整体式转向梯形的设计方法研究

为了在整体式转向梯形设计过程中考虑轮胎侧偏的影响,采用了百分比阿克曼校正率对阿克曼转角关系进行了修正.设计过程中使用了MATLAB数学工具箱以及空间运动分析的方法分析转向梯形的空间运动规律,并且考虑四轮定位参数对转角关系的影响.分析结果表明,通过考虑轮胎侧偏影响设计的转向梯形与现有车型的转向梯形参数比较接近,同时通过灵...     

A new hybrid reliability index definition and its application to the structure buckling reliability analysis of supercavitating projectiles

As structure buckling problems easily arise when supercavitating projectiles operate with high underwater velocity, it is necessary to perform structure buckling reliability analysis. Now it is widely known that probabilistic and non-probabilistic uncertain information exists in engineering analysis. Based on reliability comprehensive index of multi-ellipsoid convex set, probabilistic uncertain information is added and transferred into non-probabilistic interval variable. The hybrid reliability is calculated by a combined method of modified limit step length iteration algorithm(MLSLIA) and Monte-Carlo method. The results of engineering examples show that the convergence of MLSLIA is better than that of limit step length iteration algorithm(LSLIA). Structure buckling hybrid reliability increases with the increase of ratio of base diameter to cavitator diameter, and decreases with the increase of initial launch velocity. Also the changes of uncertain degree of projectile velocity and cavitator drag coefficient affect structure buckling hybrid reliability index obviously. Therefore, uncertain degree of projectile velocity and cavitator drag coefficient should be controlled in project for high structure buckling reliability.     

作为地铁接驳手段的公共自行车使用特性分析

本文以苏州公共自行车为研究对象,利用刷卡数据及问卷调查数据分析公共自行车作为地铁接驳手段的使用特性.研究发现,地铁型站点公共自行车的用车时长较短且较为离散,与其他类型站点有显著差异.在接驳地铁的出行者中,公共自行车经常使用者的平均学历较高,也非低收入人群.利用离散选择模型分析地铁接驳方式选择行为可知,接驳方式使用时间是最重要的影响因素,年龄、职业和出行目的等对公共自行车的选择均有显著影响.研究还发现,经常使用公共自行车的出行者在接驳地铁时同样也倾向于选择公共自行车,而不使用者则倾向于选择步行或公交车.     

自然吸气缸内直喷汽油机气流运动的模拟分析

对一台自然吸气直喷汽油机考察了进气道的性能,模拟进气及压缩过程的气流运动,比较进气道与不同燃烧室匹配的效果。结果显示,在高流量系数、中等滚流比进气道的配合下,平顶活塞燃烧室在进气过程中形成的滚流更强,利于在进气初期喷油的均质燃烧;斜坑活塞燃烧室在压缩后期形成的滚流更强,利于在压缩过程喷油的分层燃烧。     

公路隧道双洞互补式通风系统横通道角度研究

依托某公路隧道研究通风横通道角度对双洞互补式通风系统的影响。通过数值模拟,分析不同角度工况下分流3通与汇流3通因阻力损失不同而引起的送风量差别,提出联络风道中汇流3通因阻力损失是确定横通道角度的关键。计算表明,在通风风速较大时,随横通道角度的减小,汇流3通段阻力损失会急剧变大;横通道角度为60°时,有利于通风网络的气流组织。     

New metal fitting geometry and optimization of the swaging parameters for an automobile power steering hose

To solve the power steering (PS) hose oil leakage problem in automobile applications, a new geometry design of the metal fitting is required, and the swaging conditions applied to the PS hose should be optimized. In this study, a new metal fitting geometry for the PS hose was proposed. A CAE simulation for both the proposed and the conventional metal fittings was conducted, and both the stress and the strain in the PS hose were compared. An experimental verification was also performed with these two different metal fittings. Additionally, the swaging conditions were optimized by the durability cycle time, which was measured in an impulse test of the swaged PS hose. For a more economical production, practical working conditions were also recommended and experimentally verified.     

Cold performance of various biodiesel fuel blends at low temperature

This study examines the cold performance of biodiesel blends in a passenger car and a light duty truck at −16 °C and −20 °C. Six different types of biodiesels derived from soybean oil, waste cooking oil, rapeseed oil, cottonseed oil, palm oil and jatropha oil were blended with different volume ratios (B5 (5 vol. % biodiesel — 95 vol. % diesel), B10 and B20). The cold filter plugging point (CFPP) and the cloud point had an effect on the startability and driveability of both the passenger car and the light duty truck. The startability and driveability of the passenger car with all biodiesel blends (B5) were generally good at −20 °C. In the light duty truck, biodiesel blends (B10 and B20) of soybean, waste cooking, rapeseed and jatropha tended to be good at −20 °C in the startability and driveability tests than the biodiesel blends (B10 and B20) of cottonseed and palm. In particular, the palm biodiesel blend (B10) failed at −20 °C, and the palm biodiesel blend (B20) also failed at −16 °C in the startability test. The cold flow properties of biodiesel dictate that the length of the hydrocarbon chains and the presence of unsaturated structures significantly affect the low temperature properties of biodiesel.     

三维测量数据的钢结构虚拟装配过程仿真系统(英文)

The virtual erection simulation system was explained for a steel structure including ship and ocean plant blocks.The simulation system predicted the erection state to optimize any gap or overlap of blocks based on 3-D measurement data.The blocks were modified(cut) on the basis of the simulation result on the ground before erecting them by crane.The re-cutting process was not required and the blocks were erected into a mother ship speedily.Therefore,the erection time is reduced,increasing the dock turnover.     

间冷循环涡轮气动方案

以间冷循环燃气轮机总体对动力涡轮的设计要求为目标,进行了间冷循环动力涡轮气动方案改型设计研究。计算采用成熟的轴流涡轮一维气动设计软件Concept NREC Axial,在一维气动损失模型的选用方面,通过对某型机性能复算进行了验证。方案改型计算在满足间冷循环燃机总体对动力涡轮的参数进行大规模调整的前提下,以尽量保留原型机的高可靠性为目标,并综合考虑了性能与改型难度的平衡,完成了多个方案的计算。结果表明,经过改型设计的涡轮可以基本满足间冷循环的要求。     

日本桥梁防落梁系统设计

日本桥梁防落梁设计经过多年的发展以及实际地震的考验,目前已较系统,其专门针对防落梁措施规定了详细的设计流程和设计方法,并且采用“多道防线、分级破坏”的设计理念,对运营期中小震、大震和超预期地震下的设防进行了具体的规定,明确了防落梁系统各要素在不同地震作用下的性能水平,降低了地震中上部结构的落梁风险.