Piston-ring and Cylinder-liner Lubrication in Internal Combustion Engines Based on Thermo-hydrodynamic

Currently the extruded effect,roughness to the lubricant shear thinning,temperature changes and other factors or some combination of a single factor mainly considered in the lubrication study of piston ring-cylinder.In the study of the energy equation,the oil viscosity-temperature properties,adsorption layer characteristics are usually not considered.So the theoretical research is different from the actual situation of engineering.The lubrication of piston ring-cylinder liner system in internal combustion(IC) engines is studied here based on the theory of thermal flow.An unsteady and compressible hydrodynamic lubrication model with an equivalent viscosity based on shear and extruded flow factor is derived by employing the viscosity-temperature relationship,meanwhile,characteristics such as lubricating oil’s density varying with pressure and temperature,thickness of adsorbent layer and oil film’s geometry are also considered in this model.While setting up the energy equation,the effect of lubricating oil’s volume expansion and viscous dissipation on temperature,the heat conduction along oil film’s thickness direction are considered.Finite difference equation is formed by using a first-order difference scheme in time scale and second-order difference scheme in space scale.A common diesel engine is introduced as an instance to predict the distribution of the minimum oil film thickness in the piston ring-cylinder liner system.The results of simulation calculation show that the minimum oil film thickness will decrease especially around the top dead center when the oil’s volume expansion,viscous dissipation and heat conduction are considered,which implies that:it is essential to take the thermal flow idea into account during investigating piston ring-cylinder liner system’s lubrication.A more complete piston ring-cylinder liner lubrication theory was established according to thermal fluids from the perspective of research.It is more helpful to guide the practical application of engineering to improve the accuracy of forecasting the minimum film thickness.On the other hand,distribution of the minimum oil film thickness shows a nonlinear property if the thickness of piston rings and cylinder liner adsorbent layer are involved in the analysis.It may be feasible to increase the minimum oil film thickness by varying surface roughness and material properties of piston rings and cylinder liner.

THE NUMERICAL ANALYSIS OF UNSTEADY HEAT TRANSFER OF A PISTON-LINER COUPLED SYSTEM IN AN INTERNAL COMBUSTION ENGINE

This paper provides a numerical analysis model of unsteady heat trans-fer in piston-liner set of an internal combustion engine.The model simulates the un-steady heat transfer process among the combustion mixture,piston set,lubricantfilm,liner and coolant in a whole engine cycle,and can predict the temperature fluc-tuation and distribution on piston crown,inner surface of liner,piston ring and thelubricant film.A computer program is developed to calculate the unsteady heat trans-fer process of piston-liner system in a water-cooled diesel engine.

基于改进EEMD-MB1DCNN的船用柴油机缸套-活塞环故障诊断

针对船用中高速柴油机缸套-活塞环振动信号非线性非平稳性以及同类型不同损伤程度故障发生时振动信号时频域特征相似、故障难以识别等问题,利用振动信号辨识故障,提出一种基于改进集成经验模态分解方法和多模块一维卷积神经网络端到端缸套-活塞环故障诊断方法,通过设计固有模态分量IMF信息质量筛选准则对EEMD分解出的IMFs进行重新排序,获得包含更多凸显故障特征成分的重构信号,输入到上述神经网络模型,通过振动信号分析并与现有方法比较,评估所设计IMF信息质量筛选准则与所搭建模型的性能,试验结果显示该方法能准确、有效地识别缸套-活塞环故障类型。在判断该易损件同类型不同磨损程度故障诊断中有较高的准确率,能对故障状况进行有效的特征提取与故障分类。

低硫条件下船舶主机缸套-活塞环磨损现状与应对策略

国际海事组织(IMO)的“限硫令”于2020年1月在全球范围内实施后,燃用低硫燃油(LSFO)成为许多远洋公司的主要选择。对多家远洋公司船舶主机燃用LSFO后的运行状况进行调研,发现缸套、活塞环等零部件存在异常磨损及故障显著增多的现象。将LSFO对船舶主机的影响以及其实际应用案例进行分析与总结,并针对燃用LSFO的主机所出现的异常磨损和故障现象提出应对策略。该研究有助于解决LSFO条件下船舶主机缸套和活塞环异常磨损问题的实际需求,希望进一步推动LSFO条件下缸套和活塞环异常磨损的机理研究。

合金灰口铸铁气缸套组织形貌与耐磨性研究

针对5种成分和组织的灰口铸铁气缸套,包括2种贝氏体铸铁气缸套和3种珠光体铸铁气缸套,全面分析了其成分、相组成及硬度等材料特性,将喷钼活塞环与5种合金灰口铸铁气缸套对磨,通过比较各配对副的摩擦磨损性能,获得了喷钼活塞环与5种合金灰口铸铁气缸套的匹配规律。研究结果表明:5种气缸套材料均为由硬质相、基体和石墨构成的复合耐磨结构,各组分的性能、分布及其配比,是决定耐磨性的关键因素。珠光体基体气缸套的磨损量相对稳定,气缸套与活塞环的相对磨损量正常;铸态贝氏体气缸套磨损较轻,配对活塞环的磨损量比珠光体气缸套大;贝氏体气缸套和活塞环的磨损均量很小。

机体表面振动信号影响因素关联性分析

为了研究机体表面振动信号各影响因素的影响规律,在不同转速、转矩、润滑油温度及配缸间隙下,对比分析振动信号的峰值、方差、标准差及均方根等4个时域参数以及小波包分解得到的各频段能量的变化趋势。结果表明:随着转速的升高,燃烧压力峰值出现波动,在活塞惯性力的主导作用下,振动信号时域特征参数及频段5以上频率成分的能量呈增加的趋势;燃烧压力峰值随着转矩的增加而增大,振动信号时域特征参数及各频段能量均呈增加的趋势;随着润滑油温度的升高,在润滑油阻尼及燃烧压力的双重作用下,振动信号时域特征参数幅值整体呈降低的趋势,频段12以上频率成分的能量呈增加的趋势;随着配缸间隙的增加,密封性降低导致燃烧压力峰值减小,但由于活塞二次运动加剧,导致振动信号时域特征参数及频段5以上频率成分的能量呈现增加的趋势。

基于激光熔覆的缸套表面梯度材料制备及其摩擦学性能研究

目的研究功能梯度材料对缸套表面的抗磨减摩作用,提升缸套-活塞环配副的摩擦学性能。方法通过激光打标机在缸套表面制备具有30°角规则纹理排布的凹槽,在凹槽内采用同轴送粉的方式熔覆镍含量不同的铁基粉末,分析熔覆合金层的金相组织,并利用往复式摩擦磨损试验机研究在一定载荷压力下功能梯度材料缸套的摩擦学性能。结果熔覆层金相组织呈现梯度排布,熔覆层与基体材料分子原子交互扩散形成良好的冶金结合。牌号为350、镍质量分数为4.2%、铁质量分数80%的粉末所制备的功能梯度材料,减摩效果最为明显,相比未经处理的对照组,平均摩擦因数降幅为25.4%,且该组在试验中接触电阻的平均值最大,相比对照组提升了63.45%。牌号为330、镍质量分数为9%、铁质量分数为70%的粉末制备的缸套,表面支撑指数最高为0.78,相比于未处理的对照组,增幅达到35%,且试验组活塞环经摩擦后,磨损量均小于对照组。结论制备了30°角分布的功能梯度材料,能使得缸套-活塞环摩擦学系统在工作过程中摩擦副的润滑油膜厚度更厚,且在运行过程中更稳定,以减少摩擦力和降低摩擦因数。同时,增强其支撑能力和储存润滑油的能力,使所制备的缸套摩擦因数显著降低。牌号为350的材料,改善摩擦学性能的效果最优。

考虑时变效应的织构缸套润滑性能分析及试验研究

内燃机缸孔内的时变效应和气压变化对活塞环受力影响不可忽略,而织构形貌参数对发动机油耗性能的影响也有待深入研究。为此,构建考虑时变效应和缸内气体压力变化的织构化缸套-活塞环摩擦副的流体动压润滑模型,采用多重网格法求解模型获得润滑油膜压力分布规律,进而获得缸套-活塞环间的最小油膜厚度和摩擦力,并针对装配织构缸套的发动机开展台架试验。计算结果表明:缸内气体压力变化影响活塞环径向受力,时变效应使缸套-活塞环受挤压效应的影响;织构化缸套能够增加润滑油膜厚度、减少摩擦力,当微凹坑深度为4~7μm,织构面积密度较小如为5%、10%时,能够获得较佳的最小油膜厚度与摩擦力值。台架试验表明,与原发动机相比,装配织构缸套的发动机油耗性能明显改善,在中高转速下燃油耗降幅较为显著,油耗最大下降14.5%,而24 h机油耗减少26.48%。

柴油机活塞缸套摩擦副润滑和多柔体动力学耦合特性

为研究四冲程车用柴油机活塞-缸套摩擦副的动力学及润滑特性,提出了一种新的活塞-缸套摩擦动力学耦合模型.模型中采用绝对节点坐标公式(ANCF)描述活塞-连杆-曲轴多柔体动力系统,采用平均雷诺方程和微凸体接触理论描述混合润滑模型,基于商用软件结合二次开发程序实现仿真计算.对活塞缸套摩擦副的润滑动力学计算分析表明,由于缸内压力和活塞敲击作用,缸套会产生最大值为23.6μm的瞬时变形.与刚体模型相比,考虑部件的弹性变形不仅会使活塞横向位移增加40%,还会使得活塞润滑域出现油膜压力的局部集中.另外,柔体模型的循环平均功耗更小,与刚体模型相比相差17.7%.

考虑温度分布和初弹力影响的活塞环-缸套试验台研究

为探究活塞环初弹力作用下不同缸套温度对活塞环摩擦性能的影响,设计考虑缸套温度分布的活塞环初弹力摩擦性能试验台,其缸体-缸套组件基于浮动缸套方法设计,通过供油盖从顶部供润滑油,使用活塞环夹具安装活塞环,在缸套外壁安装3个环形电加热器对缸套进行预加热。当活塞环未加载荷仅在初弹力情况下,仅改变缸套温度分布,研究不同缸套温度分布对活塞环-缸套系统摩擦性能的影响。结果表明:随着缸套温度的升高,活塞环-缸套摩擦副摩擦力和摩擦功耗呈现先减小后增加的趋势,对于研究的活塞环-缸套摩擦副,在缸套温度为60~70℃时,摩擦力和摩擦功耗最小。因此存在合适的缸套温度,使得活塞环-缸套摩擦副的摩擦性能最优。

基于活塞环-缸套边界润滑模型的表面织构摩擦学性能评估

高强化柴油机活塞环-缸套在上止点处的工作环境恶劣,多处于边界润滑状态。表面微织构被证明是改善表面摩擦学性能的有效手段,然而目前仍缺少考虑表面织构的边界润滑数值模型。建立了考虑表面织构和摩擦膜影响的活塞环-缸套边界润滑模型,并应用该模型开展了考虑表面织构影响的磨损量计算,计算结果与边界润滑试验结果规律一致,且优选的表面织构方案较无织构方案磨损深度降低了33.7%。

活塞-缸套摩擦副状态表征参数选取方法研究

建立柴油机试验台架采集数据,对机体表面振动信号进行时频分析,探明不同激励源与机体表面振动信号的关系。选取变分模态分解(variational mode decomposition,VMD)算法对振动信号进行分解,提取各分量的表征参数。通过探究转矩、转速、润滑油温度及配缸间隙与各表征参数的相关性,初步确定相关性强的表征参数集。通过多评价准则对上述表征参数集进行分析,最终得出贡献度最高的表征参数为本征模态函数(intrinsic mode function,IMF)1的标准差、均方频率、峭度、最大奇异值、频域积分和IMF6的脉冲因子、标准差、重心频率、频率方差及最大奇异值。

基于CPA-FM-MEM磨粒分析的缸套-活塞系统健康状态评估

以内燃机典型摩擦副缸套-活塞系统为研究对象,设计和搭建内燃机缸套-活塞系统状态监测试验台。针对传统最大熵方法分析润滑油中磨粒监测数据存在的缺点,提出改进的分数矩最大熵方法(Fractional Moment Maximum Entropy Method, FM-MEM),并结合食肉植物优化算法(Carnivorous Plant Algorithm, CPA)对关键参数进行寻优求解。对润滑油中磨粒监测数据进行阈值划分,实现内燃机健康状态评估,然后将理论与试验相结合,以在线磨粒监测为主,从润滑油磨粒、理化指标以及表面形貌3个方面对内燃机缸套-活塞系统的运行状态进行监测,分析低速工况下缸套-活塞系统各个时间段的磨损健康状态及磨粒含量变化趋势,通过内燃机整机的在线磨粒监测试验,证明该方法可实现对内燃机缸套-活塞系统的实时状态监测。

Effect of temperature on tribofilm growth and the lubrication of the piston ring-cylinder liner system in two-stroke marine engines

This study is an optimized extension based on the authors’previous research on the tribo-chemical reaction under constant temperature field of two-stroke internal combustion engines(ICEs).It establishes a coupled analysis model that considers the tribo-chemical reactions,dynamic contact,and interface lubrication of the piston ring-cylinder liner(PRCL)system under transient temperature conditions.In this study,for the first time,the prediction of the tribofilm thickness and its influence on the surface micro-topography(the comprehensive roughness)are coupled in the working temperature field of the PRCL system,forming an effective model framework and providing a model basis and analytical basis for subsequent research.This study findings reveal that by incorporating temperature and tribofilm into the simulation model,the average friction deviation throughout the stroke decreases from 8.92%to 0.93%when compared to experimental results.Moreover,the deviation during the combustion regime reduces from 39.56%to 7.34%.The proposed coupled model provides a valuable tool for the evaluation of lubrication performance of the PRCL system and supports the analysis software forward design in two-stroke ICEs.

活塞环表面MoS_(2)薄膜在干摩擦和贫油润滑条件下的摩擦学性能研究

大功率、长冲程和高爆发压柴油机是交通运输、工程机械、国防装备和核电应急发电机领域的重要动力设备。柴油机关键运动副活塞环-缸套在冷/热启动时,缸套的上下止点位置处于干摩擦或贫油润滑状态,易发生局部异常磨损导致动力性能丧失。为抑制活塞环-缸套运动副的异常磨损,采用磁控溅射技术在活塞环表面制备了MoS_(2)薄膜;利用SRV-IV微动摩擦磨损试验机模拟柴油机频繁冷/热启动工况,评价了表面附加MoS_(2)薄膜的活塞环与缸套摩擦副的摩擦学性能;利用扫描电镜(SEM)表征了MoS_(2)薄膜微观结构和摩擦前后摩擦副的表面形貌。结果表明:相比于原始CKS活塞环-缸套,MoS_(2)薄膜活塞环-缸套在干摩擦条件下的摩擦系数从1.07大幅降低至0.11,缸套磨损率从8.61×10^(-6) mm^(3)/(N·m)降低至3.71×10^(-8) mm^(3)/(N·m);在常温贫油条件下摩擦系数从0.18降低至0.11,磨损率从1.43×10^(-7) mm^(3)/(N·m)降低至3.22×10^(-8) mm^(3)/(N·m);在高温贫油条件下摩擦系数从0.12降低至0.08,磨损率从7.08×10^(-8) mm^(3)/(N·m)降低至1.12×10^(-8 )mm^(3)/(N·m);摩擦过程中活塞环表面MoS_(2)薄膜的转移是摩擦副摩擦学性能提升的主要原因。

某柴油机拉缸原因分析与处理

为排查某型柴油机拉缸事故的原因,采用故障树的方法对可能的原因逐一进行检查分析,确定高负荷工况下紧急停车,缸套产生裂纹末及时处理是拉缸的原因。恶劣工况后的隐患排查是柴油机安全运行的重要措施。

Experimental Study on Wear Performance and Oil Film Characteristics of Surface Textured Cylinder Liner in Marine Diesel Engine

It is of a vital importance to reduce the frictional losses in marine diesel engines. Advanced surface textures have provided an e ective solution to friction performance of rubbing pairs due to the rapid development of surface engineering techniques. However,the mechanisms through which textured patterns and texturing methods prove beneficial remains unclear. To address this issue,the tribological system of the cylinder liner?piston ring(CLPR) is investigated in this work. Two types of surface textures(Micro concave,Micro V?groove) are processed on the cylinder specimen using di erent processing methods. Comparative study on the friction coe cients,worn surface texture features and oil film characteristics are performed. The results demonstrate that the processing method of surface texture a ect the performance of the CLPR pairs under the specific testing conditions. In addition the micro V?groove processed by CNCPM is more favorable for improving the wear performances at the low load,while the micro?con?cave processed by CE is more favorable for improving the wear performances at the high load. These findings are in helping to understand the e ect of surface texture on wear performance of CLPR.

Syntheses and Tribological Property of CrMoN/MoS2 Multilayer Films on Piston Rings of Heavy Vehicle Engine

In order to prolong the service life of piston rings of heavy vehicle engine and decrease the friction and wear of piston rings and cylinder liner,CrMoN/MoS_2 multilayer films were deposited on the surface of rings by magnetron sputtering and low temperature ion sulfuration.FESEM equipped with EDX was adopted to analyze the compositions and morphologies of surface,cross-section,and wear scars of the multilayer films.The nano-hardness and Young＇s modulus of the films were measured by a nano tester.Tribologicalproperties of the films were tested by an SRV~174;4 wear tester.The experimentalresults indicate that the structures of the multilayer films are dense and compact.The films possess nano hardness value of approximately 26.7 GPa and superior ability of plastic deformation resistance.The multilayer films can activate solid lubricating,and possess an excellent antifriction and wear resistance under the conditions of heavy load,high frequency,high temperature,and dynamic load.

基于缸套失圆的活塞环结构参数对密封与摩擦性能的影响研究

以某非道路高压共轨柴油机为研究对象,采用仿真和测试相结合的方法,建立了整机耦合装配模型与活塞环组动力学模型,研究了干式缸套的失圆变形。在考虑缸套失圆变形的基础上,研究了活塞环结构参数对窜气量、机油消耗量和摩擦损失的影响,并通过正交设计方法进行了活塞环径向弹力、开口间隙和侧向间隙对窜气量、机油消耗和摩擦损失的影响研究。研究结果表明,活塞环结构参数中,二环径向弹力、二环开口间隙和顶环侧向间隙对窜气量的影响最大,油环径向弹力、二环开口间隙和顶环侧向间隙对机油消耗量的影响最大,油环径向弹力、油环开口间隙和油环侧向间隙对摩擦损失的影响最大。

流体润滑条件下复合润滑织构改善缸套表面摩擦性能

为了改善缸套表面摩擦性能,以YTRC2110D型柴油机为研究对象,在缸套流体润滑区域进行复合润滑结构设计.基于摩擦试验,探讨了润滑条件下复合润滑结构改善缸套表面的摩擦性能和磨损机理,并找到性能最优的复合润滑结构.结果表明,在流体润滑条件下,复合润滑结构比单一微织构减摩性能更好.相比光滑表面,单一微织构表面平均摩擦系数下降32.86%,磨损质量最多只降低9.6%,磨损表面粗糙度Sa最高只下降了16.57%,分形维数D只上升4.67%.其表面磨损区域主要为浅犁,还伴随着少量的深犁,复合润滑结构表面平均摩擦系数可以下降42.2%,磨损质量最多减少了17.6%,磨损表面粗糙度Sa最高下降26.86%,分形维数D上升8.77%.复合润滑结构接触表面通过动压油膜和二硫化钼转移薄膜共同作用,磨损表面只产生少量浅犁.研究结果为缸套表面摩擦性能的改善提供了理论依据.