低雷诺数气液交叉流装置研究（I）——孔流液柱流动特性数值模拟

针对低雷诺数的气液交叉流气体净化过程,提出有效避免二次雾沫夹带的液柱流体力学条件。数值模拟结果表明,液柱表面随着离开孔口的距离而变化,采用公式Lb／d=2．84We^0.694能有效预测液柱的断裂行为。     

一种汽轮机组排汽焓和最优初压在线计算方法

通过对已往的汽轮机变工况计算方法的分析,提出了以汽轮机末级抽汽或次末级抽汽(过热蒸汽状态)为计算起点的汽轮机顺序变工况核算方法。根据初始假定的末级流量和现场实际的末级前热力状态和背压,用汽轮机变工况流型判别准则,判别级的流型,然后从末级前参数开始顺序进行一次级的变工况核算,得到新的排汽焓,最后算得机组热耗率和排汽焓。以此方法为变工况计算的基础,并利用系统分析方法,建立了在线确定单元机组最优运行初压的数学模型。为火电机组的优化运行提出了一种新思路。     

基于有限体积法的G4-73型离心风机三维流场数值模拟

基于有限体积法,利用Fluent软件对G4-73型离心风机内部流场进行了全三维数值模拟。结果表明:蜗壳内的低能流体区沿轴向朝流动方向推进;叶轮内的静压和动压在叶片吸力面靠近叶轮进口处最低,叶轮流道中动压等值线呈"凸"型分布,在叶片压力面靠近叶轮出口处静压和动压达到最大值,且叶轮出口相对总压损失集中在吸力面和前盘侧。     

电力系统继电保护整定计算软件探析

介绍电力系统继电保护整定计算软件的相关问题,着重探讨了对该软件的改进措施.     

基于表面反应和扩散迁移控制的灰岩单裂隙渗流—溶解模型及其数值模拟

针对碳酸盐类可溶岩地区水电站坝址流场、化学场以及固相介质属性等随时间发生改变,从而对工程安全运行造成不利影响等问题,研究了灰岩地区地下水运移过程中各物理场间的相互作用,分析了影响灰岩溶解速率的两个因素,即表面反应控制和扩散迁移控制。在此基础上,建立了单裂隙中的渗流—溶解耦合模型,并进行数值求解。模拟结果表明,在垂直裂隙延伸方向,其溶蚀锋面为非齐整平面,而是呈似“虫洞”状非均一变化,而沿裂隙延伸方向即自上游侧向下游方向溶蚀程度逐渐减轻;而通过裂隙的流量呈现随时间逐渐增大的趋势,但变幅不大;根据流量求得的等效水力隙宽,其增幅和增长速率均小于实际平均隙宽;同时,化学场中Ca2+浓度的分布与裂隙开度变化具有相似性,不同时刻下上游侧反应速率R均大于下游侧。就反应机制而言,在初期均受表面反应控制,而随反应进行,位于上游补给区部位转为受扩散迁移控制,但在下游位置仍受表面反应控制。     

Numerical Simulation of Internal Oxidation of Steels during Annealing Treatments

This paper presents a new model for simultaneous diffusion and precipitation of chemical elements in metallic matrices, a scheme for its numerical solution, and several applications to problems of internal oxidation. The model basically stands as an extension of the classical Wagner model for internal oxidation of steels, but is more much general in that it allows for an arbitrary number of diffusing chemical elements, an arbitrary number of precipitate phases with arbitrary compositions, dependence of diffusion coefficients and solubility products upon (time-dependent) temperature, etc., thus allowing for a much broader range of applications. As a counterpart, it is generally impossible to solve the complex, non-linear equations of the model analytically, but this can be done numerically. The simple but efficient numerical scheme proposed is based on explicit 1D finite differences. Experience has shown that this scheme, in spite of its rusticity and the restrictions it imposes on the time-step, is more efficient than more elaborate strategies based on the finite-element method. The applications presented are concerned with internal oxidation of steels during annealing processes. The model and associated numerical scheme allow for evaluation of the amounts of the various oxide precipitates in the external layer of the sheet. This opens the way, through numerical parametric studies of the influence of the process parameters and the chemical composition, to the improvement of existing treatments and the development of new steel grades.     

高炉铜冷却壁凝固过程数值模拟

在对铜冷却壁砂型 金属型复合铸造条件下的热态工况进行分析的基础上,利用有限元数值模拟的方法首次建立了铸型传热分析对称模型。在模型中对铸型传热系统中的对流、辐射、接触边界条件和凝固潜热进行了处理,利用有限元分析软件ANSYS,分析了紫铜冷却壁的温度场的变化。数值模拟的结果与实际生产相当吻合。     

基于数值模拟的接水盘冲压成形工艺分析与设计

分析了冰箱接水盘的形状和结构特点 ,设计了零件的冲压成形工艺 ,运用板料成形有限元软件对其中的拉伸和翻边工艺进行数值模拟 ,得到成形过程中工件各部位的厚度分布和成形极限图 ,分析了在不同工艺条件下可能产生的缺陷及其原因 ,并确定其初始毛坯和中间毛坯的合理形状 ,有效地保证了成形工艺的可靠性     

Spin Extrusion - A New Partial Forming Technology based on 7 NC-Axes Machining

Hollow shape component approaches, applied to shafts and similar workpieces, represent a major potential for ground-breaking innovations in lightweight engineering and safety designs. Among suitable forming technologies, spin extrusion is a pioneering and particularly flexible hollow-shaping technique. All outside form elements, straight or stepped cylinders, cones or spherical rotation elements emerge just from the kinematics of tools. The inside hollow shapes, as e.g. circular cross-sections, shaft to collar connections such as spherical triangles, polygons, splines or dovetail forms are manufactured with a shaping mandrel. Spin extrusion can be applied first and foremost at dimensions that are unattainable with other techniques. The application includes hollow shafts, thick-walled cups and semi-finished tubular products that are not to be found in off-the-shelf cross-sections. In these cases the possibility for using of massive bars is connected with very high price advantages. Furthermore material-saving machining is attracting special attention for high-grade materials.The paper characterizes substantial steps of process analysis and the appliance of a new, derived from the bound method, numerical simulation method for spin extrusion process. Holistic process analysis is the prime factor for process capability. The specific application of the developed special methods of simulation, the accumulation of process data and the integrating into the Computer numerical control of spin extrusion machine is a precondition guaranteeing high-quality assurance.     

ZTC4筒形件温成形扩口数值模拟

对铸造Ti-6Al-4V筒形件温成形扩口成形工艺进行了数值模拟分析,得出了优化的工艺参数,并对凸模锥角进行了优化模拟,得出了合适的锥角。