论文部分内容阅读
目前,随着可再生生物燃料的使用,考虑到从种植、燃料生产到汽车使用的整个生命周期,乙醇在弹性燃料汽车上的应用被认为是低二氧化碳排放的代用方案。在巴西,80%以上的量产汽车都使用弹性燃料。由于乙醇热值较低,为了获得相同的发动机功率,与汽油相比,乙醇的燃烧标定更为激进。这种燃用乙醇时不断增加发动机比功率的需求所产生的机械热负荷对活塞环摩擦学特性是一种挑战。乙醇的使用也带来一些特定的未被明确的摩擦学差异,如燃料稀释润滑油(尤其是在冷起动时),以及具有腐蚀性的工作环境等。在特定的驾驶条件下,曾观察到氮化钢的第1道活塞环表面剥落等早期失效情况。当采用乙醇运行时,弹性燃料发动机呈现更高的最高燃烧压力,并且该峰值出现在曲轴转角上止,点附近。这种状况增加了活塞环的磨损、擦伤的风险及摩擦学上的困难,这些都可能导致氮化层的裂纹及剥落。从摩擦学角度探讨弹性燃料发动机的第1道活塞环性能。讨论了弹性燃料发动机使用乙醇后对第1道活塞环的磨损、擦伤、氮化层剥落及摩擦等特性的影响。用发动机试验来评定耐磨损性和耐剥落性。有关擦伤,进行了环块法摩擦磨损试验,并给出了活塞环的涂层分级。还讨论了第1道活塞环的摩擦特性及对燃油耗的影响。给出了发动机浮动气缸套的试验结果。最后,讨论了克服这些挑战的活塞环技术方案。其中,有改进氮化处理以增加韧性的钢制活塞环,以及应用一种物理汽相沉积涂层,以提高耐磨损性和摩擦特性。介绍了一些摩擦试验台和发动机试验,以支持所讨论的技术方案。发动机试验基于严酷程序,目的是证明或预测弹性燃料发动机燃用乙醇时对性能的影响。
At present, with the use of renewable biofuels, the application of ethanol to flexible fuel vehicles is considered as a substitute for low carbon dioxide emissions, taking into account the entire life cycle from planting and fuel production to vehicle use. In Brazil, more than 80% of production cars use flexible fuel. Due to the lower heating value of ethanol, the combustion calibration of ethanol is more aggressive than gasoline in order to obtain the same engine power. The mechanical heat load created by this increased demand for engine specific power when burning ethanol is a challenge to the tribological properties of piston rings. The use of ethanol also brings with it some specific and undefined tribological differences, such as the dilution of fuels (especially at cold start), corrosive working conditions and the like. Under certain driving conditions, it was observed that the first piston ring surface of the nitrided steel peeled off early failure conditions. When operating with ethanol, the elastomeric engine exhibits a higher maximum combustion pressure, and the peak appears above and near the crank angle. This condition increases the wear of the piston rings, the risk of galling and the tribological difficulties that can cause cracks and flaking of the nitrided layer. Discussion on the performance of the first piston ring of the elastic fuel engine from the perspective of tribology. The effects of ethanol on the wear and abrasion, flaking and friction of the first piston ring on the elastic fuel engine were discussed. Engine testing was used to evaluate the wear and spalling resistance. For abrasion, a ring-block friction and wear test was carried out, and the coating grade of the piston ring was given. The friction characteristics of the first piston ring and its effect on fuel consumption are also discussed. The test results of the floating cylinder liner are given. Finally, piston ring solutions to overcome these challenges are discussed. Among them, there are steel piston rings with improved nitriding to increase toughness, and a physical vapor deposition coating to improve abrasion resistance and frictional characteristics. Some friction test stands and engine tests are introduced to support the technical solutions discussed. Engine tests are based on harsh procedures designed to demonstrate or predict the performance impact of EFE engines when using ethanol.