船用柴油机排气门热固耦合分析及试验

Analysis and experiment of thermo-solid coupling for exhaust valve of marine diesel engine

针对在柴油机运转工况下排气门处于高温腐蚀环境,较易发生断裂、弯曲、烧蚀等现象,采用Ansys软件对耐高温合金材料排气门进行温度场数值模拟。采用某型船用柴油机的额定工况,结合试验所得耐高温合金材料不同温度下的物性参数分析排气门的等效热边界载荷对气阀的影响,结果表明仿真温度场与失效气阀试件的特征相符合,气阀盘底中心为第一热点且变形量最大,盘底烧蚀现象明显,若存在晶粒大小分布不均或裂纹易发生阀面断裂;气阀颈部被废气冲刷产生第二热点发生颈部弯曲现象;锥面处热应力集中极易发生烧蚀。最后采用整体硬度法对仿真温度场进行验证,得出结果证明模拟具有真实可靠性,可以对气阀疲劳分析和气阀选型提供参考。

In view of the fact that the exhaust valve is in a high-temperature corrosion environment under diesel engine operating conditions,which is more prone to fracture,bending,and ablation,Ansys software is used to numerically simulate the temperature field of the high-temperature alloy exhaust valve.Using the rated working conditions of diesel engine,combined with the physical properties of the high temperature alloy material obtained at the test at different temperatures,the effect of the equivalent thermal boundary load of the exhaust valve on the gas valve was analyzed.The results showed that the simulated temperature field and the failure of the gas valve specimen The characteristics are consistent,the center of the bottom of the valve disc is the first hot spot and the amount of deformation is the largest.The phenomenon of ablation of the disc bottom is obvious.If there is uneven grain size distribution or cracks,it is prone to face fracture;the neck of the valve is washed by exhaust gas to produce the second neck bending occurs at the hot spot;the thermal stress concentration at the cone surface is extremely prone to ablation.Finally,the overall hardness method is used to verify the simulation temperature field,and the results show that the simulation has real reliability,which can provide reference for the fatigue analysis of the gas valve and the selection of the gas valve.