摘要
搅拌设备广泛应用于石油、化工、医药、食品、能源、造纸、废水处理等过程工业中,但许多反应体系的粘度变化范围从数厘泊到数万厘泊,其属于宽粘度域且大都为非牛顿型流体,因此给反应器搅拌的选择带来了难题。为此本文通过实验和数值模拟方法对三种典型的宽粘度域搅拌桨型MIG-0.7、INTERMIG-0.7、MIG-0.9的功率特性、混合特性以及流场特性进行研究,为其在工业中的选取和设计提供可靠的依据。
首先通过实验方法测出三种宽粘度域桨型在不同浓度羧甲基纤维素钠(CMC)和不同转速下的功率和混合时间。并对其进行功率特性、混合特性分析,从而得出三种桨型的Metzner常数K_s、K_p、功率特性曲线;表征混合特性的C_1、C_4~*无量纲参数;确定三种桨型在不同浓度CMC溶液中最佳混合转速。其次应用FLUENT6.2软件选用多重参考系法、Realizable k-e湍流模型对三种桨型进行不同浓度、不同转速数值模拟,并把模拟结果与实验结果进行对比,得出模拟此类搅拌器的合适数值模型。
通过实验得到三种桨型的Metzner常数K_s,MIG-0.9最大,INTERMIG-0.7次之,MIG-0.7最小;通过C_4~*～R~*曲线确定每种搅拌型式在不同浓度CMC物料内的最佳转速。
通过模拟得出三种桨型的功率、混合时间模拟结果与实验结果较吻合,因此可用模拟代替实验进行以上三种桨型的工业设计。
本文的研究结果对工业宽粘度域搅拌反应器的选择使用与优化设计都具有一定的指导意义。
Agitation equipments are commonly used in industrial mixing applications such as chemical industry, foodstuff, metallurgy, paper making, petroleum and water disposal, etc. But the viscosity of many reaction system rise from centipoises to tens of thousands centipoises, Belong to non-newton fluid of wide viscosity domain, So it is the problems to choose mixing impeller of reactors. Because of these factors, Power,mixed properties and flow characteris- tics of the broad viscosity domain impeller type, MIG - 0.7 INTERMIG -0.7 and MIG - 0.9 are researched by experiment and numerical simulation methods in the paper .And the detailed information of mixing an fluid flow in the stirred tank is studied.
Firstly power and mixing time of three paddle type are measured in the different concentration solution of sodium carboxymethylcellulose(CMC) and different rotatespeed,thereby Metzner constants K_s、K_p and Power characteristic curve , C_1、C_4~* ofcharacterizating mixed properties nondimensional parameters are obtained by analyzing the characteristics of power and mixing,determining optimal mixing speed of three impeller in different concentrations CMC solution.Secondly multi-reference frame(MRF) of FLUENT6.2 simulation software is used to simulate the impellers, and Realizable k-eturbulence model is used in the simulation of three paddle type under three kinds of different concentrations ,rotate speed.The appropriate numerical models of three paddle type are obtained by comparing the simulation results with experimental results.
Metzner constants K_s of three interference multistage counterflow impellers are obtained through experiments: MIG-0.9 maximum, INTERMIG-0.7 times, MIG-0.7 minimum .The best speed is determined by analyzing three interference multistagecounterflow impellers'curve of C_4~*～R~* .
Results of numerical simulation are mostly in line with experimental result. therefore Numerical simulation can be used in place of experiment of three interference multistage counterflow impellers industrial design.
The research results in the Paper Provide guidance for the choice and optimized design to the mechanical mixing operations when a wide change in viscosity occurs throughout the process.
引文
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