10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
M-WINS Inlet for Continuous PM2.5 Sampling
THI-CUC LE, Jung-Che Sung, Krishna Kumar Shukla, Chuen-Jinn Tsai, National Chiao Tung University
Abstract Number: 247 Working Group: Control and Mitigation
Abstract Most of PM2.5 FRM samplers and FEM monitors use filter media to capture particles after particles are size-classified by the well impactor ninety-six (WINS) or very sharp cut cyclone (VSCC). The impaction glass fiber filter substrate (GFFS) of the WINS is coated with silicone oil to eliminate particle bounce. However, the particle loading effect occurs when a particle mound is formed on the impaction substrate after a long sampling time leading to under-sampling of PM2.5. The performance of an uncleaned VSCC was claimed not to be affected by the particle loading effect. However when the sampling period was over 5 days, we found fluctuations in measured PM2.5 concentrations as compared to the concentrations of a VSCC which was cleaned daily. Our previous work (Le and Tsai, 2017) developed a modified WINS (M-WINS) with a wetted GFFS through which a small water flow was injected upward at the center to wash off deposited particles continuously. The particle loading effect was eliminated successfully. Instead of using continuous water flow, the current study uses vacuum oil which was injected periodically to wash off the deposited particles. The laboratory test results showed that the M-WINS had a similar cut-size (2.43 ± 0.02 µm) and sharpness (1.22) as the WINS. Without cleaning the substrate, the particle loading test at the laboratory for M-WINS showed that the cut-size was decreased from 2.49 to 2.18 µm as the particle mass loading was increased from 0 to 3.5 mg with a particle mound formed on the substrate. The cut-size of M-WINS was able to recover to 2.46 µm when the oil flow was injected for just 1-min at the flow rate of 3 mL/min to wash off the mound. This saves oil consumption. The field comparison tests of the M-WINS collocated with a clean VSCC and a clean WINS is being conducted at National Chiao Tung University (NCTU), Taiwan. During the field tests, the M-WINS substrate was washed with a small amount of oil every day for just 1-min at the flow rate of 3 mL/min to keep the surface clean. The preliminary results indicate that the M-WINS has a great potential to measure PM2.5 accurately for a longer sampling period without the need of maintenance and the amount of vacuum oil consumption is very small, only 3 ml per day. In addition, the used oil can be reused after being filtered.