Optical Measurement System Of Gas-liquid Two-phase Flow In Small Channels

Two-phase flow widely exists in many industrial processes, such as petroleum, chemical engineering and so on. With the rapid development of small-size industrial devices, parameter measurement of gas-liquid two-phase flow in small channels has become a new hot point in the research field of two-phase flow. The characteristics of the gas-liquid two-phase flow in small channels are different from the flow in conventional channels because of many factors such as surface tension and so on. Therefore, the parameter measurement method for the small channel is currently a hot spot in the research field of two-phase flow.An optical measurement system for gas-liquid two-phase flow in small channels is designed, and experiments are carried out to analyze the flow characteristics of the gas-liquid two-phase flow in small channels. The main contents and innovative points are summarized as follows:(1) An optical measurement system for gas-liquid two-phase flow in small channels is developed. Experiments are carried out in the small channels with three different inner diameters of 1.8mm,3.1mm and 4.0mm respectively. The experimental results show that the presented optical measurement system is effective and can be used for parameter measurement of gas-liquid two-phase flow in small channels.(2) The optical signal obtained from air-water slug flow is investigated. Research results show that the optical signal includes abundant information on the characteristics of gas-liquid slug flow. It can be used to distinguish the phase distribution on the both sides of the interface between gas and liquid and to identify the flow direction as well. These results indicate that the proposed optical method has the potential to measure the parameter of the gas-liquid two-phase flow in small channel.(3) The optical signals are processed by using probability spectral density function, Fourier transform and continuous wavelet transform. The processing results are compared for different flow patterns and it is found that there are distinct differences among four typical flow patterns in the time domain, frequency domain and time-frequency domain. Hence, it is feasible to identify the flow pattern of gas-liquid flow in small channels based on the optical signal.(4) The multi-resolution decomposition and wavelet packet decomposition are used, respectively, to extract the energy features of the optical signals in different frequency band. By using the extracted features as the input, a flow pattern classifier based on Support Vector Machine is designed to identify the flow pattern identification of the gas-liquid two-phase flow in small channels. Research results show that the proposed method is effective. The Support Vector Machine combined with either multi-resolution decomposition or wavelet packet decomposition can achieve high accuracy and good consistency performance.