柴油机双卷流燃烧系统的排放特性

为研究双卷流燃烧系统对直喷式柴油机有害排放物生成的影响,该文采用试验和计算流体力学CFD仿真分析方法,探讨燃油喷射系统中喷油提前角、喷孔直径、油束夹角和涡流比对双卷流燃烧系统(DSCS)排放特性的影响.研究结果表明:随着喷油提前角的增加和喷孔直径的减小,NOx生成量增加,碳烟生成量降低;随着油束夹角的增加,碳烟生成量降低,NOx生成量先增加后降低;涡流比和弧脊的匹配直接影响着双卷流燃烧系统中燃油的雾化、混合和燃烧过程,为了降低有害污染物的排放应采用较小的涡流比与双卷流燃烧室,确定了与双卷流燃烧室相匹配的满足NOx、碳烟排放最佳涡流比为1.该研究可为柴油机双卷流燃烧系统优化设计提供参考.

Emission characteristics of double swirl combustion system in diesel engine

The emission of diesel engines, to some extent, restricted the development of the diesel engine industry. Due to the importance of the combustion system of the diesel engine, there is a growing concern to reduce harmful emissions by improving the combustion system. Many factors influence on the engine performance and emissions, but the shape of the combustion chamber of direct injection diesel engine has a very important influence on the combustion process and the generation of harmful emissions. For Double Swirl Combustion System research focuses on reducing the detonation pressure, fuel consumption and the numerical simulation of spray mixing mechanism, and its emission characteristics of a few. To take Test and CFD simulation method to explore the fuel injection system, fuel injection timing, nozzle diameter, spray angle and swirl ratio to influence of emission characteristics of double swirl combustion system (DSCS). The results show that: with the increase of the fuel injection advance angle and the nozzle diameter decreases, NOx production increases, soot formation was reduced. Because the ignition delay period of cylinder mixture was increased with the increase in injection advance angle, the oil and gas mixing quality is improved with the increase in the ignition delay period, thus making the cylinder to an increase in the maximum combustion temperature. The temperature of the main factors of NOx generated, so NOx formation increases with the increase in injection advance angle. The reasons for the reduction of soot are the increase of the ignition delay period such that the cylinder fuel mixture better, reducing soot generation. With the increase in the diameter of the spray hole, the cylinder fuel quality deterioration, resulting in insufficient combustion produce soot emissions. With the increases in the angle of spray, soot formation was reduced, the amount of NOx first increases and then decreased. Excessively large spray angle and arc ridge, resulting the deterioration of the quality of the fuel mixture, and the high temperature region is concentrated in the top of the combustion chamber, the air of the entire combustion chamber is not fully utilized, the lack of oxygen leads to a reduction in the amount of NOx generated. Soot formation is due to the local presence of fuel too thick. The swirl ratio and arc ridge matching directly affect the fuel atomization, mixing and combustion process of DSCS, smaller swirl ratio and arc ridge matching should be used in order to reduce the emissions of harmful pollutions.