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我们通常所说的发动机热负荷,一般包含两个方面的内容:其一是指发动机受热的宏观表现。即当受热零件超过一定温度后其工作能力的降低。如材料强度下降,表面硬度减少,易于磨损;膨胀变形,配合间隙破坏,润滑油变质,工作性能恶化,直至因过热而发生烧伤和熔化等等。其二是指各零件受热后组织内部的微观变化。如活塞、气缸盖和排气阀等,由于它们的几何形状复杂,各部分温度分布不均,从而引起很大的热应力。当这种内部应力超限后,会使零件因几何变形或破坏而丧失工作能力。显然,内燃机负荷增大时,这些零件的
We usually say that the engine heat load, generally contains two aspects: One is the macro performance of the engine heat. That is, when the heated part exceeds a certain temperature, its working ability is reduced. Such as the material strength decreased, reducing the surface hardness, easy to wear; expansion deformation, with the gap damage, deterioration of lubricants, deterioration of work performance, until the overheating and the occurrence of burns and melting and so on. The second refers to the micro-changes within the organization after each part is heated. Such as piston, cylinder head and exhaust valve, due to their complex geometry, uneven temperature distribution in various parts, resulting in great thermal stress. When the internal stress exceeds the limit, it will make the parts deformed or destroyed due to geometric loss of working ability. Obviously, when the internal combustion engine load increases, these parts