双层分区燃烧系统对高强化柴油机性能的影响

柴油机的燃烧系统是混合气形成质量的关键。为改善某高强化柴油机的燃烧和排放性能,在保证原机压缩比不变的条件下,设计了一种双层双弧脊分区燃烧系统——双层燃烧室匹配双排喷孔,并基于计算流体力学软件Converge进行数值模拟,研究不同上下排喷孔油束夹角对缸内燃烧和排放的影响。研究结果表明:新设计的燃烧系统的燃烧和排放性能均优于原机,上下排喷孔油束夹角会影响燃油在上下层弧脊处的分配,较大的上排喷孔油束夹角有利于对燃烧室顶隙空间的利用和上层弧脊下侧混合气的形成,较小的下排喷孔油束夹角有利于燃烧室底部凹坑附近空气利用率的提高和混合气分布范围的增加。因此,需要对上下排喷孔油束夹角进行合理的选择和匹配,使得发动机的整体燃烧和排放性能达到最优。

Influence of Double-Layer Zone Combustion System on Performance of Highly Intensified Diesel Engine

The combustion system of diesel engine is the key of mixture formation quality.In order to improve the combustion and emission performance of highly-intensified diesel engine,a double-layer and double arc ridge zone combustion system was designed.Double-layer combustion chamber was matched with double-row nozzles in this system.Numerical simulation was then carried out with CFD CONVERGE software to study the influence of different upper and lower row nozzle hole angles on in-cylinder combustion and emission performance.The research results show that the combustion and emission performance of newly-designed combustion system is better than that of the original engine.The fuel jet angle between the upper and lower nozzle holes will affect the fuel distribution at the upper and lower arc ridges.The larger fuel jet angle for the upper row of nozzle hole is conducive to the utilization of top gap space in combustion chamber and the formation of mixture on the lower side of upper arc ridge;The smaller fuel jet angle in the lower row of nozzle hole is conducive to the improvement of air utilization rate near the pit at the bottom of combustion chamber and the increase of distribution range for mixed gas.Accordingly,reasonable selection and matching of fuel jet angle between the upper and lower nozzle holes are needed to optimize the overall combustion and emission performance.