high-energy laser diagnostics (held) for the … · need for high-energy laser diagnostics (held)...
TRANSCRIPT
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