本文選題：氣固兩相流 + 曳力模型�。� 參考：《南京航空航天大學(xué)》2016年碩士論文

【摘要】：流化床因具有優(yōu)良的傳熱傳質(zhì)特性而成為石油化工等工業(yè)領(lǐng)域的重要設(shè)備。近幾十年來,人們發(fā)展和應(yīng)用計(jì)算流體動(dòng)力學(xué)(CFD)的方法來解決流化床放大設(shè)計(jì)過程中存在的問題。能否準(zhǔn)確地描述顆粒的受力,尤其是曳力,成為數(shù)值求解方法的關(guān)鍵。本文針對(duì)低顆粒濃度條件下顆粒所受曳力下降的問題,提出改進(jìn)的曳力模型,并耦合歐拉雙流體模型對(duì)鼓泡流化床內(nèi)的流動(dòng)特性進(jìn)行數(shù)值模擬研究。隨后,本文又討論了顆粒尺寸分布對(duì)氣固流動(dòng)的影響。所開展的具體研究?jī)?nèi)容和獲得的相關(guān)數(shù)值結(jié)果如下:首先,構(gòu)建了改進(jìn)的曳力模型。改進(jìn)的曳力模型具有這樣的特點(diǎn):曳力系數(shù)kgs在顆粒濃度?s(0.1,0.38)范圍內(nèi)低于Syamlal-O'Brien模型和Gidaspow模型的曳力系數(shù),這與曳力下降的顆粒濃度區(qū)間吻合。其次,進(jìn)行了鼓泡床內(nèi)氣固流動(dòng)特性的模擬研究。研究結(jié)果表明,與Gidaspow和Syamlal-O'Brien模型相比,改進(jìn)的曳力模型對(duì)床層局部壓降的預(yù)測(cè)結(jié)果更好;隨著表觀氣速的增加,改進(jìn)的曳力模型能夠更加準(zhǔn)確地預(yù)測(cè)床層膨脹;當(dāng)表觀氣速為0.36 m/s時(shí),相比于Gidaspow模型,改進(jìn)的曳力模型對(duì)顆粒時(shí)均軸向速度的預(yù)測(cè)能力得到明顯提升;當(dāng)表觀氣速為0.46 m/s時(shí),改進(jìn)的曳力模型對(duì)徑向顆粒濃度分布的預(yù)測(cè)結(jié)果明顯好于Syamlal-O'Brien模型;在氣泡當(dāng)量直徑方面,模擬結(jié)果與實(shí)驗(yàn)結(jié)果相符;在床內(nèi)顆粒流型方面,相比于Gidaspow模型,改進(jìn)的曳力模型能夠準(zhǔn)確地預(yù)測(cè)床內(nèi)渦的分布。最后,進(jìn)行了群體平衡模型(PBM)和多粒徑模型的研究。結(jié)果顯示,多粒徑假設(shè)過高地估計(jì)了床層膨脹,而PBM粒徑假設(shè)所獲得的床層膨脹略高于單一粒徑假設(shè);PBM粒徑假設(shè)所預(yù)測(cè)的氣泡直徑與Werther計(jì)算模型基本一致;隨著顆粒粒徑范圍的擴(kuò)大,滑移速度的峰值向低顆粒濃度偏移。
[Abstract]:Fluidized bed has become an important equipment in petrochemical industry because of its excellent heat and mass transfer characteristics. In recent decades, the method of computational fluid dynamics (CFD) has been developed and applied to solve the problems in the design of fluidized bed. Whether we can accurately describe the force of particles, especially the drag force, is the key of numerical solution. In this paper, an improved drag model is proposed for the reduction of drag force on particles with low particle concentration, and numerical simulation of flow characteristics in bubbling fluidized bed is carried out by coupling Eulerian two-fluid model. Then, the effect of particle size distribution on gas-solid flow is discussed. The specific research contents and relevant numerical results are as follows: firstly, an improved drag model is constructed. The drag coefficient (kgs) of the improved drag model is lower than that of the Syamlal-O'Brien model and the Gidaspow model in the range of particle concentration (0.1 ~ 0.38), which is consistent with the decreasing particle concentration range. Secondly, the characteristics of gas-solid flow in bubbling bed are simulated. The results show that the improved drag model can predict the local pressure drop of the bed better than the Gidaspow and Syamlal-O'Brien models, and with the increase of the apparent gas velocity, the improved drag model can predict the bed expansion more accurately. When the apparent gas velocity is 0.36 m / s, compared with the Gidaspow model, the improved drag model can significantly improve the prediction ability of the particle mean axial velocity, and when the apparent gas velocity is 0.46 m / s, The improved drag model is better than the Syamlal-O'Brien model in predicting the radial particle concentration distribution, the simulation results are in agreement with the experimental results in the bubble equivalent diameter, and the flow pattern of the particles in the bed is compared with the Gidaspow model. The improved drag model can accurately predict the vortex distribution in the bed. Finally, the population balance model (PBM) and multi-particle size model were studied. The results show that the expansion of the bed is overestimated by the multi-particle size hypothesis, while the bubble diameter predicted by the PBM particle size assumption is slightly higher than that predicted by the single particle size hypothesis, which is basically consistent with the Werther calculation model. With the increase of particle size range, the peak value of slip velocity shifts to low particle concentration.
【學(xué)位授予單位】：南京航空航天大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2016
【分類號(hào)】：TQ051.13

【參考文獻(xiàn)】

相關(guān)期刊論文 前10條

1 Yingce Wang;Zheng Zou;Hongzhong Li;Qingshan Zhu;;A new drag model for TFM simulation of gas-solid bubbling fluidized beds with Geldart-B particles[J];Particuology;2014年04期

2 陳程;祁海鷹;;EMMS曳力模型及其顆粒團(tuán)模型的構(gòu)建和檢驗(yàn)[J];化工學(xué)報(bào);2014年06期

3 朱衛(wèi)兵;李錦時(shí);王猛;孫巧群;;提升管內(nèi)濕顆粒流動(dòng)特性的離散元模擬[J];中國(guó)電機(jī)工程學(xué)報(bào);2013年35期

4 李德波;樊建人;羅坤;岑可法;;氣固兩相流動(dòng)大規(guī)模并行直接數(shù)值模擬算法研究進(jìn)展與展望[J];中國(guó)電機(jī)工程學(xué)報(bào);2013年23期

5 王雪瑤;雷福林;吳學(xué)智;徐祥;陽紹軍;溫雨鑫;肖云漢;;循環(huán)流化床三維全循環(huán)模擬及實(shí)驗(yàn)驗(yàn)證[J];工程熱物理學(xué)報(bào);2013年07期

6 李s，

本文編號(hào)：1777593