Factors affecting the atomization of saturated liquids

The atomization of a liquified gas propellant, as a means of dispersing a powdered drug or non-volatile solute, was investigated. Atomization was achieved by passing the propellant through a two-orifice nozzle assembly. A number of properties of the system were shown to be predictable with reasonable accuracy, in terms of the nozzle dimensions and thermodynamic properties of the propellant, together with minor empirical factors. The properties that could be predicted were the mass flow-rate, the pressure of the propellant in the expansion chamber between the two orifices, the quality, or mass fraction evaporated, of the propellant in the expansion chamber, and the initial velocity of the spray. By application of the principle of momentum conservation the axial velocity decay of the gaseous component of the resultant spray and to a certain extent the particulate component of the spray could also be predicted. In addition to the above fundamental relationships, an empirical expression for the mass median diameter of the residual aerosol of a non-volatile solute dissolved in the propellant was determined. Information thus obtained is of assistance in the optimisation of the design of liquified gas aerosol generators as a means of administering a drug by inhalation.