Droplet Deformation and Rotation Model of Fuel Spray in Diesel Engines 2001-01-2723
A droplet deformation and rotation model (DDR) has been developed and implemented in the KIVA II CFD code for better describing characteristics of liquid fuel sprays in diesel engines, including the distribution of sprays in combustion chamber space and the spray/wall impingement. The DDR model accounts for the effects of both the droplet's frontal area and its drag coefficient as a function of its deformation and rotation on droplet drag and droplet breakup. Therefore, the DDR model can be used for calculating the fuel droplet's drag and breakup in the process of combustion in diesel engines. This makes it possible to model the highly distorted droplet's frontal area variation and its effect on the drag coefficient in sprays. The new version of the KIVA II code with the DDR model has been tested for a case of the spray/wall impingement and a case of the combustion process in a diesel engine. The results from numerical calculation by using the new version of KIVA II code with the DDR model and the corresponding experimental data are in good agreement for both cases. In addition, in the spray/wall impingement case the effect of the DDR model has been seen to be very important on both the spray penetration and the wall spray height after impingement. In contrast to earlier models, it has been found that the calculated data are insensitive to the choice of the breakup time constant B1 after impingement. This indicates that the physics of droplet destabilization processes following wall impingement are accounted for more reasonably with the DDR model.