Effect of Stratified Rich and High Turbulence Combustion on the Reduction of NOx and Particulate Emissions from a Dl Diesel Engine

Abstract

This study tried to find a concept of low emission combustion in a direct-injection diesel engine. Experiment was carried out to investigate the effects of high-pressure injection and high squish combustion chamber on combustion process and emissions. The high squish combustion chamber has a small throat diameter. The chamber intends to realize the simultaneous reduction of NO_X and particulate emissions. The chamber produces high turbulence and effectively forms stratified rich mixture region under the squish lip. NO_X reduction as well as high turbulence combustion is caused in the region. Results show that this chamber produces low particulate emissions under the condition of relatively lower injection pressure compared with the conventional toroidal chamber. When injection timing is retarded, peak heat release rate tends to decrease and diffusion combustion is promoted for the high squish chamber, although peak heat release rate increases with retarding injection timing for the toroidal chamber. Accordingly, it is possible for the high squish chamber to retard injection timing later than the toroidal chamber, leading to produce lower NO_X with less deterioration of particulate emissions. Moreover, the high squish chamber further reduces NO_X with little deterioration of particulate emissions and fuel consumption by introducing CO₂ and N₂ to intake air.