Droplet dynamics and vaporization with pressure as a parameter

The problem of fuel droplet vaporization has been analyzed by detailed numerical calculations of the Navier-Stokes equations in a relatively high Reynolds number regime (Reynolds number = 100). The calculations were performed with gas pressure as a parameter and for a fuel droplet whose properties were similar to dodecane. For all the conditions chosen there were substantial changes in Reynolds number during the droplet lifetime, and the droplet drag coefficient and Nusselt number deviated substantially from those obtained from quasi-static concepts, such as models based on Ranz-Marshall data. Early in the droplet lifetime internal convective transport is important; however, its importance decays repidly with the Reynolds number. Attempts to correlate the results in terms of the droplet liquid thermal time scale failed because of the independence of liquid vapor pressure from background gas density. It appears at this time that detailed and unsteady numerical calculations are necessary to accurately predict fuel droplet lifetimes.