4. Methanol: A Gateway to Biofuel Revolution in Global Heavy-Duty ICE-Based Transportation

This chapter reviews the various advanced combustion concepts that have shown immense potential of achieving excellent engine brake thermal efficiencies and extremely low engine-out NO_x and smoke emissions. Advanced combustion concepts like partially premixed combustion and reactivity-controlled compression ignition are well suited to work with biofuels like methanol. However, each of these advanced combustion concepts has their challenges, which further paved the way for mixed-mode combustion concepts, where the aim is to utilize such advanced combustion concepts for their ability to deliver excellent engine efficiencies in duty cycle part of engine operating zone and switch to classical diesel combustion or SI combustion in rest of engine working map. Worldwide, there are number of research laboratories and universities which have already shown close to 50% brake thermal efficiencies with NO_x emissions close to 0.25 g/kWh and smoke levels at 0.06 FSN at high load conditions. Engine with thermodynamic efficiencies level as high as 60% has already been demonstrated with very low engine-out emissions. Such research endeavours have already envisioned the way to achieve future emission levels of NO_x (nitrogen oxides) at 0.027 g/kWh. However, there are some challenges like high pressure rise rates (PRR), low load combustion stability and high turbocharger efficiency requirements for maintaining high dilution, which have to be addressed in future research work. There are other socio-economic challenges which the research organizations, original equipment manufacturer (OEMs) and government have to address to make biofuels as mainstream transportation fuel worldwide.