PMP: SUB 23 NM

REVIEW

B. Giechaskiel, G. Martini

Institute for Energy and Transport Joint Research Centre

8 January 2014

GRPE-PMP-29-03

Outlook

• Introduction• Solid <23 nm (review)• Experimental investigation at JRC• Feasibility of sub 23 nm measurement • Summary

GRPE-PMP-29-03

Dilution air conditioning

Full dilution tunnel

PN

PM

Nucleation Mode

Accumulation mode

Condensed material

Nu

mb

er

Co

nce

ntr

atio

n

100 nm10 nm

Coarse mode

1000 nm

Filter

Primary particle(Spherule)

Agglomerate

Non-Volatile Fraction(Soot and ash) Volatile Fraction

(Organics, sulfates, nitrates)

Agglomerate(soot)

Nuclei

Nucleation Mode

Accumulation mode

Nu

mb

er

Co

nce

ntr

atio

n

100 nm10 nm

Coarse mode

1000 nm

Accumulation mode

Nu

mb

er

Co

nce

ntr

atio

n

100 nm10 nm

Coarse mode

1000 nm

Measured from PNC Removed from cyclone

In the CVS After the PN sytem

GRPE-PMP-29-03

Primary particles

Limited number of TEM studies have shown solid particles <23nm (usually additives)a)Nucleated iron b)Hydrocarbonc)Chain agglomerate

GRPE-PMP-29-03

Solid <23 nm particles review

• Diesel (40 engines and vehicles)• GDIs (10 engines and vehicles)

• A shoulder at 20 nm appears. A separate solid nucleation mode is not typical, but the size distribution can peak at small sizes (20 nm or lower) in some operation modes.

• Gasoline (8 vehicles)• Moped (12 mopeds)

GRPE-PMP-29-03

JRC investigation

GRPE-PMP-29-03

Nature of sub-23 nm particles

• Low volatility components• Soot-like particles• Metal oxides• (Artifact from pyrolysis or re-nucleation)

• Further investigation is needed (eg. Low pressure impactors, DMAs, TEM, aerosol mass spectrometers, charge measurement etc.)

GRPE-PMP-29-03

Experimental investigation at JRC

>DPF regeneration >MopedVolatile artifact appears as solid particles <23 nm (3-6 nm here).

GRPE-PMP-29-03

Measurement uncertainty

  Case PMP-1 PMP-2 ARP-1 ARP-2 PMP-4xPNC CE50% 23 nm 23 nm 10 nm 10 nm 10 nm

  CE90%1 41 nm 41 nm 15 nm 15 nm 41 nm

  slope 1.00 1.00 1.00 1.00 1.00VPR PCRF15 - (2.21) - (1.55) - (2.21) - (1.55) 2.21

  PCRF30 1.30 1.28 1.30 1.28 1.30

  PCRF50 1.12 1.09 1.12 1.09 1.12

CMD σ Final PN concentration compared to inlet concentration10 nm 1.3 0% 1% 18% 35% 30%20 nm 1.4 29% 34% 64% 82% 105%30 nm 1.6 61% 64% 83% 91% 135%40 nm 1.7 78% 79% 92% 96% 151%50 nm 1.8 88% 86% 98% 98% 160%70 nm 1.9 100% 95% 105% 101% 172%90 nm 2.0 105% 98% 109% 102% 178%10 nm (50%) + 50 nm (50%)

1.3 + 1.8 44% 44% 58% 67% 95%GRPE-PMP-29-03

Measurement uncertainty

• Higher percentage of the size distribution is measured• For means 50-90 nm, the measured emissions are within -2% and

+5% of the true (inlet) emissions • The difference between different commercial systems should

remain around 5%• For means <50 nm higher percentage of the inlet distribution is

measured (compared to the PMP systems). • However, this results in higher differences between the

commercial systems and thus measurement variability (reproducibility).

GRPE-PMP-29-03

Summary

• Primary particles• Typically 25 nm, but smaller can exist• Few TEM studies with distinct solid nucleation mode

• Solid <23 nm (review)• A lot of studies have measure solid sub23nm particles• Additives (metal oxides), low volatility HCs, soot-like

• Experimental investigation at JRC• Existence of sub23nm particles was confirmed in percentages of

<60% of >23nm (GDIs at the high range)

GRPE-PMP-29-03

Summary

• Feasibility of sub 23 nm measurement for PNCs• It is advantageous to decrease the cut-off size• Down to ~10 nm no major modifications for existing equipment

• Feasibility of sub 23 nm measurement for VPRs• Penetrations decrease at small sizes. Acceptable down to 10 nm.

Small effect on measurement variability (when no solid nucleation mode)

• Evaporation of volatiles typically not an issue• Pyrolysis might be an issue with sulfur (<10nm)• Re-nucleation and growth is probable

GRPE-PMP-29-03

Summary

• With existing equipment reducing the cut-off size is not recommended

• Decreasing the size to ~10 nm is possible but the addition of a CS is recommended. However some issues need to be resolved:• Saturation with sulfur• Formation of particles

• SO2 to SO3 conversion

• Below 10 nm is extremely difficult to measure for legislation purposes.

GRPE-PMP-29-03

Next steps• No clear need for sub-23 nm regulation

• Investigation will go on (especially heavy-duty, additives, mopeds, regenerations)

• Open issues to be investigated• Regeneration• Pyrolysis• CS performance• Calibration procedures (VPR and PNC) to be updated

•

GRPE-PMP-29-03

Next steps

• Measurements in parallel with PMP systems with ET and CS devices with both 23nm and ~10 nm PNCs.

• Tests without CS should be conducted with as high PCRF as possible (at least 100x10)• Note that even with PCRF 10000, and PNC concentrations

<1000 p/cm3, artifacts can happen because they depend on the volatile species’ concentr.

• When high sub23nm concentrations are measured the tests should be repeated with 10x higher PCRF

GRPE-PMP-29-03

Thank you for your attention!

GRPE-PMP-29-03