Exploring the synergistic potential of higher alcohols and biodiesel in blended and dual fuel combustion modes in diesel engines: A comprehensive review

Biofuels have garnered much attention in recent years, attributed to the expanding demand for sustainable and renewable energy sources and concerns due to fossil fuel depletion and increased pollution levels. Biodiesel and alcohols have been identified as potential biofuels due to their renewable nature, low emissions, and reduced reliance on fossil fuels. In alcohol, an oxygenated biofuel, higher alcohols are identified as potential alcohols than lower alcohols because of their improved fuel properties. Hence, they have piqued the interest of researchers in diesel engine applications. As these biofuels are used in blended and dual fuel combustion (DFC) modes, it is apt to review the synergistic effects and applications of higher alcohols and biodiesel fuels in these modes to explore the recent research efforts on performance, combustion, and emission behaviours (PCE) of diesel engines. This study also investigates the challenges correlated with blending biodiesel and higher alcohols and highlights the possible benefits, such as fuel efficiency and decreased emissions from DFC mode. The prospects for biodiesel and higher alcohols for dual-fuel combustion modes in diesel engines are also envisaged. Research exploring the use of higher alcohol fuels alongside diesel-biodiesel fuels has shown that fuel performance mainly depends on the blend ratios. The claimed average reduction in brake thermal efficiency ranges from 3.5% to 25%. The higher DFC alcohols have reduced NOx (from 6% to 50%) and PM emissions (from 7% to 90%) under moderate load. These improvements were achieved without compromising engine performance, and the enhancement in brake thermal efficiency ranged from 1.5% to 15%. Overall, this review study provided vital insights into the possibilities of these alternative biofuels and their role in decreasing the usage of fossil diesel fuel and its associated emissions by increasing the diesel engine's performance.