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Abstract
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The main goal of the present study was to explore the impacts of various fuel injection strategies in
a heavy-duty Direct Injection (DI) diesel engine operating under diesel-syngas combustion conditions computationally
using CONVERGE Computational Fluid Dynamic (CFD) code. The SAGE combustion model
coupled with a chemical kinetic n-heptane/toluene/PAH (Poly-Aromatic Hydro-carbons) mechanism that consisted
of 71 species and 360 reactions were used to simulate the diesel-syngas combustion process and the
formation and oxidation of emissions, e.g., Nitrogen Oxides (NOx), Particulate Matter (PM), Carbon Monoxide
(CO), and Unburnt Hydro-Carbons (UHC). The separate effects of main (8 to 18 Crank Angle (CA) Before Top
Dead Center (BTDC) with 2 CA steps) and post-injection (35 to 55 CA (After Top Dead Center) ATDC with
5 CA steps) timing of diesel fuel on the combustion characteristics and exhaust gas emissions were investigated
under diesel-syngas combustion conditions. The numerical achievements revealed that the substitution part of
the diesel with a CO–H2 gaseous mixture led to a considerably lower PM and UHC emissions in the exhaust
gases with a CO penalty rate. Maximum Combustion Temperature (MCT) and Heat Release Rate Peak Point
(HRRPP) were increased as Main-Injection Timing (MIT) was advanced. Also, advancing MIT led to a considerably
higher level of NOx emissions but lower PM formation. Moreover, compared to baseline engine
operating conditions, post-injection of diesel at 35 CA ATDC reduced both PM and UHC emissions simultaneously
by nearly 26.5 and 89%, respectively.
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