Assessment of performance, combustion, and emission characteristics of a diesel engine fueled with novel emulsions of cattle dung bio-oil in diesel stabilized by biodiesel

Alternative renewable fuels are the need of the hour due to limited petroleum fuel sources and environmental degradation caused by emissions. This study aims to evaluate the feasibility of utilizing cattle dung bio-oil (CDBO) microemulsions as an alternative fuel in compression ignition engines by investigating their production, stability, performance, combustion, and emission characteristics. CDBO was produced through fast pyrolysis under optimized conditions and blended with high-speed diesel (HSD) using castor oil methyl ester as an additive to prepare stable microemulsions containing 5–20% bio-oil by volume. The experimental objectives included characterization of the bio-oil, development of microemulsions, and assessment of their influence on engine performance, combustion parameters, and emission profiles. The engine testing was conducted on a single-cylinder, 4-stroke, water-cooled, direct-injection diesel engine (Kirloskar AVI, 5 hp/3.73 kW) coupled with an eddy current dynamometer. The setup was equipped with sensors and transducers to measure all required parameters. The findings indicated that the microemulsions having 20% bio-oil exhibited higher brake specific energy consumption (BSEC) (16.4%) and lower brake thermal efficiency (13.2%) than that of diesel, while the brake power remained almost the same at full loads. The microemulsion fuels produced significantly lower carbon monoxide (27%) and hydrocarbon emissions (41.5%), and the temperature of exhaust gas was higher (10.4%). At high loads, the microemulsions generated 23.5% lower smoke emissions than HSD. The ignition delay was the same as for diesel operation at higher loads, while the cylinder peak pressure was 6.4% higher than that of diesel.