二次补气阀的技术要求和试验方法

二次补气阀是摩托车发动机排放净化的关键零部件之一,通过单向进气阀从外界吸入空气到排气管内,为氧化催化剂的高效工作补充氧含量,通过调整设定单向进气阀的金属簧片厚度、簧片止口和开口区面积等参数,可控制补气量的大小。     

解放牌汽车发动机的改造(三)——进气系统阻力分析及改进设计

一台发动机的性能取决于该发动机把最大数量的空气导进燃烧室,并以高燃烧效率利用这些空气的能力。化油器混合室直径、进气管走向及总管断面尺寸、特别是进气道的设计和进气阀直径、阀座型式、进气阀最大升程、进气阀与燃烧室壁间隙等都在影响导入空气的数量。     

乙醇汽油引起的二次进气阀负压膜片破损问题分析及对策

市场反馈某款弯梁车行驶2 000～5 000 km后,发现二次进气阀有动作异常、发生异响的故障.拆解其中几件用过的二次进气阀后,发现二次进气阀的负压膜片均膨胀和破损.     

柴油汽车驻车制动系统漏气的原因

手控阀漏气当驻车制动手控阀置"停车制动"位置时,手控阀从排气口持续漏气,此故障是该阀的进气阀与阀座封闭不严,或是阀与阀座之间存有异物,或是进气阀密封件损坏所致,更换进气阀密封件即可解决。在驻车制动时,驻车制动手控阀漏气不会产生其它的故障。然而当把手控阀手柄置     

65Mn簧片螺母断裂失效分析

本文对重型卡车中使用的簧片螺母在装配过程中发生断裂事故进行了分析,结果表明,簧片螺母材质和硬度符合相关技术要求,金相组织为正常组织,引起断裂的主要原因为簧片螺母在酸洗或镀锌过程中产生吸氢,导致材料晶界脆化,在装配过程中受力发生脆性断裂。同时,分析了氢脆的原理,提出了避免氢脆事故出现的措施。     

某大功率柴油机顺序增压系统切换过程试验研究

为提高某大功率柴油机顺序增压系统切换过程的平稳性,对柴油机不同负荷工况下切换对增压压力的影响规律,进气阀延迟时间与动作速度对系统喘振、空气倒流的影响规律进行了台架试验研究。试验结果表明:切换点选择在柴油机的较大负荷工况,可以避免切换过程中柴油机功率的大幅度下降;从1TC到2TC的切换过程中,进气阀延迟并缓慢打开,从2TC到1TC的切换过程中,进气阀延迟并快速关闭,可以避免系统的喘振和空气倒流。研究结果为顺序增压系统控制策略的制定提供了依据。     

NF50摩托车发动机簧片阀座组合的试验研究

簧片阀座组合是ＮＦ５０摩托车发动机中的重要部件，它不但影响发动机起动性，而且影响油耗和怠速波动率，通过单项试验和正交试验，找出影响的主要因素和合理技术参数，在生产中采取改进措施以后，提高了簧片阀座组合的装配合格率，效果明显。     

用平均进气马赫数Mim对四冲程发动机容积效率特性的分析

为了获得极限容积效率曲线,在四冲程发动机上,通过在一个大范围内改变进气阀有效角度面积来研究容积效率和发动机转速之间的关系。 由作者引入的平均进气马赫数Mim比广泛采用的进气马赫数Ms能更好地表征容积效率特性,并且当Mim接近0.5时,进气阀周围的流动成为临界流动,并产生流动阻塞,这使得容积效率随发动机转速的增加而呈双曲线地减少。     

流经内燃机进气阀的空气流速计算

<正> 本文主要研究了进气阀口内空气流速的计算方法,该方法考虑了进气动力过程的影响以及气流在气缸内的滞止效应。 内燃机的气阀组件是重要的部件。流经气阀组件的气体流动过程,对发动机的技术经济指标有很大影响。尤其进气阀口内的空气流动与气缸充气过程密切相关。在计算分析进气道内气体动力过程,根据实验数据确定气阀流量系数,以及为改善混合物形成在充气过程中向进气阀头喷射汽油使其从油膜表面开始蒸发以使在气缸内形成规则气流时,也会出现气阀隙内气体流速问题。     

钢板弹簧预加弯矩分配的函数计算法

为了使板簧装配压紧前各簧片中部留有一定间隙,在压紧之后又能使各簧片形成一定的负弯矩,并保证其工作状态下具有较低的复合应力,设计时应对板簧片进行预加弯矩的分配计算。本文介绍了一种用于板簧簧片预加弯矩分配计算的函数计算法,并给出了计算实例。     

Modeling and simulation of a dual-mode electrohydraulic fully variable valve train for four-stroke engines

In modern four-stroke automotive engine technology, variable valve timing and lift control offer potential benefits for making a high-performance engine. In this paper, a novel design named dual-mode electrohydraulic fully variable valve train (EHFVVT) for both engine intake and exhaust valves is introduced. The system is mainly controlled by either proportional flow control valves or proportional pressure relief valves, and hence two different families of valve displacement patterns can be achieved. The construction of the mathematical model of the valve train system and its dynamic analysis are also presented in this paper. Experimental and simulation results show that the dual-mode electrohydraulic variable valve train can achieve fully variable valve timing and lift control, and has the potential to eliminate the traditional throttle valve in the gasoline engines. With the proposed system, the engine performance at various speeds and loads will be significantly improved.     

DVVT对缸内直喷增压发动机性能影响的试验研究

通过对GDI增压发动机进行DVVT扫点试验,研究了DVVT对GDI增压发动机外特性性能、部分负荷燃油经济性和怠速稳定性的影响。试验结果表明:对于试验发动机的凸轮轴型线而言,排气VVT的开启对发动机性能起到负面影响;外特性方面,中等转速工况采用较大的气门重叠角可提高体积效率;高转速采用较小的气门重叠角可提高充量系数;怠速和部分负荷工况下,较小的气门重叠角对改善发动机稳定性有一定帮助。     

气门重叠角对HCNG发动机回火性能的影响

为研究某高压缩比HCNG发动机的回火特性,进行了发动机回火工况台架试验,结合试验数据,建立HCNG发动机三维仿真模型,对不同气门重叠角下的回火性能进行仿真计算。试验与仿真结果表明:压缩比越高,发动机越容易回火;其他条件不变,较小的点火提前角容易引起回火;原机气门重叠角较大,压缩比提高,导致进气口富氢新鲜充量受热,这是造成回火的重要原因;随着气门重叠角的减小,发动机功率以及最高燃烧压力降低,当气门重叠角为0°时,可有效避免回火。     

基于Simulink的柴油引燃式天然气发动机控制模型开发

为了提高柴油引燃式天然气发动机在中小负荷的热效率,采用具备电子节气门的电子控制系统,利用Simulink软件开发了针对该系统的具有电子节气门控制功能的发动机控制模型,通过自动代码生成工具生成嵌入式代码,并下载至发动机控制器进行试验。试验结果表明,该节气门控制算法具有较好的控制效果,发动机控制算法能够有效控制发动机中小负荷的混合气空燃比,明显提高热效率。     

Efficiency improvement for an unthrottled SI engine at part load

Variable valve timing (VVT) and cylinder deactivation (CDA) are promising methods in reducing fuel consumption and emission at part load in SI engines. An SI engine which uses electromagnetic valvetrain (EMV) will eliminate flow restriction from the throttle valve and produce higher indicated mean efficiency pressure (IMEP) due to the disabling of some of the working cylinders at part load. Therefore, pumping loss can be significantly reduced at part-load conditions. In addition, duration and timing of valve events are variably controlled at different operating conditions. This contributes to the improvement of engine efficiency. In this study, a dynamic model of an unthrottled SI engine has been developed to simulate the engine cycle. The model uses an EMV system that allows valvetrain control and cylinder deactivation techniques to be carried out in simulation flexibly. The simulated results find the optimal valve timing for different engine speeds. The optimal timing of intake valve closing depends on engine speed linearly, while the intake valve opening insignificantly influences engine performance. Additionally, this study also shows that cylinder deactivation modes can be successfully applied in improving engine efficiency at different engine loads. Different cylinder deactivation strategies have been applied for the full range of engine loads. It is concluded that the two-cylinder deactivation mode (50% CDA) considerably improves fuel consumption at low engine load. Meanwhile, one-cylinder deactivation (25% CDA) is an optimal fuel economy mode at medium engine load. With proper uses of VVT and CDA strategies, the efficiency of an SI engine can be increased more than 30% at low engine load and 11.7 % at medium engine load.     

摩托车发动机配气机构运动学和动力学分析

采EXCITE_TD软件,对某款摩托车四冲程汽油机配气机构进行运动学和动力学分析,对配气机构的性能及可提升余量有了更进一步的了解,并针对可提升的余量进行优化,以得到较满意的设计方案.优化后的配气机构进排气门升程丰满,系数有所提高,有利于提高发动机的充气效率;凸轮与摇臂间接触应力和气门落座力有所减小,无反跳、飞脱现象,整...     

柴油机配气相位的优化设计

利用AVL-BOOST软件进行了配气相位对发动机性能影响的仿真分析，依次把排气提前角和进气晚关角作为优化自变量，以燃油经济性为目标，对原型发动机的配气相位进行了优化，并通过试验验证了优化结果。     

变海拔下米勒循环对柴油机及DPF性能的影响

基于某高压共轨柴油机建立了一维热力学仿真模型,对DPF选型进行了优化,并分析了不同海拔下米勒循环对柴油机及DPF性能的影响。结果表明,选择非对称结构以及适当增加载体目数都有利于降低DPF压降,同时可降低DPF对柴油机动力性、经济性及原始排放的影响。进气门早关可以降低柴油机有效燃油消耗率,提高热效率,降低NOx排放,但会导致颗粒物排放增加;同时可降低DPF压降,提高DPF捕集效率,且随海拔升高,进气门早关的时刻越小,作用越明显。在低海拔条件下,进气门晚关策略对柴油机动力性、经济性及排放特性均影响不大;在高海拔条件下,适当增加进气门晚关时刻可以改善柴油机性能。     

Experimental study on the spray and combustion characteristics of SIDI CNG

Compressed natural gas (CNG) is regarded as one of the most promising alternative fuels. In the spark-ignition (SI) engine, direct injection (DI) technology can significantly increase the engine volumetric efficiency and reduce “pumping losses” in engines without a throttle valve. DI allows engine operation with the stratified charge which enables relatively higher combustion efficiency. In this study, a combustion chamber with a visualization system is designed. The spray development and combustion propagation process of spark-ignition direct injection (SIDI) CNG were digital recorded and analyzed. The ignition probability was also examined. The results of this study can contribute important data for the design and optimization of the SIDI CNG engine.