【作者】 于文英；

【导师】 刘波；

【作者基本信息】 河北工业大学 ， 机械设计及理论， 2012， 博士

【摘要】 活塞是内燃机的主要零部件之一，它的工作稳定性将直接影响到内燃机的可靠性、耐久性、经济性及排放等一系列重要的性能指标。活塞在工作时既要承受高温、高压燃气的周期作用，又要承受高速往复运动产生的惯性力、侧向压力、摩擦力等多重负荷的交替作用，必然会导致活塞在工作中的热损伤和机械损伤。特别是活塞顶部乃至整个活塞在高温燃气作用下温度很高，且温度沿活塞径向和轴向分布不均匀，必然导致活塞产生一定的热应力和热变形。当热负荷与机械负荷耦合后，严重时可能会导致活塞顶部、销座处出现裂纹、活塞环胶结甚至“拉缸”等各种问题。所以，对活塞温度场进行测量与分析，对温度场、应力场以及热、机械负荷共同作用下的耦合应力场进行有限元分析，了解活塞工作时的温度场分布规律及耦合应力场分布规律，对改进活塞结构，提高其工作可靠性、耐久性等是十分必要的。本文采用硬度塞测温法在不同工况下对6125型柴油发动机不同结构特点的活塞表面关键点的温度进行了测量，获得了不同工况下，不同结构特点的活塞表面关键点的温度值，分析了活塞的工作温度与结构特点及内燃机转速变化之间的关系。选取适宜的经验公式估算得到活塞表面的换热系数，采用有限元法对活塞温度场进行试算，将得到的关键点温度值与实测值进行比较和修正，较为精确的确定了6125型柴油发动机标定工况下的热边界条件。采用有限元软件MSC.Marc对6125型柴油机不同结构活塞在标定工况下的温度场、机械应力场和变形、热负荷和机械负荷共同作用下耦合应力场和变形的有限元计算结果进行了分析比较，得出活塞的温度场、应力场和变形与活塞结构特点之间的关系，为此系列活塞的结构优化设计提供了一定的理论基础。更多还原

【Abstract】 The piston is one of the central accessories of the internal-combustion engine. The stabilityof the piston has directly affected on series of important performance of the internal-combustionengine, such as reliability, durability, economical efficiency etc. The piston has a complexstructure and usually works under poor conditions. When in use, it will endure not only theperiodical action of the high temperature and high pressure gas, but also the alternant action ofthe multiple loads of inertia-pressure, side direction pressure and friction force caused by its highspeed reciprocating motion. These affections will cause thermal invalidation and mechanicaldamage of the piston when it is in work. Especially, thermal stress and thermal deformation willappear in the piston because of the high temperature at the top of the piston, and even the wholepiston, caused by the high temperature gas produced in the burning, as well as the asymmetrytemperature distribution along the axis and radical directions. When the mechanical load coupledwith the thermal load, it will cause crack in the top of the piston and in the piston bore, pistonring glued and even scuffing of cylinder bore in severe occasions. It is important for improvingthe piston structure and its reliability and durability that acquiring the temperature distributionand coupling stress distribution situation in the piston. So measuring and analyzing the pistontemperature field, finite element analysis on the temperature field, stress field and coupling stressfield caused by thermal and mechanical loads is essential.In this paper, the temperature of the key points on the surface of pistons with differentstructures in6125model diesel engine under different working conditions was determined byusing rigidity-plug temperature measurement method. The relationship between the workingtemperature of the piston with its structure characteristic and the rotate speed of the diesel enginehas been analyzed. The thermal boundary condition of the6125diesel engine under the declared working condition were determined more accurately by comparing the experimental temperaturewith that obtained by temperature field calculation using the piston surface heat transfercoefficient estimated by an empirical equation. The finite element analysis results of temperaturefield, stress field and deformation, coupling stress field and deformation under the joint action ofmechanical and thermal loads of the piston with different structures of6125diesel engine underdeclared working condition by using a MSC.Marc finite element analysis software wereanalyzed and compared. The characteristic of the temperature field, stress field and deformationof the piston and the relationship between them and the piston structure were obtained. This willlay a theoretical fundamental for the structure optimization design of the piston.更多还原