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Abstract
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This study employs combined 1D and 3D computational modeling to investigate the effects of
fuel injection timing on combustion and emission performance in a diesel engine. Injections are
timed at a baseline angle and further adjusted by +3, –3, and –6 crank angle degrees relative to
baseline. Key parameters, including the in-cylinder pressure, temperature, heat-release rate,
indicated work, and emission indices (NOx and soot), are compared across these cases. Results
show that advancing injection timing consistently produces earlier ignition, higher peak pressure
and temperature, and slightly higher indicated work and thermal efficiency, albeit with a marked
increase in NOx. Conversely, retarding injection consistently lowers peak pressure and
temperature, effectively reduces NOx formation, but leads to increased soot emissions and
reduced efficiency. The CFD predictions leveraging an extended coherent flame model accurately
replicate these observed effects. The findings highlight the inherent trade-offs in timing control:
advancing injection can improve work output but aggravates NOx, while delaying injection
reduces NOx at the cost of efficiency and a noticeable soot increase
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