Diesel engines remain the backbone of the rail cargo sector, where maximizing fuel efficiency is critical for sustainability. This study optimizes the fuel injection strategy of a high-power locomotive engine, representative of those operating on 900 km rail corridors in Brazil, by investigating the synergy between fuel injection timing and spray angle ( \(\beta \) ). Numerical simulations were performed at a constant engine speed of 996 revolutions per minute (RPM) using computational fluid dynamics with the Extended Coherent Flame Model 3-Zones (ECFM-3Z) and the \(\kappa \) - \(\zeta \) -f turbulence model. A parametric study of 25 configurations was conducted, varying the spray angle from 153.0 to 167.0 \(^{\circ }\) and injection timing from 698 to 706 Crank Angle (CA) degrees, referenced against a 160.0 \(^{\circ }\) /702 CA baseline. Results demonstrate that advancing injection to 698 CA enhances Indicated Power and Brake Mean Effective Pressure (BMEP) by up to 2.92%, though at the cost of a 42.4% increase in Nitrogen Oxide (NO) emissions. Conversely, wider spray angles ( \(\beta \) = 167.0 \(^{\circ }\) ) resulted in spray-bowl misalignment, increasing soot by up to 168% and Brake Specific Fuel Consumption (BSFC) by 9.47%. A critical trade-off was identified: while narrow angles (153.0–156.5 \(^{\circ }\) ) improve mixing through higher turbulent kinetic energy, delaying injection to 706 CA with a 160.0 \(^{\circ }\) angle yields a simultaneous reduction in NO (22.3%) and soot (28.2%) with a marginal BMEP penalty of only 1.33%. These findings provide a quantitative framework for engine calibration aimed at emission compliance without hardware modifications.
