Performance improvement of dry powder inhalers through grid and tapered chamber optimization based on CFD-DEM method

A core challenge in dry powder inhalers (DPIs) resides in achieving a balance between particle dispersion efficiency and particle retention rate. Vortexing facilitates drug particle deagglomeration, while excessive vortexing promotes particle deposition inside the inhaler. The computational fluid dynamics-discrete element method (CFD-DEM) is employed to optimize the key structures of the inhaler. Aiming to clarify the effects of structural parameters on the flow field and particle collision behavior, eleven distinct designs are proposed by modifying the grids and swirl chambers. For the grid with a 2 mm aperture and cross-arrangement, enhanced airflow uniformity in the mouthpiece and maintained moderate airflow velocity in the swirl chamber are achieved. This design promotes particle collision for deagglomeration while avoiding particle retention in the mouthpiece caused by swirling flow. The fine particle fraction (FPF), indicating deep lung deposition of drugs, is 5.86% higher than the prototype. Moreover, airflow transition between the swirl chamber and the grid is optimized with a 1 mm tapered section, which not only improves airflow velocity, but also prevents the generation of excessive swirling flow. Then, particle impact counts and impact energy in the swirl chamber increase, leading to a 5.43% increase in FPF relative to the prototype.