A preliminary theoretical study of droplet extinction by depressurization
Depressurization-induced extinction of droplets is demonstrated using an unsteady liquid-phase theory and a previously presented quasisteady gas-phase model. Numerical results show that depressurization of the gas phase causes extinction of both regressing and nonregressing droplets. For nonregressing droplets it is found that at fixed droplet size the extinction pressure is a decreasing function of the initial depressurization rate; thus results are explained in terms of the time lag needed by a droplet to respond to a change in pressure. Regressing droplets, which extinguish more rapidly than constant-size ones, show the same type of behavior. Extinction boundaries, evaluated as functions of the initial temperature profile, show that whereas for constant-size droplets the extinction pressure is a strong decreasing function of the temperature, for regressing droplets this dependence is very weak and an asymptote is reached as the temperature increases. Results obtained by varying the initial pressure show that the extinction pressure is an increasing function of the initial pressure for regressing droplets. For constant-size droplets this function is nonmonotonic and reaches a maximum at the initial pressure for which the initial temperature profile is the wet-bulb state. The thermal conductivity of the liquid phase has almost no influence on the extinction boundary.