(98al) Investigation of Multiphase Multicomponent Aerosol Spray From Pmdi Through Commercial Spacers
AIChE Annual Meeting
Monday, November 4, 2013 - 11:00am to 12:30pm
The purpose of the current study is to develop a numerical model which can characterize flow and the resulting particle metrics (surface deposition, PSD etc.) when a commercial suspension based pMDI is sprayed into a spacer. The effect of different variables like volumetric rate of coaxially flowing air, spacer geometry and delay are investigated in order to develop labeling guidelines for patient use for similar products. Flow behavior of the multiphase multicomponent aerosolic spray, in static air, and within the spacers ( Aerochamber Plus and Optichamber Advantage) in the presence of coaxial air were simulated using phenomenological 2 equation RANS models . Computational geometries of the inhaler and spacers were realized and meshed (tet dominant) using ANSYS Workbench tools. The standard k- ω model with Lagrangian tracking available within ANSYS Fluent 14.0 was used to simulate spray emanating out of the Proventil inhaler in a 2 way coupling mode with concurrent coaxial air flow at specified volumetric flow rates of 28.3 and 11 LPM flowing through the entire domain. The cone angle of the spray used as a model input was experimentally measured by high speed video imaging. The predictions made by the model were validated against known experimental results. The effect of delay (0 and 5 seconds) was also investigated for both the spacers.
The CFD model predictions favorably compared with experimental data when velocity and size data were compared at two different locations when the inhaler was sprayed in static air. The results for inhaler-spacer systems show an increase of drug escaping the spacers on increasing the volumetric flow rate in accordance with experimental determinations. The recirculation observed near obstructions in axial path of the spray within the spacer is determined to be critical in enhancing spray retention within the spacer. Introduction of a delay is found to trap more drug in the spacer. The MMAD of the drug that escapes the spacer is smaller than what is injected for all cases, while the coarser particles are trapped within the spacer surfaces. In conclusion, a validated CFD model was developed for characterizing inhaler-spacer interactions which can be used for similar systems to predict desired particle metrics.