In-Silico Prediction of pMDI performance with low-GWP propellants HFA-152a and HFO-1234ze(E)
Daniel Duke1, Lingzhe Rao1, Nirmal Marasini2, Hui Xin Ong2, David Schmidt3, Benjamin Myatt4, Phil Cocks4 & Paul Young2
1 Laboratory for Turbulence Research in Aerospace & Combustion (LTRAC), Department of Mechanical & Aerospace Engineering, Monash University, Clayton, 3800, Australia
2 Respiratory Technology, Woolcock Institute of Medical Research, Glebe, Sydney, NSW 2037, Australia
3 University of Massachusetts-Amherst, Amherst, MA 01003, United States of America
4 Kindeva Drug delivery, Charnwood Campus, 10 Bakewell Road, Loughborough, United Kingdom, LE11 5RB
Summary
The transition to low greenhouse warming potential propellants for pressurised metered dose inhalers will necessarily require a redesign of the nozzle orifice to compensate for changes in physicochemical properties such as reduced vapour pressure, density, and increased saturation temperature. New propellants have reduced spray momentum, reduced flash-evaporation, altered spray morphology resulting in larger primary droplet size at the orifice. Investigating these phenomena is challenging due to the large parameter space for orifice and actuator design and multiple propellant candidates that must be searched in order to find an optimal arrangement. A cost-effective solution to this problem is the use of in silico models which can search the parameter space quickly by running dozens of detailed computational fluid dynamics simulations on hundreds to thousands of processors. We present the first results of a parametric study of the effect of orifice diameter and length for solution formulations with propellants HFA-134a, HFA-152 and HFO-1234ze(E). The simulations are capable of capturing trends in near-orifice spray structure and accurately predicting droplet size. We show that manipulation of the orifice geometry may be able to compensate for the differences between propellants.
Key Message
Computational fluid dynamics models can predict trends in MDI spray and droplet properties when switching to alternative propellants HFA-152a and HFO-1234ze(E). The changes are within a viable range where manipulation of the orifice diameter and length can compensate for them.