Investigating effects of rotation speed and flow rate on powder evacuation from a capsule for dry powder inhalers
Athiya Azeem1, Gajendra Singh2, Hak-Kim Chan3, Runyu Yang4 & Agisilaos Kourmatzis1
1School of Aerospace, Mechanical and Mechatronic Engineering. The University of Sydney, NSW 2006, Australia
2School of Engineering, IIT Mandi, HP 175075, India
3School of Pharmacy, the University of Sydney, NSW 2006, Australia
4School of Material Science and Engineering, UNSW Sydney, NSW 2052, Australia
Summary
Capsule-based dry powder inhalers (DPIs) have long been commercially available, but their performance remains largely unpredictable despite the prevalence of such devices. This is due, in part, to a lack of understanding of how different device designs affect powder dispersion and evacuation. One common design configuration is a spinning capsule that utilises airflow to rotate a capsule while collisions with the wall aid in dispersion. This study aimed to better understand these mechanisms by decoupling rotation speed from the flow rate and investigating their effect on powder evacuation from the capsule at various flow rates and rotation speed conditions. For this study, two flow rates, 30SLPM (inlet: 16.67 m/s) and 60SLPM (inlet: 33.33 m/s) and two rotation speed settings of 1500 RPM (Low case) and 3750 RPM (High case) were chosen. High-speed backlit imaging further provided qualitative information about evacuation behaviour.
At 60 SLPM the rotation speed had no significant effect on the overall powder evacuation during the three second run time. Furthermore, holding the capsule stationary and in line with the flow at this speed also did not affect the amount of powder evacuated. Therefore, at this flow rate and for the formulations tested evacuation was independent of rotation speed. When tested at 30 SLPM, the lower rotation speed setting was found to improve evacuation significantly compared to the high rotation speed case. Further rotational speed cases and formulations should be analysed in combination with high-speed microscopic imaging to gain a better understanding of dispersion behaviour.