A centrifugal particle mass analyzer and a modified differential mobility spectrometer were used to measure the mass and mobility of particulate matter emitted by CFM56-5B4/2P, CFM56-7B26/3, and PW4000-100 gas turbine engine sources. The mass-mobility exponent of the particulate matter from the CFM56-5B4/2P engine ranged from 2.68 to 2.82, whereas the effective particle densities varied from 600 to 1250 kg∕m 3 , depending on the static engine thrust and sampling methodology used. The effective particle densities from the CFM56-7B26/3 and PW4000-100 engines also fell within this range. The sample was conditioned with or without a catalytic stripper and with or without dilution, which caused the effective density to change, indicating the presence of condensed semivolatile material on the particles. Variability of the determined effective densities across different engine thrusts, based on the scattering about the line of best fit, was lowest for the diluted samples and highest for the undiluted sample without a catalytic stripper. This variability indicates that the relative amount of semivolatile material produced was engine thrust dependent. It was found that the nonvolatile particulate matter, effective particle density (in kilograms per cubic meter) of the CFM56-5B4/2P engine at relative thrusts below 30% could be approximated using the particle mobility diameter (d me in meters) with 11.92d 2.76−3 me . Nomenclature C = mass-mobility scaling component D m = mass-mobility exponent d me = particle mobility diameter k = mass-mobility prefactor M = suspended particle mass concentration m = particle mass n = particle number concentration
Three different respirator filter media (two electrets and one fiberglass) were challenged with monodisperse multi-walled carbon nanotubes (MWCNTs) of mobility diameters 20-500 nm at 5.3 and 10.6 cm s ¡1 face velocities. The penetration data were compared with that of sphere-like NaCl particles. The MWCNT penetrations were generally lower than those of NaCl at both face velocities in all three filters. However, the MWCNTs had a slightly higher penetration than the NaCl in the fiberglass filter at 10.6 cm s ¡1 face velocity when their mobility diameters were lower than 50 nm and the alignment effect was expected to occur. Results from the scanning electron microscopic (SEM) analysis supported the hypothesis of the alignment effect, which showed that the MWCNTs tend to be straighter or with higher aspectratios at the mobility sizes less than 100 nm, leading them more readily to align with the flow. Therefore, caution should be exercised when respirators are used against the MWCNTs with the mobility diameters less than 100 nm. The single fiber theory predicted the penetration of both particles in the fiberglass filters well for the particles with below 100 nm mobility diameters but discrepancies occurred beyond 100 nm. The theory still predicted the NaCl penetration through the electret filters well for the sizes below 100 nm but only predicted the MWCNT penetration well for »20-30 nm. The Nuclepore filter and the corresponding capillary tube model were adopted to study the mechanical deposition mechanisms of MWCNTs. The model was found to predict MWCNT penetration very well when the effective length of the MWCNT was taken into account.
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