用耦合分析法研究内燃机活塞环-气缸套传热润滑摩擦问题

在以往对活塞环-气缸套润滑摩擦性能的研究中,大都忽略了活塞组-气缸套间的导热,或者将导热过程简化,这与该摩擦副的实际润滑摩擦状况相去甚远.把柴油机缸内燃气、活塞、活塞环、润滑油膜、气缸套、冷却介质作为一个耦合体,考虑各部件间及相应物理场间的耦合关系,采用耦合分析法建立了活塞环-气缸套的三维非稳态热混合润滑摩擦模型.该模型以三维瞬态热传导模型、动压润滑模型和润滑油膜传热模型为基础,并考虑了润滑油的黏温变化、燃烧室燃气泄漏、表面粗糙度、油膜破裂位置以及气缸套圆周方向上的非轴对称性等影响因素.采用上述模型,对6110型柴油机活塞环-气缸套摩擦副进行了传热、润滑、摩擦耦合分析,得到了活塞组-气缸套的温度场,并用试验证实了耦合模型的正确性;与此同时,得出了润滑油膜的温度、黏度、最小油膜厚度和摩擦热随曲轴转角和活塞环周向高度的分布曲线.

Study of Heat Transfer, Lubrication and Friction of Piston Ring-Liner in Internal Combustion Engines Using the Coupled Methods

Previous studies on lubrication and frictional performance of piston ring-liner neglected the heat conduction behavior between the piston assembly and the liner or just simplified the heat conduction process, making it away from the real lubrication and frictional characteristic. In this paper, the in-cylinder gas, the piston, the piston ring, the lubrication oil film, the liner and the coolant all included in the simulation. By considering the coupled relations of various components and the related physical fields, a 3D transient mathematical model with thermal coupled lubrication and frictional performance of piston ringliner is proposed. The model is based on the 3D transient heat conduction model, the hydrodynamic lubrication model and the heat transfer model of lubrication oil film by considering the viscosity-temperature variation of the lubrication oil, the blow-by through the piston ring pack, the surface roughness, the rupture location and the non-axisymmetry in liner circumferential direction. The coupled analysis of the heat transfer, lubrication and friction for the ring-liner of a 6110 diesel engine is performed using the above software. The analysis obtains the temperature fields of piston assembly-liner and the validity of the coupled model is compared with the experimental results. Meanwhile, the distribution curves of the temperature, the viscosity, the minimum film thickness and the friction force of the lubrication oil film versus the crank angle and ring circumferential coordinate are obtained.