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
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.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.