Compression ignition combustion of low cetane number fuels

Generally, the alternative fuels which are available for internal combustion engines have low cetane numbers. They are therefore not directly suited to compression ignition (diesel) engines. However, they can be used by adopting a mixed combustion process called dual-fuelling (DF). In this process, the alternative (ie the primary) fuel is ignited by a pilot distillate (diesel oil) spray. Dual-fuelling has the added advantage of fuel flexibility during the development of an alternative fuel distribution system. Engine tests have highlighted a number of problems associated with dual-fuel combustion. As with all modem engine development, the combination of fundamental experiments with numerical simulation is extremely important. In this paper, the literature on dual-fuel engine experiments is examined and the combustion problems discussed. A DF experimental program carried out at the University of New South Wales (UNSW) using numerical modelling and experiments on constant volume combustion bombs and rapid compression machines is then considered.