考虑润滑油供给条件的油环-缸套摩擦副润滑分析

内燃机油环-缸套摩擦副润滑分析,多采用富油条件或假定某种特殊边界条件,与油环-缸套摩擦副实际润滑油供给状况不相符。以某四行程内燃机为研究对象,研究油环-缸套间润滑油流动与供给,确定油环进口油膜厚度;在此基础上,根据流量平衡和压力平衡,确定油环上、下轨各段工作面边界条件,并分别对各段求解Reynolds方程,分析油环-缸套摩擦副在计及润滑油供给条件下的润滑性能,并与富油状况对比。研究结果表明,计及供油状况下,油环-缸套摩擦副在上、下行程的润滑性能不对称,最小油膜厚度、最大油膜压力、摩擦力及摩擦功耗与富油状况均有一定差异,特别是在上行程差别显著。可见,考虑进口润滑油供给条件分析内燃机油环润滑性能,将对活塞环-缸套摩擦副的设计信赖性产生积极影响。     

内燃机缸套活塞环系统的摩擦学设计

本文在系统思想的指导下,采用理论分析与润滑计算相结合,对内燃机摩擦副缸套一活塞环系统在正常工作时的摩擦,润滑、磨损等摩擦学行为进行了探讨,并根据研究结果。以桶面环为对象,以Ｓ１９５单缸紫机机的参数为例,编掉了通用内燃机摩这设计软件,以实现对内燃机缸套一活塞环系统的摩擦学设计和使用效果的预测。     

内燃机活塞环-缸套润滑研究的现状与展望

从润滑分析和试验测量两个方面论述了内燃机活塞环-缸套摩擦副润滑研究的现状和进展,讨论并展望了活塞环-缸套摩擦副润滑研究中需要进一步解决的问题.     

缸套温度对活塞环润滑的影响

内燃机摩擦副的摩擦学性能对整机性能和可靠性有重大的影响。低摩擦技术的开发和应用能有效的降低摩擦功耗,提高内燃机的工作效率,其中活塞和活塞环的摩擦损失所占比例最大,所以本课题通过在保证缸套平均温度相同的情况下,尝试不同的平均温度分布方式,研究有利于降低活塞环摩擦功耗的分布方式。在合适的温度分布的情况下,可以使润滑效果达到一个良好的状态,从而提高热效率,对内燃机产生较为积极的影响。     

表面粗糙度对发动机活塞环-缸套润滑状态及摩擦功耗的影响

本文应用“平均”形式的Reynolds方程研究了表面粗糙度对发动机活塞环-缸套润滑状态的影响,分析研究了活塞环-缸套间的混合润滑效应。在研究中考虑了温度效应的影响,改善了以往混合润滑模型中的不足之处。还联系实际分析了S195柴油机环组的润滑状态,定量地给出了S195柴油机环组在整个工作循环过程中的摩擦功耗值。     

表面形貌对活塞环密封及摩擦性能的影响

综合考虑活塞环表面形貌、弹性变形、运动面型线影响,建立柴油机活塞环-缸套摩擦副的弹性流体动压润滑计算模型,分析活塞环表面纹理方向及粗糙度大小对活塞环窜气及摩擦功耗的影响。研究发现,随着转速的提升,活塞的窜气量及摩擦功耗会加剧,导致发动机效率降低;活塞环-缸套摩擦副的表面纹理方向影响窜气量和摩擦功耗,采用活塞环横向纹理和缸套纵向纹理配合时,对活塞环窜气量及摩擦功耗的改善效果较好;活塞环和缸套的表面粗糙度对密封和润滑特性有较大影响,当缸套表面粗糙度增大时,窜气量先减小后增大,摩擦功耗先增大后减小,而在一定范围内,当活塞环表面粗糙度增大时,窜气量和摩擦功耗都减小。     

阳极PED技术制备活塞环表面陶瓷涂层的研究

在内燃机中,由于摩擦产生的输出功率损失达到20%,可见摩擦磨损是影响内燃机燃油效率的关键因素,其中,活塞环-缸套摩擦副产生的摩擦在内燃机摩擦中占比超过50%,因此,改善活塞环组件的摩擦学性能对提高内燃机性能有着重要的意义。本文对活塞环表面改性、活塞环表面织构、润滑条件等影响活塞环摩擦学性能的因素进行了阐述,着重对利用阳极等离子体电解沉积(PED)技术制备活塞环表面涂层的技术研究进行了介绍,并给出一种利用该技术制备陶瓷涂层的方案供参考。     

内燃机缸套-活塞环摩擦学研究回顾与展望

内燃机缸套-活塞环摩擦副是一个典型的摩擦学系统,其中含有多种类型的摩擦和磨损,润滑、摩擦、磨损的相互作用十分显著。其摩擦学性能对提高内燃机的可靠性和耐久性,保证内燃机经济、可靠地工作具有决定性的作用。其摩擦学问题的研究一直是人们关注的热点之一。     

新型活塞环的润滑密封性分析

分析发动机活塞环及其密封原理,设计一种新型发动机组合式活塞环,建立其润滑分析模型,并采用差分法进行计算。结果表明,设计的发动机组合式活塞环能满足润滑的要求,且在上止点时(360°)的润滑油膜最大压力也在承载范围之内。发动机气密分析实验表明,该组合式活塞环密封性能好于两气环,但相对三气环还存在不足。     

缸套表面环槽织构润滑性能数值分析

为了改善缸套-活塞环摩擦副润滑性能,在缸套表面采取了环槽织构措施,通过数值计算的方法,研究了环槽形新型织构的润滑摩擦机理,并对比分析了环槽与圆形凹腔织构润滑性能的差异。结果表明:当活塞环经过环槽织构时,在运动方向上,环槽中心圆柱前槽与后槽分别产生油膜压力较小与较大的动压润滑效应,即环槽能产生二次动压效应;与相同外径的圆形凹腔织构相比,存在一个最佳槽宽能有效改善润滑摩擦性能,在此数值以外,合适的槽宽能使环槽润滑性能较好,相比于圆形凹腔织构,润滑油膜压力分布更为均匀,最小膜厚比增加,摩擦力和摩擦平均有效压力均呈下降趋势,其原因是二次动压效应与面积占有率对环槽影响的叠加中,前者占据了主导地位;过小的槽宽会使得环槽织构润滑效果恶化。     

表面粗糙度和润滑油黏度对活塞裙-缸套摩擦副润滑性能的影响

以一多缸内燃机为对象,研究表面粗糙度和润滑油黏度对活塞裙-缸套摩擦副润滑性能的影响。建立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,表面粗糙度对活塞裙-缸套摩擦副润滑性能影响不明显,而随润滑油黏度增加,活塞裙-缸套摩擦副的最小油膜厚度、摩擦力和摩擦功率增加,最大油膜压力在进气和排气行程随润滑油黏度变化比较明显,在其他行程变化较小。     

Piston ring friction loss behaviour for motored and fired reciprocating engines

A previously developed piston ring lubrication model has been further extended so that the piston ring frictional losses can be predicted in both hydrodynamic lubrication and metal-to-metal contact regions for various engine operating conditions. Ring friction results for two engine types are presented for both hot motoring and engine firing conditions. The hot motoring predictions were found to be in good agreement with tests. Results show that when the engine is motored, piston ring friction losses in the hydrodynamic lubrication region predominate. If the engine is fired, the losses in the metal-to-metal contact region become dominant due to high gas pressure and temperature effects. Ring friction loss can be significantly reduced by using low tension rings with a correct ring sliding face profile.     

Analysis of ring pack lubrication

This paper describes a method developed for the simulation of ring pack lubrication characteristic in an internal combustion engine. In general, the quantity of oil supply for piston ring lubrication may be insufficient in filling the entire volume formed at the interference between the piston ring and the cylinder liner. Thus the oil starvation condition should be considered in analyzing piston ring lubrication. In order to reasonably estimate the amount of oil left over on the cylinder liner, the flow rate at the posterior portion of the interface should be calculated with an adequate boundary condition that confirms flow continuity condition. In this analysis, oil starvation and open-end boundary conditions are considered at the inlet and outlet of the piston rings. The lubrication characteristic of each piston ring is obtained by an iterative method with sequential steps. It is revealed that piston rings are operated under oil starvation in most operating cycles and the result under these conditions are quite different from that with the fully-flooded assumption.     

Friction characteristics of piston rings in a reciprocating engine

The performance of a reciprocating engine can be improved by reducing the friction between piston rings and cylinder liner, which significantly contributes to the mechanical friction losses of an engine. The friction force of a piston ring pack is calculated, based on hydrodynamic lubrication theory, for the piston rings. Calculations were carried out for three sets of conditions. Oil starvation is taken into consideration in the calculation of oil-film behaviour for a ring pack. The friction characteristics of piston rings are evaluated using the frictional mean effective pressure. The friction force of a piston assembly is measured experimentally by an improved floating liner method. The effects of lubricant viscosity and engine speed on friction characteristics are investigated by both calculation and experiment.     

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.     

Theoretical Analysis of Piston-Ring Lubrication Part I—Fully Flooded Lubrication

A one-dimensional analysis for lubrication between the piston ring and cylinder wall has been developed. A fully flooded inlet condition and axisymmetric geometry are considered. The piston ring is treated as a reciprocating, dynamically-loaded bearing with combined sliding and squeeze motion. A system of two nonlinear differential equations is used to model the lubrication including the Reynolds cavitation boundary condition. A numerical procedure is then developed to obtain the cyclic variations of film thickness, frictional force, power loss, and oil flow across the ring.

Results are presented for a typical automotive engine. The effects of ring profile, ring tension, and engine speed are examined. It is shown that this analysis can be used to study the influence of ring design parameters in order to improve the design of the ring pack in reciprocating engines.     

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。     

内燃机活塞环组密封性能研究

为检验活塞环的密封性,进一步研究其摩擦学性能,建立内燃机环组密封数值仿真模型,模型中考虑气室体积、泄漏面积、内燃机运转工况和气室温度变化项等因素对活塞环密封性能的影响.以PA6-280柴油机为例,对活塞环组的密封性能进行仿真计算.结果表明,磨损对环组的密封性能影响很大,而工况对活塞环的密封性影响不是很明显;气室温度变化项对活塞环漏量影响较大,设计时不容忽视.     

活塞环的润滑与应力分析

以边界润滑模型分析活塞环－气缸的润滑、摩擦过程,提出活塞环的粘着磨损的模型：计算活塞环的应力分布。活塞环内的应力场的分析结果表明：层状剥落的粘着磨损是活塞环磨损的主要形式。本文提出了对数母线的桶面压缩环设计,探讨活塞环的最优化设计,提高活塞环的抗磨损能力,延长使用寿命。