10th Diesel Engine Emissions Reduction ConferenceAugust 29-September 2, 2004

San Diego

Sponsor: U.S. Dept. of Energy, OFCVTProgram Manager: Gurpreet Singh

High-Energy Laser Diagnostics (HELD)for the

Measurement of Diesel Particulate MatterPeter O. Witze

Combustion Research FacilitySandia National LaboratoriesLivermore, California, USA

Outline

• Need For HELD Laser-induced Incandescence (LII)

• Laser-induced Desorption With Elastic LaserScattering (LIDELS)

• Laser-induced Breakdown Spectroscopy (Libs)

• Current Status And Future Plans

Need for High-Energy Laser Diagnostics (HELD)

• Real-time PM measurement techniques are needed to investigate transients

• Sensitive PM measurement techniques are needed to study cleaner vehicles

• in situ PM measurement techniques are needed to characterize engine-out/ aftertreatment-in conditions for design optimization and aging models

Laserport

Signalport

Window purge

6 signal ports and active purgeto keep windows clean

Optical sampling cell

Exhaust flow

Sandia HELD System (Laboratory-on-Wheels)

Laser portSignal port

Windowpurge

In Situ Optical Cell

0 2 4 6 8 10 12 14 16 18 200.00

0.05

0.10

0.15

0.20

0.25

0.30

Time (ns)

LII &

Las

er S

igna

ls (V

)

LII

Laser pulse

Measures elemental carbonvolume concentration

fv ∝ LIImax

Exhaust flow

Nd:YAG laser1064 nm

Photodetector

Blackbody radiation

assuming Tmax of soot is at sublimation temperature

Laser-Induced Incandescence

Spee

d (m

ph)

0 100 200 300 400 500

0.0

1.2

2.4

3.6

Time (seconds)

LIIM

ass

Rat

e (m

g/s)

0

60

Ignition

Typical Time-Resolved LII for Light-Duty FTP

Actu

al S

peed

(mph

)

340 350 360 370 380 390 400 4100

0.02

0.04

0.06

Time (seconds)

LII M

ass

Rat

e (m

g/s) 2nd 3rd1st 4th Accel. Accel.

0.08 60

50

40

30

20

10

0

Manual transmission

Expanded Look at a Single (Third) Cycle

• 7½ weeks of continuous operation

• 1078 individual tests logged

• ~60M laser shots

Unattended, 24/7 Operation at Cummins

0 0.02 0.04 0.06 0.08 0.10 0.120

0.02

0.04

0.06

0.08

0.10

0.12

Dry Gravimetric (mg/scf)

Cum

ulat

ive

LII (

mg/

scf) Transient (147)

Steady state (142)

Calibrated-LII/Gravimetric Correlation

LII 200™ consists of a 50x60x15 cm box that contains the laser,

optics, detectors and electronics. All operational functions are

controlled by a PC, providing true “turn key” performance for $150k.

Commercial LII Instrument

On-Road LII for a 2002 VW Jetta TDI Diesel

Getting Up to Speed

30 50 70 90 110 130 1500

10

20

30

40

50

Time (seconds)

LII (

ppb)

& R

PM/1

00

0

20

40

60

80

0

Spee

d (m

ph)

Freeway Acceleration to 67 Mph

Coasting Back Down

430 450 470 490 510 530 550 570 590 610 630 6500

10

20

30

40

50

Time (seconds)

0

20

40

60

80

0

Spee

d (m

ph)

LII (

ppb)

& R

PM/1

00Winding Descent on Two-Lane Road

= solid volume fraction5.0

11

22⎥⎦

⎤⎢⎣

⎡

−−

−−

YAGELS

YAGELS

AAAA

0 5 10 15 200.0

0.2

0.4

0.6

0.8

1.0

Time (ns)

Nor

mal

ized

Inte

nsity

(mV)

Pulse 1 Pulse 2

Laser

ELS

150 µs

5 10 15 20≈

Laser-induced desorption (LID) with elastic laser scattering (ELS)

Double-pulse laser, measure ELS

SAE 2002-01-1685

LIDELS with a Single Laser

0 20 40 60 80 100 120 140 160 180 200-5

-4

-3

-2

-1

0

1

2

3

4

5

Time (ns)

Div

isio

ns

~120 ns delay

5 GS/s = 1000 pts

~3Hz throughput rate(GPIB limited)

Time-Resolved LIDELS with Two Lasers

0 100 200 300 400 5000.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

Time (seconds)

Volu

me

Con

cent

ratio

n (V

-ns)

0

20

40

60

80

100

120

Solid

Vol

ume

Frac

tion

(%)

TPM (ELSpulse 1)EC (ELSpulse 2)

Start of secondaryinjection

Load e-prom

LIDELS during Secondary-injection Enable

250 260 270 280 290 300 310 3200.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

Time (seconds)

Volu

me

Con

cent

ratio

n (V

-ns)

0

20

40

60

80

100

120

Solid

Vol

ume

Frac

tion

(%)

Start of secondaryinjection

Load e-prom

LIDELS during Secondary-Injection Enable

• Line position provides speciesidentification

• Line intensity provides speciesconcentration

• Focused laser beam creates a plasma that emits light characteristic of neutral and ionized atoms

• Spectrometer output is imaged onto an intensified CCD camera

220 230 240 250 260 270 2800.0

0.2

0.4

0.6

0.8

1.0

Wavelength (nm)

Cou

nt/C

ount

max

Air

C III C I

C II

N NN

Wavelength (nm)

Cou

nt/C

ount

max

Diesel exhaust

C III C I

C II

NN

Laser-Induced Breakdown Spectroscopy (LIBS)

390 395 400 405 410 415 420 425 430 435 440 445 4500.0

0.2

0.4

0.6

0.8

1.0

Wavelength (nm)

Cou

nt/C

ount

max

Countmax = 15k

Ca

Delay=50 µsGate=50 µs

Ca+

LIBS of Ca from Ash in Diesel Exhaust

390 395 400 405 410 415 420 425 430 435 440 445 4500.0

0.2

0.4

0.6

0.8

1.0

Wavelength (nm)

Cou

nt/C

ount

max

Delay=50 µsGate=50 µs

Ca+

CaBkgd

Real-Time LIBS via Bandpass Filters

Current Status of HELD

• Commercial LII instruments are in use.

• LIDELS needs further validation and is more costly than LII, but there is strong industry interest.

• LIBS has yet to “spark” much interest.

Future Plans for HELD

• Time-resolved LIBS of Ca

• ELS/LII for measurement of size

• ELS using Rayleigh-Debye-Gans olydispersefractal aggregate theory (RDG/PFA) foraggregate morphology