管磨机与其中心传动减速机中心线相对位置的确定

分析了磨机和减速机对彼此中心线的影响因素;安装时磨机和减速机中心线相对位置的三个观点：居于同一轴线,减速机低于磨机,减速机高于磨机。通过在福建水泥厂安装实践认为,可以仅用垫高减速机的方法,既使减速机中心线高于磨机中心线,又满足了磨机筒体中心线水平度的要求。     

基于AMESim的风力发电机的液压马达启动特性的研究

兆瓦级大型风力发电机的偏航系统通常采用电机驱动,但是偏航速度和电机速度相差较大,造成减速机的尺寸大、质量大、安装维护比较复杂;另外还存在偏航电机启动电流大、偏航负载变化频繁、偏航位置不易精确控制的问题。针对以上问题,提出液压马达的比例系统控制方案,建立了液压马达的数学模型,利用AMESim软件对液压马达的启动、工作过程中转动惯量、负载扭矩、阻尼系数进行研究;采用阶跃信号对液压马达进行仿真,对仿真结果进行分析,验证理论的合理性和可行性。结果表明:液压控制方案在降低偏航减速比、减轻减速机尺寸和质量、提高偏航位置控制精度方面具有独特的优势。     

凸轮分度工作台的结构与设计

介绍一种利用普通电机驱动的组合凸轮机构,实现双向连续、小角度分度定位的分度工作台,阐述了其结构原理与设计方法。     

基于项目任务驱动的《模具设计技能训练》教材开发研究

"模具设计"是高职模具设计与制造专业的核心专业课程,本文分析了模具设计类课程的教材现状,提出了基于项目任务驱动的《模具设计技能训练》教材开发思路与内容框架,对模具专业课程的教学改革及教材开发有一定参考价值。     

两自由度摇摆台耦合动力学建模与仿真

考虑两自由度摇摆台内、外平台的耦合效应以及负载偏心造成的偏载力矩对驱动系统的影响,采用齐次变换方法建立了两自由度摇摆台的动力学模型。驱动系统采用齿轮齿条液压缸,考虑齿条间隙、液压流量非线性等影响,对液压伺服系统进行了仿真分析。仿真结果为驱动、控制系统的设计提供了参考依据。     

齿轮泵用被动齿轮开裂原因分析

被动齿轮在装机试压后出现开裂,通过化学成分分析、宏观和微观检验、硬度和渗碳层深度测试和磨削烧伤检查对被动齿轮开裂的原因进行了分析。结果表明：材料材质和渗碳热处理工艺均无异常,被动齿轮开裂的主要原因是由于磨削工艺不当引起的。根据分析结果提出相应的改进建议。     

Numerical simulation of density-driven natural convection in porous media with application for CO2 injection projects

In this paper we investigate the mass transfer of CO₂ injected into a homogenous (sub)-surface porous formation saturated with a liquid. In almost all cases of practical interest CO₂ is present on top of the liquid. Therefore, we perform our analysis to a porous medium that is impermeable from sides and that is exposed to CO₂ at the top. For this configuration density-driven natural convection enhances the mass transfer rate of CO₂ into the initially stagnant liquid. The analysis is done numerically using mass and momentum conservation laws and diffusion of CO₂ into the liquid. The effects of aspect ratio and the Rayleigh number, which is dependent on the characteristics of the porous medium and fluid properties, are studied. This configuration leads to an unstable flow process. Numerical computations do not show natural convection effects for homogeneous initial conditions. Therefore a sinusoidal perturbation is added for the initial top boundary condition. It is found that the mass transfer increases and concentration front moves faster with increasing Rayleigh number. The results of this paper have implications in enhanced oil recovery and CO₂ sequestration in aquifers.     

新型交流变频电驱动石油钻机

介绍了近年来国外新出现的交流变频调速电驱动石油钻机核心技术的发展概况,同机械驱动,直流电驱动石油钻机相比的先进性能及1999年我国研制成功的第1台ZJ40／2250DB型中深井交流变频调速电驱动石油钻机的特点及油田试验情况。     

工程车液压四轮转向系统的研究与实践

根据工程现场特点，设计转向灵活、适合窄小空间行驶且具有较大载重能力的工程车四轮转向系统，满足现场需要，运行效果良好。     

Numerical simulation of mixed convection in a porous medium filled with water/Al2 O3 nanofluid

The present work encloses the application of a Brinkman–extended Darcy model in a problem concerning mixed convection ina lid–driven porous cavity using nanofluids. The transport equations are solved numerically by the finite volume method on a co–located grid arrangement using the Quadratic Upstream Interpolation for Convective Kinematics (QUICK) scheme. The effects of governing parameters, namely, Grashof number (Gr), Darcy number (Da), and solid volume fraction $(\chi )$ , on the streamlines and the isotherms are studied. The present results are validated by favorable comparisons with previously published results and are in good agreement with them. The present numerical results show that the addition of nanoparticles to a base fluid has produced an augmentation of the heat transfer coefficient and it is found to increase significantly with an increase of the particle volume concentration. It is observed from the results that at the higher value of the Grashof number (Gr = 10⁴ ), the average Nusselt number increases with an increase in the Darcy number for a constant solid volume fraction. The detailed results are reported by means of streamlines, isotherms, and Nusselt numbers. © 2012 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.21029