高强化蠕铁气缸盖热强度的分析与评价

Analysis and Evaluation on the Thermal Intensity of a Highly Intensified Compacted Graphite Cast Iron Cylinder Head

采用经单缸机温度和应力测试验证过的流-固热耦合有限元模型,对某型高强化柴油机蠕墨铸铁气缸盖的冷却传热和热机耦合应力进行了计算分析。在此基础上研究了气缸盖火力面热流量、冷却液进口温度和流量等参数对气缸盖温度与热应力的影响,并引入机件热强度系数(C2因子)对气缸盖火力面鼻梁区抵抗热疲劳能力进行了评价。结果表明:C2因子能在一定程度上定量表征气缸盖的热强度,因而可对不同的结构设计方案进行快速定量对比;在高强化蠕墨铸铁气缸盖设计中采用高温冷却的思路,可提高气缸盖鼻梁区的抗热疲劳能力;增加冷却液进口流量能降低气缸盖鼻梁区的温度,但并不利于提高气缸盖鼻梁区的抗热疲劳能力。

The cooling,heat transfer and thermo-mechanical coupling stress in the compacted graphite cast iron cylinder head of a highly intensified diesel engine are calculated and analyzed with a fluid-solid thermal coupling finite element model verified by the temperature and stress testing on a single-cylinder engine. On this basis,the effects of parameters such as the heat flow through fire face and the inlet temperature and flow rate of cooling fluid on the temperature and thermal stress of cylinder head are studied,and a so called C2 factor,actually the thermal intensity coefficient of parts,is introduced to evaluate the thermal fatigue resistance ability of the bridge zone on the fire face of cylinder head. The results show that C2 factor represents the thermal intensity of cylinder head to certain extent and thus can be used for speedy quantitative comparison of different structural design schemes; In designing the highly intensified cylinder head of compacted graphite cast iron,adopting a thinking of high temperature cooling can enhance the thermal fatigue resistance of the bridge zone in cylinder head; Increasing the inlet flow of cooling liquid can lower the temperature of bridge zone in cylinder head,but is not conducive to the enhancement of its thermal fatigue resistance.