偏心搅拌槽内固液两相流动特性的研究

发布时间：2018-05-28 15:56

本文选题：偏心搅拌 + 偏心率　；参考：《北京化工大学》2015年硕士论文

【摘要】：在搅拌混合过程中,常常需要用到挡板来强化混合效果,但在某些特定的反应槽设计中,考虑到特殊槽体材质、物料等的特殊性,导致在设备内部添加挡板反而对生产不利,偏心搅拌技术能够很好的解决这一问题,此外在一些如表面加料促进粉体快速分散和结晶反应器内减少晶体的二次成核等工艺时,偏心搅拌能达到比中心全挡板更好的效果。本文通过实验以及数值模拟,研究了偏心搅拌时偏心率、转速、桨的安装高度等因素对桨功耗、漩涡特性、混合时间及上浮颗粒均匀下拉转速和临界悬浮转速等的影响,得出如下结论：(1)偏心搅拌功率消耗随偏心率的增大会先增大后减小,在偏心率为e=0.4时功率消耗和功率准数最大,最大功率准数比全挡板时高28%左右；(2)偏心搅拌内会产生漩涡,其中心随着偏心率的增加沿特定路线运动,在偏心率为0.45两侧分别各自沿近似直线运动,且恒定转速时,漩涡深度随偏心率增大按线性规律减小；转速增大时,漩涡深度也随之增大,增幅程度随偏心率增大而减弱；(3)在偏心率介于0～0.45时上浮颗粒均匀下拉转速随偏心率增大而减小,偏心率介于0.45-0.6时随偏心率增大而增大；(4)偏心搅拌桨叶区吸气转速随偏心率增大先降低后增高,在偏心率为0.3左右时达到最低,吸入气体在偏心率小于0.2时主要分散在搅拌桨以上区域而偏心率超过0.2后逐渐分散到搅拌桨下方区域；(5)偏心搅拌混合时间随偏心率的增大呈先减小后增大趋势,偏心率为0.45时为拐点,此时混合时间准数较全挡板时减小20%左右；(6)固液悬浮时临界悬浮转速均比中心全挡板时高,且随偏心率增大会先增大后减小,在偏心率为0.35时临界悬浮转速达到最大,最大约为全挡板条件下的1.4倍。
[Abstract]:In the mixing process, the baffle is often used to strengthen the mixing effect, but in the design of some specific reaction tanks, considering the particularity of the special tank material and material, it is harmful to the production to add the baffle inside the equipment. Eccentricity stirring technology can solve this problem very well. In addition, in some processes such as surface feeding to promote the rapid dispersion of powder and the reduction of secondary nucleation of crystals in the crystallization reactor, eccentric stirring can achieve better results than the central full baffle. In this paper, the effects of eccentricity, rotational speed and installation height on the power consumption, swirl characteristics, mixing time, uniform pull-down speed and critical suspension speed of the propeller during eccentric stirring are studied through experiments and numerical simulation. The conclusion is as follows: (1) the power consumption of eccentric mixing increases first and then decreases with the increase of eccentricity. When the eccentricity ratio is 0.4, the power consumption and power criterion is the largest, and the maximum power criterion is about 28% higher than that of the full baffle. With the increase of eccentricity, the center of the vortex moves along a certain route. When the eccentricity is 0.45, the swirl depth decreases linearly with the increase of eccentricity, and when the eccentricity is 0.45, the vortex depth decreases linearly with the increase of eccentricity. The depth of swirl increases, and the increasing degree decreases with the increase of eccentricity.) when the eccentricity is between 0 and 0.45, the uniform pull-down speed of floating particles decreases with the increase of eccentricity. When the eccentricity ratio is between 0.45-0.6, it increases with the increase of eccentricity.) the suction speed in the eccentrically stirred blade region decreases first and then increases with the increase of eccentricity, and reaches the lowest when the eccentricity ratio is about 0.3. When the eccentricity ratio is less than 0.2, the suction gas is mainly dispersed in the area above the impeller, but the eccentricity ratio is more than 0.2 and gradually dispersed to the area below the impeller.) the mixing time of eccentric mixing decreases first and then increases with the increase of eccentricity. When the eccentricity is 0.45, the number of mixing time datum is 20% less than that of full baffle.) the critical suspension speed of solid liquid suspension is higher than that of center full baffle, and with the increase of eccentricity, the critical suspension speed will first increase and then decrease. When the eccentricity is 0.35, the critical suspension speed reaches the maximum, and the maximum is about 1.4 times of that under the condition of full baffle.
【学位授予单位】：北京化工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ027.2

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