涡流比对柴油机双ω燃烧系统性能的影响

Effects of Swirl Ratio on Double ω-Combustion System Performance for Diesel Engines

为了改善柴油机喷雾空间分布,提高缸内混合气形成质量,提出了双ω型燃烧室及与之相匹配的双排喷孔的新型燃烧系统.在试验缸压曲线与仿真曲线基本吻合的前提下,应用AVL FIRE软件对不同涡流比的缸内喷雾、混合气形成和燃烧过程进行了数值模拟,分析了其对缸内速度场、浓度场及燃烧排放特性的影响.结果表明:随着涡流比增大,预混燃烧阶段形成的混合气增多,滞燃期缩短.当涡流比为2.0时,Soot排放最低.随着涡流比继续增大,在强涡流的作用下,油束末端撞壁后产生一个局部环状涡旋,燃烧恶化,Soot排放明显增加.

A double ω- combustion chamber matched with a double- row nozzle hole combustion system is proposed to improve the spray spatial distribution and the mixture formation quality for diesel engines. Under the premise of the test cylinder pressure curve coinciding with the simulation curve,the in- cylinder spray,mixture formation and combustion process of the new combustion system are simulated and investigated by using AVL FIRE software. By changing intake swirl ratios,the effect of which on the fuel / air equivalence ratio,velocity field and emission characteristics in the chamber are analyzed. The results show that as the swirl ratio increases,the mixture gas formation in the process of pre- mixed combustion increases and the ignition delay period shortens. The minimum Soot emission occurs when the swirl ratio is 2. As the swirl ratio increases continually,in the promotion of the strong swirl ratio,it can generate a local ring swirl in the bottom of the fuel beam and make the combustion deterioration. They lead to Soot emission increase obviously.