Content uploaded by Greg J Smallwood
Author content
All content in this area was uploaded by Greg J Smallwood
Content may be subject to copyright.
NRC Publications Archive (NPArC)
Archives des publications du CNRC (NPArC)
Fundamentals and applications of laser-induced incandescence
Smallwood, Gregory J.
Contact us / Contactez nous: nparc.cisti@nrc-cnrc.gc.ca.
http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/jsp/nparc_cp.jsp?lang=fr
L’accès à ce site Web et l’utilisation de son contenu sont assujettis aux conditions présentées dans le site
Web page / page Web
http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/ctrl?action=rtdoc&an=15474376&lang=en
http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/ctrl?action=rtdoc&an=15474376&lang=fr
LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D’UTILISER CE SITE WEB.
READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE.
Access and use of this website and the material on it are subject to the Terms and Conditions set forth at
http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/jsp/nparc_cp.jsp?lang=en
©GregSmallwood
Fundamentals and Applications of
Laser-Induced Incandescence
Gregory J. Smallwood
Institute for Chemical Process and Environmental Technology
National Research Council Canada
Ottawa, ON, Canada K1A 0R6
1st Asian Workshop on Laser-Induced Incandescence
30 October 2009 Hefei, China
©GregSmallwood
Outline
• Background
• Laser-Induced Incandescence (LII)
–Basics
– Autocompensating LII
• Applications
• Summary
©GregSmallwood
Why LII?
• there was a need for substantially
improved instruments to quantify
nanoparticle characteristics
• laser-induced incandescence
technique for the quantitative
measurement of soot nanoparticles
– concentration, active surface area,
and primary particle diameter
– species selective technique
– good sensitivity
• enhance the state of measurements
for practical applications
– nonvolatile particulate matter
emissions
What is soot?
• dry solid particles produced through incomplete
combustion of hydrocarbon fuels
• terminology varies by scientific field
– elemental carbon, black carbon, refractory carbon,
carbon black
• LII is effective at measuring all of these
1000rpm / 25% load 1000rpm / 50% load
1000rpm / 75% load 2500rpm / 70% load
[Lee al., SAE Paper No. 2003-01-3169, 2003]
©GregSmallwood
What are the issues
with soot?
Improve efficiency of combustion
technology
Engineered nanoparticle
synthesis
Assess the ecological and health impacts of
combustion
©GregSmallwood
TEM Images of
Nanoparticles Sampled
From a Flame
©GregSmallwood
TEM Images of
Nanoparticles Sampled
From a Flame
• particulate matter properties of
interest:
– concentration
– active surface area
– primary particle diameter
distribution
– aggregate size distribution
– optical properties
– volatile fraction
– composition
©GregSmallwood
Outline
• Background
• Laser-Induced Incandescence (LII)
–Basics
– Autocompensating LII
• Applications
• Summary
©GregSmallwood
What is Laser-Induced
Incandescence (LII)?
• laser-induced incandescence is a generic name for the physical
process of rapidly heating refractory nanoparticles with a laser
to the point that the radiative emission from the particles is
discernable from the background
• many variants of LII have appeared
– high fluence (most common)
• particles are heated to their sublimation temperature
– low fluence
• particles are heated to lower than sublimation temperature
– remote in situ nonintrusive measurements (some instruments)
• fundamental studies on open flames
– extractive sampling (most instruments)
• engine and combustor development and emissions measurement
©GregSmallwood
Further LII Variants
• pulsed laseror cw laser
• time-resolved(TiRe-LII) or gated
• single (narrow or broadband), two, or multiple wavelengths
• 0-D (
point measurements); 1-D (line measurements); 2-D (area
measurements); or 3-D (volume measurements)
– iso-concentration surfaces in a turbulent non-premixed flame
[Hult et al., Experiments in Fluids 33, 2002]
©GregSmallwood
What Does LII Do?
• quantitative measurement for soot:
– concentration (0.01 ppt – 10 ppm volume; 20ng/m3– 20g/m3mass)
– active surface area (50 – 200 m2/g)
– primary particle diameter (typically 5-50 nm)
– number density of primary particles
• properties are for an ensemble of particles
• measurement features:
– very high precision and repeatability
– transient concentration
– nonintrusive (dilution unnecessary)
– wide range of applicability
– potential standardized method
– measures soot
– high selectivity
[Schulz et al., Applied Physics B 83, 2006]
©GregSmallwood
Time-Resolved Laser
Induced Incandescence
00.2 0.4 0.6 0.8 1
t [μs]
incandescence [ ]
0
3500 K
T [K]
300 K
Laser
Detector
Temperature
Incandescence
©GregSmallwood
LII Calibration –
Correlation to Other Flame
Measurements
• calibration by comparison
of the LII signal to the SVF
profiles obtained by laser
extinction
–––– LII data
- - - - laser extinction/scattering data
[Ni et al., Applied Optics 34, 1995]
©GregSmallwood
LII Calibration –
Comparison to Other
Instruments
[Schraml et al., SAE Paper No. 2000-01-2002, 2000]
©GregSmallwood
Determination of Primary
Particle Diameter
• numerically
modelled LII signal
decay of soot at STP
ambient conditions
• signal decay rate
varies with primary
particle diameter
[Schraml et al., SAE Paper No. 2000-01-2002, 2000]
©GregSmallwood
Outline
• Background
• Laser-Induced Incandescence (LII)
–Basics
– Autocompensating LII
• Applications
• Summary
©GregSmallwood
Auto-Compensating LII
(AC-LII)
• two-color pyrometry coupled with LII to determine the time-
resolved particle temperature
– permits use of low-fluence
– particles are kept below the sublimation temperature
• this new technique automatically compensates for any changes in
the experimental conditions
– fluctuations in local ambient temperature
– variation in laser fluence
– laser beam attenuation by the particulate matter
– desorption of condensed volatile material
©GregSmallwood
Particle Emission
Intensities
• blackbody and soot
particle emission intensity
– over range of
temperatures
encountered in LII over
the UV-VIS-NIR
spectral range
• emissivity
• soot particles are
calculated for dp= 30 nm
and E(m) = 0.4
[Smallwood, Ph. D. Thesis, Cranfield University, 2009]
©GregSmallwood
Soot Concentration from
Two-Color Pyrometry
• temperatureis determined from the spectral radiance signals at
two wavelengths
– varies with relative E(m)at the two wavelengths
• soot volume fractionis determined from the temperature and the
spectral radiance signal at either one of the wavelengths
– depends upon absolute value of E(m)at the selected wavelength
[Smallwood, Ph. D. Thesis, Cranfield University, 2009]
©GregSmallwood
electrical and water
to/from power supply
detection package (collection
optics, beam separation
optics, and photodetectors)
Nd:YAG
laser head
(1064 nm)
beam
dump
½ wave plate
½ wave plate
thin film polarizer
vertical slit
mirror mirror
spherical lens
detector track
control and signal lines
to/from photodetectors
35º
measurement location
Experiment: LII Optical
Apparatus
measurement
location
35º
collection lens
focusing lens
40 mm
circular
aperture
2 mm
circular
aperture
collimating
lens
pulsed laser beam
long wavelength
(1064 nm) detector
Incandescent radiation + Nd:YAG (1064 nm) scattered
radiation (both are incoherent, unpolarized, collimated) dichroic #1 dichroic #2
interference
filter #1
interference
filter #2
interference
filter #3
[Smallwood et al., SAE Paper No. 2001-01-3581, 2001]
©GregSmallwood
Absolute LII Signals
[Smallwood, Canadian Section of the Combustion Institute, 2005]
©GregSmallwood
Real-time Temperature
soot temperature
exponential fit
[Smallwood, Canadian Section of the Combustion Institute, 2005]
©GregSmallwood
Impact of Low Fluence
LII
0200 400 600 800 1000
0
1
2
3
Time (ns)
Soot Volume Fraction (ppm)
high fluence
0200 400 600 800
0
1
2
3
Time (ns)
[Smallwood, Canadian Section of the Combustion Institute, 2005]
©GregSmallwood
Impact of Low Fluence
LII
0200 400 600 800 1000
0
1
2
3
Time (ns)
Soot Volume Fraction (ppm)
high fluence
low fluence
sublimed soot
0200 400 600 800
0
1
2
3
Time (ns)
[Smallwood, Canadian Section of the Combustion Institute, 2005]
©GregSmallwood
Demonstration of
Fluence Effects in LII
0.50mJ/mm2
PeakFluence
0.67mJ/mm20.83mJ/mm2
1.25mJ/mm22.50mJ/mm23.75mJ/mm2
0.50mJ/mm2PeakFluence
©GregSmallwood
Experiment: Optimum
Analysis Interval
• for high quality AC-LII measurements, the optimum analysis
interval was found to be approximately 50-100 ns after the peak
of the laser pulse
– maximum soot volume fraction and single exponential
temperature decay
–interval is dependent upon experimental conditions
ln(T-Tg)
7.6
7.7
7.8
7.9
8.0
8.1
0 50 100 150 200 250 300 350 400
t (ns)
Polydispersity
effects
Anomalous
cooling Linear
range
Experiment
Fit
ln(T-Tg)
7.6
7.7
7.8
7.9
8.0
8.1
0 50 100 150 200 250 300 350 400
t (ns)
Polydispersity
effects
Anomalous
cooling Linear
range
Experiment
Fit
[Smallwood, Ph. D. Thesis, Cranfield University, 2009]
©GregSmallwood
LII Precision
• single-shot precision of LII in
measuring soot concentration
and primary particle diameter is
good
• standard deviation is about 5%
for these examples acquired
above a quenched laminar
diffusion flame
[Smallwood, Ph. D. Thesis, Cranfield University, 2009]
©GregSmallwood
Single-shot vs. Multi-
pulse Averaging
ABOVE
• single-shot (left) and 50-
shot average (right)
RIGHT
• effect of averaging on
measurement validation
rate
[Smallwood, Ph. D. Thesis, Cranfield University, 2009]
©GregSmallwood
AC-LII Issues
• AC-LII does not always agree with gravimetric
– need improved knowledge of E(m) as a function of temperature
and wavelength
– SVF determined by AC-LII varies with fluence
0.4 0.6 0.8 1
0.2
0.3
0.4
0.5
0.6 Krishnan et al. (in situ)
Koylu & Faeth
Bruce (Diesel soot)
Schnaiter et al. (Diesel soot)
Dobbins et al.
Loess fit to above data
NRC Data (absorption)
Bond (black carbon)
This Work (LII)
Wavelength (microns)
Absorption function - E(m)
0
10
20
30
40
50
60
70
80
90
100
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
Fluence(mJ/mm2)
MassConcentration(mg/m3)
[Smallwood, Ph. D. Thesis, Cranfield University, 2009]
©GregSmallwood
Outline
• Background
• Laser-Induced Incandescence (LII)
–Basics
– Autocompensating LII
• Applications
• Summary
©GregSmallwood
LII Applications:
Present and Future
• process control of carbon black:
• aggregate size distribution
• higher sensitivity to changes in
surface area
• air quality monitoring (urban and
global):
• greater concentration sensitivity
• 0.05 parts-per-trillion (1 femtogram)
detection limit
• engine emissions (manufacturers):
• single-shot transient response
• determination of volatile organic
compound fraction
• vehicle emissions (regulators)
• improved repeatability
• on-road emissions measurements
©GregSmallwood
LII Applications: Artium
Technologies Instruments
• Artium Technologies takes an active
role, with NRC’s support, in working
with customers who have purchased
the LII 300 (top) or LII 200 (bottom)
instruments
– Easy to use
– Low maintenance system
– Low operating costs
– Very high sensitivity
– Compact rugged and portable instrument
– Built-in computer and display, touchscreen control
– Completely enclosed laser, optics, and sampling cell
– Built-in pneumatics controller and sampling system
– Includes real-time pressure and temperature
measurements to reduce data to STP
– Fail safe valve prevents sample from entering cell if
purge air or power are off
– Technologies protected by US Patents 6,154,277 and
6,181,419 under license from National Research
Council (NRC) Canada
©GregSmallwood
LII Measurement of Diesel
Nonvolatile Particulate
Emissions
0
100
200
300
400
500
0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300
Test time (seconds)
SVF (ppb) and Cum ulative Mass (mg)
0
20
40
60
80
100
Vehicle Speed (km/h)
LII SVF (ppb)
Cumulative Mass
Drive Trace
[Smallwood et al., 8th International ETH-Conference on Combustion Generated Particles, 2004]
©GregSmallwood
LII Measurement of Diesel
Nonvolatile Particulate
Emissions
0
20
40
60
80
100
120
140
200 250 300 350 400 450 500
Test time (seconds)
SVF (ppb) and Cumulative Mass (mg)
0
20
40
60
80
100
Vehicle Speed (km/h)
LII SVF (ppb)
Cumulative Mass
Drive Trace
[Smallwood et al., 8th International ETH-Conference on Combustion Generated Particles, 2004]
©GregSmallwood
HD Diesel – Steady
State
0.0
0.5
1.0
1.5
2.0
2.5
0 100 200 300 400 500 600 700 800 900
Time (s)
Soot Mass Concentration (mg/m3)
0.0
0.2
0.4
0.6
0.8
1.0
Cumulative Mass (g)
Soot Mass Concentration
Cumulative Mass
[Smallwood, Canadian Section of the Combustion Institute, 2008]
©GregSmallwood
HD Diesel – Steady
State – 6 Repeats
0.0
0.5
1.0
1.5
2.0
2.5
0 100 200 300 400 500 600 700 800 900
Time (s)
Soot Mass Concentration (mg/m3)
0.0
0.2
0.4
0.6
0.8
1.0
Cumulative Mass (g)
Cumulative Mass = 0.583 +/- 0.015 g
[Smallwood, Canadian Section of the Combustion Institute, 2008]
©GregSmallwood
HD Diesel – Transients
and Sensitivity
[Smallwood, Canadian Section of the Combustion Institute, 2008]
©GregSmallwood
HD Diesel – Transients
and Sensitivity – 4 rep.
[Smallwood, Canadian Section of the Combustion Institute, 2008]
©GregSmallwood
Real-Time On-Road
Particulate Measurements
©GregSmallwood
700 720 740 760 780 800 820 840 860 880 900
0
10
20
30
40
50
Time (seconds)
0
20
40
60
80
0
Speed (mph)
LII (ppb) & RPM/100
VW TDI: Stop-Start
Urban Driving
[Witze et al., 14th CRC On-Road Vehicle Emissions Workshop, 2004]
©GregSmallwood
Comparison to
Thermo-optical: EC
• AC-LII measurements of soot concentration compared to
elemental carbon concentration determined by the NIOSH 5040
method
– error bars represent single shot precision
y = 1.3168x
R
2
= 0.9972
0
1
2
3
4
5
6
7
8
9
10
0246810
EC (mg/m3)
LII (mg/m3
)
[Smallwood, Ph. D. Thesis, Cranfield University, 2009]
©GregSmallwood
Comparison to
Gravimetric: TPM & EC
• AC-LII measurements of soot emissions from a heavy-duty truck
on a chassis dynamometer compared to total particulate matter
(TPM) and nonvolatile particulate matter (EC) emissions
[Huai et al., 16th CRC On-Road Vehicle Emissions Workshop, 2006]
©GregSmallwood
Photoacoustic and
AMS – Ambient and
Denuded
[Smallwood, Ph. D. Thesis, Cranfield University, 2009]
©GregSmallwood
LII and AMS – Ambient
and Denuded
[Smallwood, Ph. D. Thesis, Cranfield University, 2009]
©GregSmallwood
Experiment: High
Sensitivity LII
• optimize all aspects of the laser-induced incandescence method
• use Lagrangian invariant principle to constrain design of
collection optics and receiver
• resulting design was over 500 times more sensitive (ng/m
3level)
[Smallwood, Ph. D. Thesis, Cranfield University, 2009]
©GregSmallwood
Urban Air Quality –
High Sensitivity
[Smallwood, Ph. D. Thesis, Cranfield University, 2009]
©GregSmallwood
Outline
• Background
• Laser-Induced Incandescence (LII)
–Basics
– Autocompensating LII
• Applications
• Summary
©GregSmallwood
Summary
• a significant contribution has been made to improving the
real-time measurement of nonvolatile particulate matter
emissions
• autocompensating laser-induced incandescence (AC-LII)
addresses some of the limitations of conventional LII, but
also introduces new issues
• AC-LII was demonstrated to be highly repeatable, precise,
selective, and linear with respect to some other particle
measurement techniques
– real-time measurements and high sensitivity also demonstrated
• LII however has shown uncertainty in the absolute
concentration when compared to other methods
©GregSmallwood
International
Workshops on LII
2005 2006 2008
4th InternationalWorkshopandMeetingonLaserInducedIncandescence
1920April2010,LakeComo,Italy
©GregSmallwood
International
Workshops on LII
FourthInternationalWorkshoponLaserInducedIncandescence:
Quantitativeinterpretation,modeling,andapplication
18 20April2010
VillaMonastero,LakeComo,Italy
©GregSmallwood
Acknowledgements
•NRC-ICPET
– Dave Snelling
– Kevin Thomson
– Fengshan Liu
– Hongsheng Guo
– Bob Sawchuk
– Dan Clavel
– Daniel Gareau
– Reg Smith
– Fazil Baksh
– Ron Jerome
– Dashan Wang
•Carleton University
– Prof. Matt Johnson
– Brian Crosland
– James McEwen
•Heriot-Watt University
– Prof. Doug Greenhalgh
– Vivien Beyer
•Universities of Waterloo
– Profs. Kyle Daun and James Sloan
•British Columbia
– Profs. Ruth Signorell and Steve
Rogak
•Funding
– PERD AFTER Program
– PERD P&E Program
– PERD UPAIRI Progam
– NRC/NSERC/BDC
Nanotechnology Initiative Program
– NRC/Helmholtz Program
©GregSmallwood