矩形喷动床放大过程中气固流场特性多维度效应的数值研究

发布时间：2018-05-12 12:02

本文选题：喷动床 + 颗粒动理学理论　；参考：《西北大学》2017年硕士论文

【摘要】：喷动床内部极有规律的气固流动特性,使得其在农业、化工等很多领域都有广泛的应用。自上世纪五十年代起,喷动床内部流动机理的研究与探索一直是研究者们关注的热点与核心问题,从实验尺度到工业应用尺度的放大更是困扰工程界和学术界的难点课题。由于喷动床气固流场受控因素的复杂性,以及受实验条件和测量手段的限制,使得探讨和认识其内部流动与放大的本质机理变得异常艰难。随着计算流体力学的出现、数值计算算法的逐步完善以及计算机硬件的不断更新,使得数值模拟逐渐成为了研究喷动床的重要手段之一。本文基于计算流体力学的方法,在欧拉-欧拉双流体框架下结合颗粒动理学理论对不同维度的矩形倒椎体喷动床进行数值研究。模拟中将气-固两相均当做连续相处理,采用相同的质量、动量守恒方程。为了节约计算资源均采用轴(面)对称网格进行模拟。主要研究内容包括以下三部分:第一部分:对Liu[28]等人准二维喷动床实验采用五种曳力模型和四种径向分布函数模型进行模拟,得到了不同工况下颗粒体积分数云图、颗粒轴向速度轴向分布和径向分布。通过与实验值进行对比,探索出描述该体系中气固两相动量交换的最佳曳力模型和描述颗粒径向分布概率的径向分布函数。第二部分:采用第一部分的研究结果作为基础的边界条件,针对厚度为Omm(二维)、15mm(准二维)和100mm(三维)三个维度的矩形喷动床,通过颗粒壁面滑移系数和碰撞恢复系数作为模型参数,探讨颗粒与壁面之间由于摩擦和碰撞而产生的动量交换,探索碰撞和摩擦等微观动力学事件影响宏观流场的规律。通过实验对比获得最优参数值。第三部分:采用第一部分和第二部分得出的最优边界条件,以增加喷动床厚度的方式(厚度:Omm、15mm、30mm、50mm、75mm和100mm)不断的放大矩形喷动床,分别探讨表观气速、颗粒与壁面滑移系数和碰撞恢复系数在放大过程中影响宏观流场的规律。
[Abstract]:Spouted bed has been widely used in many fields such as agriculture and chemical industry due to its regular gas-solid flow characteristics. Since the 1950s, the study and exploration of the flow mechanism in spouted bed has been the focus and core problem of researchers. From the scale of experiment to the scale of industrial application, the enlargement of scale has been a difficult problem in engineering and academic circles. Due to the complexity of controlled factors of gas-solid flow field in spouted bed and the limitation of experimental conditions and measurement methods, it is very difficult to study and understand the essential mechanism of internal flow and amplification of spouted bed. With the emergence of computational fluid dynamics (CFD), the gradual improvement of numerical algorithms and the continuous updating of computer hardware, numerical simulation has gradually become one of the important means to study spouted bed. Based on the computational fluid dynamics (CFD) method, a numerical study on spouted bed of rectangular inverted vertebrae with different dimensions is carried out under the framework of Euler-Euler dual fluid and particle kinetic theory. The gas-solid phase is treated as continuous phase with the same mass and momentum conservation equation. In order to save computing resources, the axisymmetric mesh is used to simulate. The main research contents are as follows: in the first part, five drag models and four radial distribution function models are used to simulate the quasi-two-dimensional spouted bed experiment of Liu [28], and the cloud diagram of particle volume fraction under different working conditions is obtained. Axial and radial distribution of particle velocity. By comparing with the experimental data, the optimal drag model and radial distribution function describing the probability of particle radial distribution in the system are explored. The second part: using the results of the first part as the boundary condition, the rectangular spouted bed with three dimensions of Omm (2-D) 15mm (quasi-2-D) and 100mm (3D) is applied to the spouted bed with the thickness of Omm (2-D) 15mm (quasi-2-D) and 100mm (3D). The slip coefficient and recovery coefficient of particle wall are used as model parameters to study the momentum exchange between particles and wall due to friction and collision, and to explore the law of impact of micro dynamic events such as collision and friction on macroscopic flow field. The optimal parameter values are obtained by experimental comparison. The third part: by using the optimal boundary conditions obtained in the first and second parts, the rectangular spouted bed is continuously enlarged in the way of increasing the thickness of spouted bed (the thickness of the spouted bed is: 1: Omm1 15mm / 30mm / 50mm / 75mm and 100mm), and the apparent gas velocities are discussed respectively. The slip coefficient of particle and wall and the coefficient of collision recovery affect the law of macroscopic flow field in the process of amplification.
【学位授予单位】：西北大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ021.1

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