AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
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Modeling of Multispecies Aerosol Formation and Evolution in a Capillary Aerosol Generator
Francesco Lucci, Edo Frederix, ARKADIUSZ KUCZAJ, Philip Morris International R&D
Abstract Number: 431 Working Group: Aerosol Physics
Abstract The capillary aerosol generator (CAG) concept was developed nearly 20 years ago, finding various applications, including generation of pharmaceutical aerosols. In the CAG, aerosol is generated around the capillary outlet by vigorous, often turbulent, mixing of a jet of supersaturated vapors with an ambient cold air stream. Computational modeling of such a complex process remains a challenge. We have developed a computational fluid dynamics code, AeroSolved (http://www.aerosolved.com) for simulations of the formation, transport, evolution, and deposition of multispecies aerosol mixtures. In this work, we concentrate on development of a consistent modeling approach between aerosol nucleation and condensation/evaporation processes in a multispecies context. Assuming a dilute aerosol mixture with limited impact on the total momentum and energy, we solve the transport equations for each species and phase while treating the energy and momentum only for the total mixture as a whole. A drift flux approach is used to transport each species relative to the mixture by computing relative velocities and diffusion terms. A sectional method is used to resolve the shape of the particle size distribution without making a priori assumptions. We use modified classical nucleation theory extended for multispecies mixtures. The species-specific condensation rate function introduces a modification of the standard single-species condensation rate to account for the Stefan flow. The models are tested and validated against available literature. The validated models are finally applied to the simulation of aerosol formation in the CAG. We show that in our setup, turbulent diffusion plays an important role in the gas transport and thus in the aerosol formation. The majority of the particles is formed in a ring centred on the axis of the CAG chamber. From there, particles are transported further downstream and diffuse radially. Numerical results for varying thermodynamic conditions and parametric studies will be presented in detail.