重载柴油机运行参数与燃烧室结构协同优化研究

Collaborative Optimization of Operational Parameters and Combustion Chamber Geometry for Heavy-Duty Engine

借助三维仿真软件KIVA@DUT与遗传算法耦合,针对一款重载柴油机开展运行参数和燃烧室结构协同优化研究,在不同运行工况下保持NO_(x)排放的同时能够有效降低燃油消耗率。通过优化样本分析,发现运行参数中主喷时刻和喷油压力对柴油机性能的影响最为显著,几何参数中有关活塞碗和台阶结构的参数同样较为关键。喷油参数与几何结构参数间存在较强的相互作用,需要相互配合以实现最佳的柴油机性能。优化燃烧室结构更利于燃空混合,产生更高的燃烧效率,因此相较基准算例,优化算例采用更晚的喷油时刻以延迟燃烧相位,并配合更高的喷油压力以缩短燃烧持续期。不同载荷下最佳燃烧室结构并不相同,因此上述高载荷下优化获得的燃烧室在低载荷下的改进效果有所减弱。

The collaborative optimization of operational parameters and combustion chamber geometry was conducted on a heavy-duty diesel engine by coupling the three-dimensional computational fluid dynamics software and the genetic algorithm.Through the optimization,the fuel consumption improved effectively without deteriorating NO_(x) emission under different operating conditions.According to the analysis of all the optimization cases,the operational parameters such as main injection timing and injection pressure had the most significant effects on diesel engine performance,and the geometrical parameters related to the piston bowl and step structure were also the primary factors.There were strong correlation between injection parameters and geometrical parameters,and the achievement of satisfied diesel engine performance depended on their close collaboration.The optimized combustion chamber geometry was helpful for fuel and air mixing,which produced higher combustion efficiency.Compared with the reference case,the optimized case adopted the later injection timing to delay the combustion phase and a higher injection pressure to shorten combustion duration.The optimal combustion chamber geometry was not the same under different loads and hence the above optimized combustion chamber obtained at high loads showed unsatisfied improvements on fuel consumption and NO_(x) emission at low loads.