单纯烟囱效应作用下竖井结构内火灾烟气运动规律研究

采用现场实验、理论分析及场模拟相结合的研究方法,通过设置六种不同场景,分别测试了不同时间不同竖井高度处的温度及压差变化过程,最终定量总结了单纯烟囱效应作用下竖井结构内的烟气运动规律,为高层建筑实际防火设计及人员疏散提供理论基础和实践指导依据。     

非封闭式天井形状对烟气蔓延影响的模拟

住宅建筑中非封闭式天井常被用于改善中间户型的通风和采光,构造上一般为外立面凹槽内设置敞开外廊的形式.本文采用火灾动力学模拟软件FDS对给定天井面积和高度情况下,非封闭式天井的形状对烟气蔓延特征以及外廊安全性的影响进行数值模拟和分析.研究表明非封闭式天井烟气上升过程中,会通过外廊上部镂空区域与外界进行热量和质量交换,但天...     

CFD技术在汽轮机定子线圈冷却水流量测量中的应用

利用超声波流量计检测大型汽轮发电机定子线圈冷却水流量大小,可直接判断冷却水的堵、漏,从根本上解决定子绕组冷却水堵塞问题,但超声波流量计用于弯管段测量时存在误差。本文利用CFD技术计算了某火电厂定子线圈内冷却水的流速分布,分析了管内流动对超声波测流的影响,获得了不同测点处流量误差的变化趋势。采用CFD技术可确定超声波流量计的最佳安装位置,为获得准确的流量提供理论依据。     

Recent progress in multiphase flow simulation through multiphase pumps

The multiphase flow pumps cover a wide range of industrial sectors extending across petrochemical, metallurgy, and dredging, chemical industry, paint, and construction. The major application is the handling of wet gas and vapor that will condense partially during the compression stage. The main progress in the area of multiphase pumps has been the innovation of a computational fluid dynamics (CFD) numerical approach to simulate three‐dimensional flows inside the pump and to predict pump performance. CFD undoubtedly constitutes one of the most promising approaches for the design, analysis, and performance assessment of complex machines. However, practical application of the CFD tool to determine the internal flow field in multiphase pumps is still far from reality owing to the limitations of a detailed three‐dimensional model of the pump and accuracy of multiphase flow simulation. This review accentuates the influence of different geometrical and dynamical parameters on the performance of the pump and the use of CFD simulation to predict the detailed flow patterns of fluid mixtures. CFD analysis has unearthed the fact that the pattern of inner flow varies with the flow rate and concentration of each phase and the rotation speed of the impeller and number of blades were also found to considerably impact pump performance.     

A finite volume method on distorted quadrilateral meshes for discretization of the energy equation's conduction term

A finite volume method (FVM) on distorted meshes for discretizing the energy equation's conduction term is presented. In this method, it is possible to compose the computational mesh of general quadrilateral elements (cells), namely, the cells are not required to be rectangular. The gradient of temperature on the cell's surface is computed to be second‐order accurate. Therefore, the error of numerical results by this method is smaller than using the traditional multilateral element method (MEM). The error does not depend on the degree of mesh distortion. The formulation based only on Taylor's theorem is straightforward. These are advantageous features to revise the fluid flow computation programs (based on FVM) that neglected the heat conduction term of the energy equation. The test calculations show that the convergence tendency of the numerical error using this method with the distorted mesh is the same as using an ordinary 2‐node central difference scheme on a constant‐interval rectangular mesh. By this method a conduction term was added to the energy equation of a SALE [ 1 ] program which had neglected that term originally, and z numerical calculation of a fluid flow with a heat transfer problem was performed. The numerical result of the present method with the distorted mesh well agrees with the analytical solution and the result of REM with a rectangular mesh. © 2011 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.20375     

Numerical optimization for fluid flow in turboexpander wheel of helium liquefaction plant

A radial turbine is one of the vital components of a helium liquefaction plant. The design of a turbine becomes critical due to its compact size and high-speed configuration. In this study, numerical optimization has been performed for the three-dimensional steady flow of helium gas in the radial inflow turbine of a helium liquefaction plant at a nominal condition. The mean line design is an appropriate method to obtain the approximate results. The computational fluid dynamics simulation algorithm is adopted in this study to reach the final results and Ansys CFX is used for the simulation. From the analysis, it has been reported that the number of rotor blades was overestimated in the mean line design. Performance parameters like total-to-static efficiency and velocity ratio were also found to be optimum numerically under a preliminary design condition. Finally, power of 1.7 kW was achieved at total-to-static efficiency of 71.4%. The deviation in analytical and numerical results is within $\pm 10\%$ for performance as well as geometric parameters.     

液体火箭发动机燃烧稳定性CFD分析

应用CFD方法对液体火箭发动机中的高频燃烧不稳定性进行了分析研究,建立了液体火箭发动机不稳定燃烧数值模拟的综合模型和控制方程,比较了PISO和MacCormack两种算法,得出了两种算法均能成功应用于不稳定燃烧分析的结论。阐述了ACLRECI系列程序。应用该程序对YF－860液氢液氧发动机和NAL液氧／甲烷发动机的稳定性进行了数值模拟,得出了该发动机的燃烧稳定性极限图。数值计算结果与试车数据一致。     

线-板型静电除尘器电场的三维数值算法

由于静电除尘器电场的控制方程与流体力学具有相同的数学形式,所以将计算流体力学中的上风格式应用于正电晕条件下电流守恒方程,将相应的下风格式应用于负电晕情况。同时采用迭代的方式给出电晕线处电荷密度。数值结果表明,数值解与现有的实验结果吻合较好,证明了本方法的正确性。     

大型水轮机蜗壳的CFD分析

蜗壳是水电机组中的一个重要过流部件，为了评价蜗壳与座环中三维粘性流体的流动特性，进行流体一体化数值解析是非常必要的。利用数值解析技术对大型水轮机蜗壳进行了数值解析分析，给出了蜗壳在各个计算工况点的水力损失，并计算了蜗壳的流量系数。     

220t／h CFB锅炉旋风分离器性能的数值模拟研究

旋风分离器是循环流化床（简称CFB）锅炉的关键部件之一,基于数值模拟计算,研究了220t／h节能环保型CFB锅炉旋风分离器结构对气固流动的影响,提出了改进和完善分离器效率的方法,对于CFB锅炉高效旋风分离器的研制具有重要参考意义。     

高压比跨音速离心叶轮的三维叶片型线优化

应用Fine／Design3D软件,采用CFD方法对某一高压比跨音速离心叶轮进行三维叶片型线优化设计,优化结果是效率提高了1．05％,压比和流量也都得到了提高。从几何变化分析,相对于根部、中径截面叶片型线,叶片顶部型线优化是提高跨音速离心叶轮效率的有效措施。