A Computational Fluid Dynamics Study of Particle Penetration through an Omni-Directional Aerosol Inlet

Figures & data

FIG. 1 (a) Cross-sectional view of the 100 L/min Bell-Shaped Inlet entrance section (BSI-e). In the figure: 1. Outer shell; 2. Inner shell; 3. Intake gap; 4. Between-shell passage; 5. Windows; 6. Exhaust tube; 7. Entrance of the exhaust tube; 8. Exit plane of exhaust tube; 9. Intake surface (facing the wind). (b) A 3- D view of the BSI-e.

FIG. 2 Schematic of the computational domain used in numerical simulations. Boundary conditions: Inlet surface of the domain—“Velocity Inlet” (with velocity of wind speed); Lateral surfaces of the domain—“Symmetric”; Outlet surface of exhaust tube and domain—“Outflow” (with outlet flow rate of 100 L/min at exhaust tube); Surfaces of BSI-e—“Wall.”

FIG. 5 Top view of inner shell showing CFD-simulated particle deposition.

FIG. 3 CFD simulation of the flow field at a wind speed of 8 km/h (2.2 m/s). (a) Velocity vectors in the vertical plane through the BSI-e axis and parallel to the free stream (dashed lines “b” and “c” indicate locations of the two horizontal planes for Figure 3b and Figure 3c). (b) Velocity vectors in a horizontal plane slightly above the rim of the outer shell. (c) Velocity vectors in a horizontal plane in the cylindrical section of the shells (shell radii do not change with height). Units of velocity scales are m/s.

FIG. 4 Comparison of penetration from experiments of Nene (2006) and Baehl (2007), and CFD simulations at wind speeds of: (a) 2 km/h. (b) 8 km/h. (c) 24 km/h.

TABLE 1 Estimated regional and overall penetration percentage of the BSI-e from CFD analyses

	Free stream wind speed
	2 km/h		8 km/h		24 km/h
	Aerodynamic particle diameter
Region	10 μ m	15 μ m	10 μ m	15 μ m	10 μ m	15 μ m
P 1	101%	102%	104%	105%	110%	112%
P 2	88.0%	81.5%	94.1%	81.5%	85.7%	55.3%
P 3	98.5%	96.4%	96.5%	94.7%	94.4%	90.1%
P total	87.5%	80.1%	94.4%	81.0%	89.0%	55.8%

TABLE 2 CFD predictions of overall penetration percentage of the BSI-e with and without the gravitational effect

	Free stream wind speed 2 km/h			Free stream wind speed 8 km/h			Free stream wind speed 24 km/h
Aerodynamic Particle Diameter μ m	With gravitational effect	Without gravitational effect	Difference	With gravitational effect	Without gravitational effect	Difference	With gravitational effect	Without gravitational effect	Difference
2	98.8%	99.4%	0.6%	98.5%	98.7%	0.2%	98.3%	98.4%	0.1%
5	96.7%	98.9%	2.1%	97.4%	97.7%	0.3%	96.7%	96.9%	0.2%
10	87.5%	94.4%	6.9%	94.4%	94.6%	0.2%	89.0%	89.1%	0.1%
15	80.1%	87.5%	7.4%	81.0%	81.7%	0.7%	55.8%	56.1%	0.3%
20	71.9%	80.4%	8.5%	69.0%	69.9%	0.9%	N/A	N/A	N/A

FIG. 6 Curves showing penetration predicted from correlation compared with experimental and CFD data at wind speeds of (a) 2 km/h, (b) 8 km/h, (c) 24 km/h.

TABLE 3 Curve fitting results for the coefficients in Equation (7) with corresponding uncertainties

Coefficients in Equation (7)	C 1	C 2	C 3	C 4	C 5	C 6
Curve fitting values	0.0076 ± 0.0003	0.105 ± 0.004	2.91 ± 0.08	0.072 ± 0.003	0.507 ± 0.009	0.955 ± 0.022

FIG. 7 Agreement of correlation equation predictions with experimental and CFD results.

Nene , R. R. 2006 . Design of Bio-aerosol Sampling Inlets , M. S. Thesis College Station, Texas : Department of Mechanical Engineering, Texas A&M University . Available online at: http://txspace.tamu.edu/handle/1969.1/5736?show=full

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Baehl , M. M. 2007 . Ambient Aerosol Sampling Inlet for Flow Rates of 100 and 400 L/min , M. S. Thesis College Station, Texas : Department of Mechanical Engineering, Texas A&M University .

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