Blending n-octanol with biodiesel for more efficient and cleaner combustion in diesel engines: A modeling study

Biodiesel has become a popular alternative fuel to fossil diesel. However, compared to conventional diesel en-gines, the adoption of pure biodiesel often leads to higher NOx though soot emissions can be reduced. In this study, the alcoholic fuel n-octanol was chosen as the blending fuel in biodiesel. The modeling study was carried out to investigate the effects of blending n-octanol on the combustion characteristics and emissions formation process in a diesel engine. At first, a multi-component reaction mechanism involving 115 species and 489 re-actions was constructed to better predict the combustion process of biodiesel and n-octanol. This mechanism was then coupled with KIVA-CHEMKIN to implement a three-dimensional simulation of the engine. The developed mechanisms and adopted models were validated under a variety of conditions. At last, to examine the effects of n-octanol, simulations were carried out by gradually increasing the percentage of n-octanol from 0% to 100% with an interval of 10%. Analysis of the simulation results revealed that blending more n-octanol with biodiesel could lead to a prolonged ignition delay. Due to the high latent heat of vaporization of n-octanol, the temperature at the initial stage of combustion can be reduced which subsequently mitigated the formation of NOx. The higher oxygen content of n-octanol was beneficial for the improvement in power output and the decrease of soot emissions. Overall, B20/O80 blends were found to be capable of achieving more efficient and cleaner combustion in the diesel engine at both speeds.