Influence of Carbon Chain Length on Biodiesel Combustion in an Optically Accessible Diesel Engine

This study focuses on laser-based imaging diagnostics of hydroxyl and soot during biodiesel combustion in a light-duty optical diesel engine. Planar laser-induced fluorescence of OH (OH-PLIF) and laser-induced incandescence (PLII) diagnostics were performed for two biodiesel fuels with different carbon chain lengths. The results show that longer carbon chain length leads to decreased ignition delay, which makes OH start to form closer to the bowl wall during the premixed combustion phase. For both fuels, soot formation starts to occur near the fuel-rich jet-wall impingement region at the end of the premixed combustion phase. However, it is only the longer carbon-chain biodiesel that shows additional soot formation in the penetrating wall-jet head region and overall higher amounts of in-cylinder soot.