A computational fluid dynamics-discrete element method investigation into the dispersion mechanisms and optimization of dry powder inhalers

Abstract

While pulmonary drug delivery via Dry Powder Inhalers (DPIs) offers targeted treatment for respiratory diseases, their efficiency is often hindered by an incomplete fundamental understanding of powder dispersion. This thesis addresses these knowledge gaps by establishing a unified Computational Fluid Dynamics-Discrete Element Method (CFD DEM) framework to quantify dispersion mechanisms and drive physics based optimization across two distinct platforms: the reservoir-based Symbicort® Turbuhaler® and the capsule-based Ultibro® Breezhaler®.

First, the study reveals that the carrier-blended Turbuhaler functions as a two-stage system: the circulation chamber, aided by a critical spoiler, acts as a partial deagglomeration zone, while the helical nozzle drives the high-inertia impaction responsible for the majority of fine particle generation. Second, a novel optimization strategy for the Turbuhaler introduces a four-lobed swirl pipe to create a "Helical Injection" mechanism. Specifically, a "Cross-Over" swirl design reverses the swirling direction, creating the most persistent swirling flow. This upstream flow conditioning increases oblique particle-wall impacts in the downstream nozzle, substantially improving the loaded fine particle fraction (FPF) from 46.5% to 61.9%. Third, a dynamic layering mesh method was developed for the Breezhaler to model fully coupled capsule rotation and vibration. The simulation demonstrated that the capsule's vertical vibration serves primarily as a mechanical agitator that induces crucial particle-wall collisions, yielding 100% capsule emptying. Capsule vibration also enhances carrier-wall collisions, leading to a higher FPF.

Ultimately, this research advances mechanistic DPI design by elucidating how specific geometric and dynamic features control particle-scale aerodynamics, offering a scientific roadmap for next generation, high-efficiency inhalers.

Date of Award	18 Jul 2026
Original language	English
Awarding Institution	University of Nottingham
Supervisor	Philip Hall (Supervisor) & Zheng Wang (Supervisor)