Browsing by Author "Ye, Huajun"

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Design and Testing of the NCTU Micro-Orifice Cascade Impactor (NMCI) for the Measurement of Nanoparticle Size Distributions
(2015-01-01)
Chien, Chih-Liang
;
Tien, Chi-Yu
;
Liu, Chun-Nan
;
Ye, Huajun
;
Huang, Wei
The NCTU micro-orifice cascade impactor (NMCI) was redesigned and tested to enable the measurement and adjustment of the jet-to-plate distance (S) of the impactors by using a micrometer. Each stage of the NMCI contains an impaction plate and a nozzle plate which are separated. The bottom casing for impaction plate assembly and the nozzle plate holder of each stage are separated. Calibration results show that the cutoff aerodynamic diameter (d(pa50)) of the three lower stages (d(pa50) = 180, 100, and 56 nm) are close to the nominal values given in Marple et al. (1991). In addition, the S/W (W: nozzle diameter) effects on the d(pa50) for the three lower stages were investigated and an empirical equation was developed to facilitate the prediction of d(pa50) when the nozzle diameters may change slightly from one batch to another. The relationship between the nozzle diameter and pressure drop of the micro-orifice impactors at the fixed operational flow rate of 30 L/min was also established so that the nozzle diameters can be predicted from the pressure drop measurement. An empirical equation was proposed to express the correlation between the dimensionless cutoff size and the S/W ratio when considering isentropic flow to facilitate the design of microorifice impactors for S/W > 4. It is expected that the present NMCI could improve the accuracy of size classification of submicron particles below 180 nm, especially for nanoparticles.
Ultrafine Particles and PM2.5 at Three Urban Air Monitoring Stations in Northern Taiwan from 2011 to 2013
(2015-11-01)
Lin, Guan-Yu
;
Lee, Guo-Rui
;
Lin, Sih-Fan
;
Hung, Yi-Hung
;
Li, Shih-Wei
In this study, long term measurements of PM2.5 and ultrafine particles (UFPs) for daily average mass concentration at Zhongshan (ZS), Sinjhuang (SJ), and Jhudong (JD) urban air monitoring stations were conducted from 2011 spring to 2013 autumn. The results showed that daily average UFPs mass concentrations in spring (average at 3 stations: 1.58 +/- 0.74 mu g m(-3)) and summer (average at 3 stations: 1.59 +/- 0.53 mu g m(-3)) were higher than those in autumn (average at 3 stations: 1.02 +/- 0.28 mu g m(-3)) and winter (average at 3 stations: 1.04 +/- 0.48 mu g m(-3)) due to the impacts by heavy traffic emission and new particle formation event. The effective density (rho(eff)) and dynamic shape factor (chi) for ultrafine particles (UFPs) were found to be 0.68 +/- 0.16 g cm(-3) and 2.06 +/- 0.19, respectively, suggesting that the particle morphology was irregular shape. Based on the calculated rho(eff) and chi, the average number and surface area concentration ratio of UFPs to those of PM2.5 at these monitoring stations was determined to be 89.0 +/- 5.5% and 42.1 +/- 12.8%, respectively, suggesting that UFPs contribute significantly to the health-relevant PM2.5 aerosol fraction in these stations.