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Center for Diesel Research

Issues associated with solid particle measurement

David B. Kittelson, Jacob Swanson*, Heejung Jung** Center for Diesel Research

Department of Mechanical Engineering University of Minnesota

*Engineering Department University of Cambridge, UK

**Department of Mechanical Engineering University of California, Riverside

PMP Meeting6th December 2011DG JRC, Ispra, Italy


Cazzola

Typewritten Text

PMP-26-06


Outline

• Background• UCR on-road and laboratory tests• UMN laboratory tests• Conclusions


At very low emission levels number measurements have much better resolution than mass but..• Current PMP method regulates “solid” particles larger than 23 nm

– For engines equipped with particle filters regulating to 23 nm effectively regulates all sizes

– Under extreme conditions false counts of nucleated semi-volatile have been observed– For engines without filters (advanced fuels, combustion modes, gasoline) there may be

large concentrations of solid particles below 23 nm that are not counted by current method.

– The next generation of high efficiency direct injection gasoline engines are challenged by the current standard even with the 23 nm limit

• An international solid number standard for aircraft emissions is being considered and is likely use a lower counting limit to 10 nm

• Extending solid PM measurements to 10 nm– Significant semi-volatile particles downstream of PMP VPR often observed– No significant semi-volatile formation downstream of catalytic stripper in this size range

• Extending solid PM measurements to below 10 nm – problematic– Particles as small as sub 3 nm formed in large concentrations downstream of PMP VPR– Some evidence of solid particle formation by thermal denuder– Sub 10 nm particle formation observed downstream of CS under some conditions– Downstream nucleation and solid particle losses greatly reduced in new mini CS– Removal of sulfate or other low vapor pressure species critical


Recent papers raise issues about solid particle measurements, especially when applied to particles smaller than 23 nm

• Work done at University of California, Riverside, CE-CERT– Johnson, Kent C., Thomas D. Durbin, Heejung Jung, Ajay Chaudhary, David

R. Cocker III, Jorn D. Herner, William H. Robertson, Tao Huai, Alberto Ayala, and David Kittelson, 2009. Evaluation of the European PMP Methodologies during On-Road and Chassis Dynamometer Testing for DPF Equipped Heavy Duty Diesel Vehicles, Aerosol Science and Technology, 43:962–969, 2009.

– Zheng, Zhongqing, Kent C. Johnson, Zhihua Liu, Thomas D. Durbin, Shaohua Hu, Tao Huai, David B. Kittelson, and Heejung Jung, 2011. Investigation of solid particle number measurement: Existence and nature of sub-23nm particles under PMP methodology, Journal of Aerosol Science 42 (2011) 883–897.

• Work done at the University of Minnesota, CDR– Swanson, Jacob and David Kittelson, 2010. Evaluation of thermal denuder and

catalytic stripper methods for solid particle measurements, Journal of Aerosol Science, Volume 41, Issue 12, Pages 1113-1122.

– Swanson, Jacob and David Kittelson, 2012. Evaluation of PMP APC and catalytic stripper methods for solid particle measurements, in preparation


PMP number measurement system

A specially designed CPC with a lower size cutoff of 23 nm is used


Why solid, why only larger than 23 nm?

3350

65

90

400

900

0.00E+00

1.00E+08

2.00E+08

3.00E+08

4.00E+08

5.00E+08

6.00E+08

7.00E+08

Number Concentrations

(Part./cm³)

Dilution Temperature (°C)

Residence Time (ms)

1.00E+05

1.00E+06

1.00E+07

1.00E+08

1.00E+09

1.00E+10

1 10 100 1000Dp (nm)

DN

/DLo

g D

p (P

art./

cm³)

Residence time = 1000 ms 100 ms 230 ms

Tdilution = 32 °C, Primary DR ~ 12

1600 rpm, 50% load

80

90

100

10 100 1000Dp, nm

Filtr

atio

n Ef

ficie

ncy,

%

1.25 min 2.25 min 3.25 min 4.25 min 5.25 min6.25 min 7.25 min 8.25 min 9.25 min 10.25 min

•The concentration of volatile nucleation mode particles is very dependent on sampling conditions•Most of these particles are smaller than 23 nm•If the engine is fitted with a particle filter particles below 50 nm or so are very effectively removed•Thus regulating solid particles above 23 nm is really regulating soot particles is effectively regulating all particles for a trap equipped•Without a trap the story is different


Engine out, light-load, low soot conditions: Most of the number emissions are solid with Dp < 23 nm

0.0E+00

1.0E+07

2.0E+07

3.0E+07

4.0E+07

5.0E+07

6.0E+07

1 10 100 1000Dp (nm)

dN/d

logD

p (pa

rt/c

m3 )

Mode 1 solid

Mode 2 solid

Mode 5 solid

Carbonaceous soot

Ash

Cummins 2004 ISM engine, BP 50 fuel, AVL modes

CPC cutoff


Spark ignition engines can also produce tiny solid nanoparticles, especially with metal additives

0.0E+00

1.0E+07

2.0E+07

3.0E+07

4.0E+07

1 10 100 1000Dp, nm

dN/d

logD

p, p

art/c

m3

Transient EUDC Manganese solid

Idle Manganese solid

50 kph Manganese solid

Gidney, Jeremy T., Martyn V. Twigg, and David B. Kittelson, 2010. Effect of Organometallic Fuel Additives on Nanoparticle Emissions from a Gasoline Passenger Car, Environmental Science and Technology, v 44, n 7, p 2562-2569.

CPC cutoff


Recently published results from SWRI show solid particles between 10 and 23 nm for a modern GDI car

From: Khalek, Imad A., Thomas Bougher, and Jeff J. Jetter, 2011. Particle Emissions from a 2009 Gasoline Direct Injection Engine Using Different Commercially Available Fuels, SAE paper number 2010-01-2117.


Gasoline engine running in pure HCCI mode shows no solid particles above 10 nm

• Emissions depend upon speed, load, temperature – in-cylinder thermal processing• Solid PN measured with catalytic stripper (CS) total PN without• Right plot shows solid fraction on 10x expanded scale• Most of the particles emitted are volatile but the solid ones are very small

0.0E+00

1.0E+08

2.0E+08

3.0E+08

4.0E+08

5.0E+08

6.0E+08

7.0E+08

8.0E+08

9.0E+08

1 10 100

Particle diameter (nm)

dN/d

logD

p (p

artic

les/

cm3 )

1200rpm Tin100C1200rpm Tin100C CS1500rpm Tin90C1500rpm Tin90C CS2000rpm Tin702000rpm Tin70C CS

0.0E+00

1.0E+07

2.0E+07

3.0E+07

4.0E+07

5.0E+07

6.0E+07

7.0E+07

8.0E+07

9.0E+07

1 10 100

Particle diameter (nm)

dN/d

logD

p (p

artic

les/

cm3 )

1200rpm Tin100C CS

1500rpm Tin90C CS

2000rpm Tin70C CS

From: Bika, Anil, Wei Fang, Luke Franklin, Bin Huang, and David Kittelson, 2011. Particle Emissions from a Soot Free Engine, 15th ETH-Conference on Combustion Generated Nanoparticles, June 2011.


Using a 23 nm cut with aircraft plumes will lead to undercounting a significant fraction of the particles

Han, H.-S.; Chen, D.-R.; Pui, D.Y.H.; and Anderson, B.E. A nanometer aerosol size analyzer (nASA) for rapid measurement of high- concentration size distributions, Journal of Nanoparticle Research, v 2, n 1, p 43-52, March 2000

Typical fast-scan size distributions measured from a J85-GE turbo-jet engine at various engine power settings:

78% below 23 nm 41% below 23 nm


Outline



UCR on road tests using PMP protocol show unexpected “solid” particles and many particles below 23 nm

MEL CVS MEL secondary diluter Filter sampling train (gravimetric)

PMP diluter(Clone system)

TSI 3790 CPC (23 nm)TSI 3760A CPC (11 nm)TSI 3025A CPC (3 nm)

PMP diluter(Alternative system)

TSI 3760A CPC (11 nm) TSI 3025A CPC (3 nm)

TSI 3022 CPC (7 nm)

Primarydilution

Secondarydilution

Sampling & Measurement

ETC UrbanETC CruiseARB Creep UDDS Route 1 Route 2

Par

ticle

con

cent

ratio

n (#

/cc)

1e+0

1e+1

1e+2

1e+3

1e+4

1e+5

1e+6

1e+7

3790 3760 3025 3022*

Johnson, Kent C., Thomas D. Durbin, Heejung Jung, Ajay Chaudhary, David R. Cocker III, Jorn D. Herner, William H. Robertson, Tao Huai, Alberto Ayala, and David Kittelson, 2009. Evaluation of the European PMP Methodologies during On-Road and Chassis Dynamometer Testing for DPF Equipped Heavy Duty Diesel Vehicles, Aerosol Science and Technology, 43:962–969, 2009.

A heavy-duty truck equipped with a CRT was tested on road and on a chassis dynamometer•It showed large concentrations of “solid” particles below 23 nm at high load conditions•These conditions favor sulfate particle formation. •Filtration efficiency for particles below 23 nm should be very high.


UCR chassis dynamometer tests comparing APC and catalytic stripper (CS)• Comparisons of fully compliant PMP system with measurement system

using catalytic stripper for volatile particle removal– Use a variety of counting instruments with different lower size cutoffs

• TSI 3022 – 7 nm• TSI EEPS – 6 nm• TSI 3790 – 23 nm• TSI 3772 – 10 nm• TSI 3025A – 3 nm• TSI 3776 – 2.5 nm

– Tests with exhaust aerosols from heavy-duty vehicle operating on chassis dynamometer

• Freightliner class 8 truck with 14.6 liter, 2000 Caterpillar C-15 engine, equipped with Johnson Matthey Continuously Regenerating Trap (CRTTM)

• Two steady state cruise conditions, constant speed 56 mph at 26% and 74% of full load

– Tests with laboratory challenge aerosols

Zhongqing Zheng, Kent C. Johnson, Zhihua Liu, Thomas D. Durbin, Shaohua Hu, Tao Huai, David B. Kittelson, Heejung S. Jung, Investigation of solid particle number measurement: existence and nature of sub 23 nm particles under PMP methodology, Journal of Aerosol Science 42 (2011) 883–897.


Comparisons of a Catalytic Stripper and APC Volatile Particle Remover with exhaust aerosols

Exhaust from heavy-duty vehicle with CRT



Steady state total particle number measurements

74% load26% load



Steady state 74% load strongly bimodal


Accumulation mode

Nuclei mode


At 74% load PMP compliant system closely tracks the accumulation mode



74% load 3790_APC (23 nm) and 3772_CS (10nm)

The 3790 is always connected thru the PMP system and the 3772_CS is always connected thru the CS. The lower reading with the CS is due to thermophoretic

losses ~40%

APC500 –

PMP system, 500 dilution ratio

APC100 –


CS –

Catalytic Stripper

CVS –

sampling directly from main dilution tunnel, no removal of volatile particles

Changing APC dilution ratio doesn’t change results –

it shouldn’t



74% load 3790_APC (23 nm) on APC, 3772_CS (10 nm) on CS

3772 (10 nm) switched between APC and CS

When connected thru the PMP system the 3790 and 3772 agree –

no particles between 10 and 23 nm

Switching from 100 to 500 overall dilution ratio has no impact on the APC results –

the desired result



When connected thru the PMP system the 3776 reads much higher than the 3790 due to particle formation below 10 nm, thru the stripper it also reads progressively higher than the 3772 again indicating sub 10 nm particles


3776 (2.5 nm) switched between APC and CS



Summary of results at 74% load cruise

• Downstream of PMP system– 3790 and 3772 agree – no

particles between 10 and 23 nn– 3025A and 3776 agree and read

progressively higher than 3772 and 3790 as time goes on – particles forming between 3 and 10 nm

– Same trend at 100 and 500 dilution ratio

• Downstream of CS– In first time window all

instruments agree – no particle below 23 nm

– In second and third time windows 3776 and 3025A read higher than 3772 – particle formation between 3 and 10 nm



26% load 3790_APC (23 nm) and 3772_CS (10 nm)

Dependence on dilution ratio suggests particle formation or incomplete removal

Dependence on dilution ratio suggests particle formation or incomplete removal

APC500 –


APC100 –


CS –

Catalytic Stripper

CVS –

sampling directly from main dilution tunnel, no removal of volatile particles

Changing APC dilution ratio changes results – it shouldn’t



When connected thru the PMP system the 3790 and 3772 agree –

no particles between 10 and 23 nm but some additional particles above 23 nm at the lower APC dilution ratio


3772 (10 nm) switched between APC and CS




3776 (2.5 nm) switched between APC and CS

When connected thru the PMP system the 3776 shows higher concentration than the 3790 indicating particles below 10 nm, especially at higher dilution ratio, little evidence of this with CS



26% load 3025A (3 nm) and 3776 (2.5 nm)

The 3025A and 3776 disagree at the higher dilution ratio downstream of the PMP system but agree for 50 nm calibration aerosols suggesting that the particles are near the lower detection sizes of the instruments, < 3 nm..

When connected directly to CVS, no removal of volatiles, CPCs agree and show lower concentration than when volatiles are removed at 500 DR

How can total be less than “solid”?



Summary of results at 26% load cruise

• Much lower concentrations than at 74%– Downstream of PMP system

• In first time window, DR = 500– 3790 and 3772 agree – no particles between 10

and 23 nm– 3776 and 3025A read much higher and disagree

– many particles below lower cutoff size of these instruments, 2.5 to 3 nm

• In second time window, DR = 100– 3790 and 3772 read higher but agree – no

particles between 10 and 23 nm but formation above 23 nm

– 3776 and 3025A agree but read only slightly higher than 3790 and 3772 – nearly all particles have grown to above 23 nm

– Downstream of CS • Consistently lower reading and

agreement between instruments• In last time window instruments bypass

volatile particle removal systems and are directly connect to CVS – measure total solid and volatile particles – fewer particles than DR = 500 APC, clear evidence of particle formation by APC



Laboratory and engine tests both show concentration swings tracking VPR temperature


Laboratory test aerosol Chassis dyno 74% load


Summary – UCR tests

• High load on-road tests of CRT equipped heavy-duty truck shows evidence of overloading PMP system

– Large increase in particle counts with all CPCs – even PMP 3790– May be associated with storage and release of sulfate

• Chassis dynamometer tests at 74% and 26% load highway cruise– At 74% load

• APC and CS agree above 10 nm and track accumulation mode • APC and to a lesser extent CS show significant particle formation below 10 nm• APC sub 10 nm concentration swings associated with evaporation tube temperature

– At 26% load• APC shows dilution ratio dependence – evidence of particle formation above 23 nm• APC leads to formation of extremely small particles ~ 3 nm

• Laboratory generated aerosols show formation or incomplete removal of particles larger than 23 nm with evaporation tube temperature dependence.


Outline



Performance of thermal denuder and catalytic stripper with ambient aerosol

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

1 10 100Dp, nm

dN/d

LogD

p, p

art/c

m3

Downstream TD

Downstream CS

Atmospheric aerosol

Swanson, Jacob and David Kittelson, 2010. Evaluation of thermal denuder and catalytic stripper methods for solid particle measurements, Journal of Aerosol Science, Volume 41, Issue 12, Pages 1113-1122.


Evaluating thermal denuder and catalytic stripper with pure semi-volatile challenge aerosols• The test compounds

– Sulfuric acid (reagent grade 99.9% pure, 18 M)– Solid tetracosane (C24 H50 ) flakes (reagent grade 99.9% pure)– Dioctyl sebacate liquid (C26 H50 O4 ) (technical grade 90% pure)

• An evaporation and condensation technique was used to generate nanometer sized particles. – Test compounds were heated in an alumina combustion boat to various temperatures ranging from

120°C to 250°C. – Temperatures were chosen such that the saturation vapor pressure above each compound was roughly

the same, so that the evaporation rates would be similar and they would be similar mole fractions of each in the carrier gas stream at the time they were mixed.

– The vapor(s) were entrained with hot dry air, mixed and heated to 250°C, and then cooled by dilution with a dilution ratio of ~20:1.

– The cooling causes the vapors to nucleate, forming a high concentration of nanoparticles composed of the evaporated compounds.



Test of TD and CS with laboratory generated semi- volatile particles

• Pure tetracosane challenge aerosol– Wide range of concentrations– Particles form downstream of TD– No particle downstream of CS– No particles downstream of TD + CS – particles

formed by TD volatile

• Tetracosane plus sulfuric acid challenge aerosol

– Significant particle formation downstream of TD– No particle downstream of CS– No particles downstream of TD + CS – particles

formed by TD volatile

1.0E+02

1.0E+03

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+08

1 10 100 1000Dp, nm

dN/d

LogD

p, p

art/c

m3

Downstream CS <0.01Downstream TD + CS: <0.01

Challenge aerosol380 µg/m3



Increasing challenge concentration

1.0E+02

1.0E+03

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+08

1 10 100 1000Dp, nm

dN/d

LogD

p, p

art/c

m3


Downstream CS <0.01 part/cm3

Downstream TD + CS: <0.01 part/cm3

Downstream TD



Test of TD and CS with laboratory generated semi- volatile particles

• Tetracosane plus sulfuric acid challenge aerosols

– Higher challenge aerosol concentrations

– Significant particle formation downstream of TD

– A few particles downstream of CS at highest challenge aerosol concentrations

– Particles downstream of TD + CS – particles suggesting solid particle formation by TD

1.0E+02

1.0E+03

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+08

1 10 100 1000

Dp, nm

dN/d

LogD

p, p

art/c

m3

Downstream TD + CS

Downstream TD


Downstream CS: <0.01

1.0E+03

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+08

1 10 100 1000Dp, nm

dN/d

LogD

p, p

art/c

m3

Downstream CS

Downstream TD + CS

Downstream TD 0.16 mg/m3

Challenge aerosol 3.8 mg/m3



New miniature CS for use in APC

Core length 0.038 m Core width 0.015 m Cell density 600 cells/in Wall thickness 2.5 mil Flowrate 1.5 L/min C40 H82 penetration 0.2 % SO4

2- penetration 0.0014 %50% cut off size 7 nm

Penetration curves for the CS and AVL APC. For the CS, the data are fitted to diffusion and thermophoresis loss model. For the APC, the data are fitted to a diffusion model only.

0.0

0.2

0.4

0.6

0.8

1.0

1 10 100 1000

Pene

tratio

n

Dp, nm

AVL APC - experimental

AVL APC - fitted to diffusion curve

CS - experimental

CS - fitted to diffusion + thermophoresis curve


Cleaned compressed air

Hot plate

HEPA filter

H2

SO4

reservoir

1 L/min

4 L/min

H2

O reservoir

H2

O reservoirMixing orifice

To CS or SMPS

Humidified dilution air

H2

SO4

particle generation method

RH measured = 70%

Initial acid concentration ~ 98%


H2 SO4 particle distributions

0.0E+00

2.0E+06

4.0E+06

6.0E+06

8.0E+06

1.0E+07

1.2E+07

1 10 100 1000Dp, nm

dN/d

LogD

p, p

art/c

m3

0.03 mg/m3

0.2 mg/m31.3 mg/m3

3.4 mg/m3

9.3 mg/m3

28 mg/m3


Some calculations of theoretical threshold for sulfuric acid nucleation and experimentally observed ~ 14 mg/m3

0.00001

0.00010

0.00100

0 20 40 60 80 100

H2SO4 concentration, mg/m3

Pen

etra

tion

Experimental data indicates penetration ~0.00014 or ~99.99% removal efficiency

Predicted penetration based on diffusion theory and CS conditions

Theorethical calculation of penetration required to give J = 1 part/m3- s

Threshold concentration for nucleation in perfect system

Extremely low penetration necessary to prevent nucleation


Generation of hydrocarbon particles

0.E+00

2.E+05

4.E+05

6.E+05

8.E+05

1.E+06

10 100 1000Challenge particle Dp, nm

dN/d

LogD

p, p

art/c

m3

Dp = 60 nmσg = 1.05Concentration = 5.6 ± 0.5 E4 part/cm3

Cleaned

compressed air

Hot plate

HEPA filter

C40

H82

reservoir

2 L/minMixing orifice

To DMA for

size selection


Hydrocarbon particle removal

1.E+00

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

30 40 50 60 70 80 90 100 130 150 170 190 220Challenge particle Dp, nm

Tota

l con

cent

ratio

n, p

art/c

m3

Upstream Downstream10,000 part/cm3

Corresponds to 99.98% removal


Conclusions – UMN lab tests

• Thermal denuders and related devices have significant potential for downstream nucleation and at high concentrations may create solid residue from pure volatile materials

• CS system only shows downstream nucleation of sulfuric acid at very high upstream concentrations ~ 14 mg/m3

• APC VPR system shows downstream sulfuric acid nucleation at ~ 100µg/m3

• Renucleation of sulfuric acid or other low vapor pressure species critical – need performance standard?


Outline



Conclusions

• Current PMP method regulates “solid” particles larger than 23 nm– For engines equipped with particle filters regulating to 23 nm effectively regulates all

sizes – Under extreme conditions false counts of nucleated semi-volatile have been observed– For engines without filters (advanced fuels, combustion modes, gasoline) there may be

large concentrations of solid particles below 23 nm that are not counted by current method

– The next generation of high efficiency direct injection gasoline engines are challenged by the current standard even with the 23 nm limit

• An international solid number standard for aircraft emissions is being considered and is likely use a lower counting limit to 10 nm

• Extending solid PM measurements to 10 nm– Significant semi-volatile particles downstream of PMP VPR often observed– No significant semi-volatile formation downstream of catalytic stripper in this size range

• Extending solid PM measurements to below 10 nm – problematic– Particles as small as sub 3 nm formed in large concentrations downstream of PMP VPR– Some evidence of solid particle formation by thermal denuder– Sub 10 nm particle formation observed downstream of CS under some conditions– Downstream nucleation and solid particle losses greatly reduced in new mini CS– Removal of sulfate or other low vapor pressure species critical


Acknowledgements

• All catalytic strippers used in this work were supplied by Martyn Twigg of Johnson-Matthey


Questions?


Backup slides


Outline

• H2 SO4 particle generation method• Results for challenge concentrations 0.03 to 28

mg/m3

• Brief conclusion• Previous test schematic and experimental results• Calculations • Hydrocarbon removal


H2 SO4 particle distributions for challenge concentrations <10 mg/m3

1.0E+01

1.0E+02

1.0E+03

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+08

1.0E+09

1 10 100 1000Dp, nm

dN/d

LogD

p, p

art/c

m3

0.03 mg/m3

0.2 mg/m3 1.3 mg/m3

3.4 mg/m3

9.3 mg/m3

Downstream measurements are noise


Results show renucleation of H2 SO4 vapor for particle challenge concentrations ~28 mg/m3

1.0E+01

1.0E+02

1.0E+03

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+08

1.0E+09

1 10 100 1000Dp, nm

dN/d

LogD

p, p

art/c

m3

0.03 mg/m3

0.2 mg/m3 1.3 mg/m3 3.4 mg/m3

9.3 mg/m3

28 mg/m3Downstream CS

at 28 mg/m3


Quick summary

• Current results suggest re-nucleation occurs between 10 and 28 mg/m3 upstream


Cleaned compressed air

19 L/min

1 L/min

SO2

bottle

20: 1 dilution

Permeation tube

Oxidation catalyst

HEPA filter

H2

O reservoir

To CS or SMPS

Past results ‐

H2

SO4

particle generation method


APC challenge with 12 mg/m3

1.E+02

1.E+04

1.E+06

1.E+08

1.E+10

1 10 100 1000

dN/d

logD

p, p

art/c

m3

Dp, nm

Upstream mass concentation = 12 mg/m3

Downstream APC + CS for mass concentation of 12 mg/m3 - particles are solid residues

Downstream APC - particles are mostly the result of the re-nucleation of sulfuric acid


APC challenge with 1.0 mg/m3

Highest inlet concentration possible without re‐nucleation downstream. Inlet

concentration is really 100 µg/m3

because aerosol is first diluted 10x.

1.0E+03

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+08

1.0E+09

1 10 100 1000

dN/d

logD

p, p

art/c

m3

Dp, nm

Upstream mass concentration = 1.0 mg/m3

No re-nucleation downstream -these particles are solid residuals


CS challenge – 12 mg/m3

No difference between 1 or 2 CS units, corrected for size dependant penetration

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

1 10 100 1000Dp, nm

dN/d

logD

p, p

art/c

m3

Uptream mass concentration = 12 mg/m3

Downstream CSDownstream CS + CS


CS challenge – 16 mg/m3

Use of 2 CS units shows sulfuric acid re‐nucleation

1.0E+02

1.0E+03

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+08

1.0E+09

1 10 100 1000Particle Diameter, nm

dN/d

logD

p, p

art/c

m3

Uptream mass concentration = 16 mg/m3

Downstream CSDownstream CS + CS

Re-nucleation of H2SO4


Conclusions

• New particle generation method using glass beakers eliminates solid particle residues

• Method is not completely stable due to constant uptake of water by the acid – but it works

• Current results suggest renucleation occurs between 10 and 28 mg/m3 upstream– Consistent with past result where renucleation was observed at

12 mg/m3

– Compared to renucleation in APC at ~ 100µg/m3

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