悬浮液粘度对旋流器分选下限影响的数值模拟与理论研究

发布时间：2018-03-29 14:22

本文选题：旋流器　切入点：分选下限　出处：《煤炭科学研究总院》2017年硕士论文

【摘要】：本文旨在从重介质旋流器内部颗粒受力运动的角度探索悬浮液粘度与旋流器分选下限之间的关系问题。在前人对旋流器内部速度场研究的基础上,用数值模拟的流体力学方法,得到流场数据;并结合回归分析的数学方法对数据进行拟合处理,得到结构参数确定的旋流器内部流场的具体数学公式。在前人对固液两相流研究的基础上,认为虽然固相颗粒受力众多,但是在旋流器中真正需要考虑的只有5个力:离心力、浮力、流体阻力、虚拟质量力、Basset力。结合拟合得到的速度场公式和受力分析,提出了旋流器内部颗粒运动的理论:颗粒在入料口处存在"初始命运"的差异;旋流器分选的主要任务是让"初始命运"在外旋流中的煤颗粒在离开底流口之前穿越LZVV,让"初始命运"在内旋流的矸石颗粒在进入溢流管之前穿越LZVV;分选下限颗粒,以煤颗粒为例,最终将经过LZVV与底流口的交界线,且各有50%的机会进入内、外旋流。在不同粘度下得到的Fluent数值模拟结果中分别进行同密度差不同粒度的颗粒追踪,得到不同粘度下的分选下限。从而得到粘度与分选下限的关系。这个关系与忽略虚拟质量力的情况下半定量分析的结果相同:悬浮液的动力粘度增大n倍,旋流器的分选下限增大√n倍。运用流场拟合的结果与颗粒在旋流器中的运动理论来直接计算分选下限,发现在忽略虚拟质量力的情况下,计算得出的分选下限与Fluent数值模拟得出的分选下限相差近3倍;在不忽略虚拟质量力的情况下,由于方程过于复杂,没能得出解,原因在于拟合得到的轴向速度和径向速度的数量表达式过于复杂。
[Abstract]:The purpose of this paper is to explore the relationship between suspension viscosity and the lower separation limit of hydrocyclone from the point of view of the force motion of particles in the heavy medium cyclone. Based on the previous researches on the internal velocity field of the hydrocyclone, the hydrodynamic method of numerical simulation is used. The flow field data are obtained, and the data are fitted with regression analysis, and the specific mathematical formula of flow field in hydrocyclone determined by structural parameters is obtained. On the basis of previous researches on solid-liquid two-phase flow, It is considered that although the solid particles have a large number of forces, only five forces should be considered in the hydrocyclone: centrifugal force, buoyancy force, fluid resistance, virtual mass force and Basset force, combined with the fitted velocity field formula and force analysis. The theory of particle movement in the hydrocyclone is put forward: the difference of "initial fate" between the particles at the inlet; The main task of cyclone separation is to allow coal particles in the "initial fate" outer swirl to pass through LZVV before leaving the bottom flow port, and to allow the gangue particles in the "initial fate" inner swirl to pass through the LZVV before entering the overflow pipe. Taking coal particles as an example, the particles will eventually pass through the junction of LZVV and the bottom flow, and each of them will have 50% chance to enter the inner and outer swirls. The numerical simulation results of Fluent obtained under different viscosity will be followed by the particles with the same density difference and different particle size, respectively. The relationship between the viscosity and the separation limit is obtained. This relationship is the same as that of the semi-quantitative analysis under the condition of ignoring the virtual mass force: the dynamic viscosity of the suspension increases by n times, The separation lower limit of hydrocyclone is increased by n times. The separation lower limit is directly calculated by using the flow field fitting result and the motion theory of particles in the cyclone. It is found that the virtual mass force is ignored. The difference between the calculated separation limit and that obtained by Fluent numerical simulation is nearly three times. Without neglecting the virtual mass force, the equation is too complicated to be solved. The reason is that the quantitative expressions of axial velocity and radial velocity are too complicated.
【学位授予单位】：煤炭科学研究总院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD94

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