A shrouded aerosol sampling probe

Self Cite

The U.S. 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 crosslinked, Teflon-coated inlet and manifold gas and aerosol sampling system that is being used in EPA aircraft atmospheric pollution characterization studies. The aircraftborne ambient sampling system, which consists of a Teflon-coated shrouded probe coupled to a Teflon-coated aluminum manifold, is 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/h) to 50.5 m/s (182 km/h or 113 miles/h) 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 wellcharacterized ThermoAndersen Shrouded Probe (Model RF-2-112) was also tested to check tunnel performance and test methodology. These findings suggest that shrouded probes can be used for low speed (∼100 miles/h) aircraft applications. The transmission ratio of these probes is a significant improvement over the conventional aircraft-mounted, sharp-edged isokinetic diffuser-type inlets.

Section: Use Of Shrouded Probes As Sampling Inletsmentioning

confidence: 99%

Section: Use Of Shrouded Probes As Sampling Inletsmentioning

confidence: 99%

Section: Use Of Shrouded Probes As Sampling Inletsmentioning

confidence: 99%

See 1 more Smart Citation

Wind Tunnel Evaluation of an Aircraft-Borne Sampling System

Irshad

McFarland

Landis

et al. 2004

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“…Shrouds have been used with increasing frequency to align airflow with axes of airborne aerosol and gas-sampling inlets, e.g., McFarland et al (1989), Soderman et al (1991), Ram et al (1995), Murphy and Schein (1998), and Eisele et al (1997). These shrouds have provided significant improvements in flow characteristics and particle collection efficiencies of aerosol inlets.…”

Section: Introductionmentioning

confidence: 99%

Model Calculations and Wind Tunnel Testing of an Isokinetic Shroud for High-Speed Sampling

Twohy

1998

ABSTRACT. The direction of airflow streamlines and, therefore, particle trajectories around a n aircraft will vary during a flight. A coaxial shroud was designed to align airflow and particle trajectories with the tip of a counterflow virtual impactor (CVI), despite deviations in streamlines a t the shroud entrance. Both modeling and wind tunnel studies were employed in order to optimize the shroud dimensions for high-speed use on a DC-8 aircraft. A commercial computational fluid dynamics code was used to determine the approximate dimensions necessary to straighten particle trajectories and to maintain isokiueticity within the shroud. Characteristics of one shroud then were studied in the U.S. Air Force Academy's Trisonic Wind Tunnel. Flow speeds were measured a t various locations within the shroud using small pilot-static tubes. Effects of exit to inlet area ratio and angle of attack on shroud flow speeds were studied, and a final shroud design was chosen based on this information. Model simulations were in general agreement with the wind tunnel results.

“…The isokinetic errors are due to the loss of particles to internal walls. For reducing the sampling errors McFarland et al (1989) developed a new device, a shrouded probe. The typical geometry of a shrouded probe is shown in Figure 1.…”

Section: Introductionmentioning

confidence: 99%

Numerical Prediction of the Performance of a Shrouded Probe Sampling in Turbulent Flow

Gong

Anand

McFarland

1993

A numerical simulation is presented for the performance of a shrouded probe sampling at a zero yaw angle to a turbulent flow stream. The mean turbulent flow is calculated using the standard K-E turbulence closure model. The trajectories of particles in the flow field are simulated by solving the corresponding Lagrangian equation of particle motion which includes such effects as inertia, drag, gravity, Saffmau force, and turbulent diffusion. Three parameters describing the performance of a sampling probe-aspiration ratio, transmission ratio, and wall loss-are calculated by tracking a large number of particles. Computations are carried out for free stream velocities of 8.9, 15.6, and 21 m/s, and for particle sizes of 5, 10, and 15 p m aerodynamic equivalent diameter. A comparison is made between the numerically calculated and the experimentally measured values of wall loss and aspiration ratio. The agreement between the numerical prediction and the experimental data is good. The maximum difference is 6% for aspiration ratio and 11% for the wall losses.