| Inhalable particle now become the major air pollutant of China, which severely affects people’s health. Therefore, the processes of how these inhalable particles are inhaled as well as their transport and deposition in human airway, especially the hot topics associated with nano particle, hygroscopic particle, non-spherical particle, etc., arose significant concerns of researchers. The accurate grasp of the mechanism of inhalable particle transport and deposition in human airway not only helps to understand the real cause of lung disease, but also facilitate the medical practices of researches of inhalable medicine and inhaler. Simulation and experiment were carried out to analyze the transport and deposition of inhalable particle in airway from multiple aspects.CFD-DPM (Computational Fluid Dynamics-Discrete Phase Model) approach was firstly applied to simulate the particle transport and deposition in lower airway under laminar flow condition. Its accuracy was validated by comparing with previous experiment data. A G5-G8 airway affected by chronic obstructed pulmonary disease was constructed, and numerical comparison were conducted to analyze the flow distributions, particle deposition patterns and deposition efficiencies under steady and unsteady inhalation conditions.The multi-component inhalable particle-vapor interaction model was developed and validated based on CFD-DPM method. The behavior of hygroscopic spherical multi-component particle were simulate in an idealized mouth-throat model and a G3-G6 airway model to investigate the effects of realistic airway humidity and temperature on hygroscopic growth, transport and deposition of multi-component particle. The simulation in the idealized mouth-throat model emphasized on the comparison of dry and humid airway boundary conditions, while that in the G3-G6 airway model focused on the difference between realistic temperature and humidity distribution of the boundary and idealized ones, e.g.,37℃, RH= 99.5%.The transport and deposition of spherical inhalable particle was simulated in a G3-G5 airway based on CFD-DEM (Computational Fluid Dynamics-Discrete Element Method) approach. The results showed that the deposition efficiency predicted by CFD-DEM was similar to the experimental data, and had the accuracy on the same level with CFD-DPM. It proved that CFD-DEM approach is suitable for the research of particle transport and deposition in human airway for the first time. The relationships between particles’ initial positions and final destinies were also studied.Experiment was carried out to investigate the deposition characteristics of fibrous particle. A single bifurcating airway based on Weibel’s model was constructed by 3D printing method. The deposition fractions of fibrous particles were obtained under different flow conditions. A microphotographing and image-processing method was proposed to examine the deposition characteristic of particle. It is the first time that the orientations of deposited fibers are quantitatively acquired. The relationship between the averaged, absolute orientation angles of fibers |θ| and sedimentation parameter y was revealed within the range of γ between 0.0228～0.247. The effects of fiber’s length and flow rate on |θ| were also analyzed. This experiment provides important data for the computer model validation of the transport and deposition of fibrous particle.Simulations of the transport and deposition inhalable particle with diameters of 1 to 7 μm were carried out in a G11-G14 airway model under nasal/oral flow rate of 15 to 120 L/min conditions using CFD-DPM approach. The deposition fraction data verified that the matching sedimentation parameter and Stokes number method is able to predict the particle deposition characteristics in lower airway. It also proved that the lowest deposition fraction exists in the lower airway. The empirical formula for deposition fraction against sedimentation parameter and Stokes number was also improved. |
PDF Full Text Request