激光微织构发动机缸孔表面的润滑理论与试验研究

发布时间：2018-06-21 22:00

本文选题：激光织构 + 缸孔-活塞环　；参考：《江苏大学》2016年硕士论文

【摘要】：缸孔-活塞环摩擦副系统是发动机中最为关键的摩擦副之一,其摩擦功耗占整个发动机的50~60%。激光表面微织构技术能够有效改善缸孔-活塞环摩擦副的摩擦学性能,减少摩擦磨损,提高整机燃油效率,实现节能减排的效果。本文以某型号发动机为研究对象,建立润滑理论模型,数值模拟润滑性能与织构形貌参数的关系,为设计发动机试验方案提供理论支撑,系统开展激光微织构工艺试验研究,并进行发动机的倒拖与台架对比验证性能试验。其主要内容如下。首先,考虑时变效应及缸内气体压力变化对活塞环背压的影响,建立微凹坑织构化缸孔-活塞环润滑理论模型。对数学方程进行无量纲化处理,利用有限差分法进行参数离散化,采用多重网格法求解离散后的雷诺方程,得到一个冲程全周期过程中缸孔-活塞环间的最小油膜厚度、无量纲摩擦力变化曲线,研究发现微凹坑深度与面积密度对摩擦副润滑性能影响较大,优化微凹坑几何参数能够显著提高缸孔-活塞环的润滑性能。然后,围绕缸孔激光微织构技术,开展了三种系列工艺试验。其一,为最大程度发挥缸孔表面织构形貌的优势,降低机械珩磨网纹形貌的干扰,减少发动机机油耗,应优化缸孔前处理表面粗糙度参数值,开展缸孔前处理镜面珩磨工艺试验研究。以五个缸孔表面关键参数为衡量指标(Rz"f2μm,Ra"f0.2μm和Rpk"f0.15μm,Rk"f0.4μm,Rvk"f1μm),主要研究珩磨条粒度、珩磨压力对缸孔表面粗糙度值的影响。珩磨条粒度与珩磨压力对缸孔表面参数影响较大,得到优化镜面珩磨加工工艺参数;其二,开展激光微织构工艺试验,揭示了激光工艺参数对微凹坑形貌的影响规律。结果表明,单脉冲能量、脉冲次数为关键加工参数,不同材料、涂层和波长对微凹坑几何参数的影响显著;其三,为去除激光织构产生的熔渣,减少发动机磨合时间,避免因熔渣剥落造成的磨粒磨损,需对织构后的缸孔进行去除熔渣后处理工艺试验。以缸孔表面Rz为指标参数,采用四因素二水平正交试验,确定合理的后处理工艺参数。最后,针对某型四缸汽油机,加工三种不同缸孔织构方案样机,进行装机后倒拖与台架试验。考察微凹坑形貌参数对发动机动力性能、油耗性能影响。倒拖试验结果显示,当缸孔上止点与中部行程区域面积密度为10%时,摩擦功耗表现出有益的效果。台架点火试验表明,经24小时机油耗对比,两种织构方案机油耗低于原机,最大降幅达26.48%;发动机万有特性曲线看出,发动机大部分工况下,三种织构发动机燃油耗低于原机,激光织构位置为上止点、行程中部区域,且微凹坑直径为70μm、深度为4μm、面积密度为10%时,瞬时工况的燃油耗最大降幅达15%。
[Abstract]:Cylinder hole-piston ring friction pair system is one of the most critical friction pairs in the engine, its friction power consumption accounts for 5060% of the whole engine. Laser surface microtexture technology can effectively improve the tribological performance of cylinder hole piston ring friction pair, reduce friction and wear, improve the fuel efficiency of the whole machine, and achieve the effect of energy saving and emission reduction. In this paper, a theoretical model of lubrication is established for a certain engine, and the relationship between lubrication performance and texture parameters is numerically simulated, which provides theoretical support for the design of engine test scheme. The experimental research on laser microtexture technology is carried out systematically. The performance test of the engine is compared with that of the bench. The main contents are as follows. Firstly, considering the influence of time-varying effect and the change of gas pressure in cylinder on the back pressure of piston ring, a theoretical model of micro-crater textured cylinder orifice and piston ring lubrication is established. The mathematical equation is dimensionless, the finite difference method is used to discretize the parameters, and the multigrid method is used to solve the discrete Reynolds equation. The minimum oil film thickness between the cylinder hole and the piston ring is obtained during the whole cycle of stroke. It is found that the depth and area density of micropits have a great influence on the lubrication performance of friction pairs. Optimizing the geometric parameters of micropits can significantly improve the lubrication performance of cylinder holes and piston rings. Then, three series of process tests were carried out around the cylinder hole laser microtexture technology. First, in order to maximize the advantages of the surface texture of cylinder hole, reduce the interference of mechanical honing mesh morphology and reduce engine oil consumption, the parameters of surface roughness should be optimized. Experimental study on honing process of pre-treatment mirror surface of cylinder hole is carried out. The effects of honing bar particle size and honing pressure on the surface roughness of cylinder bore were studied by using the key parameters of five cylinder holes (RZ "f 2 渭 m Ra" f 0.2 渭 m and Rpk "f 0.15 渭 m Rk" f 0.4 渭 m Rvk "f 1 渭 m),). The honing bar particle size and honing pressure have great influence on the surface parameters of cylinder hole and obtain the optimized processing parameters of mirror honing. Secondly the experiments of laser micro-texture technology are carried out to reveal the influence of laser processing parameters on the morphology of micro-pits. The results show that the single pulse energy and pulse number are the key processing parameters, and different materials, coatings and wavelengths have significant effects on the geometric parameters of the microcrater. Thirdly, in order to remove the slag produced by the laser texture and reduce the engine running-in time, To avoid abrasive wear caused by slag spalling, it is necessary to carry out post-treatment experiments on textured cylinder holes. Taking the cylinder hole surface Rz as the index parameter, four factors and two levels orthogonal test were used to determine the reasonable post-treatment process parameters. Finally, three different cylinder hole texture prototypes are processed for a four-cylinder gasoline engine, and the backward towing and bench test are carried out. The effect of microcrater shape parameters on engine dynamic performance and fuel consumption was investigated. The results of backward drag test show that the friction power consumption shows a beneficial effect when the area density between the upper stop point and the middle stroke area of the cylinder hole is 10. The bench ignition test shows that the fuel consumption of the two texture schemes is lower than that of the original engine after 24 hours' fuel consumption comparison, and the maximum decrease is 26.48. The engine characteristic curve shows that the fuel consumption of the three texture engines is lower than that of the original engine under most of the engine working conditions. When the laser texture is located at the upper stop point, the middle travel area is in the middle region, and the diameter of the microcrater is 70 渭 m, the depth is 4 渭 m, and the area density is 10, the maximum reduction of fuel consumption in the instantaneous working condition is 15%.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TK406

【相似文献】