The matching of fuel injection characteristics with air motion and combustion chamber geometry is now widely modelled for more rigorous investigations of fuel-air, mixing in direct injection (DI) diesel engines to obtain improvements in fuel economy and emission characteristics. A number of studies have contributed in the understanding of fuel spray-air motion interaction in DI diesel engines. The genesis and characterization of swirl motion both during induction and compression is discussed as it influences spray growth, its trajectory and fuel-air mixing. Different aspects of fuel spray structure eg. break-up, drop-size distribution, spray penetration, air entrainment etc. are important. These spray development aspects are also briefly discussed in the paper. Different analytical approaches to model air entrainment in turbulent jet in the engine situation are summarized. Critical aspects of spray-swirl interaction and the important features of different simulation models are discussed.
A few attempts only have been made to model the wall jet formation in engines particularly in swirling environment. A critical review of the available models is done alongwith identification of gaps in knowledge and directions for the future studies.