EXPERIMENTAL INVESTIGATION OF A CI ENGINE CHARACTERISTICS FUELLED WITH TERNARY BLEND OF BIODIESEL-DIESEL AND ETHANOL USING FUEL ADDITIVES

Abstract

Diesel continues to play a vital role in transportation and industry; however, its extensive use contributes to rising emissions and energy security concerns, particularly in import dependent countries such as India underlined the need for viable renewable alternatives capable of operating in existing diesel engines. The present study investigated the performance, combustion, and emission characteristics of a Common Rail Direct Injection (CRDI) diesel engine fuelled with ternary blends of diesel, waste cooking oil biodiesel (WCB), waste plastic oil (WPO), and ethanol. Furthermore, the study integrated advanced fuel additives, specifically Tert-bytylhydroquinone (TBHQ) as an antioxidants and Ceric Oxide (CeO2) nanoparticles as combustion catalysts, to enhance fuel stability and mitigate harmful pollutants. WCB was synthesized through a two-step transesterification process, achieving an 88% yield and meeting ASTM D6751 standards. Fuel characterization confirmed the suitability of WPO and ethanol for engine application. Engine experiments demonstrated that WCB and WPO improved ethanol miscibility in diesel, preventing phase separation. Although ternary blends showed slightly lower brake thermal efficiency (BTE) than neat diesel due to reduced heating value, significant reductions in CO, HC, smoke, and NOₓ emissions were observed. The experimental results indicated that while the BTE of ternary blends was marginally lower than that of neat diesel due to the lower heating value of biofuelsThe D60CB20E20 blend achieved approximately 10% lower NOₓ emissions compared to diesel, mainly due to the cooling effect of ethanol. The BSFC showed an upward trend with increasing biofuel fractions, though this was partially offset by the improved combustion efficiency of P a g e | vii oxygenated components. Notably, the D60CB20E20 blend (60% diesel, 20% combined biodiesel, and 20% ethanol) achieved a simultaneous reduction in both smoke opacity and NOx emissions, with NOx levels decreasing by approximately 10% relative to petroleum diesel. This mitigation was primarily attributed to the high latent heat of vaporization of ethanol, which effectively lowered peak in-cylinder temperatures through evaporative cooling. Additionally, substantial reductions in CO and HC emissions were observed across all ternary formulations, particularly at higher loads, due to the high oxygen weight percentage (approx. 35%) of the ethanol component. Statistical optimization conducted via Response Surface Methodology (RSM) based on a Central Composite Design (CCD) to optimized additive-assisted blends identified the optimal operating conditions for nanoparticle-doped (CeO2) or antioxidants (TBHQ) fuel blends. For TBHQ-treated fuels, the optimal condition (20.68% blend, 750 ppm TBHQ, 25.66° bTDC injection timing) improved BTE to 15.17% while reducing CO, HC, NOₓ, and smoke emissions. For CeO₂ nanoparticle-doped blends, the optimal configuration (40% blend, 200 ppm CeO₂, and 23° bTDC) achieved a higher BTE of 17.23% and significantly reduced emissions. Increasing CeO₂ concentration further enhanced combustion efficiency, with BTE improvement up to 4.3% and emission reductions reaching 45%. All developed models showed strong statistical reliability (R² > 0.97) with prediction errors below 5%. Overall, this research concluded that the utilization of waste- derived ternary blends, optimized through nano-additives, antioxidants and precision injection control in CRDI systems, provided a viable and environmentally superior alternative for achieving sustainable decarbonisation in the transport and agricultural sectors without engine modification.