Chemical and physical limits on vapor‐phase diffusion flames of droplets

The combustion of a fuel droplet can be described by a quasi‐steady theory at pressures up to about 1/10 of the critical pressure of the fuel. Finite rates of chemical reaction and evaporation impose lower bounds on the product of pressure and droplet size for which the theory is valid. An unsteady droplet theory becomes necessary for pressures between the highest pressure for a quasi‐steady theory and the critical pressure. Unsteady heat transfer and diffusion of dense gas are the significant processes in the combustion of a liquid fuel above its critical pressure. The burning rates above the critical pressure are likely of the same order as at lower pressures.