活塞销偏置对润滑油消耗的影响

基于润滑油消耗机制,以某型12v柴油机为研究对象,建立活塞组件动力学仿真模型,分析活塞销偏置方式和活塞销偏置量对于润滑油消耗的影响.结果表明:活塞销偏置方式总体趋势是使润滑油的消耗减少,窜油和甩油得到明显改善,其中活塞销偏副推力侧(Anti-Thrust Side,ATS)对润滑油的消耗减少的效果最好;活塞销偏置量对润...     

Observation of lubrication conditions using an ultrasonic technique

Evaluation of lubrication conditions for a real frictional surface, such as a steel bearing, becomes an important issue for safe operation of a machine. In this paper, an application of ultrasonic technique is attempted for a purpose of evaluating the lubrication conditions. Ultrasonic waves emitted towards a hydrodynamic lubrication interface are reflected multiple times in oil film, and an echo height of reflected waves from the boundary is dependent on film thickness. The results of this study indicated that the ultrasonic technique is able to measure film thickness of approximately 50 nm in the case of a standstill surface having extremely small surface roughness. Furthermore, a potential for estimating the oil film thickness between a piston ring and cylinder is also indicated. In addition, in the case of a ball bearing, quantitative measurement of a size of dent, which forms the origin of flaking, is important for an evaluation of lubrication conditions. This becomes possible with an observation of a change in the echo height reflected from a boundary surface between a housing and an outer ring of the ball bearing. In this study, quantitative measurement of an indentation having 0.32 mm width on a raceway surface of an inner ring was achieved. Copyright © 2009 John Wiley & Sons, Ltd.     

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。     

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。     

Friction model of a marine diesel engine piston assembly

In modern marine diesel engines, power output and in-cylinder firing pressures are constantly increasing, leading to higher friction in engine components and especially in the piston assembly. A good understanding of the friction contributions of the various engine components is needed, if mechanical efficiency is to be improved. A friction model for the engine piston assembly has been developed and is presented in this paper. The model, based on lubrication theory, considers the detailed engine geometry and the complete lubricant action, and thus can be applied to a wide range of engines. In detail, the analysis takes into account the friction components of compression rings, oil control rings, piston skirt and gudgeon pin of the engine piston assembly. The model was applied to a four-stroke (medium speed) marine diesel engine and the effect of engine speed and load on friction was examined and compared with results from other semi-empirical models. The engine friction was predicted at constant rotational speed (generator operation) and variable rotational speed (propulsion operation).     

表面粗糙度对不对中滑动轴承润滑特性的影响

以活塞式航空发动机滑动轴承为研究对象,综合考虑轴颈倾斜和轴瓦表面形貌等因素对轴承润滑特性的影响,建立滑动轴承润滑分析模型;以高斯随机表面、分形曲面、非高斯随机表面分别模拟轴瓦表面的粗糙程度,分析轴颈不对中和表面粗糙度耦合作用下油膜压力、端泄流量、承载力和轴承力矩等参数随偏心率和转速的变化规律。研究结果表明:考虑轴瓦表面形貌后轴承最大油膜压力变大,最小油膜厚度有小幅度减小;随着偏心率和转速增加,最大油膜压力、端泄流量、轴承承载力、工作力矩均增加;随着偏心率增加,考虑表面形貌时(高斯表面、分形表面、非高斯表面)的轴承油膜压力、承载力、工作力矩均变大;随着转速的增加,考虑表面形貌时的轴承润滑特性均变大,尤其是高斯表面,润滑特性变化较明显。     

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.     

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.     

考虑贫油和高边界压力的发动机顶环-缸套润滑与承载性能分析

为降低发动机润滑油消耗以及由此带来的排放,活塞环缸套系统一般处于贫油润滑状态,特别是顶环与缸套间的贫油状况更严重。贫油状态下,活塞环-缸套间润滑油膜在出口区破裂后很难再形成,同时在燃烧上止点附近的高边界压力下气体承载也难以忽略。因此,以某柴油机顶环-缸套系统为分析对象,基于平均雷诺方程和无再形成边界条件,分析贫油和高边界压力下顶环-缸套界面间的润滑、接触和气体承载问题。研究结果表明,贫油工况下,由于油膜破裂后没有再形成,高边界压力的影响显著,对高爆压强化机型来说顶环-缸套间的气体承载力甚至会大于油膜承载力和接触承载力。     

应用探针式电容传感器检测发动机润滑油品质的研究

应用探针式电容传感器测量润滑油中固体颗粒含量的原理,是根据固、液体混合物在电容器两极板之间介质的介电常数变化而使电容发生变化。应用该原理设计出了一套润滑油油品监测系统,简称为YPT系统。应用该系统,对发动机润滑油中的铁、硅固体微粒含量变化与电容变化的相互关系进行了初步探讨,并建立起来了一种新的润滑油品质YPT评价标准。这个新的评定标准,为确定发动机润滑油的更换周期及预测发动机的使用寿命等方面的研究,提供了一种比较简便实用的科学依据。     

基于JFO边界条件的连杆衬套润滑特性理论分析

采用有限差分法求解基于JFO(Jakobsson-Floberg-Olsson)边界条件(即质量守恒边界)下的雷诺方程,推导出连杆衬套油膜压力分布、油膜厚度、油膜承载力、润滑油端泄量表达式;建立连杆衬套在贫油润滑状态下的油膜压力分布模型,分析载荷对连杆衬套轴心轨迹位置、最大油膜压力和最小油膜厚度的影响。结果表明:在不同曲轴转速下,连杆衬套的润滑特性具有相同的变化规律,且在柴油机做功行程上止点的附近区域的油膜端泄量大于供油量,导致油膜的完整性被破会,形成空穴发生边界摩擦,甚至干摩擦或者磨损;连杆衬套与活塞销的最佳相对间隙为0.025%~0.05%。     

Temperature–friction characteristics of used lubricant from two-stroke cross-head marine diesel engines

It is now quite apparent that, in a two-stroke, cross-head marine diesel engine, the lubrication regime in the contact between piston ring and cylinder liner at the top dead centre (TDC) is of a boundary type. Therefore, the tribological performance of a system to simulate the real contact should be assessed under conditions closely resembling the operating engine environment. In the reality of engine operation, the lubricant is often contaminated by fuel and products of combustion, hence the need to study the temperature–friction characteristics of this actual lubricant under the conditions of boundary lubrication.In this paper, an oil taken from the drainage system of the engine was used. A five times heating and cooling test methodology was employed to assess tribological performance of a model contact lubricated with the actual oil. The model contact was formed by a pin sliding over a plate both made of materials used in two-stroke, cross-head marine diesel engines.Experiments showed that the general trend in temperature–friction characteristics of the used oil is similar to that of a new oil. However, the level of friction in the contact lubricated with an used oil is significantly higher than that for a new oil.     

Analytical Investigation on the Effect of Multigrade Oil in Piston Ring Lubrication

The use of multigrade oil in engine lubrication is being advocated to consumers to minimize viscosity-temperature effect. However, its effect on piston ring-liner contact has not been fully ascertained. In this work, an attempt has been made to evaluate the friction behavior of multigrade oil in piston ring lubrication. The theoretical model developed by the authors predicts thinner oil films as a result of introduction of multigrade oil in the hydrodynamic zone and a larger piston travel distance near the TDC region in the compression-power stroke cycle without any appreciable film thickness. The multigrade oils are known to offer elasticity, and this is also considered in the analysis to evaluate film thickness.     

Calculation of mixed lubrication at piston ring and cylinder liner interface

This paper reports on the theoretical analysis of mixed lubrication for the piston ring. The analytical model is presented by using the average flow and asperity contact model. The cyclic variations of the nominal minimum oil film thickness are obtained by numerical iterative method. The total friction is calculated by using the hydrodynamic and asperity contact theory. The effects of the roughness height, pattern, and engine speed on the nominal minimum film thickness, friction force, and frictional power losses are investigated. As the roughness height increases, the nominal oil film thickness and total friction force increase. Also, the effect of the surface roughness on the boundary friction is dominant at low engine speed and high asperity height. The longitudinal roughness pattern shows lower mean oil film pressure and thinner oil film thickness compared to the case of the isotropic and transverse roughness patterns.     

能量法对活塞销力信号的故障诊断

利用Pro/E软件建立单缸发动机参数化模型,导入ADAMS仿真分析不同工况且不同活塞销状态下工作情况,然后对数据进行了基于能量法的分析,得出活塞销故障诊断方法。能量值发生阶跃以及能量处于不稳定状态是活塞销的故障特征之一。     

润滑油粘度对缸套/活塞环摩擦学性能的影响

在内燃机实际运行中,润滑油的粘度直接影响到润滑油膜的状态,因而活塞环在缸套中不同位置时的摩擦、润滑状态各不相同。文中以缸套活塞环为研究对象,建立了润滑计算模型,并运用该模型对缸内压力、温度、油膜厚度和摩擦系数进行了分析。结果表明,润滑油膜厚度和摩擦系数随转速改变而发生变化,而剪切稀化导致润滑油粘度减小是引起该变化的主要原因。最后,通过对计算结果的分析,提出了适用于缸套活塞环的润滑油粘度指标。     

Lubrication characteristics analysis of slipper bearing in axial piston pump considering thermal effect

In this study, the lubrication characteristics of a slipper bearing for axial piston pump considering oil thermal effect have been investigated. A mathematical model is developed to predict the film thickness and temperature on the slipper/swash plate interface under different operating conditions. Based on the mathematical model, a parametric study is conducted to evaluate the slipper lubrication performance. It is found that the slipper is characterised by an unstable behaviour and the behaviour is enhanced by lower pressure and higher rotational speed. As the film temperature increases rapidly due to high shaft speed and piston chamber pressure, the overall result is a rather low decline in the film thickness. The leakage flow rate increases with increasing speed or oil film thickness. The structure parameter can be optimised to obtain satisfactory slipper performance. Copyright © 2015 John Wiley & Sons, Ltd.     

3D heat transfer,lubrication and friction coupled study for piston ring-liner on diesel engines

The piston ring and liner of internal combustion engines are generally used under increasingly harsh conditions. To investigate the mechanisms affecting the work ineffective, the coupled heat transfer, lubrication and friction model between the piston ring and liner is proposed by coupling the gas, piston set-liner, lubrication film and coolant. In this model, the temperature variation of lubricant, the gas blowby, the surface roughness, the rupture position and the non-axial symmetry of oil film are considered. The coupled heat transfer, lubrication and friction simulation is carried out for 6110 diesel engine, and the temperature fields of piston set-liner along with the corresponding lubrication and friction curves are obtained. The simulated results are verified by comparing with the temperature experiment of piston.

     

活塞结构对其传热及强度的影响分析

以一款满足国Ⅴ排放限值的高压共轨柴油机活塞为研究对象,采用硬度塞测温法试验测试分析了标定功率工况下活塞稳态温度场分布和热负荷的大小,结合温度场试验测试结果建立了内冷油道与活塞的流固耦合传热数值仿真模型,仿真分析了活塞销座长度、销孔直径、火力岸高度、同侧回油孔中心间距4个活塞结构参数对活塞传热与结构强度的影响。研究结果发现,活塞的火力岸、内冷油腔、回油孔和销孔处的热流密度较大并出现应力集中。选择活塞销座长度、销孔直径、火力岸高度、同侧回油孔中心间距4个参数,进一步研究活塞结构对其传热及结构强度的影响特征。结果显示,活塞的每个结构参数值改变不仅会较大程度地改变该处的传热性能和应力分布,还会导致其他关键点的应力和温度发生改变,这使得活塞结构修改需更加谨慎。适当增加销座长度、销孔直径和火力岸高度,减小同侧回油孔中心间距,可以改善活塞的受热,也可以降低活塞的整体应力。     

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。