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一般认为活塞组摩擦损失占发动机总机械功率损失的很大比例。在工作温度下,保持适宜的工作裙部型面和裙部与缸套之间的间隙,对于减少活塞摩擦是非常必要的。现代汽车发动机活塞是由铝合金制成,其热膨胀系数比发动机缸体常用的铸铁材料的热膨胀系数高80％。因此,发动机工作状况时的工作间隙与设计间隙回然不同,所以很需要一个能够计算活塞热膨胀的方法。 本文中,提出了一种三维有限元模型,用来计算活塞的工作温度及其相应的热膨胀,所说的活塞具有不对称的结构特点,如贯通槽、钢嵌片和活塞销座。模型可以用来进行裙部型面的设计,而型面设计很有潜力,能减少磨合时间,减轻摩擦和使活塞的敲击声降至最低限度。
It is generally believed that the friction loss of the piston group accounts for a large proportion of the total mechanical power loss of the engine. Maintaining a suitable working skirt profile and clearance between skirt and liner at operating temperature is necessary to reduce piston friction. Modern automotive engine pistons are made of aluminum alloy with a coefficient of thermal expansion that is 80% higher than the thermal expansion coefficient of cast iron materials commonly used in engine blocks. Therefore, the work of the engine when the working gap with the design gap is different, so it is necessary to be able to calculate a piston thermal expansion method. In this paper, a three-dimensional finite element model is proposed for calculating the operating temperature of the piston and its corresponding thermal expansion. The piston has asymmetrical structural features such as through slots, steel inserts and piston pedestal. The model can be used to design the skirt profile, while the profile design has great potential to reduce run-in time, reduce friction and minimize percussion of the piston.