Effects of 2-ethylhexyl nitrate and post-injection strategy on combustion and emission characterizes in a dimethyl carbonate/diesel blending engine

Abstract

To meet the increasingly stringent emission regulations on CI engines, a new theory that combines post-injection technology and uses dimethyl carbonate (DMC) and a certain amount of EGR to achieve ultra-low emissions of soot and nitrogen oxides (NOX) is proposed. However, DMC causes a delay in combustion phase of the mixed fuel due to its smaller cetane number (CN) value. Because the combustion phase affects thermal efficiency, economic efficiency, and emission performance of compression ignition (CI) engines, 2-ethylhexyl nitrate (EHN) can be used as a CN enhancer, to improve the combustion performance parameters of the mixed fuel. This study verifies this theory by controlling the post-injection rate (0, 5%, 10%, 15%, and 20%) of different experimental fuels for a diesel engine with four-cylinder and turbocharged. The five fuels were pure diesel and a mixture of 80% diesel with 20% DMC (DMC20). As well, EHN was added to DMC20 with a proportion of 0.5%, 1%, and 2%. Through this study, the use of 0.5% EHN allows maximum in-cylinder pressure (MINP) and maximum heat rise rate (MHRR) of the DMC/diesel blend to achieve results similar to those of diesel. And the use of EHN reduced the ignition delay time, but leading to a slightly increase of soot. As the post-injection rate increased, both NOX and carbon monoxide (CO) decreased and soot significantly decreased. The addition of 0.5% EHN with the post-injection rate of >15% has a good combustion and emission effect and extends the trade-off limits of NOX and soot.