【作者】 张勤；

【导师】 李志信；

【作者基本信息】 清华大学 ， 动力工程及工程热物理， 2011， 博士

【摘要】 作为平板玻璃成形的主要设备，浮法锡槽的温度控制对玻璃质量的提高和生产过程的节能降耗均具有重要意义。通过数值模拟获取锡槽内温度场是进行操作参数预设和在线控制的前提，但现有研究集中于锡槽的局部模型，无法对锡槽整体性能进行分析。同时，针对渗锡这一浮法工艺的固有缺陷，尚无完善、通用的数值模拟技术对渗锡的各种影响因素进行分析。论文针对浮法玻璃成形中的传热和渗锡进行了系统地研究，并实现了全锡槽的数值模拟。应用蒙特卡罗方法计算了加热器与玻璃带之间的辐射传递关系。提出了用综合经济损失来权衡温控质量与能耗之间的经济性联系，获得了加热器最佳功率分布，不仅改善了锡槽温度场，而且减少了电能消耗。采用PLIC运动界面重构技术，模拟了锡槽入口端玻璃液的运动，发现部分玻璃液向锡槽上游运动，形成滞流，唇砖坡度较小时，滞流玻璃液较少。模拟了锡槽内保护气体及锡液的流场与温度场，发现上半空间保护气体发生回流，玻璃带牵引速度越快，回流越明显；加热（冷却）元件附近保护气体的温度升高（降低）较明显；在玻璃带的牵引作用，锡液在底层及无玻璃带覆盖的表面发生了回流；锡液表面的横向温差较大。定义了用来评价锡液表面整体横向温差大小的等效温差，计算表明用直线电机控制锡液速度场和温度场时存在最佳推力及作用方向，使等效温差最小。在对各子模型模拟分析的基础上，建立了全锡槽数学模型和模拟方法，对实体锡槽进行了模拟，模拟结果与实验结果吻合。采用分子动力学方法模拟了锡离子的扩散过程，发现温度对锡离子扩散系数的影响明显，钠离子含量提高时，扩散系数增大，而钙离子比例的提高则使锡离子扩散能力下降。对玻璃样品表面的渗锡特征进行了XRF和XPS分析，获取了渗锡模拟所需的边界条件。建立了二价锡氧化速度的计算模型，结合浮法玻璃的拉制工艺，提出了渗锡过程的同步耦合模拟方法，模拟分析了各种因素对渗锡过程的影响，发现高铁玻璃的渗锡分布存在卫星峰，低铁玻璃由于四价锡积聚效应不明显而无此现象；浮抛时间提高时，卫星峰和渗锡曲线均向深度方向迁移；锡槽入口端宽度提高时，渗锡量上升。最后，依托浮法成形中温度场和渗锡模拟的主要技术、结合其他辅助功能，开发了浮法玻璃成形数值模拟软件。更多还原

【Abstract】 Tin bath is the main equipment for plate glass formation, the temperature controlof float glass tin bath has important significance on both the glass quality and energyconsumption. The detailed temperature field obtaining by numerical simulation is thepremise of the preset and on-line control for the operation parameters. But the existingresearches always focus on the sub-models, the overall performance of the whole tinbath cannot be analyzed. Meanwhile, there is no general complete numerical technologyfor the analysis of various factors on tin penetration which is the inherent defects offloat process. In the present thesis, the heat transfer and tin penetration in the floatprocess are systematically studied, and the simulation of whole tin bath is carried out.The radiative transfer coefficient between the heater and the glass ribbon iscalculated by Monte Carlo method. The overall economic loss which can balance thecontrol quality and energy consumption economically is proposed. The optimizedpower distribution is obtained by numerical simulation, with which the temperaturefield is improved while the electricity input is reduced.The moving surface of glass melt is tracked and reconstructed at the tin bathentrance using PLIC method. It is found that part of the glass melt moves toward theupstream, and stagnant glass melt which affect the uniformity is formed. When theslope of the lip brick is smaller, less glass melt is stagnated. The velocity andtemperature fields of protective gas and molten tin are simulated. Back flow and vortexare found in the top half atmosphere. The back flow is more obvious under largerdragging velocity of glass ribbon. The temperature of gas near the heating (cooling)components is heated (cooled) significantly. Back flow is also observed in the bottomhalf molten tin and near the edge of tin bath which is not covered by the glass ribbon.There exists a large lateral temperature difference at the surface of molten tin. Effectivetemperature difference is defined to evaluate the overall lateral temperature differenceof molten tin. The optimal linear motor’s output and working direction are found tominimize the effective temperature difference. Based on the simulation and analysis ofthe sub-models, the whole tin bath model and its simulation methods are set up. A realtin bath is simulated and the results match with the experimental ones. The stannic ions’ diffusion process is simulated by molecular dynamics. It is foundthat temperature has a great impact on stannic ions’ diffusion coefficient. The diffusioncoefficient increases with the increasing sodium content, while larger calcium rationwill reduce the stannic ion’s diffusion coefficient. The tin penetration characteristics aremeasured by XRF and XPS methods, and they are set as the boundary conditions for tinpenetration simulation. Combining float glass forming process, the coupled tinpenetration simulation method is developed. The influences of different factors on thetin penetration process are analyzed by the coupled simulation method. The resultshows that the satellite peak exists in the high iron glass’ tin penetration profile, whilethere is no such phenomenon in the low iron glass because of unobvious accumulationeffect of stannic ion. When float time increases, both the tin penetration profile and thesatellite peak drift to a greater depth in the glass. The amount of penetrated tin increaseswith increased tin bath entrance width.Finally, the float glass numerical simulation software is developed based on themain numerical technologies for the temperature field and tin penetration simulation.Other auxiliary functions are also supplied in the software.更多还原