【摘要】：鼓泡塔反應(yīng)器是一種廣泛應(yīng)用于化工、石油、生物和冶金工業(yè)等領(lǐng)域的多相流反應(yīng)裝置,其優(yōu)點(diǎn)有催化劑耐久性高、傳熱傳質(zhì)優(yōu)良、無(wú)移動(dòng)部件、易于操作和維護(hù)。鼓泡塔雖結(jié)構(gòu)簡(jiǎn)單,但其內(nèi)部的局部流動(dòng)、湍流結(jié)構(gòu)和氣液兩相之間的相互作用非常復(fù)雜。為了進(jìn)一步加深對(duì)鼓泡塔內(nèi)流動(dòng)特性的理解,本文以一種邊壁空氣注入式的鼓泡塔作為研究對(duì)象,運(yùn)用可視化實(shí)驗(yàn)方法,重點(diǎn)分析鼓泡塔內(nèi)的近壁效應(yīng),氣泡形狀、尺寸和液相自由表面高度;同時(shí),嵌入自編程序修正數(shù)值計(jì)算模型,驗(yàn)證鼓泡塔內(nèi)的近壁效應(yīng)和多相流模型的準(zhǔn)確性。本文的主要研究?jī)?nèi)容如下:1)采用多面體網(wǎng)格對(duì)鼓泡塔內(nèi)的單相流動(dòng)進(jìn)行了網(wǎng)格無(wú)關(guān)性檢驗(yàn)。相比于其它網(wǎng)格劃分方法,多面體網(wǎng)格具有更多相鄰的網(wǎng)格和更精確的速度求解梯度。本文運(yùn)用STAR CCM+軟件分別對(duì)水和空氣進(jìn)行了穩(wěn)態(tài)和非穩(wěn)態(tài)模擬。兩種模擬結(jié)果均顯示,為了獲得合理的單相流模擬結(jié)果,所需要的最小的網(wǎng)格數(shù)量為50萬(wàn)。通過(guò)對(duì)比模擬中監(jiān)控的參數(shù)和殘差值發(fā)現(xiàn),正交殘差和均方根殘差都可以作為收斂的判定標(biāo)準(zhǔn)。2)可視化研究邊壁空氣注入式鼓泡塔的內(nèi)流特性。實(shí)驗(yàn)中觀察到注入的氣泡貼合鼓泡塔進(jìn)氣口下游壁面前行,近壁效應(yīng)持續(xù)距離約6cm;通過(guò)高速相機(jī)捕捉到不同尺寸氣泡的形狀和分布情況,同時(shí)記錄下了液相自由表面高度(0.84m)。3)可視化實(shí)驗(yàn)結(jié)果驗(yàn)證多相流模擬的準(zhǔn)確性。本文分別采用了多面體網(wǎng)格,裁剪網(wǎng)格和結(jié)構(gòu)網(wǎng)格進(jìn)行了多相流模擬。模擬結(jié)果顯示,多面體網(wǎng)格可以獲得理想的液相自由表面高度,但是不能夠展現(xiàn)近壁效應(yīng);裁剪網(wǎng)格和結(jié)構(gòu)網(wǎng)格能夠展現(xiàn)近壁效應(yīng),但其近壁效應(yīng)持續(xù)的距離與實(shí)驗(yàn)還有較大差別,同時(shí)模擬中的氣泡形狀與實(shí)驗(yàn)的差別較大。因此,本文在裁剪網(wǎng)格中嵌入自編程序生成自適應(yīng)網(wǎng)格,該網(wǎng)格劃分法可以隨著流動(dòng)的發(fā)展對(duì)氣泡周圍的網(wǎng)格進(jìn)行自動(dòng)加密。對(duì)比分析仿真結(jié)果發(fā)現(xiàn),自適應(yīng)網(wǎng)格能夠準(zhǔn)確地捕捉氣泡形狀和近壁效應(yīng)。但是隨著流動(dòng)的發(fā)展,模擬中的液相因自由表面解的不連續(xù)性所引起的離散誤差(伴生涌流),最終會(huì)從鼓泡塔中溢出,導(dǎo)致模擬無(wú)法展示液相的自由表面。為準(zhǔn)確求解液相自由表面高度,本文在自適應(yīng)網(wǎng)格的基礎(chǔ)上增加了交界面動(dòng)量耗散模型優(yōu)化多相流模擬。模擬結(jié)果顯示液相的自由表面無(wú)溢出現(xiàn)象,其高度為0.833m接近實(shí)驗(yàn)值;但是交界面動(dòng)量耗散模型減弱了氣相與液相之間的動(dòng)量交換,導(dǎo)致近壁效應(yīng)持續(xù)的距離加長(zhǎng),精度低于采用自適應(yīng)網(wǎng)格的模擬結(jié)果。同時(shí),本文也證明了在自適應(yīng)網(wǎng)格和交界面動(dòng)量耗散模型基礎(chǔ)上,運(yùn)用歐拉模型的VOF模型能夠很好的展現(xiàn)氣泡形狀和近壁效應(yīng)。邊壁空氣注入式鼓泡塔的實(shí)驗(yàn)和仿真研究表明,本文嵌入的自適應(yīng)網(wǎng)格加密和交界面動(dòng)量耗散模型能夠準(zhǔn)確地捕捉鼓泡塔內(nèi)的近壁效應(yīng)、氣泡形狀和液體自由表面,可以為后續(xù)的仿真研究和工程應(yīng)用提供參考和新的見(jiàn)解。
[Abstract]:Bubble column reactor is a kind of multiphase flow reactor widely used in chemical, petroleum, biological and metallurgical industries. Its advantages are high catalyst durability, excellent heat and mass transfer, no moving parts, easy operation and maintenance. Bubble column has simple structure, but its internal local flow, turbulent structure and gas-liquid two-phase interaction. In order to further understand the flow characteristics in bubbling tower, a side-wall air injection bubbling tower is used as the research object in this paper. The near-wall effect, bubble shape, size and free surface height of liquid phase in the bubbling tower are analyzed with visual experimental method. The main contents of this paper are as follows: 1) The polyhedral mesh is used to verify the grid independence of the single-phase flow in the bubbling tower. Compared with other mesh generation methods, the polyhedral mesh has more adjacent meshes and more accurate velocity solution ladder. In this paper, steady-state and unsteady-state simulations of water and air are carried out respectively by using STAR CCM+ software. Both simulation results show that the minimum number of grids needed to obtain a reasonable single-phase flow simulation results is 500,000. 2) Visualization of the internal flow characteristics of a side-wall air-injected bubble column. It was observed that the injected bubbles were placed in front of the downstream wall of the inlet of the bubble column and the near-wall effect lasted for about 6 cm. The shape and distribution of bubbles with different sizes were captured by a high-speed camera, and the free surface of the liquid phase was recorded. Height (0.84m). 3) Visualization experiment results verify the accuracy of multiphase flow simulation. Polyhedron mesh, trimmed mesh and structured mesh are used to simulate the multiphase flow. The lattice can show the near-wall effect, but the lasting distance of the near-wall effect is quite different from the experiment. At the same time, the bubble shape in the simulation is quite different from the experiment. Comparing the simulation results, it is found that the self-adaptive mesh can accurately capture the bubble shape and near-wall effect. However, with the development of the flow, the discrete error (associated inrush) caused by the discontinuity of the free surface solution will eventually spill out of the bubble column, resulting in the simulation can not display the free surface of the liquid. In order to accurately calculate the free surface height of liquid phase, an interfacial momentum dissipation model was added to optimize the multiphase flow simulation based on the adaptive mesh. At the same time, it is proved that the VOF model based on the adaptive mesh and the momentum dissipation model at the interface can display the bubble shape and near-wall effect very well. Experiment and Simulation of the air injection bubble column with side wall The results show that the adaptive mesh refinement and the momentum dissipation model of the interface embedded in this paper can accurately capture the near wall effect, bubble shape and liquid free surface in the bubble column, which can provide reference and new insights for the follow-up simulation and engineering application.
【學(xué)位授予單位】：江蘇大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TQ053.5

【參考文獻(xiàn)】

相關(guān)期刊論文 前3條

1 張玉卓;;中國(guó)煤炭液化技術(shù)發(fā)展前景[J];煤炭科學(xué)技術(shù);2006年01期

2 Takashi Ogawa,Norio Inoue,Tutomu Shikada,Yotaro Ohno;Direct Dimethyl Ether Synthesis[J];Journal of Natural Gas Chemistry;2003年04期

3 賈復(fù),柳綺年,陳學(xué)武;上升氣泡群引起的湍流特性[J];中國(guó)科學(xué)(A輯 數(shù)學(xué) 物理學(xué) 天文學(xué) 技術(shù)科學(xué));1991年05期

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本文編號(hào)：2243095