高黏度流体组合桨混合特性的数值模拟

发布时间：2018-05-17 14:49

本文选题：高黏度流体 + 组合桨　；参考：《北京化工大学》2015年硕士论文

【摘要】：本文利用计算流体力学(CFD)数值模拟方法,在直径为0.476 m的搅拌槽内,以高黏度牛顿流体为研究体系,对直段桨为双螺带式和Paravisc式以及底桨为锚式和变径螺带式的一系列组合桨功率和混合时间进行了研究,并对其中的优选桨型进行了放大规律探索。通过对数值模拟结果的分析发现,双螺带式桨、Paravisc式和锚式桨功率均随桨叶宽度增加而增加,且螺距对于双螺带式桨的功率影响更加显著。根据模拟结果,拟合得到了四类组合桨中组合桨的Kp关联式,这对于高黏度流体组合桨的设计提供了重要参考。对各组合桨混合特性的研究发现,绝对混合时间的确定会因示踪剂监测点位置不同而有所差异,但是各组合桨的混合特性却表现出一致的规律：以锚式桨为底桨的各组合桨的混合时间均小于以变径螺带式桨为底桨的组合桨混合时间,其中Paravisc-锚式组合桨达到完全混合时的绝对混合时间最小,所转圈数最少,较圈数最多的双螺带-3号变径螺带式桨少将近三分之一；此外,该组合桨的单位体积耗能也最低,无量纲剪切量随转速变化斜率最大,各种混合效果评定方法均表明Paravisc-锚式组合桨混合特性优于本文中其他组合桨。最后将体积为100 L的搅拌槽放大至200 L和500 L的搅拌槽,选用Paravisc-锚式组合桨,在模拟物料保持一致的情况下,组合桨功率曲线在不同尺度下完全一致,并于三个尺度的最佳转速下进行模拟发现其符合桨端线速度的放大准则。本文对各桨型的功率特性、混合特性和放大规律的分析,可为工业设计和优化高黏度流体组合桨参数提供重要参考。
[Abstract]:In this paper, the numerical simulation method of computational fluid dynamics (CFD) is used to study the high viscosity Newtonian fluid in a stirred tank with a diameter of 0.476 m. The power and mixing time of a series of combined propellers with straight propeller being double screw belt type and Paravisc type and bottom propeller with anchor type and variable diameter screw belt type are studied. Through the analysis of the numerical simulation results, it is found that both the power of the double screw belt propeller Paravisc and the anchor propeller increase with the blade width, and the pitch has a more significant effect on the power of the double screw belt propeller. According to the simulation results, the KP correlation of four kinds of combined propellers is obtained, which provides an important reference for the design of high viscosity fluid composite propellers. It is found that the determination of absolute mixing time varies with the location of tracer monitoring points. However, the mixing characteristics of the combined propellers show the same regularity: the mixing time of the combined propellers with anchor propellers as the bottom propeller is shorter than that with the variable diameter propeller as the bottom propeller. The absolute mixing time of Paravis c- anchor combined propeller is the smallest and the number of cycles is the least, which is nearly 1/3 less than that of the double screw belt-3 variable diameter propeller with the largest number of cycles. In addition, the combined propeller has the lowest energy consumption per unit volume. The slope of dimensionless shear varies with rotational speed is the largest, and all kinds of mixed effect evaluation methods show that the mixing characteristic of Paravisc- anchor combined propeller is better than that of other combined propellers in this paper. Finally, the volume of 100L agitator is enlarged to 200L and 500L agitator, and Paravisc- anchor type combined propeller is selected. The power curve of the combined propeller is completely consistent at different scales under the condition that the simulated material remains the same. At the optimal speed of three scales, it is found that the model accords with the magnification criterion of linear velocity at the end of the propeller. In this paper, the power characteristics, mixing characteristics and amplifying rules of each propeller type are analyzed, which can provide important reference for industrial design and optimization of the parameters of high viscosity fluid combination propeller.
【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

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