Acoustic unsteadiness of sprays from pressurised metered-dose inhalers

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A technique has been developed for the measurement of acoustic unsteadiness of sprays from pressurised metered-dose inhalers.An ensemble (n≥126) of acoustic measurements of sprays were obtained for two formulations with and without ethanol. Acoustic signals were analysed using the Hilbert-Huang Transform to obtain their amplitude envelopes, allowing the instantaneous energy to be determined. Ensemble statistics of each formulation’s instantaneous energies allowed the determination of time-variant unsteadiness. The performance of the technique is demonstrated using two formulations with different steadiness characteristics; internal flow pattern phase contrast visualisations are presented that show the flow pattern varies by formulation. Unsteadinesses are presented for both formulations and is approximately 50% higher for the propellant-only formulation in the first 100 ms of injection. Variation of the unsteadiness with low-pass filtering of the acoustic energy demonstrates that the unsteadinesses are more separable when short-duration fluctuations are removed.
Original languageEnglish
Title of host publicationProceedings of the 20th Australasian Fluid Mechanics Conference (AFMC)
Subtitle of host publication5-8th December, 2016, Perth, Western Australia
PublisherAustralasian Fluid Mechanics Society
Number of pages4
ISBN (Electronic)9781740523776
Publication statusPublished - 2016
EventAustralasian Fluid Mechanics Conference 2016 - The University of Western Australia, Perth, Australia
Duration: 5 Dec 20168 Dec 2016
Conference number: 20th


ConferenceAustralasian Fluid Mechanics Conference 2016
Abbreviated titleAFMC 2016

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