【作者】 冯伟；

【导师】 伍悦滨；

【作者基本信息】 哈尔滨工业大学 ， 流体力学， 2007， 硕士

【摘要】 搅拌设备被广泛地应用到许多工业过程中,其中机械搅拌反应器是化工、水处理等行业必不可少的设备,用来实施流体混合、气体分散与固相悬浮以及促进传热、传质,在化工过程及相关的工业中占有很重要的地位。目前,搅拌反应器的选型和设计在很大程度上依赖于实验和经验,对内部流场缺乏深入的认识,而且无法向几何参数、操作条件不同的过程推广。设计不合理的搅拌器既影响了工艺过程的混合效率,同时也增加了能耗。近年来计算流体动力学(CFD)技术在搅拌混合过程的研究中得到广泛应用,这种方法可以方便地对新型结构、不同操作状况等情况进行模拟,可以获得搅拌器内的局部信息,使预测结果可视化,对搅拌反应器的优化设计及放大提供了依据。本文利用Fluent软件对机械搅拌反应器中混合过程的三维流场进行了数值模拟,分析了流场速度和湍流动能分布情况以及挡板对消除流场“打漩”现象的作用,对功率的模拟结果与理论推导结果进行了对比,通过改变搅拌器桨片直径、跨距等结构参数,分析了桨片直径和跨距对搅拌效果的影响。经过模拟分析可知,RNGk -ε湍流模型能够对机械搅拌反应器的流场进行正确的模拟和预测的;对功率的模拟结果与理论推导结果进行了对比,发现有很好的吻合;由于桨叶和挡板的周期性作用,叶轮所产生的流动场也是周期性的;挡板的设置使得流场在搅拌器内两挡板与搅拌轴间形成涡流,增大了被搅拌液体的湍流程度,促进物料微观尺度上的混合,从而改善搅拌效果,但是挡板也在一定程度上增加了能耗;为减少能耗,在满足混合效率的情况下,应尽量减小搅拌桨的直径;跨距对功率和流场内速度及湍流强度的大小几乎不产生影响,它主要影响搅拌器内流场的分布均匀性,选取恰当的跨距可以使主流扩散和涡流扩散的混合效果更佳。研究结果对机械搅拌反应器的设计及应用具有一定的指导依据。更多还原

【Abstract】 Mixing equipments are widely used in many industry processes. The mechanical stirred reactor is necessary and important in chemical industry and water treatment to mix different fluid, disperse different gas, suspend solid phase and promote heat and mass transmission. Nowadays the lectotype of stirred reactor and design of interior component mostly depend on experiments and experience. The farther information about the field is little. The design can not be applied when the structural parameter and operation condition change. The stirred reactors designed unreasonably not only reduce the mixing effect in industry processes, but also waste the valuable energy.These days the computational fluid dynamics (CFD) is applied more and more in the mixing research. It can simulate the flow field of new structural and different operational stirred reactors. The CFD technology is able to not only review the local inner mixing situation in the reactor, but also make the computational result visual, which avoids the heavy and complicated experiment, provides reliable reason for the optimization of the stirred reactors.This paper uses the software FLUENT to simulate the three dimension flow field of mechanical stirred reactor. This paper uses the software FLUENT to simulate the three dimension flow field of mechanical stirred reactor. The distribution of velocity and turbulence intensity in the flow field and the effect of the baffle to the vortex are analysed. The computation results of the power are compared with the one of the theoretical derivation. According to the change of the diameter and the span of the blade, the effect of the diameter and the span of the blade to the mixing effect are analysed. Based on the analysis, it can be get that RNG k -εturbulence model is able to simulate the flow field in the mechanical stirred reactor. The experimental and stimulant results are matching through the contrast. As the periodic action of the blades and baffles the flow field is also periodic. The baffle makes the vertox between the two baffles and the shaft, which enlarges the turbulence intensity of field and promotes the microcosmic mixing effect. But the baffle increases the energy wasting. For saving energy the diameter of blade should be cut short as soon as possible when the mixing effect satisfies the technics. The span of the blades hardly affects the power, the velocity and turbulence intensity of the flow field. But the span mainly affects the distribution of the field, and reasonable span makes the mixing effect better of the diffusion. The research has some guide to the design and operation of the mechanical stirred reactor.更多还原