impact of fuel injection timing on combustion characteristics and emissions in a diesel engine: a cfd study

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.