Design and Testing of the NCTU Micro-Orifice Cascade Impactor (NMCI) for the Measurement of Nanoparticle Size Distributions

Figures & data

FIG. 1. (a) Schematic diagram of the present NMCI stage and (b) the method to determine the jet-to-plate distance.

FIG. 2. Relationship of the resistance coefficient versus the free-area coefficient for the nozzles with known diameters at the flow rate of 30 L/min.

TABLE 1 Calibration results and the design parameters of the four lower stages of the original and redesigned NMCI

	Marple et al. (1991)				Original NMCI (Liu et al. 2013)				Redesigned NMCI
Stage	Nominal dpa50 (nm)	Nozzle dia. (µm)	S/W	P/Pa	dpa50 (nm)	Nozzle dia. (µm)	S/W	P/Pa	dpa50 (nm)	Nozzle dia. (µm)	S/W(S, µm)	P/Pa
7	320	140	4.1	0.95	323	138.7	2.52	0.95	318.6	135.8	4.04 (548.6)	0.95
8	180	90	6.4	0.89	178.5	109.5	3.01	0.89	180.4	108.1	5.38 (581.3)	0.89
9	100	55	10.6	0.76	102	54.3	13.44	0.72	101.7	54.1	14.39 (778.6)	0.72
10	56	52	11.1	0.53	55.7	50.9	24.75	0.34	56.4	53.8	12.68 (682.5)	0.47

^a S = jet-to-plate distance, W = nozzle diameter.

^b P = absolute pressure at stage exit with all upstream stages in place, P_a = ambient pressure.

FIG. 3. Particle collection efficiency of (a) 8th, (b) 9th, and (c) 10th stage of the NMCI at different jet-to-plate distance.

FIG. 4. Effect of the S/W ratio on the pressure drop across the 8th–10th stages of the NMCI.

FIG. 5. Effect of the S/W ratio on the cutoff characteristics of the 8th–10th stages of the NMCI.

FIG. 6. (a) Effect of the S/W ratio on the cutoff characteristics assuming isentropic flow of the 8th–10th stages of the NMCI and (b) comparison with the experimental data of Gudmundsson et al. (1995).

FIG. 7. Relationship between nozzle diameter and (a) jet-to-plate distance and (b) cutoff aerodynamic diameter when the d_pa50 is close to 100 nm.

Marple, V. A., Rubow, K. L., and Behm, S. M. (1991). A Microorifice Uniform Deposit Impactor (MOUDI): Description, Calibration and Use. Aerosol Sci. Technol., 14:434–446.

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Liu, C. N., Awasthi, A., Hung, Y. H., and Tsai, C. J. (2013). Collection Efficiency and Interstage Loss of Nanoparticles in Micro-Orifice-Based Cascade Impactors. Atmos. Environ., 69:325–333.

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Gudmundsson, A., Bohgard, M., and Hansson, H. C. (1995). Characteristics of Multi-Nozzle Impactors with 50 μm Laser-Drilled Nozzles. J. Aerosol Sci., 26:915–931.

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