本文選題：非牛頓流體 + 氣泡運(yùn)動(dòng)　； 參考：《大連理工大學(xué)》2016年碩士論文

【摘要】：非牛頓流體中的氣泡運(yùn)動(dòng)行為廣泛存在于石油化工、環(huán)境保護(hù)、能源開發(fā)及利用等工程領(lǐng)域。由于非牛頓流體特殊的流變性質(zhì)以及氣液兩相之間相互作用的復(fù)雜性,對(duì)于非牛頓流體中的單氣泡生成、上升以及雙氣泡聚并行為的研究目前仍不夠完善。本文做了以下工作：(1)采用高速攝影技術(shù)以及數(shù)字圖像處理技術(shù)對(duì)去離子水和不同濃度CMC水溶液中單氣泡的生成及上升運(yùn)動(dòng)進(jìn)行實(shí)驗(yàn)研究,考察了單氣泡的形成過程,討論了氣泡上升過程當(dāng)量直徑、運(yùn)動(dòng)軌跡及運(yùn)動(dòng)速度的變化規(guī)律。研究發(fā)現(xiàn),單氣泡的形成過程可細(xì)分為三個(gè)階段。在去離子水及CMC水溶液中,氣泡的平均當(dāng)量直徑、擺動(dòng)幅度以及擺動(dòng)的隨機(jī)性受噴嘴內(nèi)徑及CMC水溶液濃度的影響較大。在去離子水中,氣泡先呈直線上升,當(dāng)z28mm時(shí),氣泡開始振蕩,呈螺旋形上升；而在CMC水溶液中,氣泡運(yùn)動(dòng)軌跡幾乎均呈直線。隨著CMC水溶液濃度的增加,進(jìn)氣流量的降低,氣泡水平速度的波動(dòng)及氣泡垂直速度逐漸減小。隨著噴嘴內(nèi)徑的增大,CMC水溶液中氣泡水平速度的波動(dòng)變大,同時(shí)高濃度CMC水溶液中氣泡的垂直速度也隨之增大,但對(duì)低粘度溶液中運(yùn)動(dòng)氣泡的垂直速度的影響并不明顯。此外,建立了在一定無量綱參數(shù)數(shù)值范圍內(nèi),適用于去離子水與CMC水溶液中,氣泡的Rｅ與We、Mo之間的函數(shù)關(guān)系式。(2)采用FLUENT軟件,基于流體體積法(VOF)對(duì)單氣泡生成及上升運(yùn)動(dòng)進(jìn)行數(shù)值模擬,并與實(shí)驗(yàn)結(jié)果進(jìn)行對(duì)比分析,進(jìn)而研究氣泡周圍液相場的特點(diǎn)。研究了單氣泡形成過程中氣泡及其周圍液相壓力場和速度場的分布規(guī)律,并重點(diǎn)對(duì)CMC水溶液中上升氣泡周圍液相速度場的影響因素進(jìn)行討論分析。隨著CMC水溶液濃度的升高,氣泡周圍液體運(yùn)動(dòng)速度降低,氣泡的影響區(qū)減小；而隨著進(jìn)氣流量及噴嘴內(nèi)徑的增加,氣泡周圍液體速度增加,氣泡影響區(qū)域變寬變長。(3)采用高速攝影對(duì)平行雙氣泡的生長聚并過程進(jìn)行實(shí)驗(yàn)研究并與數(shù)值模擬結(jié)果對(duì)比。結(jié)果表明,雙氣泡的生長及聚并過程可分為四個(gè)階段。重點(diǎn)分析平行雙氣泡聚并前后氣泡縱橫比變化的影響因素。氣泡聚并之前,氣泡縱橫比會(huì)隨著進(jìn)氣流量、噴嘴內(nèi)徑的增加而分別升高和降低。在較低氣量、較大噴嘴內(nèi)徑以及大噴嘴間距的情況下,平行雙氣泡較晚發(fā)生聚并。氣泡聚并之后,隨著進(jìn)氣流量、噴嘴內(nèi)徑的增大及噴嘴間距的減小,氣泡縱橫比增大,且整個(gè)過程中CMC溶液濃度對(duì)聚并過程的影響都較為微弱。
[Abstract]:Bubble motion behavior in non-Newtonian fluids is widely used in petrochemical engineering, environmental protection, energy development and utilization. Due to the special rheological properties of non-Newtonian fluids and the complexity of the interaction between gas-liquid phases, the studies on the formation, rise and aggregation of double bubbles in non-Newtonian fluids are still insufficient. In this paper, the following works have been done: (1) the formation and rising motion of a single bubble in deionized water and CMC aqueous solution with different concentrations have been studied experimentally by using high-speed photography and digital image processing technology, and the formation process of single bubble has been investigated. The changes of equivalent diameter, trajectory and velocity of bubble rising are discussed. It is found that the formation process of single bubble can be divided into three stages. In deionized water and CMC aqueous solution, the average equivalent diameter, swing amplitude and randomness of the bubble are greatly affected by the inner diameter of the nozzle and the concentration of CMC aqueous solution. In the deionized water, the bubbles first rise in a straight line, and when the bubbles begin to oscillate, the bubbles rise in a spiral shape, while in the aqueous solution of the z28mm, the trajectory of the bubbles is almost in a straight line. With the increase of CMC aqueous solution concentration and the decrease of inlet air flow rate, the fluctuation of bubble horizontal velocity and bubble vertical velocity gradually decrease. With the increase of nozzle diameter, the fluctuation of the horizontal velocity of bubbles in CMC aqueous solution becomes larger, and the vertical velocity of bubbles in high concentration CMC aqueous solution increases, but the effect on the vertical velocity of moving bubbles in low viscosity solution is not obvious. In addition, a functional relationship between re and Weimo of bubbles in deionized water and CMC aqueous solution in a certain dimensionless parameter range is established. (2) fluent software is used. Based on the fluid volume method (VOF), the formation and rising motion of a single bubble are numerically simulated, and compared with the experimental results, the characteristics of the liquid field around the bubble are studied. The distribution of pressure field and velocity field of liquid phase during the formation of a single bubble is studied, and the factors affecting the velocity field of liquid phase around a rising bubble in CMC aqueous solution are discussed. With the increase of CMC concentration, the velocity of the liquid around the bubble decreases and the influence zone of the bubble decreases, while the velocity of the liquid around the bubble increases with the increase of the inlet air flow rate and the inner diameter of the nozzle. (3) High-speed photography was used to study the growth and coalescence process of parallel double bubbles, and the results were compared with the numerical simulation results. The results show that the growth and coalescence of double bubbles can be divided into four stages. The influence factors of the aspect ratio of the bubbles before and after the parallel double bubbles are analyzed. Before bubble coalescence, the aspect ratio of bubble increases and decreases with the increase of inlet flow rate and nozzle diameter. Under the conditions of lower gas flow, larger nozzle diameter and larger nozzle spacing, the parallel double bubbles converge later. After bubble coalescence, with the increase of inlet air flow rate, the increase of nozzle inner diameter and the decrease of nozzle spacing, the aspect ratio of bubble increases, and the concentration of CMC solution has a weak effect on the coalescence process in the whole process.
【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2016
【分類號(hào)】：TQ021.1

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