本文關(guān)鍵詞： 振動(dòng)流化床 流體力學(xué) 歐拉模型 DEM模型 CFD數(shù)值模擬　出處：《青島科技大學(xué)》2015年碩士論文　論文類(lèi)型：學(xué)位論文

【摘要】：振動(dòng)流化床是將機(jī)械振動(dòng)的能量加入到流化床的一種流化床形式,由于振動(dòng)力的加入可以降低床層壓降、起始流化的速度,提高床層的均一性和穩(wěn)定性等優(yōu)點(diǎn),并且振動(dòng)流化設(shè)備是一種具有高效傳質(zhì)傳熱特性的設(shè)備,所以廣泛地應(yīng)用于干燥、噴霧造粒及分選等諸多工業(yè)過(guò)程。隨著CFD的不斷發(fā)展,將理論分析和計(jì)算結(jié)合的數(shù)值方法越來(lái)越展現(xiàn)巨大的發(fā)展?jié)摿?對(duì)于多相流研究起著重要作用。本文采用CFD數(shù)值模擬方法,利用流體力學(xué)模擬軟件Fluent,自行編寫(xiě)振動(dòng)網(wǎng)格UDF程序,對(duì)振動(dòng)流化床內(nèi)局部流體力學(xué)特性進(jìn)行了系統(tǒng)的模擬研究。通過(guò)數(shù)值模擬與實(shí)驗(yàn)測(cè)定結(jié)果的比較分析,為設(shè)計(jì)開(kāi)發(fā)此類(lèi)反應(yīng)器、優(yōu)化過(guò)程操作和提高反應(yīng)效率提供詳細(xì)的數(shù)據(jù)支持和可靠的理論指導(dǎo)。(1)綜述了前人對(duì)振動(dòng)流化床實(shí)驗(yàn)與數(shù)值模擬等多方面的研究進(jìn)展。歐拉方法是最早應(yīng)用到流化床模擬的方法之一,但是歐拉模型不考慮顆粒的尺寸、形狀、碰撞等微觀特點(diǎn),相比而言DEM模型更適合研究振動(dòng)流化床,而且所需經(jīng)驗(yàn)參數(shù)較少。但是由于DEM模型復(fù)雜將消耗大量計(jì)算時(shí)間,以往文獻(xiàn)只是針對(duì)二維振動(dòng)流化床或偽二維振動(dòng)流化床進(jìn)行模擬,顆粒數(shù)量級(jí)較小,并不能準(zhǔn)確反應(yīng)振動(dòng)流化床的顆粒運(yùn)動(dòng)特性。這些問(wèn)題是進(jìn)行本文研究工作的原因。(2)對(duì)二維振動(dòng)流化床進(jìn)行了實(shí)驗(yàn)研究和數(shù)值模擬,實(shí)驗(yàn)研究了振動(dòng)流化床中床層壓降的變化,并采用歐拉模型模擬了振動(dòng)方向、固含率、顆粒速度的影響。實(shí)驗(yàn)研究發(fā)現(xiàn)振動(dòng)力的加入會(huì)增強(qiáng)顆粒的流動(dòng)性,床層壓降更接近于理論值。數(shù)值模擬發(fā)現(xiàn)豎直振動(dòng)作用使床層底部形成低顆粒濃度區(qū)域,振動(dòng)間隙出現(xiàn)并產(chǎn)生大氣泡,而水平作用使床體側(cè)壁出現(xiàn)振動(dòng)間隙；振動(dòng)強(qiáng)度的增大有利于流化效果,振動(dòng)頻率增大到一定程度效果減弱。(3)采用DEM模型的CFD數(shù)值模擬方法,突破以往二維模型、少量顆粒的數(shù)值模擬限制,建立了10萬(wàn)顆粒數(shù)量級(jí)的三維模型。模型能更好的模擬三維振動(dòng)流化床各個(gè)方向顆粒碰撞,更真實(shí)的預(yù)測(cè)流體流動(dòng)特性和顆粒的分布,隨著計(jì)算機(jī)技術(shù)的不斷發(fā)展,10萬(wàn)顆粒數(shù)量級(jí)的三維模型模擬時(shí)間更快了。研究了振動(dòng)對(duì)固含率、顆粒速度、床層空隙率等的影響。
[Abstract]:Vibratory fluidized bed is a kind of fluidized bed in which the energy of mechanical vibration is added to the fluidized bed. Because of the addition of vibration force, the pressure drop of bed can be reduced, the velocity of initial fluidization can be reduced, and the uniformity and stability of bed can be improved. And vibratory fluidization equipment is a kind of equipment with high efficiency mass transfer and heat transfer, so it is widely used in drying, spray granulation and sorting, etc. With the development of CFD, The numerical method which combines theoretical analysis with calculation has more and more great potential for development and plays an important role in the study of multiphase flow. In this paper, the CFD numerical simulation method and fluid dynamics simulation software Fluentare used to write the UDF program of vibrating grid. The characteristics of local fluid dynamics in vibratory fluidized bed were studied systematically. By comparing the results of numerical simulation and experimental measurement, the authors developed this kind of reactor in order to design and develop this kind of reactor. Optimization of process operation and improvement of reaction efficiency provide detailed data support and reliable theoretical guidance. (1) A review of previous researches on vibratory fluidized bed experiments and numerical simulation is presented. Euler method is the first to be applied to flow. One of the methods of chemical bed simulation, However, the Euler model does not take into account the microscopic characteristics of particle size, shape and collision. Compared with the DEM model, it is more suitable for the study of vibratory fluidized beds and requires less empirical parameters. However, because of the complexity of the DEM model, a large amount of computational time will be consumed. In the past, only two-dimensional vibrating fluidized beds or pseudo-two-dimensional vibrating fluidized beds were simulated, and the order of magnitude of particles was relatively small. These problems are the reason for the research work in this paper. The experimental study and numerical simulation of two-dimensional vibrating fluidized bed are carried out, and the variation of bed pressure drop in vibrating fluidized bed is experimentally studied. Euler model was used to simulate the effects of vibration direction, solid holdup and particle velocity. The pressure drop of the bed is closer to the theoretical value. The numerical simulation shows that the vertical vibration results in the formation of low particle concentration region at the bottom of the bed, the vibration gap appears and produces large bubbles, and the horizontal action results in the vibration gap on the side wall of the bed. The increase of vibration intensity is beneficial to the fluidization effect. The vibration frequency increases to a certain extent and weakens. The CFD numerical simulation method based on DEM model is used to break through the limitation of numerical simulation of two dimensional model and a small amount of particles. A three-dimensional model of 100,000 particle order is established. The model can better simulate particle collision in all directions of three-dimensional vibrating fluidized bed, and more truly predict the fluid flow characteristics and particle distribution. With the development of computer technology, the simulation time of 3D model of 100,000 particle order is faster. The effects of vibration on solid holdup, particle velocity and bed voidage are studied.
【學(xué)位授予單位】：青島科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：TQ051.13

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本文編號(hào)：1503393