射流循环DTB结晶器的水力学模拟与实验

发布时间：2018-01-04 18:24

本文关键词：射流循环DTB结晶器的水力学模拟与实验　出处：《大连理工大学》2016年硕士论文　论文类型：学位论文

更多相关文章： DTB结晶器 射流泵 数值模拟 PIV

【摘要】：射流技术广泛应用于混合和传动过程,用射流实现DTB结晶器内搅拌桨轴向推进功能,可有效降低由搅拌桨和晶体碰撞引起的二次成核,提高产品粒度。本文通过模拟,优化以及实验,研究了DTB结晶器导流筒的结构和流场,为射流循环DTB结晶器设计和优化提供指导。具体的研究内容如下：采用RNG k-ε湍流模型对直导流筒射流DTB结晶器的单相流流场进行了数值模拟,选取最优导流筒筒径,并利用欧拉多相流模型对该结构下的结晶器进行模拟分析。结果表明,导流筒内射流满足线性扩展,轴向速度分布基本满足高斯分布。刚进入导流简内的射流主体段,轴线速度倒数与流程呈良好的线性关系,随射流发展,轴线速度加速衰减。在喷嘴入口直径恒定时,循环速率比(γγ)随导流筒挡板间环隙面积与导流筒横截面积比(β)的增加呈先增大再减小的趋势,存在最优值。直导流筒为最优直径时,射流DTB结晶器中导流筒内颗粒浓度分布沿径向方向减小,其循环速率比较单相流模拟结果略低,但基本可实现颗粒浓度较为均匀的分布,满足DTB结晶器的水力学要求。参照射流泵结构对结晶器导流筒进行优化,利用RNGk-ε湍流模型模拟了不同结晶器内的流场,分析不同导流筒结构下射流DTB结晶器内流体流动；利用组分输运模型对结晶器有效区域进行阶跃示踪法实验,考察其混合特性；利用滑移网格法模拟常规DTB结晶器内的流动性质,并与射流DTB结晶器的流场和能耗进行对比；利用欧拉多相流模型模拟不同导流筒结构的射流DTB结晶器的颗粒浓度场,对比颗粒浓度分布。结果表明,参照射流泵结构优化的导流筒提高了内循环量,本例中较直导流筒最高提升23%,同时对结晶器内的混合有一定的促进作用。同时,相同内循环流量下,射流泵DTB结晶器与常规DTB结晶器相比,单位体积能耗稍小。射流循环可较好的实现DTB结晶器内颗粒悬浮,且相比于其它射流DTB结晶器,结构优化的射流泵DTB结晶器颗粒分布更加均匀,颗粒相的内循环量更高。因此射流泵导流筒的优化,不仅使射流方案满足DTB结晶器溶液充分混合、颗粒均匀悬浮的水力学要求,在能耗上较常规DTB结晶器也有一定优势。利用粒子图像测速法(PIV)考察不同搅拌位置与转速下常规DTB结晶器的流场,以及不同喷嘴直径与外循环流量下射流DTB结晶器的流场,并与数值模拟结果对比。结果表明,RNGk-ε湍流模型可较为准确有效的模拟常规DTB结晶器与射流DTB结晶器内的流场。
[Abstract]:Jet technology is widely used in mixing and transmission process, with the realization of DTB jet crystallizer impeller axial push function, can effectively reduce the two secondary nucleation and crystal caused by impeller collision, improve the product size. Through the simulation, optimization and experimental research, the structure and flow field of DTB crystallizer of the tube. Provide guidance for the design and optimization of jet loop DTB crystal. The specific contents are as follows: single RNG k- turbulence model of straight guide tube jet DTB mold flow field numerical simulation was carried out to select the optimal draft tube diameter, and the Eulerian multiphase flow model of the mould structure is carried out simulation analysis. The results show that the draft tube jet linear expansion, axial velocity distribution satisfies the Gauss distribution. Just enter the main jet section of the diversion in the axis, reciprocal velocity is a linear relationship with the flow With the development of the jet axis, and accelerate the speed of decay. At the nozzle entrance diameter constant, circulation rate ratio () with draft tube baffle between the annular area and diversion tube cross-sectional area ratio (beta) increases firstly increased and then decreased gradually, there is an optimal value. The optimal diameter of the straight flow tube. Is the crystallization of DTB guided jet flow decreases along the radial direction, the particle concentration distribution in the cylinder, the comparison of the simulation results of single-phase flow circulation rate is slightly lower, but can achieve the basic particle concentration distribution is uniform, meet DTB crystallizer hydraulic requirements. According to the draft tube crystallizer to optimize structure of jet pump, numerical simulation of different crystallization is the use of RNGk- turbulence model, DTB analysis of fluid jet flow in the mould of different draft tube structure; the component transport model of the effective area of crystallizer step experimental tracer method, the mixing characteristics by sliding; Simulation of flow properties of conventional DTB mold moving grid method, and the flow and energy consumption and jet DTB crystallizer were compared; the particle concentration distribution by using Eulerian multiphase flow model to simulate the jet DTB mold different draft tube structure, concentration of particle size distribution. The results show that the optimization of draft tube structure of the pump flow and irradiation the increase in circulation, in this case a straight guide tube up 23%, and mixed in the mold to a certain extent. At the same time, the same internal circulation flow, compared with conventional jet pump DTB crystallizer DTB crystallizer, energy consumption per unit volume smaller. Jet loop can realize particle suspension DTB mold good, and compared to other DTB jet mould structure optimization of jet pump is the crystallization of DTB particle distribution is more uniform, the particle internal circulation quantity higher. Therefore the optimization of jet pump draft tube, not only make the jet program Meet the DTB mold solution mixing, hydraulics particles suspended, in energy consumption compared with the conventional DTB mold also has certain advantages. By using particle image velocimetry (PIV) effects of different mixing flow field position and speed of conventional DTB crystallizer, and different nozzle diameter and jet flow straight DTB crystallizer circulating flow the results of numerical simulation and comparison. The results show that the RNGk- turbulence model can accurately simulate the conventional DTB crystallizer and jet DTB crystallizer effectively in the field.

【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TQ051.63

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