| In the current long-distance land transportation pipeline and offshore oil and gas field mixing system,the slug flow is a common flow form.Due to the intermittent,volatility and instability of this flow pattern,it is a flow safety problem that must be broken in the development of deep water oil field,and that effective real-time detection technology is one of the key issues to solve the slug flow.Acoustic emission technology as a non-invasive dynamic detection method has been widely used in various types of mechanical structure detection,the detection of energy from the measured object itself,without the need for external ultrasonic transmitter or ray source,it is easy to use and has high sensitivity.The use of acoustic emission method for the detection of gas-liquid two-phase pipe flow not only reduces the cost of operation and installation in the oil production process,but also avoids the harm of the radiation source to the body and has a very real-time monitoring and safety detection of oil and gas production significance.In this paper,the feasibility analyze of the bubble acoustic signals in gas-liquid two-phase pipe flow by single bubble experiment.The effects of different nozzle size,different liquid physical properties and different sensor placement on bubble acoustic signal were discussed.At the same time,through the high-speed camera shooting,analyzed of the bubble generated sound mechanism,and the correlation between the peak frequency of the acoustic signal and the size of the bubble was proposed.The experimental results show that the acoustic emission technique could effectively detect the acoustic signal of the bubble in the tube,which had high sensitivity and provide the theoretical basis for the application of the acoustic emission technology to the bubble dynamics.Furthermore,this paper simulated the mechanism of the head of the slug plug,and made the measurement of the sound signal of the liquid in the pipeline.The distribution of axial and circumferential acoustic signals along the fixed liquid plugs under different layer opening and different liquid flow rates was analyzed.Through the self-developed acoustic emission acquisition and processing software,the acoustic emission parameters were measured and extracted in real time.The acoustic signal was analyzed by means of parametric statistical method,time domain waveform method,clustering methodology,Fourier transform and wavelet packet transform.The success of the distinction between the liquid plug the bubble signal,the liquid tube wall signal and the background noise signal frequency range.The results show that the acoustic signal frequency of the bubble was mainly distributed in the range of 125-500 kHz.The acoustic signal decreased with the increase of the axial position of the starting point,and the maximum acoustic signal was distributed in the lower part of the pipeline of the liquid plug head.The flow mechanism of the internal plug was verified from the perspective of acoustics,which provided a theoretical basis for the application of acoustic emission technology to the actual slug flow detection.Finally,the correlation analysis between the acoustic emission parameters and the gas void fraction of the liquid plug was carried out by using the Pearson correlation coefficient method.The fitting of the gas void fraction correlation was carried out by the 1stOpt software.The error between the fitting value and the theoretical value was small.And the calculation model of the bubble volume of the slug area was put forward,so the quantitative description of the flow parameters of the plug was realized by the acoustic emission parameters. |
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