气液两相流管壁超声回波衰减特性及其应用

发布时间：2018-11-14 11:06

【摘要】：气液两相流动广泛存在于石油、化工、能源、动力等多个领域,与单相流动相比,气液两相流的流动界面复杂多变,受相间作用力和速度滑移等因素影响。描述气液两相流动的参数主要有流型、相分率、段塞流型下的液塞频率、液塞长度、液塞速度等。对多相流流动规律和机理的研究以及对气液两相流动过程的设计、检测、和控制都依赖于对其特征参数的准确测量。鉴于多相流动的复杂性和随机性,对气液两相流参数的检测至今依然是一个未能很好解决的难题。而高压、强腐蚀、易燃易爆、快速流动的两相流系统的广泛应用对检测方法提出了更高的要求,研究新一代气液两相流参数检测的理论和装置,不但有重要的科学意义,还具有广泛的工程应用价值。鉴于超声波具有良好的穿透性、指向性以及非接触性等特点,本文以在管壁中多次往返传播所形成的超声波余振衰减谱为研究对象,提出了基于超声回波原理的气液两相流非介入式测量的新方法。论文建立了气液两相流管道超声场的预测模型,结合公式计算等方法模拟研究了超声波在管壁中的传播和衰减特性。研究了超声波在传播过程中的能量损失、声能与传播介质质点振动幅值或者速度幅值之间的关系,开展了对超声波传播过程中衰减因素的分析。经过模拟发现由管壁-液体所构成的界面由于其透射作用较强,相当一部分声能被液体吸收从而使得超声回波衰减十分剧烈;而由管壁-气体所构成的界面由于其透射作用较弱,使得大部分的声能被反射回了固体管壁使得管壁内的超声回波衰减十分缓慢。通过分析超声的回波衰减特性即可判断出探头所在位置处管壁内侧接触的介质是气还是液,进而实现两相流的非介入式测量。本文以空气和水为工作介质,在气-液两相流试验环道上开展了超声流型识别的试验,测试管段水平布置,试验流型包括分层流、段塞流和环状流。试验采用频率为5MHz的超声探头,通过Olympus超声发生器实现信号的发射和接收,采用泰克示波器对回波进行监测和记录。探头分别布置在管道顶部(12点钟)、侧面(3点钟)以及底部(6点钟)位置。经试验发现:对于分层流,顶部探头和侧面探头所测得的结果基本一致,反映的是气-固界面超声回波特性,而底部位置的探头,因其所处位置处的管壁内侧与液体接触,故其超声回波的衰减速率远高于顶部和侧面探头,反映的是液-固界面超声回波特性;对于环状流,由于管道内壁周向被液膜覆盖,故三个探头所测结果均为液-固界面回波特征;对于段塞流,当液塞头部开始通过超声探头所在位置时,顶部和侧面的超声探头检测到的结果会因管道内介质的变化而发生突变。根据采集的三个特征观测点上的超声回波数据,提取信号的包络面积,成功实现了流型的在线识别。构建了一种基于超声回波信号的段塞流参数检测系统,将两个频率相同的超声探头进行配对分别进行超声波的发射和接收,并将二者紧靠布置在管道外壁同一截面上的12点钟方向位置。另一对探头按照相同方式布置于管壁上,两对探头之间相距3m,分别作为上下游回波测量装置。当液塞来临时,上下游的回波测量装置可以检测出发生回波衰减波形突变的时间差,即液塞通过两对超声探头间距的时间间隔,进而求出液塞速度。同样可以根据单个接收探头的超声回波突变时间获得液塞通过单个超声接收探头的时间,结合得到的液塞速度,根据时间速度法即可获得液塞的长度。将测量结果与传统差压法所测结果进行对比分析,二者结果基本一致。由于基于壁面回波测量方法的研究对象为在管壁内传播的超声波,该方法不依赖管道内的气、液介质的声波特性,基本不受温度、压力、气液组分等参数影响,无需声速矫正,不受气-液界面波动干扰。
[Abstract]:The gas-liquid two-phase flow is widely existed in many fields such as petroleum, chemical industry, energy, power, etc. Compared with the single-phase flow, the flow interface of the two-phase flow of the gas liquid is complex and changeable, and is influenced by the factors such as the phase-to-phase force and the speed slip. The parameters of the two-phase flow of the gas-liquid are mainly the flow pattern, the phase fraction, the plug frequency of the slug flow, the length of the liquid plug, the speed of the liquid plug, etc. The study of the flow law and mechanism of the multiphase flow and the design, detection and control of the two-phase flow of the gas are dependent on the accurate measurement of the characteristic parameters. In view of the complexity and randomness of the multi-phase flow, the detection of the two-phase flow parameters of the gas liquid is still a difficult problem. The wide application of the two-phase flow system with high pressure, strong corrosion, inflammable and explosive and fast flow has put forward a higher requirement for the detection method, and studies the theory and the device of the two-phase flow parameter detection of a new generation of gas liquid, which not only has important scientific significance, but also has a wide application value. In view of the good penetration, directivity and non-contact characteristics of the ultrasonic wave, this paper presents a new method for non-interventional measurement of two-phase flow of gas liquid based on the principle of ultrasonic echo. In this paper, the prediction model of the ultrasonic field of the two-phase flow pipeline of the gas liquid is established, and the propagation and attenuation characteristics of the ultrasonic wave in the pipe wall are simulated by using the method of formula calculation and the like. The relationship between the energy loss, the acoustic energy and the vibration amplitude or the velocity amplitude of the propagation medium is studied, and the analysis of the attenuation factors in the process of ultrasonic propagation is carried out. it is found that the interface composed of tube wall-liquid can be absorbed by the liquid so that the attenuation of the ultrasonic echo is very severe due to the strong transmission effect of the interface, and the interface composed of the tube wall and the gas is weak due to its transmission effect, such that most of the sound can be reflected back into the solid wall such that the attenuation of the ultrasonic echo in the tube wall is very slow. by analyzing the echo attenuation characteristics of the ultrasonic, the medium which is in contact with the inside of the tube wall at the position of the probe is judged to be gas or liquid, and the non-interventional measurement of the two-phase flow is realized. In this paper, air and water are used as working medium, and the test of ultrasonic flow pattern recognition is carried out on the gas-liquid two-phase flow test loop. The test tube section is arranged horizontally. The test flow pattern includes stratified flow, slug flow and annular flow. The ultrasonic probe with a frequency of 5MHz is used to transmit and receive the signal through the Olympus ultrasonic generator, and the echo is monitored and recorded by the Tick oscilloscope. The probes are arranged at the top of the pipe (12 o 'clock), the side (3 o' clock) and the bottom (6 o 'clock) position, respectively. It is found that for stratified flow, the results of the top probe and the side probe are basically consistent, reflecting the ultrasonic echo characteristics of the gas-solid interface, and the probe at the bottom position is in contact with the liquid at the inner side of the tube wall at the position at which it is located, Therefore, the attenuation rate of the ultrasonic echo is much higher than that of the top and the side probes, reflecting the ultrasonic echo characteristics of the liquid-solid interface; for the annular flow, because the inner wall of the pipeline is covered by the liquid film in the circumferential direction, the results measured by the three probes are liquid-solid interface echo characteristics; and for the slug flow, When the head of the liquid plug begins to pass through the position of the ultrasonic probe, the results detected by the ultrasonic probe at the top and the side will change due to the change in the medium in the pipeline. according to the collected ultrasonic echo data on the three characteristic observation points, the on-line identification of the flow pattern is successfully realized. A segment plug flow parameter detection system based on an ultrasonic echo signal is constructed, and the two ultrasonic probes with the same frequency are paired to transmit and receive ultrasonic waves respectively, and the two ultrasonic probes are arranged in close proximity to the 12 o' clock direction position arranged on the same section of the outer wall of the pipeline. The other pair of probes are arranged on the pipe wall in the same way, and the distance between the two pairs of probes is 3m, which is used as the upstream and downstream echo measuring devices respectively. when the liquid plug is used for temporary, the echo measuring device at the upstream and downstream can detect the time difference of the change of the echo attenuation waveform, that is, the time interval of the liquid plug passing through the interval of the two pairs of ultrasonic probes, and then the liquid plug speed is obtained. and the length of the liquid plug can be obtained according to the time speed method according to the time of the ultrasonic echo mutation time of the single receiving probe to obtain the time of the liquid plug through a single ultrasonic receiving probe and combining the obtained liquid plug speed. The result of the measurement is compared with that of the conventional differential pressure method, and the results are basically the same. Since the research object based on the method of wall echo measurement is the ultrasonic wave propagating in the pipe wall, the method does not rely on the acoustic wave characteristics of the gas and liquid medium in the pipeline, and is not affected by the parameters such as temperature, pressure, gas liquid component, etc., and does not need sound speed correction, and is not disturbed by the fluctuation of the gas-liquid interface.
【学位授予单位】：中国石油大学(华东)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ021.1

【参考文献】