A group combustion model for treating reactive sprays in I.C. engines

A model is presented and discussed treating the complex interactions between the fluid dynamics, the size, space, and time distributions of droplets as well as the combustion chemistry in a Diesel spray. The three-dimensional droplet characteristics are modeled with an overset gridding scheme, CHIMERA, and time dependent solutions of the Navier-Stokes equations have been carried out with the digital computer. The chemistry is treated with global and detailed reaction kinetics in a two-stage model. The global kinetics were used with the detailed Navier-Stokes equations, and the detailed kinetics were employed with a time dependent one-dimensional model that used information from the detailed model. The typical thermodynamic conditions of a modern truck engine have been used to provide insight into the details of ignition, combustion, and pollutant formation in spray commbustion. The study has considered droplet groups that have both uniform and different size droplets, and different groupings of the droplets have been investigated. The present model allows the droplets to move and vaporize in time, and the time development of ignition has been studied. The results indicate that group combustion effects have a dominant influence on all aspects of spray combustion.