【作者】 宋薇；

【导师】 董峰；

【作者基本信息】 天津大学 ， 检测技术与自动化装置， 2010， 硕士

【摘要】 气液两相流是自然界和工业生产过程中广泛存在的流动形态。气水弹状流是气液两相流的重要组成部分,由于其流动状态复杂、参数多、变化大,对于弹状流流动特性的研究以及参数的准确预测一直是国内外科学研究的重点与难点。国内外对于弹状流流动特性的研究主要以现场实验与理论分析为主,并已取得很大的进展,而以现代计算流体力学技术为手段的研究尚属少数。本文将从两相流的流动机理出发,利用数值仿真技术,对水平管气水两相弹状流的流动特性进行了研究。主要完成工作如下:1.从弹状流流动机理出发,应用FLUENT软件完成水平管道气水两相弹状流的二维非稳态仿真,得到弹状流形成过程以及弹单元内气相含率、速度、压力、湍流粘度分布情况。通过对预设截面处速度变化情况的观察,得出弹单元内的膜区和弹区的速度关系,并且由波动重复性研究弹状流弹单元间的结构特点。通过对压力随位置变化趋势的分析,阐述了弹单元内各区域压降产生的原因,并在此基础上归纳了压降公式。2.为进一步提取弹状流特性,研究弹状流发展过程中的流动状态与数值信息,在弹状流研究中提出“初始位置”概念,采用统计学方法,得到不同条件下弹状流初始位置的分布情况,总结出初始位置随管道长度变化不明显,与管道内径和入口水相表观速度的变化呈正比关系,与入口气相表观速度的变化呈反比关系。3.根据不同入口速度下距初始位置相同距离处的弹长分布情况,以及管道内不同观测处的液弹长度分布情况,得出液弹长度随入口气相表观速度增大而增大,随入口水相表观速度增大而减小,弹状流完全发展至少需要300D的直管段长度,管道内任意位置处液弹长度分布近似服从正态分布,且最大液弹长度约为平均液弹长度的2倍等结论。更多还原

【Abstract】 Two-phase flow widely exists in natural and industrial processes where slug flow is one of the most commonly encountered flow phenomenons. Because of the complex, unsteady and variant character of slug flow, the study of its flow characteristics and parameters measurement becomes a difficult and urgent issue in the field of engineering and science.Slug flow characteristics have been discussed by many researchers based on both experimental studies and the theoretical models, and great advances have been made. However, utilizing modern computational fluid dynamics technique to study slug flow has just come to a start. In light of the flow mechanism of two-phase flow, the characteristics of slug flow are studied through numerical simulation.The main achievements in this paper are as follows:1. Based on flow mechanism of two-phase flow, flow characteristics of gas-water slug flow were studied through computational fluid dynamics unsteady simulations. The formation of slug flow and the gas holdup, velocity, pressure as well as turbulent viscosity distribution are observed. The relationship between film velocity and slug velocity in a slug unit is obtained, and inter-slug structure is studied with the repeatability of slug fluctuations. The contributions to the pressure drop across a slug are also analyzed, and formulas are summed up to demonstrate such pressure drop.2. In order to further extract details of flow characteristics of slug flow and to investigate the flow condition and the numerical feature through the development of slug flow,“initial position”is proposed which analyzes the distributions of initial position under different conditions by statistical method. The results show that the pipe length has little effect on the initial position, and initial position increases with the increase of the pipe inner diameter and the inlet water velocity, and decreases with the increase of the inlet gas velocity.3. At the same distance from the initial position, the distribution of liquid slug length are observed with different inlet velocity, which shows the liquid slug length increases with the increase of inlet gas velocity, and decreases with the increase of inlet water velocity. The distribution of liquid slug length along the pipe shows that the length of the horizontal pipe required to reach quasi-stable slug flow is at least 300 times of pipe inner diameters, the distribution of liquid slug length at any part of the pipe is in agreement with normal distribution, and the maximum length is about 2 times of the mean slug length.更多还原