本文選題：非牛頓流體　切入點：平行氣泡　出處：《天津理工大學》2015年碩士論文　論文類型：學位論文

【摘要】：非牛頓流體中平行氣泡的生成過程和聚并特征對研究氣泡間相互作用機理及氣液接觸設備設計優(yōu)化具有指導意義。本文分別采用水平集與流體體積法(CLS-VOF)和高速攝像儀分別對不同條件下非牛頓流體中氣泡聚并行為進行研究,并對微通道中氣泡破裂行為進行數值模擬。本文采用CLS-VOF對羧甲基纖維素鈉(CMC)溶液中平行氣泡生成過程中聚并行為進行模擬,并對比實驗結果,證明模擬方法的有效性。分別考察了氣泡聚并過程,以及溶液濃度,表面活性劑(十二烷基硫酸鈉,SDS)濃度,氣體流速,噴嘴內徑及噴嘴間距對氣泡形變的影響。結果表明,氣泡聚并前,氣泡縱橫比(E)隨氣相流速和噴嘴內徑增加而增加,而CMC濃度、SDS濃度以及噴嘴間距對其影響不明顯;氣泡聚并之后,縱橫比隨CMC濃度、SDS濃度和氣相流速增加而增加,隨噴嘴內徑增加而減小。采用CCD高速相機觀測了的不同條件下氣泡聚并過程,分析了平行氣泡聚并原因,結果表明,平行氣泡聚并的先決條件是氣泡相互間的接觸時間必須大于聚并所需的擠壓時間;氣泡聚并時流體內外流場共同作用的結果。分析了氣相流速、CMC濃度、SDS濃度等因素對氣泡聚并行為的影響,結果表明:氣相流速對聚并概率有很大影響;表面活性劑抑制氣泡聚并;CMC促進氣泡聚并。噴嘴間距及噴嘴內徑對氣泡聚并影響不明顯。另外,采用CLS-VOF法研究了不同出口夾角微通道中氣泡破裂行為,結果表明,在氣泡破裂過程初期隨著氣相流速的增加,氣泡頸部厚度增加,在后期隨氣相流速的增加,氣泡頸部厚度反而快速的減小;隨聚丙烯酰胺(PAM)濃度的增加,氣泡頸部厚度增加;隨著氣泡長度的增加或微通道出口夾角的減小,氣泡破裂概率增加。
[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.
【學位授予單位】：天津理工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TQ021.1

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