变冲程发动机配气切换机构设计

针对实现变冲程发动机工作模式及配气定时切换的问题,根据其工作原理,利用计算与仿真手段,设计了配气切换机构的凸轮廓线和切换机构的结构,验证了凸轮的运动学和动力学特性,在某单缸四冲程发动机配气机构的基础上,开发出了一种变冲程发动机配气切换机构,经加工成型及装机试验,结果表明切换机构工作良好。     

滑阀式压缩空气发动机实验研究

为优化气动发动机设计,提高气动发动机的工作性能,在一台由四冲程汽油机改装的二冲程气动发动机上进行了详细的台架试验。提出一个评价气动发动机性能的新指标——气动发动机平均有效压力和缸内平均压力的比值。采用钢、铝和尼龙三种材料制作相同尺寸的配气滑块进行试验,结果表明配气滑块的质量,对气动发动机动力性有影响。对进气持续角为128 °、143 °和156 °的尼龙材料配气滑块进行试验,试验结果表明增大进气持续角可以提高压缩空气的膨胀效率。在三种不同压缩比的状况下进行了气动发动机试验。试验证明在传统内燃机的基础上改装气动发动机时,增大发动机压缩比,会降低压缩空气的膨胀效率。     

气动绞车远程控制系统的设计

1　配气系统改进设计原理与结构气动绞车是一种以活塞式气动机为动力的手操纵型式的绞车 ,主要是供油田钻井 ,金属矿、煤矿等采掘矿场 ,建筑工程等部门拖运或提升重物之用。气动绞车的配气系统根据绞车结构形式的不同 ,可分为内置式和外置式两种形式 ,无论是内置式配气系统还是     

进气相位对三角转子气动发动机性能的影响

分析了三角转子气动发动机的配气系统特点,采用旋转阀式配气机构的工作过程,建立了发动机工作过程的数学模型,在进气压力为0．6MPa的情况下,针对不同的进气提前角和进气持续角对发动机的性能进行了数值仿真。仿真结果表明：进气相位在高速时对气动发动机性能影响大;设置合适的进气提前角对发动机的整体性能有利,且提前角随着发动机的转速的提高而增大;设置最佳的进气持续角对发动机的动力性能有利,且随着转速的提高进气持续角减小。因此在三角转子气动发动机设计工作过程中,需要设置合适的进气提前角和进气持续角,提高三角转子气动发动机的动力性能和经济性能。     

多气阀气动发动机设计及特性分析

随着环境问题的日益严重,气动发动机作为一种清洁能源的动力装置而逐渐被人们所关注。然而,能量利用效率低和输出功率低已经严重影响了气动发动机的发展。分析了气动发动机工作过程中的能量损失,并在此基础上提出了一种多气阀的新型气动发动机机构。建立了气动发动机工作过程数学模型。为了验证模型的准确性,搭建实验平台对气动发动机进行实验研究。通过误差与进气压力和曲轴转速之间的关系对所建立的模型进行修正,得到精确的气动发动机工作过程的数学模型。在此模型的基础上得到多气阀气动发动机的扭矩和能量利用效率特性。结果显示,在同样的结构参数下,进气压力为2MPa时,相比单进气和排气的气动发动机机构,多气阀气动发动机气输出扭矩提高了26.2~41.9N·m,能量效率提高了8%~10%。     

探析内燃机配气机构的技术现状及发展

内燃机可靠性及性能的发挥主要是靠配气机构控制内燃机的换气过程的结构来决定的,笔者整理了国内外内燃机配气机构的研究现状,然后研究配气机构的工作方法,并指出设计配气机构时存在的问题以及目前已被证明和广泛推广的配气机构的研究方法,最后选择先进的技术对当代发动机配气机进行分析,为内燃机配气机的合理设计提供依据。     

气动发动机的试验研究

为优化气动发动机的设计,提高气动发动机的工作性能,在一台由R175柴油机改装的二冲程气动发动机上进行详细的台架试验研究,并提出两个评价气动发动机性能的新指标--比质量流量和总能量效率.采用变压器机油、冷冻油和特制机油等三种不同的润滑油进行气动发动机的润滑油试验,试验结果表明润滑油对气动发动机的经济性和动力性影响很大.针对水套中无水、注入常温水和开水等三种不同换热条件进行气动发动机的换热试验,试验结果表明加强换热条件对气动发动机的经济性和动力性帮助有限,但多级利用压缩空气可以提高气动发动机的总能量效率.利用三种不同进气提前角的进气凸轮,进行三种不同配气相位的速度特性和负荷特性试验.试验表明:气动发动机在低速阶段拥有较好的经济性和动力性,进气提前角为10 ℃A时,气动发动机性能最好.     

凸轮轴磨削工艺分析

1凸轮轴加工材料以及外形 凸轮轴作为汽车发动机配气机构的重要组成零件，用于控制发动机缸体上气门阀杆的开合。通常在发动机的设计开发阶段就已经确定了凸轮轴的形式。     

浅谈发动机配气机构优化改进设计

配气机构是发动机重要的组成,配气机构功能要按照发动机各气缸工作循环与发火次序要求对进、排气门进行定时开启与关闭。发动机动力和经济的性能是不是具有优越性和可靠性,将噪声和振动控制到较低限度内,这都与配气机构的设计有着直接的关系。配气机构要具备良好换气性能和良好运动学、动力学的性能,保持平稳工作和低振动,小噪声。本文通过对配气机构的研究与优化改进设计,将理论与实际应用结合,为发动机配气机构的设计积累经验。     

内燃机配气机构技术现状及发展

配气机构控制内燃机的换气过程,其设计的优劣直接影响内燃机的可靠性及性能。介绍了内燃机配气机构的国内外研究状况;通过分析配气机构的工作原理,提出设计配气机构时存在的矛盾以及当前已得到广泛应用的配气机构的研究方法。对现代发动机配气机构采用的先进技术进行总结分析,对其发展方向进行展望,从而为配气机构的相关性能研究提供判断依据．为内燃机配气机构的优化设计提供参考。     

DYNAMIC MODEL AND SIMULATION OF A NOVEL ELECTRO-HYDRAULIC FULLY VARIABLE VALVE SYSTEM FOR FOUR-STROKE AUTOMOTIVE ENGINES

In modern four-stroke engine technology, variable valve timing and lift control offers potential benefits for making a high-performance engine. A novel electro-hydraulic fully variable valve train for four-stroke automotive engines is introduced. The construction of the nonlinear mathematic model of the valve train system and its dynamic analysis are also presented. Experimental and simulation results show that the novel electro-hydraulic valve train can achieve fully variable valve timing and lift control. Consequently the engine performance on different loads and speeds will be significantly increased. The technology also permits the elimination of the traditional throttle valve in the gasoline engines and increases engine design flexibility.     

An analysis of valve train behavior considering stiffness effects

To maintain the specific volumetric efficiency of a heavy-duty diesel engine, an understanding of the behavior of each part of the valve train system is very important. The stiffness of the valve train system has a strong influence on the behavior of the valve train than valve clearance, heat-resistance, or the durability of parts. In this study, a geometrical cam design profile using a finite element model of the valve train system is suggested. The results of the valve behavior according to the change in stiffness is analyzed for further tuning of the valve train system.     

一种新型汽车进气道被动式导流翼片

针对自然吸气式发动机,设计了一种新型被动式导流翼片。该翼片安装在节气门后端,用于改善进气道内气流的均匀性。仿真研究结果表明：对于自然吸气式发动机,安装了该翼片的节气门体在常用开度范围内,其后端流场以较小的流量损失换取了涡流比的大幅度提升,且流动更均匀。节气门性能实验和发动机外特性实验结果表明：节气门体后端流场在被动式导流翼片的作用下,基本没有流量损失,且燃烧室内燃烧更加充分、燃油利用率得到一定程度提高。仿真及实验结果表明：被动式导流翼片以低成本和高可靠性,使燃油利用率有一定提升。     

航空发动机引气转换装置建模仿真与改进设计

为解决某航空发动机引气转换装置转换不可靠问题,对装置进行受力与节流面分析,根据活门、壳体及弹簧参数在AMESim平台上构建模型。以发动机试车数据为算例进行计算,分析凸台尺寸及装置后节流面积对转换特性的影响。仿真结果表明,将凸台直径或装置后节流面积减小均有利于活门转换;由于改变装置后节流面积对润滑系统影响较大,通过将引气转换装置活门凸台直径减小2 mm,解决转换不可靠问题,经发动机整机试验验证有效。     

某发动机气门弹簧校核与分析

气门弹簧是发动机配气机构气门组的重要零件。对某发动机气门弹簧进行理论校核,应用Excite-Timing Drive软件对配气机构进行模拟分析。理论校核及模拟分析结果显示:由于气门升程较大,导致簧丝余隙较小,气门弹簧并圈现象较明显。通过优化气门弹簧设计参数,消除了弹簧并圈现象,配气机构采用新设计的弹簧后仍能稳定工作。     

Investigation of dynamic characteristics of a valve train system

A valve train dynamics model of internal combustion engine has been developed using the kineto-elastodynamics method. The dynamics behavior for flexible components such as the valve springs in the valve train system was described by the wave equation. The contact force at the cam/tappet interface was estimated by the elasto-hydrodynamic lubrication theory of finite line conjunction. Component submodels were integrated into the whole valve train model by coupling the corresponding contact and friction forces, and solved simultaneously considering transient effect of lubrication, as well as the torsional and bending vibrations of camshaft. Experimental validation was performed on a motored test rig. The predicted results agree well with experiments at difference camshaft speeds. The effects of the bending deflection and torsional vibration of camshaft on performance of the valve train system were also studied.     

内燃机配气机构噪声控制

为降低内燃机配气机构振动噪声,以某125型摩托车发动机配气机构为研究对象,利用高次多项式对凸轮型线进行优化设计.配气机构多体动力学仿真表明:优化后的配气机构没有出现"飞脱"和"反跳"现象,进、排气气门丰满程度有所增加,在各个转速下,气门的最大振动加速度降低了65%左右,气门与摇臂的撞击力有所降低,且气门与气门座间的撞击力明显下降.在此基础上,制作了凸轮样件并对优化前后配气机构进行声功率测试试验.结果表明:在测量转速范围内声功率级均降低1.5～2dB.     

Oil Degradation in a Diesel Engine with Dual-Loop Lubricating System

A common lubricating oil sump is used in most modern internal combustion engines for cooling, wear protection, and friction reduction. This requires compromises during base oil and additive selection as a result of differing needs for lubricant performance in engine subsystems. The use of a dual lubricating loop, providing separate oil sumps for the power cylinder and valve train subsystems, was investigated experimentally to determine the effect of system segregation on oil degradation. A small diesel engine was modified, installed in a commercial generator unit, and operated for one oil drain cycle. Oil sampling was tailored to assess base and acid numbers, oxidation, soot concentration, water content, and viscosity changes. The experiment complemented an earlier study that investigated the fuel economy benefits of such a lubricating configuration. These include longer drain intervals for the cylinder head and power cylinder subsystems, improved wear performance for the valve train, and opportunities for alternative material selection during engine design. The experiment demonstrated protection of the valve train subsystem from soot contaminants in the power cylinder. Lower total acid number and oxidation tendency was also observed in the valve train.     

列车空调用空气制冷系统的方案设计

比较了应用在列车空调中的空气制冷系统各种可行性方案以及各种方案的特点，分析了提高空气制冷系统性能的方法如回热技术、多级压缩、喷水技术等。得出了最适合列车空调制冷系统的方案是开式负压空气制冷系统。     

Novel method of measuring tappet rotation and the effect of lubricant rheology

One of the main drivers for developing lubricant technology is engine durability. Researchers and scientists are using new technologies, materials and advanced lubricant formulations to reduce overall engine friction and wear. One of the main engine tribological components is the valve train. This is one of the most challenging components to lubricate effectively because of the higher contact loadings and accounts for 10–20% of the total engine friction loss. The two main factors affecting the performance of engine valve trains are wear and friction, and a wide range of mechanical configurations are used to improve these. For example, direct-acting overhead camshaft valve train configurations use a rotating tappet design. Normally, the tappet is slightly offset from the cams and the cam is slightly conical to match the domed tappet to facilitate tappet rotation for even wear and to reduce slippage. In this paper, a novel innovative technique has been described to monitor tappet rotation in a real production engine having a direct overhead cam–tappet arrangement. The monitoring technique was applied to a VW Tdi engine head, and tests were carried out under different operating conditions. Lubricant compositions, oil temperature, pressure and camshaft speeds on tappet rotation were measured and all are shown to have an effect. The balance of forces between the cam–tappet and tappet-bore was found to be interlinked and the design of the hydraulic lash adjuster had a significant effect.This unique tappet rotation monitoring system can be used on most of the direct overhead camshaft engines, with minor engine modifications, to measure lubricant and hardware effects under both motored and fired conditions.