pmp: sub 23 nm review b. giechaskiel, g. martini institute for energy and transport joint research...
TRANSCRIPT
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
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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
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Primary particles
Limited number of TEM studies have shown solid particles <23nm (usually additives)a)Nucleated iron b)Hydrocarbonc)Chain agglomerate
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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)
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JRC investigation
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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.)
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Experimental investigation at JRC
>DPF regeneration >MopedVolatile artifact appears as solid particles <23 nm (3-6 nm here).
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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).
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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)
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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
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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.
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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
•
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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
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Thank you for your attention!
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