凸台撞壁对分区燃烧系统性能影响的仿真

Numerical simulation of impinging convexity on partition combustion system performance of diesel engines

为了更好地利用油束喷射动能,改善柴油机喷雾的空间分布,提出了一种基于凸台撞壁引导下的分区燃烧系统.运用CFD软件FIRE对该燃烧系统的喷雾与燃烧过程进行了3维仿真研究,从不同角度分析了凸台撞壁对分区燃烧系统的燃烧与排放特性的影响.结果表明:分区结构提高了缸内平均湍动能,增加了压缩过程中流入燃烧室内的气流量,促进了油气的快速混合与燃烧;在凸台面上不发生油束堆积的各撞壁方案中,凸台锥角越大,缸内平均湍动能峰值就越小,同时膨胀过程中气体流出燃烧室的速度也越低,从而扩散燃烧现象就越明显,soot排放值也越低.

In order to strengthen the utilization of jet kinetic energy,a partition combustion system with spray impinging convexity was proposed to improve the spatial distribution of spray for diesel engines. The in-cylinder spray,the mixture formation and the combustion process of partition combustion system were simulated by AVL FIRE software to analyze the influence of convexity impingement on the combustion and emission characteristics of the system. The results show that by the partition-structure,the average turbulent kinetic energy in the cylinder is improved,and the airflow into combustion chamber in compression process is strengthened. In the case of convexity impingement with no significant accumulation of oil beam,the increasing cone angle of convexity leads to the reduced peak of average turbulent kinetic energy in the cylinder and slows down the air flow out combustion chamber in expansion process,and the diffusion combustion becomes more obvious with lower soot emission.