A circumferential slot In-line Virtual Impactor (IVI) has been designed using
Computational Fluid Dynamics (CFD) simulation tools and experimentally characterized
using monodispersed liquid aerosols to validate simulation results. The base design,
IVI-100, has an application as a pre-separator for sampling inlets, where the device
scalps large particles from the aerosol size distribution. The IVI-100 samples air in at
111 L/min and deliver the fine aerosol fraction in a 100 L/min flow and provide a
cutpoint particle size of 10 µm, with a pressure drop of 45 Pa.
An inverted dual cone configuration encased inside a tube provides the IVI-100
with a characteristic circumferential slot of width 0.254 mm (0.100 inches) and a slot
length of 239 mm (9.42 inches) at the critical zone. The upper cone causes the flow to
accelerate to an average throat velocity of 3.15 m/s, while the lower cone directs the
major flow toward the exit port and minimizes recirculation zones that could cause flow
instabilities in the major flow region. The cutpoint Stokes number is 0.73; however, the
cutpoint can be adjusted by changing the geometrical spacing between the acceleration nozzle exit plane and a flow divider. Good agreement is obtained between numerically
predicted and experimentally observed performance.
An aerosol size selective inlet for bioaerosol and other air sampling applications
using an upgraded prototype of IVI-100, mounted inside a BSI-100 inlet shell was tested
in an aerosol wind tunnel over a speed range of 2 – 24 km/hr. The BSI-IVI-100 inlet has
a cutpoint of 11 µm aerodynamic diameter and delivers the fine fraction at 100 L/m. The
geometric standard deviation of the fractionation curve is 1.51 and the performance is
not affected by wind speeds.
An IVI-350, which is an adaptation of the IVI to be used as a powder
fractionator, was designed based on computational simulations, and provides a cutpoint
of 3 µm AD, while operating in a total flow rate of 350 L/min. Four Identical IVI -350
units will be operated in parallel to fractionate aerosolized powders in a 1400 L/min
flow. An optimized inlet, with a contoured tear-drop shaped insert provides uniform
flow to four identical IVI units and prevents powder accumulation in the system
entrance.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2382 |
| Date | 2007 December 1900 |
| Creators | Seshadri, Satyanarayanan |
| Contributors | Haglund, John S., McFarland, Andrew R. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | thesis, text |
| Format | electronic, application/pdf, born digital |
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