Investigating the pollutant formation and combustion characteristics of biofuels in compression ignition engines: A numerical study

•CFD analysis employing chemical kinetics for various biodiesel generations.•Decreased autoignition for longer carbon chain unsaturated FAME.•Reduced NOx observed for diesel–biodiesel blends compared to conventional diesel.•CFD results showed decreased CO2 emissions than IPCC factors. In an effort to reduce carbon dioxide emissions, carbon–neutral biofuels are gaining attention as alternatives to fossil fuels. Biofuels produced from non-edible and algal biomass, which have combustion properties similar to conventional fuels and can be used in existing internal combustion engines, are one such fuel. This research employs numerical analysis to examine the combustion and pollutant formation characteristics of various biofuel generations, including biodiesel from coconut oil, waste coffee grounds, tomato seeds, and microalgae. The combustion process was modelled using the computational fluid dynamics software AVL FIRE™ and biofuel chemical mechanism from the University of Connecticut and validated on experimental results in internal combustion engine. The simulation conditions were evaluated based on an internal combustion operating point, with spray injection modelled using the Euler Lagrangian spray approach and liquid properties defined by the biofuel's saturated and unsaturated components. By altering the biodiesel/diesel mixture content, the results of in-cylinder pressure, temperature, rate of heat release, and pollutant emissions were compared to those of conventional fuel. Upon comparison of the conventional fuel with fixed released heat, a decrease of 4.6% and 1.2% in nitrogen oxides (NO) was observed for a mixture of 20% biodiesel (B20) and 50% (B50), respectively. The highest concentration of nitrogen oxide (NO) was found on the outer edges of the cylinder wall, however, due to more intense combustion, NO was more uniformly dispersed within the cylinder than diesel fuel and B20 with lower fuel injection.