Improving incomplete combustion and reducing engine-out emissions in reactivity controlled compression ignition engine fueled by ethanol

Abstract

In this paper, various fuels with different reactivities were implemented as a strategy to optimize the heat release rate which could be a dominant combustion controller in an internal combustion engine. Using a blend of ethanol and gasoline fuels is one of the best approaches to decrease heat release rate, as well as prolonging combustion duration and retarding combustion phasing. Application of ethanol fuel, however, may lead to misfire and unstable combustion in reactivity controlled compression ignition engines. A multi-dimensional model coupled with a detailed chemical kinetic mechanism was applied to investigate the effects of single and double injections within misfire zones in a research engine using iso-octane, n-heptane, and ethanol fuels. A parametric approach is employed to analyze the engine model behavior through varying energy fraction of fuels through both single and double injections strategies. Three performance maps of engine at varying total fuel energy with different ratios of the port to direct fuel injections have been simulated. The first map is related to using net iso-octane and n-heptane fuels; the other two maps are related to the use of 20% and 40% ethanol fuels instead of net iso-octane fuel, respectively. The results highlight that double injection strategy with the injection timing between 27° and 47° before top dead center is capable of improving misfire points also effective on reducing both nitrogen oxide formation and ringing intensity, as well as improving engine gross indicated efficiency.