academic value and application prospect.This thesis aims to study the parameter measurement of gas-liquid two-phase flow system in small channel. Based on optical measurement technique, the bubble flow and the slug flow in horizontal small channel are investigated.Main innovations and works of this thesis are listed as follows:1. Based on a 12×6 photodiode array sensor and a laser diode, a parameter measurement system of gas-liquid two-phase flow in small channel is designed and established. The experiments are carried out in horizontal small channels with inner diameter of 1.08mm,2.16mm,3.22mm and 4.04mm, respectively. And, the voltage signals obtained by the photodiode array are analyzed in both time domain and frequency domain.2. Based on a photodiode array, a cross-sectional parameter measurement method for the bubble flow and the slug flow in small channel is proposed. Firstly, the voltage signals, which reflect the cross-sectional information of the bubbles/slugs in small channel gas-liquid two-phase flow, are acquired by the photodiode array sensor. Then, Principal Component Analysis (PCA) and Support Vector Machine (SVM) technique are applied to develop the measurement models of the cross-sectional diameter and the cross-sectional center position of bubbles/slugs, respectively. Finally, the measurements of the cross-sectional diameter and the cross-sectional center position of bubbles/slugs are implemented. The experimental results show that the proposed method is effective and the relative errors of the cross-sectional diameter and the cross-sectional center position of the middle part of bubble/slug are both less than 10% in four small channels with different inner diameters.3. Based on the obtained cross-sectional diameter of bubbles/slugs, a void fraction measurement method for the bubble flow and the slug flow in small channel is proposed. The cross-sectional voidages of bubble flow and slug flow are calculated by using the cross-sectional diameters of bubbles/slugs. The volume void fraction is calculated by integral accumulation of the obtained cross-sectional voidages. The volume void fraction measurement models for bubble flow and slug flow are developed by Least Squares (LS) method. The experimental results in four small channels with different inner diameters indicate that the proposed method is feasible and the established model is effective. The maximum absolute errors are all less than 10%.This thesis verifies the feasibility of the proposed parameter measurement method based on photodiode array. The cross-sectional parameters are measured by the voltage signals, which can provide a new approach for parameter measurement of gas-liquid two-phase flow in small channel. Meanwhile, this system uses low-cost laser diode as a competent replacement of the expensive standard laser source and has the advantages of low cost, stable power and higher reliability.