Performance, Combustion, and Emission Analysis of a Ternary Hybrid Ethyl Ester Blend and Its Impact in a Single-Cylinder Compression Ignition Engine

Heavy-duty diesel engines significantly contribute to environmental degradation, motivating the search for sustainable alternatives like plant-derived biodiesel. This study investigates the performance and emissions of a novel ternary hybrid biodiesel blend made from shea butter, neem oil, and waste kitchen oils (40.41:19.73:39.86 w/w) in a direct-injection, four-stroke, single-cylinder diesel engine. Various fuel blends (B0, B10, B20, B30, B40, B100) were evaluated against conventional diesel. The experimental results show that all tested biodiesel blends exhibit consistently shorter ignition delays than diesel due to higher cetane numbers (57 for B100 versus 52 for B0). At full load, biodiesel blends reduced carbon monoxide and hydrocarbon emissions by up to 26.79% and 41.06%, respectively. B30 blend demonstrated the most favorable balance between emission reductions and overall engine performance, despite a moderate increase in brake-specific fuel consumption (0.42 kg/kWh versus 0.35 kg/kWh for B0). Conversely, nitrogen oxide emissions increased by 15.8% for B100 because of higher in-cylinder peak temperatures. Crucially, this hybridization showed no significant synergistic improvement in performance: a scientifically valuable negative finding proving multi-feedstock blending does not automatically enhance fuel quality, likely due to counteracting effects from distinct saturated, monounsaturated, and mixed fatty acid profiles. For real-world applications, recommendations include fuel preheating (60–80 °C) and injection timing retardation (2–3 °CA) for B30–B40, alongside a 10–15% injection pressure increase for B100. Despite achieving an impressive 78% carbon dioxide reduction, several research gaps remain regarding long-term engine impact and comprehensive lifecycle analyses, which are vital for scaling this ternary biodiesel adoption.