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Wind Tunnel Evaluation of An Aircraft-Borne Sampling System

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Abstract:The US Environmental Protection Agency (EPA), the Florida Department of Environmental Protection (FLDEP), and Texas A&M University collaborated in the design, construction, and testing of a unique highly cross-linked Teflon coated inlet and manifold gas and aerosol sampling system that are being used in EPA aircraft atmospheric pollution characterization studies. The aircraft-borne ambient sampling system consists of a Teflon coated shrouded probe coupled to a Teflon coated aluminum manifold that are designed to collect reactive gases (e.g., mercury and halide species) and aerosols for subsequent analysis and characterization. The shrouded inlet probe was tested for particle transmission ratios in a high-speed aerosol wind tunnel. An existing wind tunnel was upgraded from a maximum wind speed of 13.4 m/s (48 km/h or 30 miles/hr) to 50.5 m/s (182 km/h or 113 miles/hr) to test this probe. The wind tunnel was evaluated for compliance with the criteria of ANSI 13.1 to establish the acceptability of its use in testing probes. The results demonstrated that the velocity and tracer gas concentration profiles were within the specified limits. A well characterized ThermoAndersen Shrouded Probe (Model RF-2-112) was also tested to check tunnel performance and test methodology. The results obtained from these tests are in close agreement with data published earlier.

The aircraft-borne shrouded probe showed a transmission ratio of about 0.76 at 45 m/s (162 km/h or 100 miles/hr) for 10 m aerodynamic diameter particles at a sampling flow rate of 90 L/min. To improve the transmission ratio of the sampling probe, the sampling flow rate was reduced to 80 L/min and the air speed increased to 50.5 m/s, which increased the transmission ratio to about 0.9 for 10 m particles. Further reduction of the flow rate to 60 L/min increased the transmission to 1.2. The Teflon coated manifold downstream of the shrouded probe, was statically tested for transmission ratio at flow rates of 90 L/min and 30 L/min. The results were a transmission ratio about 0.80 for 10 m aerodynamic diameter particles. The combination of the shrouded probe operated at 60 L/min with a transmission ratio of 1.2 and the manifold with its transmission of 0.8, will give an overall transmission of about unity for 10 um aerodynamic diameter particles at a flight speed of 50.5 m/s.

These findings suggest that shrouded probes can be used for low speed (~100 miles/hr) aircraft applications. The transmission ratio of these probes is a significant improvement over the conventional aircraft-mounted, sharp-edged isokinetic diffuser-type inlets.

This manuscript has been subjected to Agency Review and approved for publication. Mention of trade names or commercial products does not constitute an endorsement or recommendation for use.
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Citation:Irshrad, H., A. Mcfarland, M. S. Landis, and R. K. Stevens. Wind Tunnel Evaluation of An Aircraft-Borne Sampling System. AEROSOL SCIENCE AND TECHNOLOGY 38(4):311-321, (2004).
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Contact: Liz Hope - (919) 541-2785 or hope.elizabeth@epa.gov
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Division: Human Exposure & Atmospheric Sciences Division
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Branch: Environmental Characterization & Apportionment Branch
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Product Type: Journal
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Published: 04/01/2004
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Bullet Item Wind Tunnel Evaluation of An Aircraft-Borne Sampling System
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Related Entries:
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Bullet Item Atmospheric Mercury Research
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