非牛顿流体中平行气泡聚并行为研究

发布时间：2018-03-13 21:30

本文选题：非牛顿流体　切入点：平行气泡　出处：《天津理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：非牛顿流体中平行气泡的生成过程和聚并特征对研究气泡间相互作用机理及气液接触设备设计优化具有指导意义。本文分别采用水平集与流体体积法(CLS-VOF)和高速摄像仪分别对不同条件下非牛顿流体中气泡聚并行为进行研究,并对微通道中气泡破裂行为进行数值模拟。本文采用CLS-VOF对羧甲基纤维素钠(CMC)溶液中平行气泡生成过程中聚并行为进行模拟,并对比实验结果,证明模拟方法的有效性。分别考察了气泡聚并过程,以及溶液浓度,表面活性剂(十二烷基硫酸钠,SDS)浓度,气体流速,喷嘴内径及喷嘴间距对气泡形变的影响。结果表明,气泡聚并前,气泡纵横比(E)随气相流速和喷嘴内径增加而增加,而CMC浓度、SDS浓度以及喷嘴间距对其影响不明显;气泡聚并之后,纵横比随CMC浓度、SDS浓度和气相流速增加而增加,随喷嘴内径增加而减小。采用CCD高速相机观测了的不同条件下气泡聚并过程,分析了平行气泡聚并原因,结果表明,平行气泡聚并的先决条件是气泡相互间的接触时间必须大于聚并所需的挤压时间;气泡聚并时流体内外流场共同作用的结果。分析了气相流速、CMC浓度、SDS浓度等因素对气泡聚并行为的影响,结果表明:气相流速对聚并概率有很大影响;表面活性剂抑制气泡聚并;CMC促进气泡聚并。喷嘴间距及喷嘴内径对气泡聚并影响不明显。另外,采用CLS-VOF法研究了不同出口夹角微通道中气泡破裂行为,结果表明,在气泡破裂过程初期随着气相流速的增加,气泡颈部厚度增加,在后期随气相流速的增加,气泡颈部厚度反而快速的减小;随聚丙烯酰胺(PAM)浓度的增加,气泡颈部厚度增加;随着气泡长度的增加或微通道出口夹角的减小,气泡破裂概率增加。
[Abstract]:The formation process and coalescence characteristics of parallel bubbles in non-Newtonian fluids are of guiding significance for the study of the interaction mechanism between bubbles and the design optimization of gas-liquid contact equipment. In this paper, the level set and fluid volume method (CLS-VOF) and high velocity photography are used, respectively. The coalescence behavior of bubbles in non-Newtonian fluids under different conditions was studied by the imager. In this paper, the coalescence behavior of parallel bubbles in CMCs solution was simulated by CLS-VOF, and the experimental results were compared. The effects of concentration of solution, concentration of surfactant (12 alkyl sodium sulfate), gas flow rate, nozzle diameter and nozzle spacing on bubble deformation were investigated. Before bubble coalescence, the aspect ratio (E) of bubbles increased with the increase of gas flow rate and nozzle diameter, while the concentration of CMC and the distance between nozzles did not affect it, but the aspect ratio increased with the increase of CMC concentration and gas velocity after bubble coalescence. The process of bubble aggregation under different conditions observed by CCD high-speed camera is reduced with the increase of nozzle diameter. The causes of parallel bubble aggregation are analyzed. The results show that, The precondition of parallel bubble coalescence is that the contact time between bubbles must be longer than the extrusion time required for aggregation. The effect of gas flow rate (CMC) concentration and SDS concentration on bubble aggregation behavior is analyzed. The results show that gas flow rate has great influence on coalescence probability. The effect of surfactant on bubble aggregation is not obvious. In addition, CLS-VOF method is used to study the bubble rupture behavior in microchannels with different outlet angles. In the initial stage of bubble rupture, the thickness of bubble neck increases with the increase of gas velocity, and decreases rapidly with the increase of gas velocity at the later stage, and increases with the increase of polyacrylamide (PAM) concentration, the thickness of bubble neck increases with the increase of concentration of polyacrylamide (PAM), the thickness of bubble neck increases with the increase of gas velocity. The bubble rupture probability increases with the increase of bubble length or the decrease of the angle at the exit of the microchannel.
【学位授予单位】：天津理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ021.1

【参考文献】