针对天然气发动机气缸盖排气孔口产生裂纹这种故障，本文以有限元方法为基础，对某天然气发动机气缸盖建立模型，进行了热-固耦合计算。结果表明正常工作状态下气缸盖温度及压应力最高处发生在排气孔口间“鼻梁处”，温度为280℃，压应力为1640MPa。当冷却水侧换热恶化或发动机突加载荷状态下会导致气缸盖工作温度及应力升高，“鼻梁处”温度达到372℃，压应力达到2000MPa，这时气缸盖“鼻梁处”会在高温下产生压塑性变形，导致该处产生裂纹。%In view of cylinder head crack that happened in the natural gas engine, this paper built a model for the cylinder head with finite element method, and made a thermo -structural cou- pling calculation. The results showed that the maximum temperature and stress occurred at the valve bridge region between of exhaust valves when the cylinder head was working under normal working conditions. Its maximum temperature was , and the maximum stress was 1640MPa. When heat transfer of cooling water got degraded or the engine load changed suddenly , the temperature of the cylinder head in this region would increase to and its stress reached 2000MPa, therefore, the valve in bridge region would get deformed due to high temperature and further was cracked.
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