Improved Load-Carrying Capacity of Crosshead-Pin Bearings by Incorporating Taper Geometry in Oil-Grooves

大型二冲程柴油机十字头销轴承在低速时以小角度振荡，且始终承受较大的向下载荷，因此其工作在严格的润滑条件下。最近的趋势是更紧凑的发动机增加了输出，提高了轴承的比负载，从而导致润滑严重程度显着增加。因此，提高十字头销轴承的承载能力是十分重要的。本文采用动载轴承夹持试验装置，研究了间隙比和油槽几何形状对承载能力的影响。测定了油膜的电阻，评价了油膜的形成程度。主要结果是：(1)对于具有常规油槽的轴承，减小间隙比可以有效地增强对整个轴瓦的挤压作用，从而降低油膜压力。这反过来又增加了承载能力。但是，当间隙比过低时，会降低形成足够动水楔膜的能力，从而导致承载能力下降；(2)在油槽两侧采用优化的锥度几何形状，油膜压力仅增加很小，但油膜厚度更厚。因此，可以预期承载能力的显著改善；(3)支撑长度为5度、锥度角为0.1度的锥度几何形状实现最大承载能力。

The crosshead-pin bearing in large two-stroke diesel engines operates under severe lubrication conditions, because the bearing oscillates within a small angle at a low speed and is always subject to a high downward load. The recent trend towards more compact engines with increased output raises the bearing specific load, thereby causing the lubrication severity to increase significantly. Thus it is very important to improve the load-carrying capacity of the crosshead-pin bearing. In the present study, experiments using a dynamically loaded bearing seizure test apparatus were carried out to clarify the influences of the clearance ratio and the oil-groove geometry on the load-carrying capacity. The electrical resistance of the oil film was also measured to evaluate the extent of the oil film formation. The major results are : (1)In the case of bearings with conventional oil-grooves, a decrease in the clearance ratio is effective in enhancing squeeze action on the entirety of the bearing pads, thereby lowering the oil film pressure. This, in turn, increases the load-carrying capacity. However, when the clearance ratio becomes too low, the ability to form an adequate hydrodynamic wedge film is degraded, thereby causing the load-carrying capacity to decrease ; (2)Incorporating an optimized taper geometry on both sides of the oil-groove promotes a thicker oil film with only a small increase in the oil film pressure. Thus a significant improvement in the load-carrying capacity can be expected ; and (3)The maximum load-carrying capacity is achieved by the taper geometry of a subtended length of 5 degrees and a taper angle of 0.1 degree.