【作者】 张桂昌；

【导师】 张俊红；

【作者基本信息】 天津大学 ， 动力机械及工程， 2012， 博士

【摘要】 “能源”与“环境”是21世纪车用发动机产业的两大研究主题，其中，发动机的噪声和排放控制已经成为社会普遍关注的挑战性问题之一。发动机工作过程中活塞敲击噪声是主要的机械噪声源之一，活塞环润滑导致的机油消耗以及由此窜入气缸内的机油燃烧对排放有重要影响。因此，本文结合一款国产车用柴油机，通过理论研究、台架试验和虚拟设计等手段，考虑热负荷和机械负荷，对活塞敲击噪声产生机理、活塞环—缸套润滑特性、缸内机油消耗机理、以及活塞及活塞环的优化设计进行了深入细致的研究。在活塞敲击噪声研究和低敲击噪声活塞优化设计方面，首先对活塞进行热机耦合分析，研究活塞在热负荷和机械负荷共同作用下的应力和变形，然后将其代入活塞—连杆—曲柄机构动力学模型，逼近发动机实际工作状态，求解动力学模型得到活塞对缸套的敲击力；建立整机的有限元模型并结合模态试验进行模型修正，计算整机在活塞敲击力下的动力学响应，利用边界元方法分析活塞敲击噪声；最后以降低活塞敲击噪声为目标，以减小活塞对缸套的敲击力为优化途径，利用神经网络对活塞销偏置、裙部中凸点位置和配缸间隙等结构参数进行优化设计；结果显示优化后的活塞敲击力与敲击噪声显著降低；分别进行优化前后整机振动噪声试验，结果表明优化后的气缸处机体表面振动明显降低，这对降低活塞敲击噪声、提高活塞及缸套的使用寿命具有积极意义。在活塞环—缸套润滑特性研究、缸内机油消耗研究和低机油消耗活塞优化设计方面，在流体润滑理论基础上，考虑空穴效应，建立活塞环—缸套的二维润滑控制方程，运用控制体积质量守恒原理求解方程，计算并分析了包括空穴区域在内的润滑油膜压力分布、密度分布和空穴效应对最小油膜厚度和摩擦力的影响；建立基于缸壁蒸发、顶环开口窜油、顶环甩油和活塞顶岸刮油四种模式的缸内机油消耗模型，计算缸内机油消耗量，分析不同运行工况、活塞环闭口间隙和切向弹力对缸内机油消耗的影响规律；以低机油消耗为目标，利用神经网络对活塞环参数进行优化设计；同优化前计算结果相比，优化后的活塞环明显降低了缸内机油消耗量；进行优化前后柴油机机油消耗试验，结果表明优化后的活塞环显著降低了机油消耗量，这对降低柴油机颗粒物排放具有重要作用。更多还原

【Abstract】 Energy and environment are two main research subjects with the development ofthe automotive engine industry in the21st century, among which engine noise andemission have been a challenging problem and drawn universal attention. Impactnoise caused by piston is one of the main compositions of mechanical noise, whilepiston rings are the primary source of oil consumption and the entrance of cylinderwhere oil burns. Therefore, this dissertation studied mechanisms of impact noise andoil consumpution of a new domestic diesel engine piston assembly consideringthermal-mechanical coupling loads, and proposed an optimization design schemevarified by simulations and bench tests.In the research of impact noise and low noise optimization design, coupledthermal-mechanical analysis of piston assembly were carried out firstly. Thedistribusions of piston stress and deformation under heat and mechanical loads wereobtained. By considering the effects of coupled loads, the dynamic model ofpiston-connecting rod-crank mechanism was much closer to actual working condition.Secondly, the piston impact force was calculated by dynamic mechanical analysis.Then the finite element model of the whole engine was developed and revised usingmodal tests. Under the impact force, dynamic responses of the engine were calculated,and impact noise was obtained by using the boundary element method. Finally, a BPneural network was used to optimize the piston impact noise. The results showed thatboth impact force and noise decreased significantly. In the validation of optimaldesign, bench tests were carried out before and after the optimization and the resultsshowed that the impact force and noise of the optimized piston greatly reduced.For the studies of piston ring-cylinder liner lubricating property, oil consumption,and low oil consumption piston optimization design, a2D control equation of pistonring-liner lubrication was established considering the cavitation effect. The massconservation principle of control volume was applied to solve the equation. And theoil film pressure distribution including cavitation regions and density distributionwere calculated. In addition, cavitation effects on the minimum oil film thickness andfriction were analyzed. Secondly, four types (evaporation from liner wall，throw-offabove the top ring，oil blow through the top ring end gap，and oil scraping of piston top land edge) of oil consumption in cylinder were modeled and calculated. Influencesof main parameters of piston rings on oil consumption were analyzed. Then in orderto reduce the oil consumption, piston rings were optimally designed by neuralnetworks. The computation results showed that the oil consumption in cylinderdecreased. Finally, oil consumptions before and after the optimizations were testedand the results showed that the optimized piston rings significantly reduced the oilconsumption.更多还原