Spray formation by flashing of a binary mixture: A parametric study

A binary liquid mixture which consists of a low-vapor-pressure liquid and a propellant has been considered. When the mixture is discharged through an appropriate injection system, the propellant undergoes a rapid flash boiling process which results in a disintegration of the continuous liquid phase into small droplets. In the present work, the effect of the injection system design on the spray characteristics is investigated experimentally. It is concluded that: (1) the real behavior of the solution, as compared to ideal solution behavior, is an important factor; (2) the important stage of nucleation occurs at the metering orifice and apparently, the main duct does not play any significant role in the bubbles' nucleation; (3) neither the expansion chamber diameter nor its length has any significant effect on the droplet Sauter mean diameter (SMD), (4) an orifice's diameters ratio (metering to discharge) between 0.6 and 0.9 results in a minimum SMD; and (5) the SMD is correlated well with a modified version of the Jakob number of the form of J_a^* = xβ(c_pΔT/h_fg).