进气涡流与油束夹角对柴油机燃烧性能的影响

进气涡流与喷孔结构对柴油机缸内混合气分布有着决定性的影响,通过合理匹配二者可以优化缸内燃烧过程,从而获得更好的性能.对某小型高强化柴油机燃烧系统进行了多维仿真研究,综合分析了进气涡流与油束夹角的交互作用对缸内混合气分布、燃油蒸发、油气混合以及放热过程的影响机理,得到了二者对该机型的优化匹配准则.结果表明:增大和减小进气涡流和油束夹角可以分别增加上止点前后的燃油蒸发速率;涡流可以加速油气混合过程,而油束夹角过大则会减缓喷油中后期的油气混合速率;涡流比与油束夹角匹配得当时,缸内的混合气更均匀、索特平均直径更小,从而可以显著优化预混燃烧过程.

Effects of Intake Swirl and Spray Angle on Combustion Performance for Diesel Engine

Multi-dimensional simulation was conducted on a small high intensified diesel engine. The influence mechanism of the interaction of intake swirl and spray angle on the in-cylinder mixture distribution, fuel evaporation, mixing and heat release processes was analyzed. Optimum matching criteria was finally acquired. The results showed that increasing and decreasing the intake swirl and spray angle could accelerate the fuel evaporation rate before and after TDC respectively. Swirl could accelerate the process of mixing fuel and air, but if spray angle was too large, the mixing rate in the later part of injection could be retarded. When the swirl ratio and spray angle were matched appropriately, the mixture would be more uniform and the SMD would be smaller, which could significantly optimize the premixed combustion process.