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

Primary particles Limited number of TEM studies have shown solid particles <23nm (usually additives) a)Nucleated iron b)Hydrocarbon c)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 >Moped Volatile artifact appears as solid particles <23 nm (3-6 nm here). GRPE-PMP-29-03

Measurement uncertainty CasePMP-1PMP-2ARP-1ARP-2PMP-4x PNCCE 50% 23 nm 10 nm CE 90%1 41 nm 15 nm 41 nm slope1.00 VPRPCRF 15 - (2.21)- (1.55)- (2.21)- (1.55)2.21 PCRF PCRF CMDσFinal PN concentration compared to inlet concentration 10 nm1.30%1%18%35%30% 20 nm1.429%34%64%82%105% 30 nm1.661%64%83%91%135% 40 nm1.778%79%92%96%151% 50 nm1.888%86%98% 160% 70 nm1.9100%95%105%101%172% 90 nm2.0105%98%109%102%178% 10 nm (50%) + 50 nm (50%) % 58%67%95% GRPE-PMP-29-03

Measurement uncertainty Higher percentage of the size distribution is measured For means 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 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 SO 2 to SO 3 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