Biodiesel-Based Ternary Fuel Blends in Compression Ignition Engines: A Comprehensive Review of Combustion, Performance, and Emission Characteristics

The increasing dependence on fossil diesel fuel and the associated environmental and energy security concerns have intensified research efforts toward sustainable and renewable alternatives for compression ignition (CI) engines. Biodiesel derived from non-edible oils and waste cooking oil has emerged as a promising substitute due to its renewable nature, biodegradability, and favorable combustion characteristics. However, the widespread application of biodiesel is constrained by inherent drawbacks such as higher viscosity, lower calorific value, increased brake-specific fuel consumption, and a tendency to elevate nitrogen oxide emissions. To overcome these limitations, the present research investigates the performance, combustion, and emission characteristics of ternary fuel blends comprising diesel, biodiesel, and higher alcohols. In this study, biodiesel produced from selected non-edible and waste-based feedstocks is blended with diesel and higher alcohols such as butanol, pentanol, hexanol and n-octanol in varying proportions. Experimental investigations are conducted on a single-cylinder, four-stroke, water-cooled compression ignition engine under different load conditions. Key performance parameters, including brake thermal efficiency and brake-specific fuel consumption, are evaluated alongside detailed combustion analysis involving in-cylinder pressure, ignition delay, and heat release rate. Exhaust emissions such as carbon monoxide, unburned hydrocarbons, nitrogen oxides, and smoke opacity are also analyzed and compared with baseline diesel operation. Furthermore, statistical optimization techniques such as the Taguchi method and Response Surface Methodology are employed to identify optimal blend compositions that achieve a balanced trade-off between engine performance, combustion stability, and emission reduction.