本文選題：氣固系統(tǒng)　切入點：EMMS　出處：《中國科學(xué)院大學(xué)(中國科學(xué)院過程工程研究所)》2017年博士論文　論文類型：學(xué)位論文

【摘要】：氣固兩相流是具有多尺度復(fù)雜結(jié)構(gòu)的非線性非平衡系統(tǒng),往往在介于微尺度單顆粒與宏尺度反應(yīng)器之間呈現(xiàn)諸如團(tuán)聚物或氣泡等介尺度結(jié)構(gòu)特征,從而對系統(tǒng)的反應(yīng)和傳遞性能產(chǎn)生重要影響。為了對這種復(fù)雜系統(tǒng)進(jìn)行描述,人們基于平均假設(shè)建立了各種經(jīng)驗或半經(jīng)驗的關(guān)聯(lián)模型,但在適用性和準(zhǔn)確性方面都有較大的局限性。因此,從理論上實現(xiàn)對介尺度結(jié)構(gòu)的表征以及對流動參數(shù)非均勻分布的預(yù)測成為量化調(diào)控氣固反應(yīng)系統(tǒng)的關(guān)鍵問題。在考慮氣固系統(tǒng)中的多尺度相互作用并建立介尺度穩(wěn)定性條件的基礎(chǔ)上,能量最小多尺度(Energy-Minimization Multi-Scale,EMMS)模型合理預(yù)測了氣固系統(tǒng)中諸如介尺度結(jié)構(gòu)和噎塞等本征流動特征。本論文以氣固兩相流控制機(jī)制相互協(xié)調(diào)所產(chǎn)生的介尺度非均勻結(jié)構(gòu)及其加減速動態(tài)演化特征為切入點,進(jìn)一步解決氣固系統(tǒng)中介尺度結(jié)構(gòu)的定量表征、相間耗散的表達(dá)、以及宏尺度非均勻分布的求解等問題。建立了氣固系統(tǒng)的團(tuán)聚物動態(tài)演化方程,并在邊界條件等約束下實現(xiàn)了氣固EMMS模型的軸徑向二維擴(kuò)展,最終形成了氣固反應(yīng)器的全系統(tǒng)多尺度穩(wěn)態(tài)建模的統(tǒng)一方法和工業(yè)應(yīng)用軟件包。各章主要內(nèi)容安排如下:第一章介紹了氣固兩相系統(tǒng)的研究進(jìn)展,首先對氣固系統(tǒng)的多尺度研究現(xiàn)狀進(jìn)行了綜述,并進(jìn)一步介紹了 EMMS模型及其工業(yè)應(yīng)用。在此基礎(chǔ)上詳細(xì)介紹了氣固系統(tǒng)的經(jīng)驗性全循環(huán)建模方法和虛擬過程工程技術(shù)。第二章分析了顆粒團(tuán)聚物在循環(huán)流化床提升管過渡段的動態(tài)演化機(jī)理,并進(jìn)一步考慮顆粒加速度,建立了軸向EMMS模型,在模型中通過引入顆粒團(tuán)聚物體積平均數(shù)密度的概念和變量分離的方法,實現(xiàn)了對模型的數(shù)值求解。軸向模型在無需借助經(jīng)驗關(guān)聯(lián)式的情況下實現(xiàn)了對循環(huán)流化床提升管軸向非均勻分布的預(yù)測。計算結(jié)果和實驗對比基本一致。第三章根據(jù)固相顆粒在局部稀密兩相之間相互傳遞關(guān)系建立了團(tuán)聚物動態(tài)演化方程,并用此方程替換原團(tuán)聚物尺寸方程,改進(jìn)了 EMMS單元模型。改進(jìn)模型不僅可以應(yīng)用于CFD數(shù)值模擬網(wǎng)格內(nèi)的結(jié)構(gòu)非均勻曳力計算,還避免了原團(tuán)聚物尺寸方程無法直接應(yīng)用到順重力場或低固體通量工況的計算問題。第四章通過考慮壁面效應(yīng)和界面剪切作用對提升管徑向動力學(xué)的影響,完善了徑向EMMS模型。采用團(tuán)聚物動態(tài)演化方程來定量表征局部微元的非均勻結(jié)構(gòu),從而有效的解決了原團(tuán)聚物方程不適用于近壁面處顆粒速度為負(fù)時的計算問題。另外,針對徑向模型方程非線性強(qiáng)、難以直接數(shù)值求解的特點,采用了函數(shù)逼近的方法實現(xiàn)了模型的近似求解。只要給定截面平均空隙率和氣固表觀速度,模型就可對其徑向環(huán)核結(jié)構(gòu)和壁面處顆粒向下運動等典型動力學(xué)特征進(jìn)行預(yù)測。模型的計算結(jié)果和實驗體現(xiàn)了很好的一致性。第五章將EMMS模型和相關(guān)拓展模型應(yīng)用于氣固反應(yīng)器系統(tǒng)的各離散單元,發(fā)展和完善了基于EMMS模型的復(fù)雜氣固系統(tǒng)全循環(huán)穩(wěn)態(tài)建模方法,并以此為基礎(chǔ)初步實現(xiàn)了穩(wěn)態(tài)虛擬過程工程(VPE)的示范。第六章開發(fā)了基于EMMS理論的可視化虛擬流態(tài)化軟件包Virtual Fluidization(?)。利用該軟件可以對大型工業(yè)反應(yīng)器內(nèi)的全局穩(wěn)態(tài)動力學(xué)進(jìn)行準(zhǔn)實時的快速預(yù)測。本研究工作發(fā)展和完善了 "先整體分布、后局部模擬、再細(xì)節(jié)演化"的EMMS多尺度計算模式,打下了以工業(yè)過程的實時模擬為特征的虛擬過程工程的基礎(chǔ),而且還拓展了 EMMS模型直接工業(yè)應(yīng)用新領(lǐng)域,為化工工藝過程的設(shè)計和放大提供了定量參考。
[Abstract]:Gas solid two-phase flow is a complex structure with multi-scale nonlinear non-equilibrium systems often appear as clusters or in between bubble and meso scale structure characteristics between micro scale and macro scale single particle reactor, which has an important effect on the system response and transfer performance. As described in this complex system, based on the people the average hypothesis to establish the correlation model of various empirical or semi empirical, but there are limitations in applicability and accuracy. Therefore, the characterization of meso scale structure and the key problems of non uniform distribution of flow parameters prediction become quantitative regulation of gas-solid reaction system theoretically. Based on the consideration of many the scale of gas solid interactions in the system and the establishment of meso scale stability conditions, energy minimization multi-scale (Energy-Minimization Multi-Scale, EMMS) model to predict reasonably the gas-solid system In the system, such as meso scale structure and choking intrinsic flow characteristics. In this paper, the gas-solid two-phase flow control coordination mechanism produced by the meso scale heterogeneous structure and dynamic evolution characteristics of acceleration and deceleration as the starting point, to further solve the gas-solid system of medium scale structure and quantitative characterization, expression of dissipation, and macro the scale for solving non uniform distribution. Established the evolution equation of agglomerate dynamic gas-solid system, and boundary conditions are realized under the constraints of axial radial gas-solid the extension of EMMS model, and eventually formed a unified method of gas-solid reaction system for multi scale steady state modeling and industrial application software. The main content each chapter is as follows: the first chapter introduces the research progress of gas-solid two-phase flow system, this paper summarizes the status quo of multi-scale of gas-solid system, and further introduces the EMMS model and its industry . based on the detailed empirical technology of gas-solid system full cycle modeling and virtual process engineering. The second chapter analyzes the agglomeration of particles in circulating fluidized bed to enhance the dynamic evolution mechanism of the transition section, and further considering particle acceleration, establishes axial EMMS model by introducing aggregates volume average number density the separation of concepts and variables in the model, the numerical solution of the model. In the axial model without the help of empirical correlation under the condition of the tube axial circulating fluidized bed to enhance the non uniform distribution prediction. The result of calculation and experiment are consistent. The third chapter according to the comparison between the local density of solid particles in two-phase interaction transfer relationship established dynamic agglomeration evolution equation, and this equation is used to replace the original agglomerate size equation, improved EMMS element model. The improved model not only CFD can be applied to numerical simulation of non uniform drag calculation structure within the grid, but also avoids the original agglomerate size equation cannot be applied directly to the calculation of gravity magnetic field or low solid flux conditions. In the fourth chapter, by considering the wall effect and shear effect to improve the effect of radial dynamics, improve the radial EMMS model. The cluster's dynamic evolution equation to characterize local micro inhomogeneous structure, which effectively solves the original cluster equation is not suitable for the near wall particle velocity for calculation of negative. In addition, the radial model equation of nonlinear characteristics of strong, difficult to direct numerical solution, using the method of function approximation the approximate solution of the model. As long as the given section average voidage and gas-solid apparent velocity model can be on the radial ring core structure and wall particles and other typical downward movement The kinetic characteristics were predicted. The model calculation results and experiment shows good agreement. The fifth chapter of the discrete element model of EMMS and the related development model is applied to the gas-solid reactor system, the development and improvement of the EMMS model of complex gas solid system modeling method based on cyclic steady state, and on the basis of preliminary the steady state of virtual process engineering (VPE) demonstration. The sixth chapter developed the visualization software EMMS virtual fluidization theory based on Fluidization package Virtual (?). The software can be used for the large-scale industrial global steady state reactor dynamics of quasi real-time rapid prediction. The development of this research work and improve the overall after the local distribution, simulation, calculation model of multi-scale EMMS and detailed evolution ", laid the foundation of virtual engineering process to real-time simulation of industrial process characteristics, but also expand the EMMS mode The new field of direct industrial application provides a quantitative reference for the design and enlargement of chemical process.

【學(xué)位授予單位】：中國科學(xué)院大學(xué)(中國科學(xué)院過程工程研究所)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：TQ018

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