Analytical Model Development for Stokes-Type Settling in a Solidifying Fluid

Analytical modeling was used to track the mudline displacement of a simulated fluid dispersion that underwent a simulated linear increase in the fluid viscosity as a function of time following an induction period. Modeling results indicate two regimes of settling behavior from the driving force of density differences between the particles and the fluid. A linear mudline movement was first determined in the regime of constant viscosity, and a logarithmic retarded mudline movement was numerically determined following a linear rise in fluid viscosity. The results show that the combination of settling and solidification leads to a transitional mudline movement similar to batch settling curves described by early settling theories.     

流场尺寸对质子交换膜燃料电池性能的影响

流场的形状和尺寸是设计双极板的核心。合理的流场既要确保电极各处均能获得充足的反应剂供应,同时又要保证反应产物水的排出。研究了不同流场尺寸对质子交换膜燃料电池性能的影响。实验结果表明:在一定范围内,随着开孔率的增加,电极与流场本相及接触电阻也逐渐增加;开孔率相近时,这一电阻相差不大。在相同开孔率的情况下,沟槽尺寸越小,电池性能越好。     

全钒液流电池隔膜在钒溶液中的性能

考察了Nafion、日-160、日-80、FYM(日本产Nafion膜)和均相膜5种离子交换膜的两个关键性能(渗透性和面电阻)及其影响因素,对均相膜的化学稳定性进行了初步研究,并对两种膜进行了改性。实验发现:均相膜的钒扩散系数最小,但面电阻较大,化学稳定性不好;用二乙烯苯(DVB)对均相膜改性,综合性能较好;减小电场可降低钒离子扩散,提高钒溶液中氢离子浓度可减小面电阻。     

Velocity Distribution in the Roughness Layer of Rough-Bed Flows

Several models for the vertical distribution of the double-averaged (in time and in the plane parallel to the mean bed) longitudinal velocity in the flow region between roughness troughs and roughness tops are suggested. We found that the same model for velocity distribution may be applicable to a range of flow conditions and roughness types, which share some common features. The suggested models for velocity distribution in the near-bed region are: (1) Constant velocity; (2) exponential velocity distribution; and (3) linear velocity distribution. The measured velocity distributions may be approximated by a single model or by a combination of models depending on roughness geometry and flow conditions. The validity of these models for velocity distribution is supported by laboratory data.     

High order finite difference methods for unsteady incompressible flows in multi-connected domains

Using the vorticity and stream function variables is an effective way to compute 2-D incompressible flow due to the facts that the incompressibility constraint for the velocity is automatically satisfied, the pressure variable is eliminated, and high order schemes can be efficiently implemented. However, a difficulty arises in a multi-connected computational domain in determining the constants for the stream function on the boundary of the “holes”. This is an especially challenging task for the calculation of unsteady flows, since these constants vary with time to reflect the total fluxes of the flow in each sub-channel. In this paper, we propose an efficient method in a finite difference setting to solve this problem and present some numerical experiments, including an accuracy check of a Taylor vortex-type flow, flow past a non-symmetric square, and flow in a heat exchanger.     

小流量灰浆泵组合密封设计

用于输送含有细小颗粒流体的小流量（0．5～5t／h）氢氧化钙浆液泵的机械密封，极易被溶液中含有的固体颗粒磨损而丧失密封性能。针对这一问题，提出了一种背叶片加上橡胶波纹管机械密封组合的密封结构，并辅之以溢流结构来保护电机，从而解决了灰浆泵的密封问题，延长了泵的使用寿命，使泵装置的体积大大缩小，且易于维修。本文阐述了这种组合密封结构的原理及尺寸设计。     

阀门流场的数值模拟及流噪声的实验研究

采用非结构、非交错网格的有限体积法求解用二方程模型封闭的雷诺平均N S方程组 ,对水管路系统中 3种常见阀门的三维分离流动进行数值模拟。模拟结果表明 ,随着蝶阀、闸阀和球阀开度的减小 ,流体在蝶阀背面、球阀阀门内外分别形成两个方向相反的漩涡 ,闸阀的漩涡出现在挡板与管道的壁角处 ,并且漩涡在阀门下游逐渐消失。同时实验表明 ,阀门下游的流噪声大于阀门上游的流噪声 ,涡声是阀门噪声的主要来源     

网络等值与互联电网潮流分析

基于互联电网解合环潮流分析的现实需求。开发了一个应用软件。它采用潮流网络等值算法进行电网解合环分析。介绍了该算法的基本思路。并以实际算例阐明其计算精度高。具有普遍应用意义。在等值模式的选择中,通过分析端口模式和局部网络模式的优缺点。认为在可获得较多主网数据的情况下应优先采用局部网络模式。同时还指出。在软件的实现中应注意操作界面的图形化、数据对接的自动化和数据传送的信息化等问题。     

液滴旋转模型在重力场和均匀流场中的应用

本文主要应用单液滴旋转模型,研究了重力分离空间均匀蒸汽流场中液滴行为,定性描述了均匀蒸汽流场中液滴轨迹,分析了液滴在重力场和均匀蒸汽流场中运动的影响因素。主要讨论了液滴旋转及升力的影响,为液滴旋转模型的定量分析及其应用奠定了基础。     

经济评价方法中内部收益率的分析与研究

内部收益率是经济评价中的一项重要指标,反映项目收回投资时间的快慢,可用试差法计算,也可近似等于偿还期的倒数.