Real time measurements of ash particle emissions. David Kittelson, David Gladis, and Winthrop Watts

Real time measurements of ash particle emissions David Kittelson, David Gladis, and Winthrop Watts

Outline Introduction and background Results Tests performed Lube oil spray calibration experiments Steady state engine exhaust ash measurements Transient ash measurements Ash measurements downstream of DPF Apparatus and procedure Lube oil spray calibration experiments Steady state engine exhaust ash measurements Transient ash measurements Ash measurements downstream of DPF Conclusions

Outline Introduction and background Results Tests performed Lube oil spray calibration experiments Steady state engine exhaust ash measurements Transient ash measurements Ash measurements downstream of DPF Apparatus and procedure Lube oil spray calibration experiments Steady state engine exhaust ash measurements Transient ash measurements Ash measurements downstream of DPF Conclusions

Why do we care about ash emissions? Degradation of exhaust aftertreatment systems Deposition in Diesel particulate filters (DPF) Plugging exhaust catalysts Health concerns with metallic nanoparticles Diesel or SI Mainly a concern for engines without exhaust filters Relationship with lube oil consumption Ash distribution in exhaust filter channels (Helbel and Bhargava, 2007) Accumulation of poorly crystalline Mn 3 O 4 on the face of a TWC (Hayhurst, et al., 2006)

Particle formation history 2 s in the life of an engine exhaust aerosol Particles formed by Diesel combustion carry a strong bipolar charge Carbon formation/oxidation t = 2 ms, p = 150 atm., T = 2500 K Formation There is potential to form solid nanoparticles here if the ratio of ash to carbon is high. Ash Condensation t = 10 ms, p = 20 atm., T = 1500 K Increasing Time This is where most of the volatile nanoparticles emitted by engines usually form. Exit Tailpipe t = 0.5 s, p = 1 atm., T = 600 K Sulfate/SOF Nucleation and Growth t = 0.6 s, p = 1 atm., D = 10, T = 330 K Atmospheric Aging Exposure Fresh Aerosol over Roadway Inhalation/Aging t = 2 s, p = 1 atm., D = 1000 T = 300 K Kittelson, D. B., W. F. Watts, and J. P. Johnson 2006. On-road and Laboratory Evaluation of Combustion Aerosols Part 1: Summary of Diesel Engine Results, Journal of Aerosol Science 37, 913 930.

Predicted equilibrium distribution of calcium compounds in diesel engine exhaust 1.5E-07 Mole Fraction 1.0E-07 5.0E-08 CaOH Ca(OH)2 CaO(cr) CaSO4(II) 0.0E+00 0 200 400 600 800 1000 1200 1400 1600 1800 2000 Temperature (C) Assumptions: 50 ppm sulfur fuel, equivalence ratio 0.5, lubrication oil containing 5000 ppm Ca, oil consumption 0.1% of fuel consumption.

Ash particles typically decorate the surface of soot particles but may also nucleate independently metallic ash semi volatile droplets Without Exhaust Aftertreatment

Engine out, light-load, low soot conditions: Most of the number emissions are solid with Dp < 23 nm 6.0E+07 Carbonaceous soot Mode 1 solid 5.0E+07 Mode 2 solid dn/dlogd p (part/cm 3 ) 4.0E+07 3.0E+07 2.0E+07 CPC cutoff Ash Mode 5 solid 1.0E+07 0.0E+00 1 10 100 1000 D p (nm) Cummins 2004 ISM engine, BP 50 fuel, AVL modes

Lube oil consumption leads to ash emissions Sources: mostly lube oil additives, engine wear, fuel additives Principle ash constituents: Ca, Zn, Mg, Fe, P, S Leaky valve Modified from Hill et al., (1991) Crank case ventilation and EGR Piston ring blow-by

Objectives To develop and validate a real-time method to measure engine ash emissions Testing the sensitivity of measurement method to specific metallic lube oil constituents To validate the method for steady-state and transient Diesel engine emission application

High temperature oxidation method (HTOM) overview Oxidize soot and HC PM within high temperature tube furnace Cooled particles measured using real/near-real time particle instruments Diesel exhaust or other metallic ash containing aerosol Stable metal oxides and other refractory metal compounds are formed or survive high temperature tube furnace

Outline Introduction and background Results Tests performed Lube oil spray calibration experiments Steady state engine exhaust ash measurements Transient ash measurements Ash measurements downstream of DPF Apparatus and procedure Lube oil spray calibration experiments Steady state engine exhaust ash measurements Transient ash measurements Ash measurements downstream of DPF

Lube spray apparatus Supply Air Vent Activated Carbon 2-Stage Ejector Dilution Manifold Vent Atomizer Ash Sample Point* Catalytic Stripper Tube Oven Total Sample Point* Sample flow controlled by SMPS SMPS sample flow, 1 lpm *Sample Location Manually Switched

Engine exhaust apparatus CAI Analyzer Raw NO Horiba NO Analyzer Dilute NO SMPS Engine Exhaust Supply Air Vent Ejector pump diluter with critical orifice Tube Oven (1 LPM) Oven Temperature Logger SMPS Other Thermocouple instruments, Wires EAD, EEPS

Outline Introduction and background Results Tests performed Lube oil spray calibration experiments Steady state engine exhaust ash measurements Transient ash measurements Ash measurements downstream of DPF Apparatus and procedure Lube oil spray calibration experiments Steady state engine exhaust ash measurements Transient ash measurements Ash measurements downstream of DPF Conclusions

Lube oil spray calibration experiments Investigate high temperature stability of likely ash constituents Atomize specially formulated lubricating oils with different additive packages Measure particle size distribution upstream and downstream of the furnace Determine penetration vs. temperature Compare with expected solid ash fraction

Specially blended lubricants provided by Castrol Base stock Metal mass fractions in ppm 104A 101A 100A 103A 102A B <5 <5 <5 285 <5 Ca <2 <2 3946 <2 3724 Mg <2 <2 8 ~500 <2 P 2 976 1052 <10 13 S 55 1998 802 57 8804 Zn <5 1008 <5 <5 <5

1.E+06 Upstream and downstream volume weighted particle size distributions dv/dlogdp [um 3 /cm 3 ] 1.E+05 1.E+04 1.E+03 1.E+02 1.E+01 1.E+00 1.E-01 1.E-02 1.E-03 1.E-04 Atomized Lube Oil 100A - Ca,P,S 101A - Zn,P,S 102A - Ca,S 103A - B,Mg Ca,P,S - 100A 2.6E2 µm 3 /cm 3 Typical Atomized Lube Oil 3.6E4 µm 3 /cm 3 Ca,S - 102A B,Mg - 103A 2.3E2 µm 3 /cm 3 Zn,P,S - 101A 2.7E1 µm 3 /cm 3 3.7E-1 µm 3 /cm 3 1 10 100 1000 Dp [nm]

Particle volume fraction penetrating 1.E+00 the tube oven 100A - Ca,P,S 101A - Zn,P Particle Volume Fraction Remaining - 1.E-01 1.E-02 1.E-03 1.E-04 1.E-05 102A - Ca,S 102A - Ca,S 100A - Ca,P,S 103A - B,Mg,S 101A - Zn,P,S 103A - B,Mg,S 1.E-06 0 200 400 600 800 1000 1200 Maximum Oven Temperature [ C]

Expected metallic mass compared to measured Metallic Volume Fraction Blend # Element Compound Concentration [ppm] Expected Measured Measured/Expected 100A Ca CaCO3 3946 2.9E-03 7.3E-03 2.51 101A Zn ZnSO4 1008 5.9E-04 9.6E-06 0.02 102A Ca CaSO4 3724 3.4E-03 7.2E-03 2.10 103A Mg MgCO3 500 5.3E-04 7.8E-04 1.48 Note: Expected concentrations are based on the assumption of spherical particles of the compounds listed

Outline Introduction and background Results Tests performed Lube oil spray calibration experiments Steady state engine exhaust ash measurements Transient ash measurements Ash measurements downstream of DPF Apparatus and procedure Lube oil spray calibration experiments Steady state engine exhaust ash measurements Transient ash measurements Ash measurements downstream of DPF Conclusions

Volume weighted particle size distributions from VW TDI engine dv/dlogdp [µm 3 /cm 3 ] 1.E+05 1.E+04 1.E+03 1.E+02 1.E+01 1.E+00 1.E-01 2009/11/02 - Total Exhaust 2009/11/10 - Total Exhaust 2009/11/12 - Total Exhaust 2009/11/02 - Ash 2009/11/10 - Ash 2009/11/12 - Ash 2009/11/10 - Ash 1.3 µm3/cm3 2009/11/02 - Ash 0.5 µm3/cm3 Ambient 2009/11/12 - Ash 1.2 µm3/cm3 1100 C 1.E-02 1 10 100 1000 Dp [nm]

Ash volume fraction of exhaust particles for different engine conditions Ash Particle Volume Fraction 1.E-02 1.E-03 1.E-04 2009/11/12 - VW 1400RPM - Volume 2009/11/12 - VW 1700RPM - Volume 2009/12/07 - GenSet 3600RPM - Volume 1.E-05 0 20 40 60 80 100 Engine Load [%]

Outline Introduction and background Results Tests performed Lube oil spray calibration experiments Steady state engine exhaust ash measurements Transient ash measurements Ash measurements downstream of DPF Apparatus and procedure Lube oil spray calibration experiments Steady state engine exhaust ash measurements Transient ash measurements Ash measurements downstream of DPF Conclusions

Transient engine ash emissions 0.25 Length Concentration [mm/cm 3 ] 0.20 0.15 0.10 0.05 PM Length Concentration Load 100 80 60 40 20 Load [N-m] 0.00 12:40 15:33 18:25 21:18 24:11 27:04 29:57 32:49 35:42 38:35 Time [mm:ss] 0

Outline Introduction and background Results Tests performed Lube oil spray calibration experiments Steady state engine exhaust ash measurements Transient ash measurements Ash measurements downstream of DPF Apparatus and procedure Lube oil spray calibration experiments Steady state engine exhaust ash measurements Transient ash measurements Ash measurements downstream of DPF Conclusions

Soot and ash particle volume concentration downstream DPF 1.E+04 SMPS - DPF Out Exhaust (Test 1) SMPS - DPF Out Ash (Test 1) EEPS - DPF Out Exhaust (Test 2) SMPS - DPF Out Ash (Test 2) Volume Concenration [µm 3 /cm 3 ] 1.E+03 1.E+02 1.E+01 1.E+00 1.E-01 1.E-02 1.E-03 Total Particulate SMPS Test 1 Metallic Ash Test 1 Metallic Ash Test 2 Total Particulate EEPS Test 2 00:00 07:12 14:24 21:36 28:48 36:00 Time Normalized to Start of DPF Loading [min:sec]

Soot surface area and ash volume concentrations downstream DPF SMPS - DPF Out Ash (Test 1) Volume SMPS - DPF Out Exhaust (Test 1) Surface Area 1.E+01 SMPS - DPF Out Ash (Test 2) Volume EEPS - DPF Out Exhaust (Test 2) Surface Area 1000000 Volume Concenration [µm 3 /cm 3 ] 1.E+00 1.E-01 1.E-02 1.E-03 100000 10000 1000 100 Surface Area Concentration - [µm 2 /cm 3 ] 1.E-04 10 00:00 07:12 14:24 21:36 28:48 36:00 Time Normalized to Start of DPF Loading [hh:mm]

Outline Introduction and background Results Tests performed Lube oil spray calibration experiments Steady state engine exhaust ash measurements Transient ash measurements Ash measurements downstream of DPF Apparatus and procedure Lube oil spray calibration experiments Steady state engine exhaust ash measurements Transient ash measurements Ash measurements downstream of DPF Conclusions

Conclusions HTOM calibration experiments lube oil sprays showed that Ash constituents of Ca and Mg additives were conserved Expected Zn compounds were not found apparently due to formation of volatile materials lost to the walls This suggests possible different deposition mechanisms within a DPF Steady-state ash measurements showed a slight increase of ash fraction of exhaust particles with load Ash emissions under changing engine conditions were highly transient and history dependent Ash volume concentrations were successfully measured downstream a loading DPF and were shown to track better with soot surface area than volume concentration Ongoing work includes TEM analysis and ATOFMS analysis of particles treated by HTOM

Acknowledgements We wish to acknowledge the generous support of this work by contributions from BP-Castrol and Corning Thank you for your attention

References Kittelson, D. B. (1998). Engines and Nanoparticles: A Review. Journal Aerosol Science, 29(5/6), 575-588. Kittelson, D.B., W.F Watts, J.P. Johnson, (2006) On-road and laboratory evaluation of combustion aerosols-part1: Summary of diesel engine results, 37(8), 913-930 Hill, S. H., S. J. Sytsma (1991). A Systems Approach to Oil Consumption. SAE Technical Paper Series, 910743, Warrendale, PA. Heilbel, H., R. Bhargava (2007). Advanced Diesel Particulate Filter Design for Lifetime Pressure Drop Solution in Light Duty Applications, SAE Technical Paper Series, 2007-01-0042, Warrendale, PA.

1.E+05 Volume weighted particle size distributions from Cummins APU 0.0% - Total Exhaust 1.E+04 37.5% - Total Exhaust dv/dlogdp [µm 3 /cm 3 ] 1.E+03 1.E+02 1.E+01 1.E+00 75.0% - Total Exhaust 0.0% - Ash 37.5% - Ash 75.0% - Ash Ash - 75.0% 3.4E0 µm3/cm3 Ash - 37.5% 1.7E0 µm3/cm3 1.E-01 Ash - 0.0% 6.3E-1 µm3/cm3 1.E-02 1.0E+00 1.0E+01 1.0E+02 1.0E+03 Dp [nm]