The current direction for Diesel combustion system
development is towards homogenization, in order to
reduce particulate and NOx emissions. However, a
strong increase of carbon monoxide emissions (CO) is
frequently noted in combination with enhanced
homogenization.
Therefore, the current investigation focuses on a
detailed analysis of the particulate - CO trade-off using a
laser-optical and multidimensional CFD investigation of
the combustion process of a swirl HSDI system. The
CFD methodology involves reduced kinetics for soot
formation and oxidation and a three-step CO model.
These models are validated by a detailed comparison to
optical measurements of flow, spray penetration and the
spatial distribution of soot, temperature and oxygen
concentration.
The results obtained show that high concentrations of
CO occur as an intermediate combustion reaction
product. Subsequently, CO and soot are oxidized in
large areas of the combustion chamber. In part load
operation, CO emissions are mainly caused by dilution
effects in the early phases of combustion. However, the
engine’s soot emissions are caused by insufficient
oxidization.
Soot generation and oxidation are found to be strongly
impacted by the slight non-homogeneity of the swirl
motion. The gaseous emissions are not affected by the
small differences in local flow, which are outlined further
in the text.
方案
高速直喷柴油燃烧系统,碳烟,一氧化碳,汽车发动机中减排方法,速度场检测方案(粒子图像测速)