Impact of injection timing and EGR on the combustion characteristics and emission behavior of DI diesel engines fueled with renewable alcohol based oxygenated blends

Reducing carbon emissions from diesel engines has increased interest in oxygenated biofuels that offer cleaner combustion without engine modifications. Among higher alcohols, n-pentanol offers a promising combination of high oxygen content, renewable origin, and favorable combustion properties. This study experimentally demonstrates an additive-free strategy for operating a 40% n-pentanol/diesel blend (D60P40) in a common-rail direct injection diesel engine through the synergistic integration of advanced injection timing (15° BTDC) and exhaust gas recirculation (10% and 20%) across 20–80% engine loads. Advancing injection timing to 15° BTDC improved combustion, with an 8.85% increase in peak cylinder pressure and 15.19% higher heat release rate compared to diesel. Brake thermal efficiency (BTE) of D60P40 at this timing was only 2.36% lower than diesel, while retarded timing (9° BTDC) reduced BTE by 15.7%. EGR at 20% reduced NOx by 15.15%, but increased HC and CO due to thermal quenching. However, the inherent oxygen in pentanol helped limit these increases. The synergy of advanced injection timing with moderate EGR resolved the NOx–CO/HC trade-off, maintaining combustion efficiency while reducing emissions. These findings demonstrate a viable, retrofitting-free pathway for diesel engine decarbonization using oxygenated fuel blends, supporting global efforts toward cleaner and sustainable transport energy systems. • Injection timing–EGR synergy enables stable operation of high n-pentanol blends. • Advanced injection timing mitigates ignition delay of D60P40 fuel. • Moderate EGR reduces NOx with acceptable HC and CO penalties. • Diesel-like combustion performance achieved at high loads without additives.