Combustion characteristics of biodiesel fuel in high recirculation conditions

The potential of biodiesel as an alternative fuel for various applications leads to an investigation to understand the combustion characteristics of pure and blended biodiesel. The concept of internal recirculation of combustion products is employed in a high swirl and low emission burner to reduce emissions. Due to high boiling point (613 K) and SMD (37 μm) of biodiesel, air preheating with minimum temperature above the boiling point of biodiesel is considered. Air at different temperatures of 623, 673 and 703 K is injected tangentially. Swirl flow pattern in the combustor creates the central low pressure zone due to vortex breakdown and improves the recirculation of combustion products. Results in improved mixing and high residence time of reactants. Biodiesel is blended with diesel to reduce the surface tension and viscosity and improve the combustion characteristics. Literature has little consensus on NOx emissions from the combustion system operating with biodiesel. Therefore, the present study aims to reduce the thermal NO formation through the concept of exhaust gas recirculation. The CO, HC, NOx emissions and soot-volume fraction from biodiesel (100B0D), 50% blending (50B50D), diesel and kerosene are compared at different air preheating temperatures. A drastic reduction in emissions is observed in 50B50D as compared with pure biodiesel.