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Title: Revealing pMDI Spray Initial Conditions: Flashing, Atomisation and the Effect of Ethanol

Sprays from pressurised metered-dose inhalers are produced by a transient discharge of a multiphase mixture. Small length and short time scales have made the investigation of the governing processes difficult. Consequently, a deep understanding of the physical processes that govern atomisation and drug particle formation has been elusive. X-ray phase contrast imaging and quantitative radiography were used to reveal the internal flow structure and measure the time-variant nozzle exit mass density of 50 µL metered sprays of HFA134a, with and without ethanol cosolvent. Internal flow patterns were imaged at a magnification of 194 pixels/mm and 7759 frames per second with 150 ps temporal resolution. Spray projected mass was measured with temporal resolution of 1 ms and spatial resolution 6 µm × 5 µm. The flow upstream of the nozzle comprised large volumes of vapour at all times throughout the injection. The inclusion of ethanol prevented bubble coalescence, altering the internal flow structure and discharge. Radiography measurements confirmed that the nozzle exit area is dominantly occupied by vapour, with a peak liquid volume fraction of 13%. Vapour generation in pMDIs occurs upstream of the sump, and the dominant volume component in the nozzle exit orifice is vapour at all times inmore » the injection. Furthermore, the flow in ethanol-containing pMDIs has a bubbly structure resulting in a comparatively stable discharge, whereas the binary structure of propellant-only flows results in unsteady discharge and the production of unrespirable liquid masses.« less
Authors:
 [1] ;  [2] ;  [2] ;  [3] ;  [3] ;  [3] ;  [4] ;  [1] ;  [1]
  1. Monash Univ., Clayton (Australia)
  2. Argonne National Lab. (ANL), Lemont, IL (United States)
  3. Sydney Medical School, Sydney (Australia)
  4. Chiesi Ltd., Chippenhaum (United Kingdom)
Publication Date:
Grant/Contract Number:
AC02-06CH11357
Type:
Accepted Manuscript
Journal Name:
Pharmaceutical Research
Additional Journal Information:
Journal Volume: 34; Journal Issue: 4; Journal ID: ISSN 0724-8741
Publisher:
Springer
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
Australian Research Council; USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; 42 ENGINEERING; phase contrast imaging; pressurised metered-dose inhaler; radiography; synchrotron radiation
OSTI Identifier:
1373922