Flow visualisations of the spray from a novel soft mist inhaler using planar laser illumination
Vishal Chaugule1, Wietze Nijdam2, Bernhard Muellinger3, Varsha Komalla4, Imco Sibum3, Hui Xin Ong4,5, Daniela Traini4,5, Nicolas A. Buchmann3, & Julio Soria1
1Laboratory for Turbulence Research in Aerospace and Combustion (LTRAC), Department of Mechanical and Aerospace Engineering, Monash University, Clayton Campus, Melbourne, VIC 3800, Australia
2Medspray B.V., Enschede, The Netherlands
3Resyca B.V., Enschede, The Netherlands
4Respiratory Technology, Woolcock Institute of Medical Research, Sydney, NSW 2037, Australia
5Macquarie Medical School, Faculty of Medicine, Health and Human Sciences, Macquarie University, NSW 2109, Australia
Summary
Soft mist inhalers are next-generation inhaled drug delivery devices that use mechanical energy to convert a liquid formulation into a fine mist suitable for inhalation. Some soft mist inhalers create an inherently unstable liquid jet that spontaneously undergoes breakup to produce a low-momentum aerosol cloud suitable for lung delivery. The PulmosprayTM is one such soft mist inhaler and the characteristics of the spray from its mouthpiece were qualitatively evaluated in this study using the planar laser illumination technique. The working liquid used was water for injection. The mouthpiece was provided with a steady liquid flow rate of 0.37 mL/min and steady airflow rates of 15, 30, 45 and 60 SLPM. An ensemble of single-exposure images of the spray droplets illuminated by the laser sheet were recorded at 100 Hz using a high-speed camera and are processed to obtain the mean spray image, for all the examined airflow rates. The macroscopic spray characteristics determined are the mean spray pattern, spray width and spray angle. Cross-correlation analysis of single exposure images acquired at 8000 Hz was performed to determine the mean spray centreline velocity. The instantaneous spray snapshots depicted emergence of a turbulent spray for all examined airflow rates. A narrower spray was generated with increasing airflow rates, but the spray spread remained similar for the examined airflow rates greater than 30 L/min. There was a monotonic decrease in the spray centreline mean axial velocity with increasing downstream distance from the mouthpiece for the examined airflow rates.