GAS/DIESEL DUAL-FUEL COMBUSTION MODELLING FOR ENGINE CONDITIONS
RÉSUMÉ
Gaseous fuels have important emission and resource benefits but are unsuitable for CI (diesel) engines. However, the dual-fuel (DF) concept provides a method for their use. At UNSW, fundamental studies are being followed with the development of a DF combustion bomb and a rapid compression machine. A 3-D Finite Volume Method (FVM) code has been developed to describe the constant volume, DF combustion in these rigs. The recent focus of the work is towards understanding the influence of different factors on dual-fuel combustion in engines and the occurrence of knock. The numerical results predict that swirl velocities of 550 rad/s are required to produce suitable burning rates for engines. This requires shallow ramp helical inlet ports. The effect of ignition delay on the combustion knock is illustrated, liquefied petroleum gas (LPG) being more likely than compressed natural gas (CNG) to result in spark ignition (SI) type knock.