The engine performance can change after diesel fuel is replaced with a blend of CH4 and n-heptane at varying percentages. This study investigates the effects of fuel injection timing on the performance, efficiency, and emissions of a dual-fuel diesel engine running on a CH4 and n-heptane mixture. The analysis uses computational fluid dynamics (CFD) and AVL Fire software with advanced chemical kinetics tools, such as Chemkin, to transition from liquid to gaseous fuels. To accomplish this, the fuel injection timing was adjusted to three settings: 22° before top dead center (BTDC), 18° BTDC, and 14° BTDC. Methane was blended with n-heptane at ratios of 90 %:10 %, 85 %:15 %, and 75 %:25 %. The findings from the numerical simulations demonstrated that prolonging the fuel injection duration in the dual-fuel diesel engine resulted in an escalation in the temperature within the combustion chamber and an augmentation in the maximum cylinder pressure. Additionally, both the ignition delay and the distance from top dead center to the peak ignition pressure were diminished. With the rise in peak cylinder pressure, the output torque experienced a 16 % increase. Conversely, increasing the ratio of liquid fuel in the blend resulted in a shorter ignition delay, which caused a decline in peak cylinder pressure, accompanied by a 17 % drop in output torque and a 70 % decrease in indicator power. The implementation of early fuel injection at elevated engine speeds led to an enhancement in indicator power and an improvement in emissions, culminating in a 31 % reduction in nitrogen oxides (NOx) and a 16 % decrease in soot levels.

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