基于Pro/E的内燃机活塞裙部精确造型

精确活塞裙部形状是活塞CAE/CAM的基础。文中研究在Pro/E环境下采用曲线方程控制活塞裙部多个横断面形状,进而完成活塞裙部的精确建模。     

UG软件在活塞丝网印刷型面设计中的应用

用UG软件中的缠绕/展开曲线功能,精确设计活塞裙部丝网印刷图案,对其边缘进行圆滑处理,以1:1的比例输出,即可得到丝网印刷图案。此丝网面与活塞裙部型面精确吻合,不论多么复杂的裙部型面均可简单精确的设计。     

活塞裙部异形外圆套车

活塞是发动机的心脏,是重要的零配件之一,活塞的质量及精度直接影响发动机的性能。因此,活塞在结构、材料和几何形状等方面都在不断地改进和提高。就活塞裙部的几何形状来说,从过去单一正圆或单一椭圆发展到     

渐近法加工活塞立体靠模

为提高活塞工作性能 ,活塞裙部设计成中凸变椭圆形 ,常用立体靠模仿形车削活塞裙部 ,阐述在平面磨床上用渐近法磨削活塞立体靠模的简易方法     

基于280ZJB组合式活塞裙部的摩擦特性研究

在组合式活塞裙部摩擦学和动力学已有研究的基础上,建立适用于大功率机车组合式活塞裙部的二阶运动和动力润滑耦合模型,并在Matlab环境下,编写了耦合模型的计算方法,研究各项参数变化对组合式活塞裙部摩擦特性和动力学行为的影响。结果表明,润滑油动力黏度、发动机转速、活塞销偏置对活塞裙部的摩擦特性有重要影响。     

活塞加工变椭圆车削机构

活塞是发动机的一个重要零件。发动机工作时,活塞承受较大的机械负荷和热负荷。因此,要求它与汽缸套间隙小,使发动机起动时不发生活塞敲击缸壁和因热胀而发生咬死现象。所以,活塞裙部必须加工成椭圆形状,使活塞受热后留有膨胀的余地(即向销孔方向膨胀)。活塞受热梯度是从上到下逐渐减少,这种现象对重型柴油机活塞更为明显,所以一般多采用变椭圆活塞。根据活塞材料、结构、工作条件的不同,采用不同的椭圆曲线。关于椭圆曲线有如下公式:式中:△R──活塞长半轴在每个角度上的缩 短量; D──活塞裙部长轴直径; d──活塞裙部短轴直径; a──主…     

活塞裙部中凸变椭圆异形面磁性研磨新工艺的研究

活塞是发动机的重要零件，为了提高活塞的工作性能，活塞裙部型面不断得到改进，如今广泛采用了中凸变椭圆异型表面。目前，大批量的活塞磨削加工、光整加工往往借助于数控磨床，通过型面编程来加工，设备昂贵，加工成本高，技术难度大。鉴于此，笔者在深入研究磁性研磨光整加工的基础上，研制出针对活塞裙部光整加工的磁性研磨装置。     

某发动机活塞强度与疲劳分析

建立包括活塞、连杆和缸套等构件的有限元模型,较真实地模拟了活塞在工作过程中的受力特征,对活塞等构件进行热机耦合分析,建立了考虑活塞与活塞销、活塞销与衬套、活塞裙部与缸套之间的油膜接触及压力计算模型。此外,发动机整机动力分析还为活塞强度分析提供不同曲柄角下的荷载及加速度信息。实际工程应用表明,该方法实用、可行,计算结果与实测一致,所建立的计算模型能准确反映活塞的真实工作状况,对活塞裙部压力、关键部位应力与疲劳可以进行定量评估,为发动机活塞的优化设计提供基础数据。     

裙部型线对内燃机活塞二阶运动和活塞裙部润滑的影响研究

以某多缸内燃机为研究对象,研究活塞裙部纵向型线对活塞二阶运动和活塞裙-缸套摩擦副润滑性能的影响。考虑活塞裙部和缸套的表面粗糙度与微凸体接触,建立了活塞二阶运动方程与平均Reynolds方程相结合的活塞裙-缸套摩擦副润滑分析模型。活塞二阶运动方程采用Broyden方法求解,应用有限差分法进行活塞裙-缸套摩擦副的润滑分析。结果表明,采用二次曲线型活塞裙部有利于改善活塞裙-缸套摩擦副润滑性能、降低内燃机摩擦损失、减轻活塞对气缸套的冲击和提高内燃机工作的平顺性。     

提高铝活塞检测精度的研究

铝活塞的质量在很大程度上决定了汽车发动机乃至整车的质量。由于铝活塞结构的特殊性,其销孔轴线对裙部轴线的垂直度误差检测难度很大,误差也较大。根据机械测量与机械制造原理,对两种常用的检测方法进行分析,确认检测存在较大误差的原因,进而提高检测精度,降低漏检率,并最终提高铝活塞的产品质量。     

A new numerical analysis for piston skirt–liner system lubrication considering the effects of connecting rod inertia

A new numerical analysis for the piston skirt is conducted to consider the effects of the connecting rod inertia on the piston skirt–liner system lubrication. The piston dynamics, the oil film and the friction loss of the system are analyzed and compared with one earlier model that has been adopted widely. The results on a gasoline engine show that the connecting rod inertia does have some influence on the system lubrication as well as the piston dynamics, especially when engine runs at high speeds.     

二甲醚发动机活塞二阶运动-润滑耦合模型建立及数值分析

通过改造潍柴WP6发动机的供油、燃烧系统,开发出一台二甲醚发动机。试验采集二甲醚发动机燃烧参数,针对活塞运动和润滑分析,建立活塞裙部系统以及由曲轴、连杆、活塞组成的多体系统的耦合润滑模型。基于拉格朗日乘子法建立多体动力学方程,并采用有限单元法对润滑模型进行求解。将耦合计算结果与实验对比,验证模型准确性。根据现有二甲醚发动机活塞裙部的结构参数,研究不同活塞结构参数对敲缸及润滑的影响。结果表明,活塞间隙越小时,活塞二阶运动的空间越小,导致敲缸现象减弱,磨损降低,但较小的间隙会产生比较高的油膜剪切力,微凸体表面接触也会加剧,引起较大的摩擦力及摩擦功耗;活塞裙桶形面最高点的位置也会影响活塞裙-缸套系统的运动和润滑特性;桶形面与活塞销中心的距离越小越容易满足力与力矩平衡条件,有利于降低敲缸以及摩擦损耗。     

Piston Assembly Design for Improved Thermal-Tribological Performance

The tribological system in the piston assembly of an internal combustion engine includes contacts at interfaces of piston/piston ring/cylinder liner, piston skirt/cylinder wall, and piston/piston pin/ connecting rod. The thermal and tribological properties of the piston, piston rings, and cylinder wall are critical to the life and quality of the engine. Severe wear and scuffing failure, especially at the ring/ring groove and ring/liner interfaces, may present a major problem if the piston temperature is too high. Temperature considerations for the piston often limit the effort to increase the engine power.

A new engine piston incorporating the heat pipe cooling technology has been developed for reducing the piston temperature, especially in the ring land and along the piston wall. The current work aims at investigating the effect of reciprocating heat pipes on heat conduction in the piston, and thus the tribological behavior of the piston assembly. Due to the high thermal conductance of the reciprocating heat pipe, a considerably large amount of combustion heat, which is conventionally conducted through the piston wall, is transferred through heat pipes. This new design will result in a lower temperature on the piston wall and a reasonably low temperature distribution in the piston.     

Thermo-elasto-hydrodynamic lubrication analysis of piston skirt considering oil film inertia effect

Influence of oil film inertia forces on thermo-elasto-hydrodynamic lubrication performances of a piston skirt is analyzed, based on a proposed Reynolds lubrication equation for the consideration of oil film inertia force effects. Further, a scheme to solve the inertia effects is given. The numerical results show that oil film inertia forces can result in increments in film pressure and temperature, hydrodynamic friction force and load capacity, deformation, and transverse displacements of the piston skirt. Moreover, the influences are obvious for a big reduced Reynolds number. Therefore, oil film inertia force effects on thermo-elasto-hydrodynamic lubrication performances of a piston skirt in a high speed internal combustion engine should be considered.     

Transient Tribo-Dynamics of Thermo-Elastic Compliant High-Performance Piston Skirts

Advanced piston technology for motorsport applications is driven through development of lightweight pistons with preferentially compliant short partial skirts. The preferential compliance is achieved through structural stiffening, such that a greater entrainment wedge is achieved at the skirt’s bottom edge through thermo-elastic deformation, whilst better conforming contact geometry at the top of the skirt. In practice, the combination of some of these conditions is intended to improve the load-carrying capacity and reduce friction. The approach is fundamental to the underlying ethos of race and high-performance engine technology. Contact loads of the order of 5 kN and contact kinematics in the range 0–35 m/s result in harsh transient tribological conditions. Therefore, piston design requires detailed transient analysis, which integrates piston dynamics, thermo-elastic distortion and transient elastohydrodynamics. The paper provides such a detailed analysis as well as verification of the same using non-invasive ultrasonic-assisted lubricant film thickness measurement from a fired engine under normal operating conditions, an approach not hitherto reported in literature. Good agreement is noted between measured film thickness and predictions.     

增压条件下活塞的动压润滑分析

根据流体动力润滑理论与活塞动力学方程建立的分析模型，依据发动机燃气压力的变化，计算了增压前后的活塞裙部最小润滑油膜厚度和摩擦力。结果表明，发动机增压后，主推力边和次推力边的最小润滑油膜厚度分别变小，裙部的摩擦力和摩擦功耗增大。因增压后活塞润滑能力降低，并且摩擦功耗增加，会对整机的可靠性产生影响，这些都应当在增压改进设计时予以重视。     

内燃机活塞裙部-缸套间润滑油输送状况*

活塞裙部-缸套间的润滑油输送情况对内燃机活塞组件摩擦副润滑状态、润滑油消耗、排放和润滑油性能退化等都有重要的影响。结合活塞二阶运动模型、流体润滑模型和润滑油流动模型等,进行不同内燃机工况下活塞裙部-缸套间润滑油输送状况的计算,主要分析活塞向下运动行程中活塞裙部运动后气缸套表面润滑油的滞留量。结果表明,在不同工况下对应行程中润滑油滞留量的变化规律基本相同,不同时刻的润滑油滞留量不相同,活塞上下止点处的润滑油滞留量基本相同。内燃机负荷相同时,随转速增加,进气行程中和膨胀行程中后期的润滑油滞留量减少,膨胀行程前期的润滑油滞留量增加。内燃机转速相同时,膨胀行程前期的润滑油滞留量一般随负荷增加而增加,膨胀行程中后期的润滑油滞留量基本不随负荷变化,不同转速下进气行程中润滑油滞留量随负荷的变化规律不一致。     

A study on the characteristivs of heat transfer in an engine piston

The piston temperature distribution with varying engine torque and speeds for a real engine operation has been determined by a numerical model. The model is developed by the finite element conduction method combined with engine simulation. In this model, the two boundary temperature concept instead of one constant boundary temperature was presented to approximate the ambient temperatures along the piston skirt. The two temperatures were first estimated, then adjusted by the iterated proces, for predicting piston temperatures, according to the energy balance of the whole engine energy system. In order to verify the predicted values, input data for cycle simulation were obtained, the piston temperatures were also measured. In this way the good agreement between the model and experimental results could be checked.     

考虑活塞裙部润滑状态的活塞二阶运动分析及活塞设计参数的研究

将活塞的动力学方程与活塞裙部一缸套间流体动力润滑分析相结合,分析了活塞的二阶运动。并从减小活塞的二阶运动和摩擦功耗两个方面研究了活塞结构参数的设计。所获得的结果对实际具有指导意义。