活塞结构对其传热及强度的影响分析

以一款满足国Ⅴ排放限值的高压共轨柴油机活塞为研究对象，采用硬度塞测温法试验测试分析了标定功率工况下活塞稳态温度场分布和热负荷的大小，结合温度场试验测试结果建立了内冷油道与活塞的流固耦合传热数值仿真模型，仿真分析了活塞销座长度、销孔直径、火力岸高度、同侧回油孔中心间距4个活塞结构参数对活塞传热与结构强度的影响。研究结果发现，活塞的火力岸、内冷油腔、回油孔和销孔处的热流密度较大并出现应力集中。选择活塞销座长度、销孔直径、火力岸高度、同侧回油孔中心间距4个参数，进一步研究活塞结构对其传热及结构强度的影响特征。结果显示，活塞的每个结构参数值改变不仅会较大程度地改变该处的传热性能和应力分布，还会导致其他关键点的应力和温度发生改变，这使得活塞结构修改需更加谨慎。适当增加销座长度、销孔直径和火力岸高度，减小同侧回油孔中心间距，可以改善活塞的受热，也可以降低活塞的整体应力。

Influence Analysis of Piston Structures on Heat Transfer and Strength

The pistons of a high pressure common rail diesel engine that met state-Ⅴ emission standards were taken as the object of study. The steady-state temperature field distributions and heat loads of the pistons under the rated power conditions were analyzed by hardness plug temperature measurement method. Based on the test results of temperature field tests, the numerical simulation models of fluid-solid coupling heat transfer of internal cooling oil and piston were set up. The influences of the four piston structure parameters (the piston pin length, the pin hole diameter, the height of the fire bank and the center distance of the oil return hole) on the piston heat transfer and structural strength were analyzed by simulations. The results show that the heat flux density of the piston fire bank, the inner chamber, the oil return hole and the pin hole is greater and the stress concentration were appeared. The four parameters of the piston pin length, pin hole diameter, height of the fire bank and the center distance of the oil return hole were selected to further study the influences of the piston structures on the heat transfer and structural strength. The simulation results also show that each changes in the structures of the pistons will change the heat transfer performances and stress distributions, and will cause the stresses and temperatures of other key points to change, which makes the modification of the piston structures should be more cautious. Appropriate increase pin length, pin hole diameter and fire bank thickness, reduce the center distance of the oil return hole, may improve the piston heat, and reduce the stress of the pistons.