Numerical study of the simultaneous impacts of pilot fuel injection timing strategies and piston bowl geometry in a RCCI engine with dieselsyngas fuel

This numerical study the simultaneous impacts of diesel direct injection timing (pilot injection at 25-40-55 Crank Angle (CA) Before Top Dead Center (BTDC) and main injection at 10 BTDC), combustion chamber geometry (re-entrant (baseline), and wide-shallow chamber), and applying syngas, 20% and 40% of total energy per cycle, in a heavy-duty off-road RCCI engine. This numerical research is conducted using CONVERGE computational fluid dynamic code. The SAGE combustion model was used coupled with a detailed chemical kinetic mechanism consist of 72 species and 360 reactions. The results showed that increasing the syngas to diesel ratio up to 40% caused the combustion speed increased compared to the baseline pure diesel combustion and the start of combustion occurred near the top dead center. Also use of the wide-shallow combustion chamber along with diesel injection at 55 CA BTDC at diesel- 40% syngas combustion operating condition significantly reduced the maximum pressure rise rate compared to other combustion conditions. Additionally, at this combustion condition emissions of Nitrogen Oxides (NOx), soot and Hydro-Carbons are 17.18, 0.015, 0.1 g/kg of fuel which are decreased by 63.5%, 96.5% and 80.2%, respectively, compared to the baseline pure diesel combustion. However, the use of syngas increased the emission of carbon monoxide.
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