Effect of intake valve swirl on fuel-gas mixing and subsequent combustion in a CAI engine

A fully three-dimensional model was used to investigate the optimal value for intake valve lift in a CAI engine. Uniform mixing in the engine is a key parameter that affects the auto-ignition reliability and thermal efficiency. The method of intake of the air supply often determines the uniformity (or quality) of the fuel-air mixture. In this paper, four strategies were applied for controlling the swirl intensity of intake air. The variation of the intake valve lift induces different swirling and tumbling intensities. Both experimental data and 1D WAVE software (Ricardo, Co.) were coupled with the 3D model to provide pressure and temperature boundary conditions. The initial condition of the EGR mass fraction was also provided by the 1D model. The benchmark scenario (Case 1) was considered as a valve lift with 2 mm for all intake valves. We found that an intake valve lift of 6 mm with the other intake valve closed (i.e., Case 5) yielded the largest swirling (helical motion in the axial direction) and tumbling, which in turn rendered optimal fuel-gas mixing. We also found that fuel distribution affected the auto-ignition sites (or spot). The better the mixing, the greater the gas temperature and combustion efficiency achieved, as seen in Case 5. The NOx level, however, was increased due to the gas temperature. The optimal operating condition is selected from the viewpoints of environmental protection and combustion efficiency.     

Influence of shock absorber wearing on vehicle brake performance

In order to safely maintain a vehicle, it is necessary to verify the most important systems that affect safety during Periodic Motor Vehicle Inspections (PMVIs). In a previous paper, a test method and validation criteria were suggested by the authors to verify shock absorber status during PMVIs, as they are a fundamental component that may wear out during a vehicle’s life. In this paper, variations of the performance of the vehicle’s brakes resulting from shock absorber wearing have been analyzed, in order to confirm whether the suggested criteria is valid for taking into account longitudinal forces and pitch movement on the vehicle. A simulation-based study was conducted with several configurations of a worn damper on a vehicle driving on two virtual roads: smooth and undulating. The results confirmed that the damping coefficient established as an acceptable value to verify the shock absorber status in PMVIs is also valid considering the forces involved in a braking maneuver.     

插装阀在立式双孔拉床液压系统中的应用

分析了插装阀在机床液压系统中的应用依据,分析了原拉床液压系统的工作原理,用插装阀设计了立式双孔拉床机床的液压系统,很好地替代了原拉床的液压系统。分析了插装阀工作原理。在拉床液压系统中,采用插装阀具有许多优点,在技术和经济上可行,符合技术发展趋势。     

载货汽车中后翻动气室串气故障分析

介绍载货汽车中后桥制动气室的工作原理,分析其串气故障。     

简述汽车行人保护的现状与发展方向

近年来汽车碰撞安全的发展一日千里。但相对于日臻完善乘员保护研究,对行人的保护在过去并没有受到同等的重视。为此,欧洲自2005年开始把行人保护要求视为车辆设计必须考虑的因素。本文将从各个方面简要介绍汽车工业在行人保护上的发展现状,面临的挑战及未来可能的发展方向。     

基于AVL EXCITE TD的凸轮型线仿真优化

在现代发动机开发过程中,CAE软件的应用已经成为降低开发成本和缩短开发周期的主要手段.针对某微小型汽车发动机性能提升的改进工作,利用AVL Excite Timing Drive软件对发动机凸轮轴型线进行优化设计.建立了该发动机的单阀系统模型,在给定的配气机构零件基础上利用多段函数的数学方式优化了凸轮轴的缓冲段和工作段型线.优化后的结果表明,采用梯形函数形式的缓冲段,以及分段函数形式的工作段的凸轮轴型线,既能满足配气机构的动力学和运动学要求,同时达到了提高发动机中低速扭矩的性能目标,有效降低了整机的开发成本和周期.     

汽车制动颤鸣现象的仿真分析

汽车的制动颤鸣现象是制动盘与摩擦块间的相对运动引起的两个摩擦表面间的粘滑运动,且由于其非线性振动的特性导致高自由度下的粘滑运动难以进行解析计算.建立了一个6自由度的制动颤鸣模型,通过数值仿真分析了汽车低速时制动压力、初始时刻制动盘与摩擦块之间的相对运动速度对制动颤鸣现象的影响,并指出通过合理控制这两个要素,可抑制制动颤鸣现象的产生.     

柴油机低温余热利用数值模拟研究

本文针对柴油机低温尾气余热的利用提出了一种新的方案,并建立了模型,应用CFD数值模拟技术对模型进行了数值计算,模拟了模型的温度场分布。结果表明,在低温尾气余热利用方面,保证冷却流体无相变的情况下,此方案具有可行性。并由模拟的温度场分布,可确定冷却液达到稳定温度的轴向距离,为实际设计中长度参数的选取提供参考。     

发动机制动工况下汽车制动器摩擦性能分析

建立了基于恒速制动车辆纵向力平衡方程、制动器耗散功率及其温度变化微分方程、管路压力调节等子模型的恒速长下坡汽车制动器摩擦性能分析系统.以两轴中型汽车为例,对前后制动器在不同挡位发动机制动时的温度、制动副摩擦因数、制动力分配及管路压力变化进行了计算.结果表明,在不影响车速情况下,合理使用各挡发动机制动可改善汽车前、后制动器热负荷,减小或避免制动摩擦力矩热衰退,保证汽车下长坡安全行驶.     

新型汽车液压增力制动控制器

为了提高汽车制动效率开发一种汽车液压增力制动控制器（HBI）.它主要由增压缸等组成,串联于汽车制动主缸与前制动轮缸之间,将制动主缸输出压力制动液增压,送往前制动轮缸.同时还将压力制动液直接送往后制动轮缸,实现汽车增压制动,其制动效率高于现有减压分配阀组成的制动系统效率10%以上.对具有HBI系统的制动性能检测表明,HBI可用于多种车型的制动系统中,制动踏板力明显下降100 N左右,制动稳定性明显提高.