Influence of Aiding Buoyancy on the Suppression of Flow Separation for Power-Law Fluids Around a Circular Object

Numerical computations are performed to analyze the influence of aiding thermal buoyancy on the phenomenon of suppression of flow separation in power-law fluids around a circular object. The idea has been borrowed from some recent similar works in Newtonian fluids. Owing to the contradictory behavior of shear-thinning and shear-thickening fluids in regard to the separation mechanism, we intend to understand the role of superimposed thermal buoyancy on the suppression phenomena in non-Newtonian power-law fluids, for which a range of power-law indices (0.4 to 1.8) is considered. The Reynolds numbers are kept intentionally low, within 10 to 40, such that the isothermal flow remains steady and separated without imposition of thermal buoyancy. The buoyancy causes a delay in the separation, thereby affecting the suppression phenomena. We determine the critical heating parameter (Richardson number) for the complete suppression of the flow separation and from there we construct a bifurcation diagram to show the typical flow regime evolved due to the complex interplay between the aiding thermal buoyancy and fluid rheology. The Richardson number in the simulation lies in the range 0 to 0.35, keeping the Prandtl number fixed at 50. The heat transfer rates from the object are also obtained and important inferences are drawn in regard to the inhibition/augmentation of heat transfer due to fluid rheology.     

一次筒节整体脆断的原因分析

介绍一次锅炉汽包筒节卷制整体脆断的现象,通过金相实验分析找出原因,改进工艺方案杜绝汽包筒节脆断的现象.     

离心铸造铁素体基球墨铸铁燃烧环的研制

阐述了铁素体基体球墨铸铁燃烧环的生产工艺,通过对原材料的选择和化学成分的控制．可以离心铸造生产铁素体基球墨铸铁。结果表明,选择合适的球化剂加入量,合理的冷却工艺参数,优化孕育方法,简便有效的退火方式,其球化性能、基体组织、力学性能都能达到或超过了国家标准。     

O_2/CO_2气氛下电站锅炉汽水系统仿真模型研究

基于O2/CO2气氛下烟气侧换热特点,建立了电站锅炉汽水系统整体动态数学模型。以某300 MW O2/CO2煤粉燃烧锅炉为仿真对象进行仿真试验,仿真结果表明,燃料量、O2/CO2容积比的增加可导致燃烧速率和燃烧温度迅速升高,进一步引起工质参数不同程度的变化。     

变频器谐波分析与抑制对策

变频设备中的变频器产生大量6k±1次谐波,此特征谐波使电网电流波形严重畸变,THD超过国标（GB/T14549-93）限值。对此本文提出有效的谐波抑制方案,并给出了单调谐滤波器的详细设计过程,同时通过仿真分析验证了谐波抑制效果的明显性。     

三种基流分割方法在黄河源区应用中的对比分析

基于黄河源区唐乃亥水文站1961~2004年的实测逐日径流量资料,分析基流年内分配规律,分别选取典型年径流量过程单峰型(2003年)、双峰型(1963年)、多峰型(1967年)进行标准化处理,运用数字滤波法、加里宁试算法和改进的经验斜割法计算基流过程和基流指数(BFI),并对比分析了气候、冰川(积融雪)和冻土过程对各种方法分割结果的影响。结果表明,黄河源区径流年内分配规律受自然条件的影响不同于其他流域;基流计算中数字滤波法计算结果稳定,加里宁试算法更贴合实测径流过程,经验斜割法在枯水年份基流分割中更为简便,应根据不同的年内径流过程及基流计算目的选择合适的基流分割方法。     

浅析离心铸造镶圈分层问题

镶圈加工后出现明显痕迹而报废,致使有两三批次的镶圈的废品率达到了30%,造成了很大的浪费.通过分析,断定该废品形式是分层而不是裂纹,初步确定是铸造的问题.又进一步分析,找出了产生该问题的根本原因,是随流孕育的时机掌握不好,孕育剂没充分熔化好就随液流进入了模具型腔所致,从而找出了正确的随流孕育的时机.降低了缸套及镶圈铸造废品损失,为其他同行厂在降低铸造废品方面具有借鉴意义.     

Performance of a Circular Fin in a Cylindrical Porous Enclosure

The problem of natural convection heat transfer from a vertical cylindrical fin to a saturated porous medium in a cylindrical enclosure is solved numerically. A conjugate conduction-convection analysis is accomplished by solving the equation of heat conduction in the fin together with the mass, momentum and energy balance equations in the porous medium. Numerical results are obtained by using ADI method. The effects of the conduction-convection ratio parameter, aspect ratio and Darcy number on local heat transfer coefficients and fin efficiency are discussed. Comparison of the local heat transfer coefficients and fin efficiency is shown with those for non-porous medium.     

简体非径向大开孔的有限元分析

本文采用有限元分析技术,对开孔大小超过GB150限制范围的非径向大开孔进行了数值模拟计算,有限元模型采用参数化建模,对参数化建模的优点进行了介绍。结合应力分布云图对结构危险位置进行了应力线性化处理并根据应力分类图对危险路径进行了应力评定。最后,就改善结构受力给出了建议和措施。     

Numerical Analysis of Natural Convection in a Cylindrical Envelope with an Internal Concentric Cylinder with Slots

Detailed numerical analysis is presented for natural convection heat transfer in a cylindrical envelope with an internal concentric cylinder with slots. Governing equations are discretized using the finite volume method, and solved using SIMPLE algorithm with QUICK scheme. The results show that the system can reach steady state and be symmetric when the Rayleigh number is below 4 × 10⁵. When the Rayleigh number is greater than 6 × 10⁵, an asymmetric periodical solution is obtained although the initial field and boundary conditions were symmetric. As the Rayleigh numbers increase further, a quasi-periodic solution of the system is achieved at Ra = 2 × 10⁶, and the periodicity is lost at Ra = 6 × 10⁶. It is ascertained that the oscillatory flow undergoes several bifurcations and ultimately evolves to a chaotic flow.     

钢锭冷凝过程仿真及试验研究

提出了直接对凝固潜热进行差分计算的一套计算方法，在此基础上开发了三维非稳态凝固传热的计算程序。应用该程序计算了包钢Ｂ９６钢锭模内２０钢钢锭冷却的温度分布和凝固率随时间的变化规律。根据理论计算的预报情况，进行现场工业试验。理论和现场两者相结合确定了最佳的镇静时间和开脱时间。     

Comparison of the Discrete-Ordinates Method and the Finite-Volume Method for Steady-State and Ultrafast Radiative Transfer Analysis in Cylindrical Coordinates

The time-dependent equation of radiative transfer is solved for an axisymmetric cylindrical medium using both the discrete-ordinates method and the finite-volume method. Steady and transient flux profiles are determined for absorbing and scattering media. Results for each solution method are compared and shown for various grid numbers, scattering albedos, and optical thicknesses. A comparison of computational time and memory usage between the methods is presented. It is found that the finite-volume method uses more memory and has a longer convergence time than the discrete-ordinates method for all cases, due to the difference in angular treatment.     

现浇钢筋混凝土楼板裂缝的分析和防治措施

对楼板裂缝的产生原因进行了分析并提出防治措施。     

铸造缺陷修补机在发动机铸件缺陷焊补方面的应用及分析

通过铸造缺陷修补机在灰铁250、球铁500及铝合金101三种材质试块上焊补效果的显微分析，以及对HT250发动机缸体、删气缸套、ZL101发动机缸体缺陷渗漏的焊补效果检测，说明铸造缺陷修补机在灰铁、球铁、铝合金三种材质上的焊补效果满足性能要求，是一种值得推广的新技术。     

Dynamic Thermal Postbuckling Analysis of Piezoelectric Functionally Graded Cylindrical Shells

Dynamic thermal postbuckling behavior of functionally graded cylindrical shells with surface-bonded piezoelectric actuators subjected to the combined action of thermal load and applied actuator voltage is analyzed using an incremental numerical technique. The shell is graded across the thickness according to a power law form function. The material properties of the functionally graded cylindrical shells are considered to be temperature dependent. The theoretical formulations are based on the classical shell theory with Sanders' nonlinear kinematic relations. Then, using Hamilton's principle, equations of motion are derived for the piezoelectric FGM cylindrical shell. A finite difference based method combined with the Runge–Kutta method is employed to predict the postbuckling equilibrium paths, and the dynamic buckling temperature difference is detected according to Budiansky's stability criterion. Numerical results are presented to demonstrate the effects of the applied actuator voltage, shell geometry, volume fraction exponent of FGM, and the temperature dependency of the material properties on the postbuckling behavior of the shell. The results for simpler states are validated with the known data in the literature.     

Dynamic Thermal Postbuckling Analysis of Shear Deformable Piezoelectric-FGM Cylindrical Shells

Dynamic thermal postbuckling behavior of functionally graded cylindrical shells with surface-bonded piezoelectric actuators subjected to the combined action of thermal load and applied actuator voltage is studied. The shell material is graded across the thickness according to a power law. The material properties of the functionally graded cylindrical shells are considered to be temperature dependent. The theoretical formulations are based on the Sanders nonlinear kinematic relations, which account for the transverse shear strains, and the third-order shear deformation shell theory is employed. Hamilton's principle is used to derive the equations of motion governing piezoelectric FGM cylindrical shells. A finite difference approximation combined with the Runge-Kutta method is employed to predict the postbuckling equilibrium paths, and the dynamic buckling temperature difference is detected according to Budiansky's stability criterion. Numerical results are presented to demonstrate the effects of the applied actuator voltage, shell geometry, volume fraction exponent in the power-law variation of the FGM, and the temperature dependency of the material properties on the postbuckling behavior of the shell. The results for simpler states are validated with the known results in the literature.     

Simultaneous Reconstruction of Thermal Field and Retrieval of Parameters in a Cylindrical Enclosure

This article deals with the reconstruction of temperature/heat flux profile and retrieval of parameters in a transient conduction and radiation heat transfer problem in a concentric cylindrical enclosure. Reconstruction and retrievals are achieved through the genetic algorithm (GA). In the conduction problem, the lattice Boltzmann method coupled with the GA is used for the reconstruction and retrievals; whereas in the radiation problem, the same are achieved through the discrete transfer method and the GA. The accuracies of the estimated parameters are studied for the effects of measurement errors, genetic variables such as the best fitness, the population size, and the number of generations. Reconstructed temperature and heat flux profiles and the estimated parameters are in good agreement with the exact ones.     

基于Moldflow的进气岐管硅胶模真空注型分析

应用Moldflow软件对硅胶模真空注型过程进行了流动填充分析和翘曲变形分析,拓展了MPI的应用范围。通过应用Hypermesh和其它相关软件,对前期导入的数据格式进行有效处理,获得了满足Moldflow分析要求的高质量网格。通过汽车发动机进气岐管的实例,验证了此方法的可行性。     

山西建设国家新型能源和工业基地的思考

本文分析了山西在建设国家新型能源和工业基地中面临的主要问题,提出了发展循环经济、建设国家新型能源和工业基地的思考及建议。     

石羊河流域基流分割及特征分析

针对基流分割是水文预报中产汇流模型模拟、流域水文分析计算、区域水资源评价中经常遇到的问题,以石羊河流域为例,采用数字滤波法对流域的8条主要河流进行了基流分割和模型计算,分析了计算结果与流域水文特征值,探求了各指数指标的响应机制.结果表明,基流值与降水、地形等因素密切相关,该模型计算为流域水资源保护和合理分配提供了依据.