【作者】 卢熙群；

【导师】 张文平；

【作者基本信息】 哈尔滨工程大学 ， 轮机工程， 2013， 博士

【摘要】 当前,人们对于活塞组件等运动部件的关注已经不只局限于传统的动力学特性,而是对运动与润滑、摩擦、磨损等摩擦学问题的耦合考虑。这种耦合特性对于发动机的可靠性、经济型、振动噪声等指标都有着重要的影响。活塞组件是内燃机中最重要的运动部件之一,建立一个基于动力学与摩擦学性能耦合分析的活塞组件性能仿真模型对于发动机性能预测有着重要的意义。本文开展了完整活塞组件(裙部以及活塞环组)动力学与摩擦学耦合性能分析的建模方法研究以及活塞环面和活塞裙部润滑油膜厚度测量试验研究。耦合模型基于活塞受力方程以及润滑油膜的平均雷诺方程建立,考虑了部件表面微观形貌特征对润滑状态的作用效果,采用FROTRAN语言编程求解,求解算法采用有限差分方法实现,从而实现润滑油膜厚度、压力分布规律、活塞横向运动、围绕活塞销旋转运动、活塞环跳动以及扭转、窜气以及滑油消耗、摩擦损失功等性能的预测。本文工作还包括往复摩擦试验机的设计以及在摩擦机上开展的活塞环-缸套摩擦副模拟运行试验,测量得到了活塞环与缸套间的干摩擦条件下的摩擦力系数,并以此作为数值仿真模型中微凸体直接接触时的摩擦系数。油膜厚度测量试验研究基于激光诱导荧光原理开展,荧光强度信号采集系统由自制完成。试验中采用波长为532nm的激光作为激发光源,并筛选出效率较高的荧光物质;再将此荧光物质掺混到发动机的滑油中,通过自制的信号校准装置对油膜厚度信号进行校准,并在缸套上加装玻璃窗口的发动机倒拖试验台上开展油膜厚度测量,从而验证数值仿真模型的有效性,探索活塞组件润滑油膜分布规律。膜厚测量系统得到的测量曲线能够清晰地反应出活塞环组以及裙部处的结构几何参数变化以及油膜分布规律。结合活塞组件润滑油膜分布的分析结果,本文完成了活塞组件-缸套耦合系统的传热模型,在传热模型中将润滑油膜的导热作用采用等效热阻来描述,探讨了分布在活塞组件周围的润滑油膜对活塞热负荷的影响,并从相反方向探讨了热负荷对活塞组件摩擦学性能的影响。润滑分析与活塞热固耦合分析结果表明,组合式活塞的活塞环处润滑油膜对活塞的冷却作用并不明显,滑油粘度对于活塞组件的动力学性能有较显著的影响;另外,热负荷作用效果下,活塞裙部型线变化显著,并且裙部中凸点位置会稍微向上偏移,从而影响活塞的二阶运动,并导致活塞冷、热态条件下的动力学性能差异较大。以上述耦合模型为手段,本文以摩擦损失功和接触情况为裙部结构优化目标,以通过顶环处的窜气量为环组结构优化目标,开展了结构参数敏感性分析,得到了影响活塞裙部摩擦损失功以及窜气量的各因素的主次顺序;并以敏感性分析的结论为依据,结合实际设计案例,开展了裙部优化设计工作。更多还原

【Abstract】 Nowadays,people pay attention to the characteristic of moving components,for example,piston assemblies,not only in view of traditional Dynaimcs,but also in coupled way of consideration on dynamic motion and lubrication,friction and wear since the coupled characteristics have strong influence on the performance of engines such as,reliability,econominal efficiency,and vibration and noise.Piston assembliy is one of the most important moving components in internal combustion engines,therefore,it isvery meaningful to develop a medel for the coupled prediction on Dynamics and Tribology of piston assembly.The modeling of coupled Dynamics and Tribology of piston assembly,including skirt and ring pack,and the measurement of oil film thickness of piston ring running face as well as skirt were studied in this thesis.The coupled model was deduced according to the equation of force and moment balance of piston and Average Reynolds Equation for lubrication analysis.The effect of asperities on lubrication was introduced in the Average Reynolds Equation in forms of some factors.The equations were solved with the program coded in Fortran language with the algorithm of Finite Difference Method and the model was successful to predict the performance of piston assemblies,including oil film thickness,lubricant oil pressure distribution,piston lateral motion,tilting,fluttering and twist of rings,blow-by,lubricant oil consumption and power loss of components as well.The design of a reciprocating machine was also included in this thesis and a series test runs for ring-liner pair was conducted on it so that the friction coefficient of dry sliding measured was used as friction coefficient between asperities in the model of Dynamics.A system for measurement of lubricant oil film thickness was designed with Laser Induced Fluorescence in this thesis.The laser in 532nm wavelength was chosen as excitation and a special fluorescence dye was selected according to its higher efficiency of fluorescence light emission.A tiny amount dye was mixed in the lubricant oil of the engine and the fluorescence signal was calibrated in a certain concentration on a specially designed gage.The measurement of oil film thickness was conducted on a motored diesel engine with glass window in the cylinders in order to verify the validity of the model to study the distribution of oil film around the piston assemblies.According to the test results,the designed measurement system could give the reasonable curve and clearly describe the structure of piston assemblies and the distribution of oil film.Combined with the distribution of oil film around the piston assemblies,the modeling for thermal conduction for piston assemblies and cylinder liner was accomplished with the assumption of equivalent thermal resistance on oil film thickness in order to study the interactive between the piston performance under thermal load and that of coupled Dynamics and Tribology.Results of Lubrication analysis and themo-mechanical analysis showed that the oil film around ring pack had small effect on cooling of piston and the viscosity of oil played important role on piston motion.Moreover,the profile of piston skirt changed remarkably under thermal load and position of maximum radius would move upward slightly so that the second motion of piston under steady working condition would differ from that under cold condition.The sensibility of structuralcharacteristic on piston assemblies was conducted with the consideration of power loss and blow-by through top ring as the optimization goal and the structural parameters were ranked according to the importance of effect on the power loss and blow-by.At last,the optimization of skirt profile for a real design case was conducted acoording to the conclusion from sensibility analysis.更多还原