Computational fluid dynamics for dense gas-solid fluidized beds

Many computational fluid dynamics (CFD) models for describing the hydrodynamics of dense gas-solid flows in fluidized beds have been put forward in the past few decades. These models treat the solid phase as continuum or discrete particles, which leads to Eulerian-Eulerian or Eulerian-Lagrangian formulations, respectively. Different governing equations and closure relations essentially result from an insufficient understanding of the complex gas?particle and particle?particle interactions for gas?solid flows. The current status of these models is discussed briefly in this paper. All the approaches in the literature modify only the solid phase momentum balance equation introducing various forms of the solid phase stress tensor and the solid phase pressure drop in the Eulerian-Eulerian models. Taking them into consideration, a new model for predicting the fluid behavior of dense gas?solid flows in fluidized beds has been developed, which contains new terms in both the particle and gas phase momentum balance equations and requires only the use of an experimental drag force correlation. Several results are shown to verify the model’s reliability, which include the homogeneous fluidization of Geldart type A particles, the bubbling and jetting fluidization of Geldart type B particles in rectangular beds, and fluid dynamics in a complicated geometry for a bubbling?bed of a fast internally circulating fluidized?bed biomass gasifier.     

搅拌设备的CFD分析与软件对比

对搅拌设备CFD分析的特点和分析方法进行了阐述，论述了不同方法适用的场合。此外，通过对一简单案例进行计算，对比了两大CFD软件包STAR—CD和FLUENT应用于搅拌设备的异同。     

改进TM法控制贴体网格节点分布的研究

在分析微分方程法控制网格节点分布方法的基础上，对改进的ＴＭ法控制网格生成进行研究，并以柴油机ＭＰＣ排气管分支为例，用改进的ＴＭ法生成二维贴体网格．应用实例表明，增加角度控制参数后，该方法能对复杂区域生成合理的贴体网格     

CFD在汽车空气动力学研究中的应用

阐述了ＣＦＤ方法在汽车空气动力学研究中的应用现状，分析了各种数值方法目前的局限性。     

喷油器控制阀中流体阻尼间隙

建立了共轨燃油喷射系统喷油器控制阀的力学模型,在计算流体动力学和试验的基础上对控制阀阻尼间隙进行了研究.结果显示:在阀芯与阀体之间的阻尼间隙为0.02~0.03 mm时,最能满足控制阀阀芯关闭时反弹的最小要求.     

质子交换膜燃料电池性能影响因素的数值分析

为研究交指流场质子交换膜燃料电池的输出性能,分析影响其性能的因素,寻找改善其性能的可行措施,探讨了使用交指流场流道的必要性和优越性,建立了包括质子交换膜燃料电池阴极/阳极侧流道、扩散层和催化层以及质子交换膜在内的完整的稳态、三维、两相数学模型.基于计算流体力学方法,用该模型对交指流场质子交换膜燃料电池的全流场进行了统一的数值计算以模拟其输出性能,分析了流场流型、氧化剂种类、反应气体进气速度、质子交换膜厚度和双极板筋宽对质子交换膜燃料电池输出性能的影响,确定了提高质子交换膜燃料电池输出性能的一些方法.将理论模型的模拟计算结果与实验结果进行比较,两者较为吻合.     

微通道热沉的稳健优化设计

将田口稳健设计方法用于硅基微通道热沉的优化设计，建立了微通道热沉的简化性能分析模型，确定了影响其散热性能的关键参数，利用正交试验和信噪比分析实现了参数的稳健优化。利用外部监控程序对CAD和CAE软件的脚本进行动态修改，并且创建专门的进程来执行修改后的脚本，采用共享文件和延时的方法实现主进程、几何建模进程和性能分析进程的同步运行，实现了稳健设计过程的自动化。     

Two typical phenomena from the numerical simulation of fire and smoke transport in a gymnasium fire

Building a large centralized atrium in a building has become favourable both to designers and owners. The space of an atrium in a hall, theatre or gymnasium, can occupy an area as large as thousands of square meters and a height as high as 10―30 meters[1…     

CFD在汽车空气动力学研究中的应用

阐述了CFD方法在汽车空气动力学研究中的应用情况,并对CFD分析所用的数值方法、常用软件和CFD分析的过程做了介绍,论述了CFD与汽车车身造型的相互依存关系.     

建筑间行人高度处的风环境设计

为使用简单的方法对居住区的风环境进行评价,采用CFD软件模拟,运用正交试验的方法选取模拟的工况.根据模拟的结果,推导出建筑尺寸、建筑间距与建筑通道间行人高度处最大风速比的函数关系式,并且进行实例验证.验证表明:该方法简单可行,对建筑师进行风环境设计具有较好的辅助作用.