PMP: SUB 23 NM

MEASUREMENT RECOMMENDATIONS

B. Giechaskiel, G. Martini

Institute for Energy and Transport Joint Research Centre

3 April 2014

Sub23nm particles

• Percentages around 30-40% (over a cycle)

Mamakos et al. 2011 ETHGiechaskiel, PMP 29

GDI, vehicle Khalek et al. 2010 Ronkko et al. 2014

GDI, produces nanoparticles even when not fueled, coming from oil

Monitoring GDI important

Formation of particles in the VPR

• Indications when sulfur exists• Formed solid particles were <10 nm• Difficult to justify (pyrolysis?)• Example is reaction of sucrose with strong sulfuric acid• Experimental suggestions:

• HC and sulfuric acid through PMP• Both as gaseous and liquid droplets• SMPS and CPC downstream PMP• Check PCRF effect

Volatile Removal efficiency (ET)

• Hydrocarbons• Tetracontane will re-nucleate at >107 p/cm3 or 3 mg/m3

• Sulfuric acid• Sulfuric acid will re-nucleate at 0.7-3.5 μg/m3

• Growth after the ET• The re-nucleated nucleis are 1-2 nm.• Organics are necessary for the nucleis to grow• Theoretical calculations and experimental results show that they can

grow to 6 nm (1011 p/cm3 organics) or 20 nm (1014 p/cm3 hexadecane, <5 ppm C3)

Sulfur compounds in DPFs

• Partial DPF• Alumina based coating

with Pt as active metal• No artifact from

sampling lines etc.• Formation of sulfuric

acid particles from SO2 to SO3 conversion

Kajalainen et al. 2014

SO2

DPF regeneration

Volatile artifact appears as solid particles <23 nm (CVS)PCRF: 100x10

No artifact >6 nm (tailpipe)PCRF: 15x15

Typically no artifact above 10 nm (Zheng et al. 2012, Mamakos et al. 2013)

DPF regeneration

• Gaseous HCs do not correlate with PN<23

• Probably heavy HCs• Sulfates probably

important• Artifact probably from

desorption after tailpipe• Pre-conditioning of

setup is important

PCRF selection

• PCRF 100x10• Still >3nm artifact• Lower solid surface

nucleation vs condensation

• Probably no issues with >10nm measurements

Moped

Volatile artifact even with high dilution (1000x10)

With EEPS connected to PMP (350x20) no detectable artifact.Similarly with a 10 nm CPC

Thus artifact around <6nm

Volatile Removal Efficiency (CS)

• Catalytic Stripper (CS)• Removes volatiles by oxidation

• Even >35 times highest HC concentration (eg moped)• Better removal efficiency of tetracontane

• Traps sulfur • Up to 10 mg/m3

• Might oxidize SO2 to SO3

• Particles might be formed if saturated• Higher particle losses

CS has also limitations

• Silica-alumina coating with Pt and Barium oxide

Amanatidis et al. 2013

Summary

• Monitoring of sub23nm is recommended• Decreasing the size to ~10 nm is possible. VPRs should be

used with high dilution (>1000:1)• Special attention to GPFs and DPFs (no soot)• The CS is an alternative solution that has to be

investigated:• Saturation with sulfur• Formation of particles

• SO2 to SO3 conversion

Summary

• To measure below 10 nm:• A dilution system with minimum losses of sub23 nm is

necessary.• A catalytic stripper well documented is necessary• A full flow CPC with low cut-off size is necessary

Next steps

• The setup has to be well pre-conditioned• Organics, sulfates would be useful• Measurements in parallel with PMP systems with ET

and CS devices with both 23nm and ~10 nm PNCs.• Support from instrument manufacturers needed

especially for CS, or setting a second CPC

Next steps

• Tests without CS should be conducted with as high PCRF as possible (at least 100x5)• Note that even with PCRF 10000, and PNC concentrations

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

• When high sub23nm concentrations are measured (>100%, at emissions 10^11 p/km) the tests should be repeated with 10x higher PCRF• Lower concentrations could be background noise

Thank you for your attention!

Draft report is ready for anyone interested!

barouch.giechaskiel@jrc.ec.europa.eu