An optical study on the cross-spray characteristics and combustion flames of automobile engine fueled with diesel/methanol under various injection timings

The fundamental research on the spray and combustion characteristics of diesel/methanol dual injection was explored in this study. A constant-volume combustion chamber was modified to accommodate cross-fuel injection by adding another fuel supply and an injection system. The effects of diesel/methanol injection timings on cross-spray and flame development were analysed for various injection intervals and pressures. The results showed that as the injection pressure increased, the high atomisation of the diesel–methanol mixed spray plume promoted its combustion. After diesel–methanol impingement at injection pressure of 100 MPa, a significant increase in the spray area occurred up to 62.5 % compared to its value at 60 MPa, resulting in a shortened combustion ignition delay, increased flame lift-off length and reduced soot generation. In addition, when methanol was used prior to diesel injection, the combustion ignition delay and flame lift-off length increased and soot generation decreased, as the diesel injection timings delay increased. Soot generation can be reduced by up to 33.3 % compared to that generated via the simultaneous injection of diesel/methanol at 60 MPa, by utilising a high injection pressure and proper injection timing. The study findings will provide a theoretical basis for the development of diesel/methanol dual-fuel direct-injection engines.