Airflow simulation testing using CFD

Challenge

Use the energy from the user’s inhaled breath to evacuate powder from a capsule and deliver it to the deep lung.

Approach

Computational fluid dynamics (CFD) were used to simulate the airflow and particles in the inhaler before designing the prototype and testing it in the laboratory.

Outcome

The inhaler device was able to evacuate and deagglomerate the powder into respirable particles, while reducing the likelihood of powder deposition in the user’s mouth.

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CFD was required for this project to understand how to achieve a high performance dose delivery with solely the energy available from a user’s breath.

This dry-powder inhaler contains an aerosolisation engine that harnesses energy from the user’s inhaled breath to deliver a dose aerosol of solid particles. The engine is required to evacuate powder from the loaded capsule and to deagglomerate the powder into particles small enough to reach the user’s deep lung for therapeutic effect.

Achieving high-performance dose delivery with solely the energy available from the user’s breath represents a significant challenge, and CFD proved to be a highly valuable tool for meeting this challenge during development of the TAE device.

Our approach

With CFD we were able to simulate the flow of air and particles through the inhaler in a virtual environment, which was much faster and less costly than equivalent experimental testing in the laboratory.

Physical testing remained an essential part of the development process, but with insight from CFD we were able to quickly narrow down design ideas, reduce the number of expensive prototypes to test and significantly increase our understanding of prototype performance.

Outcome

The performance of the TAE dry powder inhaler device was optimised with the help of CFD by fine tuning various design parameters to enhance a range of key performance metrics, such as:

Swirl balance

The airflow path through the TAE device includes three separate swirl chambers, and the balance of the available energy expended across each chamber is critical to performance. With insight from CFD, we were able to make changes to the swirl chamber geometries that target energy usage to where it is most effective.

Particle dynamics

CFD quantification of aerodynamic and impaction forces delivered to dose particles within the inhaler, led to the development of TAE design features that maximise the magnitude and duration of these forces. This acted to improve the break-up of agglomerates into respirable particles for an increased fine particle fraction.

Flow conditioning

CFD was used to ensure that strongly swirling flow within the device engine is straightened as much as possible before exiting the mouthpiece. This helped to improve overall device efficiency through pressure recovery and also to reduce the likelihood of dose powder deposition in the user’s mouth.