Simplification and applicability studies of a hydrogen-air detailed reaction mechanism

The research of hydrogen fuel internal combustion engine (HICE) had great significance facing the challenges of energy and environmental problems. Based on the detailed hydrogen-air reaction mechanism, the pre-mix model of CHEMKIN-Pro software was selected to simplify the detailed mechanism GRI-3.0. The most important elements and reactions was chose to construct framework mechanism firstly based on the sensitivity coefficient for H₂O and NO formation, and additional elements and reactions were added to framework mechanism for complementing the oxidation path of N2 and H₂. A simplified mechanism including 24-step elementary reaction was obtained and the laminar burning velocity calculated by this simplified mechanism matches well with the detailed mechanism in a wide range. This simplified mechanism was also applied in a CFD model which predicted the cylinder instantaneous pressure and NOx emission accurately within a large range of fuel air equivalent ratio. Showing that this mechanism has good applicability.     

二级剪叉式液压升降机液压缸布置方式研究

分析了二级剪叉式液压升降机的三种主要布置方式,以及液压缸倾斜布置时的三种液压缸安装位置方案。对于其中的一种方案,应用虚位移原理计算求解液压缸推力,并以液压缸推力最小为目标建立优化设计数学模型,通过MATLAB软件得到液压缸推力最小时的液压缸安装位置。通过研究液压缸布置方式,提高了二级剪叉式液压升降机的设计效率和传动质量。     

Constructing developable surfaces by wrapping cones and cylinders

We model developable surfaces by wrapping a planar figure around cones and cylinders. Complicated developables can be constructed by successive mappings using cones and cylinders of different sizes and shapes. We also propose an intuitive control mechanism, which allows a user to select an arbitrary point on the planar figure and move it to a new position. Numerical techniques are then used to find a cone or cylinder that produces the required mapping. Several examples demonstrate the effectiveness of our technique.     

Impact of shape representation schemes used in discrete element modelling of particle packing

In different computer models, shape is represented using different methodologies, to varying degrees of precision. This paper examines two approaches to shape representation, and their effects on accuracy in the context of cylindrical particle packing. Two discrete element method (DEM) based software packages are used. A X-ray CT scan of a packed bed provides the experimental measurements for comparison. Eight sphere-composite representations of the same cylindrical pellet were tested. Two of these gave results that quantitatively follow experimental measurements. A range of factors that in theory could affect accuracy of the simulation results are examined, including edge roundedness, surface roughness and restitutional behaviour as a function of sphere-composite representations. The conclusion is that, for packing at least, matching the object's overall shape and dimensions is not enough. Only when a high enough resolution is applied to corners and edges, could the sphere-composite approach possibly match the experimental data quantitatively.     

穿孔机顶杆循环装置液压控制系统的研究

设计穿孔机区域顶杆循环装置中顶杆小车油缸控制系统,对长行程高速重载液压系统油缸的速度、加速度、两腔液压力进行分析,对该类液压控制系统的运行机制、控制策略进行研究,进行了理论计算、仿真分析和实测验证,为类似工况液压控制系统的研究提供参考。     

轴向柱塞泵摩擦副耐磨可靠性设计

本提出了以摩擦副的（ｐυ）应力模型和应力一强度干涉模型为基础，建立轴向柱塞泵缸体一配流盘这对关键摩擦副可靠性设计模型，并以ＸＢ４０型轴向柱塞泵为实例，作了缸体一配流盘的耐磨可靠性设计。     

PCCP管在万家寨引黄工程中的成功应用

结合万家寨引黄工程实例,详细地介绍了PCCP管道的制作,从沟槽开挖、管道安装、管道回填等方面探讨了PCCP管道的安装,以便使预应力钢筒混凝土管更好地服务于引黄北干线工程建设及国内大型管道引水工程和给排水工程。     

基于数值模拟的筒盖冲压工艺及模具设计

本设计零件为筒盖,是三级阶梯拉深和一反拉深、浅正拉深及冲孔的拉深件,结构较复杂,在分析成形工艺基础上,采用两套复合模。由于拉深成形时会出现拉裂、起皱等问题,因此设计时设计压边圈,避免了零件起皱;利用模拟软件分析材料成形工艺,以确定所设计模具是否会拉裂,减少不必要的损失;对筒盖进行三维造型,可以解决零件结构复杂、毛坯尺寸计算繁琐的问题。     

发动机缸盖导管阀座压装技术分析

介绍汽油发动机缸盖导管阀座压装技术的发展和领先的压装技术,对传统压装技术和新压装技术分别做了详细的技术分析和对比。     

某型柴油机拉缸原因分析及解决措施

本文针对某型柴油机在国产化过程中出现的拉缸问题,从原理上分析了某型柴油机拉缸的原因,并提出了在制造、安装、使用过程中应采取的预防措施。