Unsteady Influences in Droplet Dynamics and Combustion

Abstract

This research investigation addresses the problem of the unsteady dynamics associated with the vaporization. ignition and hurning of hydrocarhon fuel droplets in laminar and turhulent flowfields. The method of approach is numerical. and detailed solutians of the Navier-Stokes equations have heen carried out to determine the important physical processes which occur around a burning droplet. For the relatively high pressure conditions of the present problem the most unsteady feature of the flow was the ignition and flame formation process. The ignition process causes major changes in the drag and heat transfer compared to the influences of eddy turhulence or the natural decay of the frecstream velocity between the droplet and the surroundings. However, both eddy turbulence and the natural decay of the freestream velocity play a very important role in the history over the droplet lifetime. All of the flow processes comhine to cause the trajectory or the history of the droplet to he much different than would be expected from a quasi-steady analysis. Therefore, it must he concluded that the use of detailed numerical solutions will play a pivotal role in the understanding and prediction of the dynamics of vaporizing droplets in gas streams.