Combustion Enhancement of Bergamot Peel Oil–Diesel Blends Using 2-Ethylhexyl Nitrate as a Cetane Improver in a CRDI Diesel Engine
K.Karthkeyan1, M.Thambidurai2
1Mechanical Engineering,FEAT,Annamalai university
1Mechanical Engineering,FEAT,Annamalai university
1. INTRODUCTION
The continued dependence on petroleum-derived diesel in compression ignition (CI) engines presents a persistent challenge for energy security and environmental sustainability. Diesel engines remain the backbone of heavy transport and many industrial applications due to their high thermal efficiency and durability, yet the need to meet stringent emission standards (e.g., BS-VI/Euro-VI) and reduce greenhouse-gas and particulate emissions has intensified the search for renewable fuel alternatives (Kaur et al., 2026). Plant- and fruit-derived oils recovered from waste streams have attracted attention as partial diesel substitutes because their intrinsic oxygenation, volatility, and biodegradability can improve combustion quality and reduce soot and unburned hydrocarbon emissions (Han et al., 2025). Studies across different low-viscosity bio-oils reveal consistent trends: improved atomization and reductions in smoke, CO and HC are often achievable at moderate blend ratios, albeit with trade-offs in ignition quality that must be addressed for safe, wide-scale adoption (Ashok et al., 2018).
Recent experimental work has broadened the set of low-viscosity bio-oils evaluated in diesel engines and shown promising outcomes under optimized injection and blending strategies (Nguyen et al., 2024). For example, eucalyptus oil–diesel blends demonstrated favorable performance and emission trends when injection parameters were adapted, increased the brake thermal efficiency and reduced the smoke by 60% (Chivu et al., 2024). Investigations of orange and other citrus peel oils showed substantial smoke and CO reductions at modest blend fractions when paired with optimized injection pressure and pilot injection strategies (Hoang et al., 2023). Broader reviews and comparative studies of low-viscosity essential oils emphasize that while many such fuels increase brake thermal efficiency from 2% to 4% and lower particulate emissions, the reduction in cetane number and associated ignition delay often exacerbates NOx formation from 5% to 10% and causes combustion phasing shifts that require compensatory control measures (e.g., timing adjustments, EGR, or ignition additives) (Ramalingam et al., 2023). Recent work has also explored alternative waste-to-fuel routes (e.g., citrus peels, turpentine, and certain hydrothermal liquefaction oils), showing that operational gains in some pollutants can be realized but that each feedstock imposes a unique set of physical-chemical trade-offs (Mercado-Cordova, 2025).
