| Summary: | 碩士 === 國立交通大學 === 環境工程系所 === 103 === In this study, to make sure the jet-to-plate distance of micro-orifice cascade impactor can be measured more accurate, a new micro-orifice cascade impactor (NMCI) was designed and improved base on the cases of Micro-Orifice Uniform Deposit Impactor (MOUDI) (Marple et al. 1991). Besides the improvement of the cases, the new nozzles with more smooth and stronger structure which was designed by Liu et al. (2013) were also placed on it.
The particle collection efficiencies of the 7th, 8th, 9th and 10th stage impactors of the NMCI were calibrated first. Before calibration, the nozzle diameter of these nozzle were measured by optical microscope, and result show that the nozzle diameter of 7th -10th stages imapactor were 135.8 ± 0.9、108.1 ± 0.8、54.1 ± 0.6 and 53.8 ± 0.6 m, respectively. Due to the number of these nozzle plate are very large, the relationship between the pressure drop through the nozzle plate and the average nozzle diameter was established. Validation result shows that the different of nozzle diameter measured by optical microscope and estimated by the relationship are less than 1%.
The calibration result shows that when S/W ratio (S: jet-to-plate distance, W: nozzle diameter) of 7th -10th stages of NMCI were adjusted to 4.04, 2.63, 14.27 and 12.64, respectively, the corresponding dpa50 were changed to 318.6 ± 0.5, 180.4 ± 0.5, 101.7 ± 0.9 and 56.4 ± 0.8 nm, respectively, which were very closed to the dpa50 of 7th -10th stages of MOUDI. Due to the dpa50 of impactor are very sensitive to the variation of jet-to-plate distance, the particle classification characteristic of 8th -10th stages of NMCI was investigated by compressible flow equation and the relationship between S/W ratio and Stk50, isen1/2 was also established based on experimental results as the design parameter of micro-orifice cascade impactor in the future.
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