A New Dual-type DMA for the Measurement of Nanoparticles from Engines

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1 8 th ETH-Conference on Combustion Generated Particles, 16 th -18 th August 2004 A New Dual-type DMA for the Measurement of Nanoparticles from Engines Kazuo Takeuchi 1,2), Junsuke Yabumoto 1,2), Yoshiki Okada 1,2) 1) RIKEN, 2) Wyckoff Co., Ltd., 2-1 Hirosawa, Wako-shi, Saitama , Japan Akio Kibayashi 3) 3) Shimadzu Corp. 1, Nishinokyo-Kuwabara-cho, Nakagyo-ku,, Kyoto , Japan Terunao Kawai 4), Yuichi Goto 4) 4) National Traffic Safety and Environment Laboraotry Jindaiji-higashi-machi, Chofu, Tokyo , Japan The differential mobility analyzer is the only practically applicable apparatus which can measure nanoparticle size distribution smaller than 300 nm in air. In the past, we have developed a DMA of which accuracy of the measurement was confirmed using fullerene C 60 sublimated in the carrier gas as a new standard nanoparticle. A C 60 monomer in the gas phase was produced by heating C 60 powder under low-pressure conditions, and its mobility spectrum was observed using a low-pressure differential mobility analyzer. Pressure dependence for the C 60 monomer in the spectrum was measured in order to examine the influence of C 60 aggregates on the peak profile of the C 60 monomer. Taking into account the diameter of the collision partner Ar atom, the diameter of the C 60 monomer was estimated in the framework of Stokes law. This DMA is also sensitive enough to identify the geometric isomer of an observed C 60 dimer. However, generally speaking, conventional DMAs are not suitable to detect the transient behavior of nanoparticles from engines because the required voltage scanning time is relatively long (typically a few minutes). Therefore, in order to detect the transient behavior of airborne nanoparticles with diameters of both ~ 10 nm and ~ 100 nm in automobile exhaust gas, a new dual-type differential mobility analyzer (dual-type DMA) has been developed. In this dual-type DMA, the gas sample is divided into two parts, with each part being introduced into two respective coaxially nested sections for analysis. The nanoparticles are charged by 241 Am and their size distributions in the vicinities of 10 nm and 100 nm are then measured by scanning the applied voltage within 2 min (scanning mode measurement). In the transient mode measurement, on the other hand, the voltages for the two sections are fixed at peaks near 10 nm and 100 nm in order to monitor the transient behavior of the automobile exhaust s nanoparticles. In the first experiment, we produced airborne model nanoparticles with a bimodal size-distribution when we mixed the NaCl nanoparticles (~10nm) produced by the sublimation-condensation method with the fume nanoparticles from burnt incense (~100nm). When -1-

2 8 th ETH-Conference on Combustion Generated Particles, 16 th -18 th August 2004 the corona charger for the charging of the nanoparticles was switched on and off, the transient behavior of the dual-type DMA was studied. In the second experiment, the exhaust gas from a diesel engine was introduced into the dual-type DMA and the transient behaviors of nanoparticles in the nuclei mode and in the accumulation mode were successfully detected by the dual-type DMA. The measurement principles and the design of the dual-type DMA are thus explained together with experimental data regarding its resolution, sensitivity, and time response using both model nanoparticles and real nanoparticles in automobile exhaust. In conclusion, it was shown that the dual-type DMA is simple, robust and capable to become the standard apparatus for the measurement of airborne nanoparticles from engines. 1) H. Tanaka and K. Takeuchi: C 60 Monomer as an Inherently Monodisperse Standard Nanoparticles in the 1nm Range, Jpn. J. Appl. Phys., 41, 922(2002). 2) H. Tanaka and K. Takeuchi: Structure Identification of a C 60 Dimer Using Electrical Mobility Measurement, Jpn J. Appl. Phys., 43, 7A, 4462(2004). 3) H. Tanaka and K. Takeuchi: Experimental Transfer Function for a Low-pressure Differential Mobility Analyzer by Use of a Monodisperse C 60 Monomer, J. Aerosol Sci., 34, 9, 1167(2003). -2-

3 A New Dual-type DMA for the Measurement of Nanoparticles from Engines Kazuo Takeuchi 1,2), Junsuke Yabumoto 1,2), Yoshiki Okada 1,2) 1) Wyckoff Co., Ltd., 2) RIKEN Akio Kibayashi 3) 3) Shimadzu Corp. Terunao Kawai 4) and Yuichi Goto 4) 4) NTSEL 1. Measurement of Gas-borne Nanoparticles 2. Calibration of Size Measurement 3. Difficulties in Conventional DMAs 4. Dual-type DMA as a Solution 5. Experiment 6. Conclusion 8th ETH CONF. Zurich 8/16/04

4 Measurement of Air-Borne Nanoparticles Nanoparticles: 1 nm < d p < 300 nm method in-situ? problems TEM measurement after collection no tedious procedure that requires preservation of the size distribution light scattering mobility measurement using DMA yes (yes) scattered light intensity d p 6 not practically applicable to nanoparticles sensitivity and stability (historically). calibration method below 10 nm.

5 Differential Mobility Analyzer (DMA) Q ae Q ex DMA Faraday Cup Q sa Electrometer Q sh Size-selected particles Sheath gas Size distribution of particles Size-selection of nanoparticles using DMA V Electrical mobility of particles Z * = = Q sh n ln( R2 / R1 ) 2πLV p ec 3πµ D c p D p : Particle diameter C c : Cunningham correction factor µ: Gas viscosity n p : Number of elementary charges on a particle

7 Sheath Gas = Ar Q ae =1slm Ion Intensity (arb. units) Q sh =30slm 5.33 x 10 4 Pa (400 Torr) 2.67 x 10 4 Pa (200 Torr) geometry isomer C 60 experimental (this work) Vsm Peanut 56/56 (C 60 ) 2 [2+2] 66/66 (C 60 ) theoretical Vsm x 10 4 Pa (50 Torr) 5-6 stick (C 60 ) Inverse Mobility / Vsm Strout et al., Chem. Phys. Lett. 214, 576 (1993). Shvartsburg et al., J.Phys.Chem.A101, 1684 (1997). Pressure Dependence of of Mobilities for for C 60 and 60 and C 60 Oligomers 60 Calculated Mobilities for for C 60 and 60 and C 60 Dimer 60 Dimer

Problem for Conventional DMAs in Automobile Exhaust Measurement Typically, conventional

behaviors in automobile exhaust Number density DMA with a multi-channel detector

Diameter (nm) Typical particle size distribution of nanoparticles in engine exhaust

8 Problem for Conventional DMAs in Automobile Exhaust Measurement Typically, conventional DMAs need to scan the voltage for 2 minutes Cannot cope with the quick transient behaviors in automobile exhaust Number density DMA with a multi-channel detector dual-type DMA with both scanning measurement mode and transient measurement mode Diameter (nm) Typical particle size distribution of nanoparticles in engine exhaust Image reproduced from D.B. Kittelson and W. Watts, Third Joint ESF-NSF Symposium Abs., Dublin, Sept. 6 (2000).

9 Dual-type DMA of Wyckoff Sheath gas inlet #1 Central electrode Aerosol gas inlet Sheath gas inlet #2 HV Cover Mobility analyzer #1 Aerosol gas inlet Common electrode Mobility analyzer #2 LV Housing Excess gas outlet #1 Base reservoir FC2 PA2 Excess gas outlet #2 FC1 PA1 Vacuum pump

10 Features of the Dual-type DMA (DDMA) 1) The DDMA can be operated both in scanning measurement mode and in transient measurement mode. 2) In transient measurement mode, voltages are fixed at the peak values of the nuclei mode and the accumulation mode. 3) Particle number density can be obtained by assuming that the shape of the size distribution is unchanged. 4) DDMA can be operated with intentionally reduced resolution.

11 MFC NaClparticles generator Regulator Furnace Sm oke particles generator MFC C orona C harger A m 241 Neutralizer DC Supply 0-±300V FC 1 PA1 DC Supply 0-±3kV Dual-DMA FC 2 PA2 Qsh2 Qsh1 Qex1 Qex2 Qs2 Press. sensor P2 P1 S U S Filter (15μm ) MFC MFC MFM MFM MFC S U S Filter (10nm ) FC valve FC valve Surge tank Press. sensor P3 C ooler (A ir cooled) 3L Tem p. sensor T Press. guage 2L Press. guage B ack press. valve Circulation pum p Qs1 MFC A ir Electrom eter 1 Electrom eter 2 Vacuum pum p Generation of model nanoparticles with bimodal size distribution

12 Number PNC density [#/cc] (#/cc) 7.0E E E E E E+06 DMA1 Model nanoparticles corresponding to nuclei mode DMA2 Model nanoparticles corresponding to accumulation mode 1.0E E dp (nm) 非定常排気微粒子数濃度計測結果 Scanning Mode Measurement of Model Nanoparticles

13 Corona charger ON OFF 1.0E E+06 DMA1(for nanoparticles of ~10nm) DMA2(for nanoparticles of ~ 100nm) Number density #/cc 6.0E E E E time sec Transient Mode Measurement of Model Nanoparticles

14 System Schematic Fuel Blower Controller PC Chassis Dynamometer PC D-DMA SMPS Measurement of nanoparticles from a Automobile Engine

15 Result for JE-05 Driving Mode 2.0E+06 DM A -1(10 nm ) C oncentratio n N / c c 1.5E E E E Tim e second 2.0E+06 D M A -2 (75 nm ) C oncentratio n N / c c 1.5E E E E Tim e second V ehicle speed Km /h Km /hr Tim e second

16 Concluding Remarks 1) We have introduced the dual-type DMA (DDMA) of Wyckoff. 2) The DDMA is simple and robust, and would be easy to use as a standard apparatus for the measurement of nanoparticles in automobile exhaust. 3) At the completion of this project, Shimadzu Co. will commercialize the DDMA and will be capable of large-scale production. Acknowledgement: We would like to thank JRTT for financial support. We would also like to thank Dr. Montajir and the scientists and technicians of NTSEL, Wyckoff, RIKEN and Shimadzu for their technical support and advice.

The new 11-R (one part of the Mini WRAS) and GRIMM MINI-WRAS Andreas Jaksch. Symposium Stockholm Mai

The new 11-R (one part of the Mini WRAS) and GRIMM MINI-WRAS Andreas Jaksch Symposium Stockholm Mai 2014 1 Outline Optical Particle Detection Method 11-R Main features of the GRIMM 11-R Measurement principle