Optimization of swirler type dry powder inhaler device design – Numerical investigation on the effect of dimple shape, inlet configuration and mouthpiece constriction

Abstract

Dry powder inhalers (DPIs) are recognized as one of the most convenient drug delivery devices via the respiratory tract. However, there is a large variation in their dispersion efficiencies due to the cohesive nature of the inhalable pharmaceutical powders. This paper presents a thorough numerical investigation of the effect of various design modifications in swirler type DPI devices. One-way coupled Computational Fluid Dynamics-Discrete Phase Modeling simulations were implemented to evaluate the flow field and particle behaviour in DPIs under 60 L/min inhalation condition. The dispersion behaviour of entrained particles in relation to the particle-wall impactions was evaluated in six different in-house designed and one commercial DPI devices, with variations in dimple shape, inlet orientation, inlet numbers, and mouthpiece pipe constriction. We found that the shape of dimples varies the swirling capability of both fluid and particles and mouthpiece pipe constriction reduced the turbulence kinetic energy. Meanwhile, the axial velocity and impaction frequency are increased as the size of particles are increased. The constriction of mouthpiece pipe did not show significant improvement on the frequency of particle-wall impactions for particles smaller than 10 μm, whilst higher impaction frequencies were observed for particles larger than 10 μm. Overall, the sphere shape dimples with mouthpiece pipe constricted design is optimal in terms of device efficiency.