Effect of supercharging in neat biodiesel fuelled naturally aspirated diesel engine combustion, vibration and emission analysis

Diesel engines are the most efficient internal combustion engines widely used in automotive, agriculture and industry applications. However, their harmful exhaust emissions contribute to an increase in environmental air pollution. Therefore, different green fuels, often called biodiesels, have inspired researchers to examine. In this work, neat palm methyl ester (PME) is used as an alternative fuel to examine the combustion performance, engine cylinder vibration and exhaust emissions. The experiments are conducted on a single-cylinder diesel engine at naturally aspirated and supercharged modes. The combustion results at three-fourth and full loads reveal that maximum in-cylinder combustion pressures are attained for Supercharged PME (S-PME), which helps to produce high power with better torque conversion. The brake thermal efficiency (BTE) of 33.06% and 32.87% at 0.45 and 0.54 equivalency ratios is attained for naturally operated PME (N-PME). The FFT vibrations measured vertically on the cylinder head reveal that the high-frequency vibrations are attenuated and better combustion with low-frequency vibrations (<50 dB) is achieved with the implementation of S-PME. Furthermore, low-level CO, NOx, UHC and smoke emissions are reported for S-PME. Supercharging is found to be beneficial by achieving low exhaust emissions and vibrations.