Development of a toroidal-shaped differential mobility analyzer for effective measurements of airborne particles: Experiment and modeling

Figures & data

Figure 1. Schematic diagram of the toroidal Hy-DMA.

Table 1. Representative cylindrical DMAs for classifying large particles.

DMA	Electrode length [cm]	DMA size [cm]	Weight [kg]	Reference
TSI standard DMA	44	61 × 8×8	5.4	Commercial
GRIMM L-DMA	35	47.8 × 14 × 15.6	7.9	Commercial
GRIMM M-DMA	8.8	23.4 × 14 × 15.6	5.7	Commercial
ACLDMA	30	n/a	n/a	Seol, Yabumoto, and Takeuchi (2002)
Hauke 10/1000	60	n/a	n/a	Winklmayr et al. (1991)
LDMA	60	90 (height)	9	Myojo et al. (2004)

Figure 2. Experimental schematics for the evaluation of the toroidal Hy-DMA (a) using a TSI standard long-DMA and CPC for sizing accuracy and (b) using two identical Hy-DMAs to obtain the transfer functions of the toroidal Hy-DMA.

Figure 3. Calculation domain for the numerical study of the toroidal Hy-DMA and the boundary conditions.

Figure 4. (a) Normalized velocity magnitude at the injection line in the aerosol inlet and (b) schematic explanation of the single particle tracking method.

Figure 5. Central electrical mobility as a function of voltage applied to the toroidal Hy-DMA for the sheath-to-aerosol flow rate ratio of 3:0.3 and 5:0.5 L/min.

Figure 6. (a) Comparison between experimental and predicted TDMA curves for the toroidal Hy-DMA for 68 nm particles and (b) transfer functions of the toroidal Hy-DMA for 23, 68, and 238 nm particle sizes obtained via the deconvolution process at the sheath-to-aerosol flow rate ratio of 3:0.3 L/min.

Figure 7. Schematic diagram of (a) velocity streamline and (b) vectors of electric field colored by electric potential at the aerosol inlet and monodisperse outlet. The units are [m/s] for the velocity streamline and [V] for the electric potential.

Figure 8. Exemplary particle trajectories of different-sized particles in the toroidal Hy-DMA under the voltage of 320 V and sheath-to-aerosol flow rate ratio of 3:0.3 L/min: (a) 90 nm; (b) 94 nm; (c) 98 nm; (d) 102 nm; (e) 106 nm.

Figure 9. Transmission probabilities of the toroidal Hy-DMA as a function of particle diameter obtained by the single particle tracking analysis for the sheath-to-aerosol flow rate ratio of (a) 3:0.3 and (b) 5:0.5 L/min.

Table 2. Comparison of central particle sizes obtained by experiments and numerical simulations.

3:0.3 L/min	Applied voltage [V]		20	40	80	160	320	640	1280	2560
	Central particle size [nm]	Exp.	23.16	32.57	46.36	67.63	99.82	151.6	238.1	394.9
		Simul.	22.13	31.68	45.64	66.40	98.13	148.2	231.5	379.6
	Error [%]		4.4	2.7	1.6	1.8	1.7	2.2	2.8	3.9
5:0.5 L/min	Applied voltage [V]		30	60	120	240	480	960	1920	3840
	Central particle size [nm]	Exp.	21.68	30.80	44.05	63.78	94.07	142.2	222.5	366.9
		Simul.	20.97	29.93	43.19	62.75	92.47	139.1	215.8	351.3
	Error [%]		3.3	2.8	2.0	1.6	1.7	2.2	3.0	4.3

Figure 10. Normalized transmission probabilities as a function of normalized particle electrical mobility obtained by the single particle tracking analysis for the sheath-to-aerosol flow rate ratio of (a) 3:0.3 and (b) 5:0.5 L/min.

Figure 11. (a) Heights and (b) FWHMs, (c) area and (d) sizing resolution of the toroidal Hy-DMA transfer function plotted with those of different types of DMAs from other literatures.

Seol, K.S., J. Yabumoto, and K. Takeuchi. 2002. A differential mobility analyzer with adjustable column length for wide particle-size-range measurements. J. Aerosol. Sci. 33 (11):1481–92. doi:10.1016/S0021-8502(02)00094-0.

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Winklmayr, W., G.P. Reischl, A.O. Lindner, and A. Berner. 1991. A new electromobility spectrometer for the measurement of aerosol size distributions in the size range from 1 to 1000 nm. J. Aerosol. Sci. 22 (3):289–96. doi:10.1016/S0021-8502(05)80007-2.

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Myojo, T., K. Ehara, H. Koyama, and K. Okuyama. 2004. Size measurement of polystyrene latex particles larger than 1 micrometer using a long differential mobility analyzer. Aerosol. Sci. Technol. 38 (12):1178–84. doi:10.1080/02786826.2004.10399460.

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