微通道中气液两相流的分布和操作稳定性

发布时间：2018-02-22 18:21

本文关键词： 微通道气液两相流稳定性分布模型　出处：《天津大学》2016年博士论文　论文类型：学位论文

【摘要】：微通道技术是实现化工过程强化和安全可控的重要手段,其微米级的通道结构带来了对流动过程的精确控制。为了确保微通道中多相流的可控性和可操作性,本文基于不同操作条件、流体物系和通道结构尺寸对微通道中气液两相流动稳定性和分布规律进行实验研究,并构建相应的评判准则和理论模型以描述和预测流动过程的稳定性,为微通道在工业应用中的可操作性提供实验和理论基础。本文实验采用CCD高速摄像机和多点光纤检测系统对气液两相流动状态进行检测,前者借助自编程序实现对图片信息的批量处理,后者以精度高和响应时间短的优点,实现流体流动数据的高效采集。对于两相流的开车过程,使用压力传感器检测气相通道入口的压强值以识别开车过程,并利用CFD软件对气相压强边界的开车过程进行数值模拟。对于弹状流气泡尺寸的分布、气液两相流动的稳定性以及在多通道中的分布规律,选择宽操作条件(气相0.2~50 mL/min,液相0.05~20 m L/min)、多种液相物系(去离子水、乙醇、葡萄糖溶液和煤油)以及不同通道结构和尺寸的T型微通道进行实验研究,并基于偏差系数和特征参数Kolmogorov熵值来评价气泡尺寸的均匀性、流体分布规律以及流动状态的稳定性。实验结果表明,泡状流和弹状-分层流的流动状态不稳定,而弹状流相对稳定,且其气泡尺寸的偏差系数随毛细管数的减小而增大。此外,高液相流量有利于实现两相流在多通道的均匀分布,并可形成稳定的弹状流。理论模型方面,通过量化微通道中的压力扰动构建压力模型用以预测弹状流中气泡尺寸的分布;基于Kolmogorov熵的定义和对不稳定流动的成因分析,构建拟抛物线型的方程预测Kolmogorov熵值,描述复杂两相流的流动稳定性并确定可操作区间;通过质量衡算、动量衡算和通道间压力扰动的量化,构建多通道中两相流分布模型预测分布结果。上述模型不仅可以有效地预测微通道中气液两相流动状态和分布情况,还可确定稳定流动的操作区间,为微通道的工业应用提供操作指南。
[Abstract]:Micro channel technology is an important means to realize the chemical process intensification and safety control, the micro channel structure brings the accurate control of flow process. In order to ensure that the micro channel in the multiphase flow of controllability and maneuverability, this paper based on the different operating conditions, fluid system and channel structure for the experimental study of gas liquid the two-phase flow in microchannels stability and distribution, and constructs the evaluation criteria and the corresponding theoretical models to describe and predict the stability of flow process, micro channel in industrial application operation to provide experimental and theoretical basis. This experiment used CCD high speed camera and multi point optical fiber detection system to detect the state of gas-liquid flow two, the former by means of program batch processing the picture information, the advantages of high accuracy and short response time, high fluid flow data mining Set. For the two-phase driving process, using a pressure sensor for detecting gas phase pressure values to identify the channel entrance drive process, numerical simulation and CFD software is used to drive the gas pressure boundary. The distribution of slug bubble size, the stability of the two-phase flow and the distribution in multi channel wide selection, operating conditions (gas phase 0.2~50 mL/min, m L/min, 0.05~20 liquid phase) of various liquid phase systems (deionized water, ethanol, glucose solution and kerosene) and different channel structure and size of the T type micro channel were investigated, and the deviation coefficient and characteristic parameters of Kolmogorov based on entropy to evaluate the uniformity of bubble the size of the fluid distribution and flow stability. Experimental results show that the flow state of bubble and Slug - stratified flow instability, and slug flow is relatively stable, and the gas bubble size deviation Coefficient decreases with the capillary number increases. In addition, the high liquid flow rate is conducive to the realization of two-phase flow in uniform distribution channels, and can form a stable slug flow. Theoretical model, through quantitative micro channel pressure perturbations in the construction of air bubble size distribution by flow to slug pressure prediction model; analysis the definition of Kolmogorov entropy and the unstable flow causes based on the construction of quasi parabolic equation to predict Kolmogorov entropy, the flow stability description of complex two-phase flow and determine the operating area; through the mass balance and momentum balance between channels and quantify the pressure disturbance, constructing multi channel distribution model of two-phase flow distribution forecast results. The model not only can effectively predict the gas-liquid two-phase flow in microchannels and distribution, can also determine the steady flow of the operating range, provide the operating guidelines for the industrial application of the micro channel.

【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TQ021.1

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