Numerical Simulation of the Flow Field and Fuel Sprays in an IC Engine

A two-dimensional, implicit finite-difference method of the control-volume variety, a two-equation model of turbulence, and a discrete droplet model have been used to study the flow field, turbulence levels, fuel penetration, vaporization and mixing in Diesel engine-type environments. Good agreement with the droplet penetration data of Hiroyasu and Kadota has been obtained for a range of ambient pressures neglecting the effects of void fraction, droplet coalescence and droplet collisions in the simulation. The model has also been used to study the effects of the intake swirl angle on the flow field, turbulence levels, fuel penetration, vaporization and mixing in a two-stroke Diesel engine operating under motored conditions. Numerical simulations indicate that as the intake swirl angle is increased, the fuel penetration, vaporization and mixing increase. For the largest intake swirl conditions investigated, some droplets strike on the cylinder wall and remain trapped in the boundary layer. The amount of liquid fuel found in the boundary layer is small and most of the fuel vaporizes before some droplets strike on the cylinder wall. The flow fields, fuel penetration, vaporization and mixing obtained under different intake swirl levels are illustrated by means of velocity profiles. Sauter mean diameter, and gaseous fuel distribution plots.