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Published August 1984 | public
Journal Article

High-Velocity Inertial Impactors

Abstract

Cascade impactors with large pressure drops across individual stages are useful for classifying submicron aerosols even though the flow becomes compressible when the ratio of the downstream to upstream stagnation pressure falls below r = 0.95 and sonic when r < 0.53 (for air). The variation of collection efficiency with pressure ratio is examined experimentally. The cutoff Stokes number does not exhibit significant dependence on the pressure ratio in the range from r = 0.97 (incompressible flow) to r = 0.19 (choked flow). The impactor stage pressure ratio may be estimated by modeling the stage as a nonideal, compressible flow nozzle with a discharge coefficient which is well correlated with the jet Reynolds number divided by the nozzle throat aspect ratio. Predictions of the variation of the cutoff diameter with flow rate, temperature, and inlet pressure are presented for impactors with high Mach number jets.

Additional Information

© 1984 American Chemical Society Received for review July 28,1983. Accepted February 3,1984. Funding for this research was provided by the Office of Research and Development, US. Environmental Protection Agency, under Grant R-809191010. The conclusions represent the views of the authors and do not necessarily represent the opinions, policies, or recommendations of the US. Environmental Protection Agency.

Additional details

Created:
August 19, 2023
Modified:
October 23, 2023