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Using phase Doppler anemometry & high speed imaging to analyze MDI spray plume dynamics

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conference contribution
posted on 01.03.2017, 12:12 by Hendrik Versteeg, Graham Hargrave, Ben Myatt, David Lewis, Tanya Church, G. Brambilla
Characterisation of inhalation aerosols focuses in the first instance on aerodynamic particle size, which is measured using cascade impactors. The aerosol must contain large quantities of particles in the respirable size range 1-5 m. Deposition on impactor stages depends on the velocity of the particles as well as their size. Pressurised metered dose inhalers (pMDIs) produce very fast-moving spray plumes, so it is important to understand the dynamic nature of droplet formation processes and spray plumes. This paper presents a selection of findings from an optical diagnostics study of aerosol plumes generated by a Bespak 630 series actuator in conjunction with a series of HFA134a placebo formulations containing ethanol up to 20% w/w. Spray plume dynamics in the vicinity of the spray orifice and further downstream were characterised using phase-Doppler anemometry (PDA), high-speed imaging and particle image velocimetry (PIV). The findings of the work demonstrate the complementary capabilities of these instruments. PDA provides simultaneous values of mean droplet size and velocity (and their associated statistics), but it is time-consuming to sample a sufficient number of locations to characterise the rapidly changing spray plume. PIV, on the other hand, provides information on entire flow fields albeit at lower spatial and temporal resolution. PIV and PDA data for the velocity of various spray plumes were found to be in good agreement, which validates both techniques. High-speed imaging also captures the overall characteristics of the plume. The diffraction limit of the optical configuration used for imaging is around 10 m, so it is not possible to observe respirable droplets individually. However, the dynamics and trajectories of larger droplets can be studied. These larger droplets were found to be produced by highly localised atomisation processes, so the resulting droplets can be easily missed or undersampled in PDA surveys. These results suggest that further research on pMDI sprays with these combined tools will provide useful insights into the processes responsible for changes in droplet size and velocity, and can be expected to make a major contribution to improving the development of the next generation of pMDI inhalers.

History

School

  • Mechanical, Electrical and Manufacturing Engineering

Published in

Proceedings of RDD Europe 2017

Citation

VERSTEEG, H.K. ... et al, 2017. Using phase Doppler anemometry & high speed imaging to analyze MDI spray plume dynamics. IN: RDD Europe 2017, Nice (Antibes), France, 25th-28th April 2017.

Version

VoR (Version of Record)

Publisher statement

This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/

Acceptance date

30/01/2017

Publication date

2017

Notes

Versteeg HK, Hargrave G, Myatt BJ, Lewis DA, Church T, Brambilla G: Using phase Doppler anemometry & high speed imaging to analyze MDI spray plume dynamics. In RDD Europe 2017. Volume 1. Edited by Dalby RN, Peart J, Suman, J, Young PM, Traini D. DHI Publishing; River Grove, IL: 2017: 129–142. Provided with permission from RDD Europe 2017, Virginia Commonwealth University and RDD Online.

Language

en

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