氣固鼓泡床反應(yīng)器在能源、化工等領(lǐng)域均有重要應(yīng)用,如烯烴聚合,煤/生物質(zhì)燃燒,礦石焙燒等。氣固流態(tài)化中往往呈現(xiàn)顆粒聚團(tuán)或氣泡等介尺度結(jié)構(gòu),且實際應(yīng)用中顆粒通常具有多分散性（涉及不同顆粒尺寸或密度）,這使得介尺度結(jié)構(gòu)的形成機制更加復(fù)雜。這種多分散性還會導(dǎo)致床內(nèi)出現(xiàn)顆粒分層等現(xiàn)象,在低速的密相床中尤為顯著,影響了相間動量傳遞和反應(yīng)行為。深入理解多分散流態(tài)化中的顆粒分離和混合現(xiàn)象對于合理設(shè)計反應(yīng)器以及確定最佳的操作條件至關(guān)重要。近年來,隨著多相流理論和計算流體力學(xué)（CFD）技術(shù)的迅速發(fā)展,特別是介尺度理論的興起,使得CFD成為研究多相復(fù)雜流動行為的強大工具。在各種模擬方法中,連續(xù)介質(zhì)模型（又稱為歐拉模型）由于其較少的計算量被廣泛用于工程計算。而在模擬氣固流動時,曳力系數(shù)對于準(zhǔn)確捕捉氣固流動中的介尺度結(jié)構(gòu)等典型特征起到關(guān)鍵作用。很多研究者指出,在低速多分散密相床（如鼓泡床）中曳力是影響不同顆粒分離和混合的關(guān)鍵因素。在過去的十幾年中,以能量最小多尺度模型（EMMS）為代表的介尺度模型被成功應(yīng)用于氣固流化床反應(yīng)器的模擬,但是絕大部分的研究都基于均一顆粒的流態(tài)化系統(tǒng)（或稱單分散流態(tài)化系統(tǒng)）。由于單分散... 

【文章來源】：中國科學(xué)院大學(xué)(中國科學(xué)院過程工程研究所)北京市

【文章頁數(shù)】：132 頁

【學(xué)位級別】：博士

【文章目錄】：
摘要
ABSTRACT
CHAPTER 1 INTRODUCTION
    1.1 LITERATURE REVIEW
    1.2 TYPICAL CHALLENGES IN LOW-VELOCITY FLUIDIZATION
        1.2.1 Heterogeneous structures
        1.2.2 Characteristics of bubbles
        1.2.3 Bubble size
        1.2.4 Bubble velocity
        1.2.5 Fluidization of binary particles
    1.3 MODELING APPROACHES
        1.3.1 Direct Numerical Simulation
        1.3.2 Discrete Particle Method
        1.3.3 Multi-fluid model
        1.3.4 Governing equations
        1.3.5 Drag force
    1.4 OBJECTIVES AND OUTLINE
CHAPTER 2 NUMERICAL EXPERIMENT ON GAS-SOLID FLUIDIZATION
    2.1 INTRODUCTION
    2.2 SIMULATIONS OF A PERIODIC DOMAIN
        2.2.1 Simulation settings
        2.2.2 Results and discussions
        2.2.3 Solid velocity distribution in different local position
        2.2.4 Effects of pressure drop on solid velocity distribution
    2.3 EXPERIMENTAL DATA FOR THE SIMULATION OF A BUBBLING FLUIDIZED BED
        2.3.1 Simulation settings
        2.3.2 Results and discussions
    2.4 SUMMARY
CHAPTER 3 PARAMETER ANALYSIS OF EMMS/BUBBLING MODEL FOR MONODISPERSE SYSTEM
    3.1 INTRODUCTION
    3.2 EMMS/BUBBLING MODEL FOR MONODISPERSE SYSTEM
        3.2.1 Multi-scale description
        3.2.2 Hydrodynamic equations
    3.3 EFFECTS OF BUBBLE SIZE
        3.3.1 Different bubble size correlations
        3.3.2 Effects of bubble size correlation on structural parameters
        3.3.3 Effects of bubble size correlation on H_d
    3.4 DISCUSSION ON STRUCTURAL PARAMETERS
        3.4.1 The volume fraction of dense phase and the dense phase voidage
        3.4.2 Gas velocities in dense and dilute phases
        3.4.3 Acceleration term
        3.4.4 Variation of Nst with voidage
    3.5 SUMMARY
CHAPTER 4 EXTENDING THE EMMS/BUBBLING MODEL TO THE BINARY MIXTURE:FORMULATION AND STEADY-STATE VALIDATION
    4.1 INTRODUCTION
    4.2 EMMS/BINARY BUBBLING MODEL
        4.2.1 Multiscale resolution
        4.2.2 Hydrodynamic equations for steady state
        4.2.3 Numerical Method
    4.3 MODEL VALIDATION FOR STEADY STATE
        4.3.1 Validation for monodisperse system
        4.3.2 Validation for binary particle system
    4.4 SUMMARY
CHAPTER 5 EMMS/ BINARY DRAG MODEL AND PARAMETER ANALYSIS
    5.1 INTRODUCTION
    5.2 MODEL DESCRIPTION
        5.2.1 Hydrodynamic equations for unsteady state:
        5.2.2 Structure-dependent drag coefficient
        5.2.3 Solution scheme
    5.3 PARAMETER ANALYSIS
        5.3.1 The model input parameters
        5.3.2 Sensitivity analysis
        5.3.3 Effects of the assumption of particles inside bubbles
        5.3.4 Effects of the assumption for equal accelerations
    5.4 SUMMARY
CHAPTER 6 VALIDATION OF THE EMMS/BINARY DRAG MODEL
    6.1 INTRODUCTION
    6.2 EXPERIMENTAL DESCRIPTION
        6.2.1 The case of size segregation
        6.2.2 The case of combined size and density segregation
    6.3 MATHEMATICAL MODEL
        6.3.1 Conservation equations
        6.3.2 Constitutive relations
        6.3.3 The KTGF-based solid stress
        6.3.4 The gas-solid drag force
        6.3.5 The solid-solid drag force
        6.3.6 The determination of maximum packing Limit
    6.4 SIMULATION SETTINGS
    6.5 RESULTS AND DISCUSSION
        6.5.1 Simulation of Case 1
        6.5.2 Voidage distribution
        6.5.3 Solid concentration for flotsam and jetsam
        6.5.4 Solid velocity
        6.5.5 Axial profile of jetsam
        6.5.6 Simulation of Case 2
        6.5.7 Voidage distribution
        6.5.8 Solid concentration for flotsam and jetsam
        6.5.9 Solid velocity
        6.5.10 Axial profile of jetsam
    6.6 SUMMARY
CHAPTER 7 CONCLUSIONS AND PROSPECTS
LIST OF ABBREVIATIONS
REFERENCES
CURRICULUM VITAE
ACKNOWLEDGEMENT



本文編號：3493101