Chemical and Physical Properties of Sub-Micron Particle Emission from a Diesel Engine

Michael Alexander, Jian Wang, Yong Cai, Alla Zelenyuk, John Storey, Jay

Slowik, Peter DeCarlo, Jose Jimenez, and Douglas Worsnop

PNNL, NTRC, Boston College, University of Colorado, Aerodyne Research

Complimentary Measurement Techniques

Aerodyne AMS* SPLAT-MS**

• ensemble average of particles –size and composition

• real-time, quantitative measurement of certain chemical classes

• large dynamic range (>103 observed at ORNL)• sufficient time response 4 sec to study transients

• Single particle analysis to 50 nm • Classification of particle types • Detection of refractory compounds

**single particle TOF mass spectrometer*aerosol mass spectrometer

Mass Concentrations from AMS Over a Range of Engine Conditions

12x103

10

8

6

4

2

0

Mas

s C

once

ntra

tion

(µg

m-3

)

10:00 AM4/16/2004

11:00 AM 12:00 PM 1:00 PM

Date and Time

500

400

300

200

100

0

Mass C

oncentration of Sulfates

Water Ammonium Nitrate Sulphate Chloride Organics PAH

Engine warm-up

1400 rpm470 ft/lbs torrque

800 rpm4 ft/lbs

Reduce Rail Pressure1000 rpm327 ft/lbs

10

100

1000

Vac

uum

Aer

odyn

amic

Dia

met

e

10:00 AM4/16/2004

11:00 AM 12:00 PM 1:00 PM

Date and Time

12008004000

dM/dlogD

va (µg m-3)

Organics

SPLATSoot Particles are Most Prevalent

The most prevalent particles are composed of almost pure soot as evident by the carbon progression

SPLATPAHs Volatilize from Particles using Laser Heating

PAH Dominated30 NO

152 178-C2H2178 phenanthrene

192 C1 Alkyl phenanthrene

202 Pyrene

216 Alkyl pyrene

234 C4 Alkyl phenanthrene

252 Benzo pyrene

PAH

HCsoot

PAH dominated particles are most common under high RPM and low load conditions

See Poster 6PB7 – Yong Cai for more details on SPLAT

1 0

8

6

4

2

0

Nitr

ate

Equi

vale

nt M

ass

Con

cent

ratio

n (µ

g m

-3)

1 5 01 4 01 3 01 2 01 1 01 0 09 08 07 06 05 04 03 02 01 0m / z

S p e c i e s

O t h e r s 4 . 5 2 ± 0 . 2A i r 1 7 1 ± 0 . 2W a t e r -0 . 2 4 1 ± 0 . 1A m m o n iu m 0 . 4 ± 0 . 0 2N i t r a t e 0 . 1 5 3 ± 0 . 0 0 7S u l p h a t e 0 . 9 6 7 ± 0 . 0 4C h l o r i d e 0 . 0 9 7 6 ± 0 . 0 1P A H 0 . 0 6 6 4 ± 0 . 0 0 8O r g a n i c s 6 7 . 9 ± 0 . 1

Diesel Vehicle Exhaust

Mass Spectrum of AMS organic from heavy duty off road exhaust

NYC, Canagaratna et al, in press

Heavy duty off road MS is virtually identical to that observed in ambient data.

This mass spectrum is very similar to that of lubricating oil (see next slide)

0.01

0.1

1

10

100N

itrat

e Eq

uiva

lent

Mas

s C

once

ntra

tion

(µg

m-3

)

3202802402001601208040m/z

Species

Others 169 ± 0.4Water -1.22 ± 0.1Ammonium 0.456 ± 0.02Nitrate 0.175 ± 0.01Sulphate 1.03 ± 0.05Organics 78.1 ± 0.1

? Oil 78.7 ± 0.2

SPLAT - At Rated Speed, Oil Components and Engine Wear and Tear Appear Products Appear in Particles

Ca Al and Zn indicate lube oil consumption and engine wear and tear

0.0001

0 .001

0.01

0.1

1

10

100

Equ

ival

ent M

ass

Con

c

29 528126 725323 922 52 1119 71 8316 91 5514 11271 13998571574329150M ass / am u

0.0 01

0.01

0.1

1

10

Sig

nal

Inte

nsity

20151050Num ber of Carbons

0.50.40.30.20.10.0

Car

bons

1-4

0.4

0.3

0.2

0.1

0.0

Car

bons

5-6

0.30

0.20

0.10

0.00

Car

bons

7-1

5

-7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6

Delta

1.0

0.8

0.6

0.4

0.2

0.0

rela

tive

Sig

nal

15 16 17 30 46 48 64 80 81 9 8

AM U

45.9%

26.8%

23.4%

0.1 : 1 : 1.42 5.16 : 1 1 : 0.96 : 0.8 : 2.12 : 0.35

Particle Composition (µg/m3)-0.8% Water -1.21960.3% NH4 0.456460.1% NO3 0.174620.7% SO4 1.027449.7% Org 78.07250% Oil 78.651 (NH4)m eas/(NH4)expt =NaN

∆ = 2 29 / 43 ∆ = 0 13 / 55

star t/max

Runs Averaged: 1081 to 1084 (4/9/2004 10:02 to 10:05)

200

150

100

50

0dM

/dlo

gDva

(µg

m-3

)

102 3 4 5 6 7 8 9

1002 3 4 5 6 7 8 9

10002

Diameter (nm)

2500

2000

1500

1000

500

0

dVol/dlogDm

ob (nm3m

-3)15

10

5

0

DMA Volume

1400 nm3/cm3 (?)

AMS mass loading

Organic 70 ug/m3

Sulfate 2Nitrate 0.2

x10

x10

PRELIMINARY (4/11/04, DRW)

Comparison of AMS Massand SMPS Volume

Distributions

Dva < Dmobfractal particles

Effective Density: ρeff ~ Dva/Dmob ~ 0.5 g/cc

This comparison of AMS (mass) and SMPS (volume) distributions isvery similar to what we have observed in ambient urban data, particularly during morning rush hour when primary combustion particles tend to dominate total sub-micron aerosol loading.

FIRST ATTEMPT at MASS BALANCE:

AMS (organic) vs SMPS (total)

DMA volume (1400 nm3/cm3) x ρeff (0.5g/cc) ~ 700 ug/m3 (total)-- AMS Mass (80 ug/m3)) x 1.35 /.9 ~ 120ug/m3 (organic matter)

____________

Black Carbon ~ 580 ug/m3

“BC/OC” ratio ~ 5

cf. ambient (literature) measurements,

typical BC/OC ~ 1-3

Conclusion:

On a mass weighted basis, ~3x less oil from off road engine is ~3x “cleaner” for lube oil emissions compared to typical diesel engines.

ESTIMATE of OC Emission Index for off road engine

~120 ug/m3 / ~7000 ppm ~ 0.017 ug/m3/ppm ~ 0.030 g NRPM / fg Fuel

This engine

OM Emission Indexes for Diesel TrucksComparison of Mexico City and New York City

0.40.30.20.10.0

Frac

tion

9876543210Emission Ratio (g NRPM/ kg Fuel)

0.40.30.20.10.0

Sample Size NYC 19 MC03 24

MC03

NYC

NYC_AMS_Figs4to6_wMexDat.pxp

NYC mean = 0.5

MC03 mean = 1.6

JohnDeere

Manjula R. Canagaratna, et al. “Chase Studies of Particulate Emissions from in-use New York City Vehicles”, Aerosol Science & Technology, submitted March 2003

Particle Density: DMA in front of AMS

2.0

1.5

1.0

0.5

0.0

dM/d

logD

va (µ

g m

-3)

102 3 4 5 6 7 8 9

1002 3 4 5 6 7 8 9

1000Vacuum Aerodynamic Diameter (nm)

200

150

100

50

0

Polydisperse r1080_1085 (DMA bypass)

60 nm r1140_1150 100 1115-1134 200 1096_1115

mass numberug/m3 #/cc

66 >100000 0.05 6300 0.31 5500 0.27 900

4

5

6

7

8

9

1 0 0

2

Vac

uum

Aer

odyn

amic

Dia

met

er (D

va, n

m)

4 5 6 7 8 91 0 0

2 3 4

M o b ili t y D ia m e te r (D m o b , nm )

C o a te d s o o t fr a c ta l d im e n s io n ~ 3

F la m e s o o t f d im e n s i o n ~ 1 .8

"J o h n D e e r e " s o o t f d im e n s io n ~ 2 .5 ? ?

1 0 -1 2

1 0-1 1

1 0-1 0

10-9

10-8

Mas

s pe

r Par

ticle

(ug/

parti

cle)

4 5 6 7 8 910 0

2 3 4

M o b i lity D ia m e te r (D m o b , n m )

T o ta l M a s s p e r P artic le - 2 .5 D F ra c t a l P a tic le s

m a s s _ p e r_ p = C (D m o b )2 .5

p e r m o d e l o f J a y S lo w ik a n d P e te r D e ca rlo D av id o v its ( B C ) a n d J im e n e z (C U ) O C M a ss p e r P a rtic le

fo r O C /B C ra tio ~ 6

M e a su re d O C M a s s p er P a rtic le

= A M S M a s s / C P C N u m b er C o n c

Slowik, et. Al (in press)

Particle Density: DMA in front of AMS

Same Engine Different Day

25

20

15

10

5

0

dM/d

logD

va (µ

g m

-3)

102 3 4 5 6 7 8 9

1002 3 4 5 6 7 8 9

10002

Vacuum Aerodynamic Diameter (nm)

7x106

6

5

4

3

2

1

SM

PS

Cou

nts

800

600

400

200

0

500 nm 300 nm 400nm 200 nm 100 nm SMPS (counts) AMS Polydisperse

Related Talk by Jian Wang 12A3 on Friday

-0.8

-0.6

-0.4

-0.2

0

0.2

1.9 2 2.1 2.2 2.3 2.4 2.5 2.6 2.7

log

(den

sity

)

log (mobility diameter)

Diesel soot density and fractal dimension from SPLAT

Density = Daero/Dm

Density = CDmDf-3

Df = 1.87

Df = 1.96

Off-road John Deer 4045H

1.7L Mercedes A-Class

These values are consistent with fractal dimension predicted for diffusion-limited cluster-cluster agglomeration

The simultaneous measurements of particle size density and composition makes it possible to derive the fractal dimension of the freshly emitted soot

AMS Beam Width Probe Data

1.0

0.9

0.8

0.7

86420Wire Position

6.0x106

5.5

5.0

4.5

4.0

3.5

Airb

eam

10:45 AM 10:50 AM4/16/2004

10:55 AM 11:00 AM 11:05 AM

10

8

6

4

2

0

Organic

AvgWirePositions(161, 3, "org",7) 1400 RPM 352 ft/lbs torque -high load

AMS Organics Signal form On-Road Engine Running in Regen

2500

2000

1500

1000

500

0

4:15 PM4/28/2004

4:30 PM 4:45 PM 5:00 PM 5:15 PM 5:30 PM 5:45 PM

dat

Regen - throttle bodyand injector - 4sec every 30 sec

Regen - throttle bodyand injector - 8 sec every 60 sec

Regen - injector only4sec every 30 sec

Regen - throttle bodyand injector - 8sec every 60 sec

AMS Organic Signal and Laser Induced Incandescence

0.7

0.6

0.5

0.4

0.3

0.2

0.1

LLI S

igna

l Arb

. Uni

ts

4:15 PM4/28/2004

4:30 PM 4:45 PM

Time

3000

2500

2000

1500

1000

500

AMS organic signal ug/M

3

Regen ModeThrottle Body and Injector

4 sec every 30 sec

Regen ModeThrottle Body and Injector

8 sec every 60 sec

LII Org

AMS PAH and Nitrate follow Organics(Negligible Sulfate and Ammonia)

100

80

60

40

20

0

4:30 PM4/28/2004

5:00 PM 5:30 PM 6:00 PM

dat

NO3 PAH

Aerodynamic Size Distribution from AMSOrganics Dominant Species, Small Sulfate, Nitrate

1600

1400

1200

1000

800

600

400

200

0

dM/d

logD

va (µ

g m

-3)

102 3 4 5 6 7 8 9

1002 3 4 5 6 7 8 9

10002

Vacuum Aerodynamic Diameter (nm)

Ammonium Nitrate Sulphate Chloride Organics PAH

AMS Size Distribution and Intensity of Organics vs. Time

Conclusions

• AMS and SPLAT provide complimentary view of Diesel exhaust

• New generations of diesel engines much cleaner

• AMS signal from engine due to fractal carbon particles with adsorbed lube oil

• AMS aerodynamic organic mass vs size distribution is bimodal – larger mode dependent on engine conditions

• Regeneration operation of engine has large effect on organic species

Acknowledgements

• Department of Energy Energy Efficiency Program

•ORNL National Transportation Research Center and Staff

• Aerodyne Research Staff

• Jose Jimenez and group at U. of Colorado

• Davidovitz group at Boston College