Numerical modeling on a diesel engine fueled by biodiesel-methanol blends

A modeling study was conducted to investigate the impact of methanol addition on the performance, combustion and emission characteristics of a diesel engine fueled by biodiesel. 3-D CFD simulations were conducted using the KIVA4 code coupled with CHEMKIN II for neat biodiesel and its blend fuels with 5%, 10% and 15% (in vol.) of methanol under 10%, 50% and 100% loads and a fixed engine speed of 2400 rpm conditions. A skeletal reaction mechanism was developed to mimic the significant species and reaction pathways of biodiesel and methanol fuels, and it was validated by performing the ignition delay calculations for biodiesel and methanol, as well as 3D numerical simulations against the experimental results for biodiesel. Good agreements in terms of ignition delay, cylinder pressure and heat release rate predictions were obtained. The simulation results revealed that with partial replacement of biodiesel by methanol, tangible improvement on the cylinder pressure was observed under 10% load condition especially for the case with 5% methanol blend ratio. Whereas, under 50% and 100% engine load conditions, only comparable cylinder pressure curves were seen. In terms of performance characteristics, almost linearly increased indicated thermal efficiency with respect to methanol blend ratio were observed under all the engine load conditions. Overall, the indicated CO and soot emissions decreased.