Two-dimensional virtual impactors. Final report
Theoretical predictions using both potential flow analyses and solutions to Navier-Stokes equations are made for the operating characteristics of a two-dimensional virtual impactor. Experiments were performed with 2.5 ..mu..m, uranine tagged, di-octylphthalate (DOP) oil droplets for a wide range of prototype geometries to measure the magnitude of internal losses and to fully characterize the instrument response. The influence of geometry including the throat angle (38/sup 0/ less than or equal to ..beta../sub 0/ less than or equal to 58.2/sup 0/) and normalized void width (0.7 less than or equal to h/w less than or equal to 1.5) on the particle cutoff diameter, efficiency curve steepness and properties of the internal particle loss factor are presented for fixed instrument Reynolds numbers Re = 1540 and bleed flow f = 0.1. The theory, supported by trends in the empirical data, predicts that internal particle losses reduce to zero as the normalized void width increases to h/w = 1.4 +- .1 while the data show a minimum at h/w = 1.6 +- .1. Increasing the void width, however, is shown to substantially reduce the steepness of the particle efficiency curves. Visual observations of the onset of fluid separation for two-dimensional jets impinging upon a void were conducted with a scaled-up water model and correlated with theory. It was found that the limiting void width h/sub lim//w marking the onset of fluid instabilities peaked for an intermediate value of the fluid deflecting plate angle ..beta.. approx. = 80/sup 0/ with larger values of h/sub lim//w corresponding to smaller throat angles ..beta../sub 0/. The limiting void width h/sub lim//w also increased with larger bleed flows into the void. These instabilities may make it difficult to correlate experimental virtual impactor data with theory.
- Research Organization:
- Georgia Inst. of Tech., Atlanta (USA); Illinois Univ., Urbana (USA). Dept. of Physics
- DOE Contract Number:
- AS02-77EV04319
- OSTI ID:
- 6607947
- Report Number(s):
- COO-4319-6
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
Atmospheric-- Chemicals Monitoring & Transport-- (-1989)
54 ENVIRONMENTAL SCIENCES
AEROSOL MONITORING
AEROSOLS
AIR POLLUTION
COLLOIDS
DATA
DATA ANALYSIS
DATA COMPILATION
DESIGN
DISPERSIONS
EQUIPMENT
ESTERS
FLUID FLOW
INFORMATION
LOSSES
MONITORING
NUMERICAL DATA
ORGANIC COMPOUNDS
PARTICLE SIZE CLASSIFIERS
PERFORMANCE
PHTHALIC ACID ESTERS
POLLUTION
SOLS