离心力场中的稠密相气固两相流动与传热研究及其介观分析

Granular media play an important role in the industrial production. The granular media flow and heat transfer mechanics, the fundamental problems of the dense-phase granular media in the granular processing, will be researched by experiments, theory and numerical simulation mainly on wet granules with a rotary drum as an experimental framing in this project. A visualizable set-up for a rotary drum will be built. By analyzing the physical properties of particle will and varying boundary conditions of particle systems, the movement rules and heat transfer phenomena of the granules in the rotary drum will be investigated by temperature and velocity measurement by measuring instruments and methods, such as magnetic resonance imaging (MRI) and three-dimensional electrical capacitance tomography (ECT). The heterogeneous structure of granular media will be characterized in meso-scale by MRI combined with least-energy principle and self-affine fractal theory. Granular media hydrodynamics of a complex wet granular system will be modelled, giving the results of two-phase flow measurement and theoretical analysis full consideration. The meso-scale particle-trajectory model and fractal model for thermal contact conductance in porous media will be used to explore the harmonizing and controlling mechanics of meso-scale flow and heat transfer in granular media. Then granular media flow and heat transfer will be investigated simultaneously by meso-scale Monte Carlo simulation with DEM and CFD coupling. Combining with experimental data, variational data assimilation methodology will be applied by inverse computation to analysis entropy, velocity field and temperature field of granular media, and more accurate transport coefficient of granular media is obtained. Therefore, the meso-scale method to investigate the granular media flow and heat transfer mechanics will be developed.

颗粒物质在工业生产中扮演着重要角色。本课题针对稠密相颗粒物质加工过程基础问题——流动与传热机理，以回转鼓构造实验装置，湿颗粒为研究对象，采取实验、理论及数值模拟进行研究。搭建回转鼓“可视化”实验平台，通过三维核磁共振成像、三维电容层析成像等测试手段，运用能量最小原理和自仿射分形理论，尝试从介观尺度表征颗粒物质的非均匀结构，并通过颗粒物性分析和体系边界改变，探讨颗粒物质的运动规律和热传递现象。通过两相流测试实验与理论分析，研究湿颗粒复杂系统的颗粒物质流体动力学，构建介观颗粒轨道模型和颗粒相分形导热模型，探究颗粒物质介观流动与传热协调控制机理，通过DEM和CFD耦合，进行介观Monte Carlo模拟，并结合实验，经变分数据同化反演计算，分析颗粒物质的熵、速度场和温度场，获取颗粒物质更精确的迁移系数，发展颗粒物质流动与传热机理的介观研究方法。

颗粒物质在工业生产中扮演着重要角色，尤其是在能源领域、制药以及食品行业，为了更好地掌控颗粒物质输运过程的行为和节能效果，从流动、传热机理的基础角度出发，研究颗粒物质热物理加工过程的输运规律。以回转鼓为构造框架，湿颗粒为主要研究对象，搭建了粗旷的板式内构件回转鼓冷态可视化平台和热态平台，结合欧拉法所建的板式回转鼓CFD数值模型，对回转鼓内颗粒流动及传热特性进行了研究。颗粒质量流量、回转鼓倾角、转速是颗粒平均停留时间影响较大的三个参数，构建了一个BP神经网络预测模型；随鼓转速和填充率的增加，颗粒床的升温减慢，而鼓内内置构件有利于强化传热，无论是定壁温还是定热流，回转鼓存在着最佳的物料填充率和转速区间，使得鼓内颗粒体系存在最佳的有效传热系数。基于离散元法（DEM）的软球模型，以球型颗粒为研究对象，采用Physalis方法，研究气相与颗粒间的相互耦合作用，并运用空间分割算法，结合GPU+CPU并行计算平台，基于GPU编程计算进行全尺度颗粒模拟研究。考虑湿颗粒的液桥力，分析液桥的作用规律和演化，并采用DMT弹性接触模型，探讨气固体系内湿颗粒间相互作用力学模型，并结合物理统计方法和分形理论，根据不同的边界和运动状态，进行稠密气固体系非均匀结构颗粒物质流的研究分析，为发展颗粒物质流动与传热机理的介观研究方法和颗粒体系的流变学研究积累基础。