Soot and nanoparticulate optical measurements
Transcript of Soot and nanoparticulate optical measurements
Soot and nanoparticulateoptical measurements
F. Cignoli, S. De Iuliis, S. Maffi, G. [email protected]
CNR – IENI (Istituto per l’Energetica e le Interfasi)Via Cozzi 53 – 20125 Milano
Advanced Measurement MethodsMilano, 11‐03‐2010
2
OUTLINE
2
Introduction: soot & diagnostics
Generality on soot diagnostic techniques
Extinction technique
Scattering/extinction
Two-color emission technique
Laser-Induced Incandescence(LII), also applied to other
nanoparticles
33
Soot particles. Result of non-complete combustion processes.
Nanoparticles produced by combustion processes
Increase of the heat transfer (i.e. in furnaces)
Particle formation in industrial processes (i.e carbon black to produce
rubber, inks, …)
Reduction of combustion efficiency
Environmental pollution (i.e. PM10) and health implication.
1. Soot presents aromatic molecules adsorbed on the
surface, some of which carcinogenic.
2. Due to its dimension, it can be easily inhaled and deposit on
lungs, resulting in respiratory problems.
4
dp = 10-60 nm
Cluster of 100 or more primary particles
Linear chains to fractal-like structures (experimental conditions) 4
Soot particles parameters are:
fv : soot volume fraction (cm3/cm3)
Np (#/cm-3): total number of particles / V,
dp: soot primary particle diameter
Soot characteristicsSoot consists of carbon atoms, at which hydrogen is bounded (C/H = 8).
Hydrogen content depends on the combustion residence time (aged
particles having lower H2)
The average density is about 1.8 g/cm3 (lower than the graphite) From TEM analysis
55H. Richter, J.B. Howard, Progress in Energy and Combustion Science 26, 565 (2000)
Soot formation mechanims
6
understanding of chemical & physical processes responsible
for aerosol formation
6
Challenging topic of the combustion community
From a theoretical point of view:
- Developing of a chemical kinetics code able to describe soot
formation mechanisms under different experimental
conditions
From an experimental approach:
- Measurements of the main parameters of soot particles.
Important to validate and improve the previous codes.
77
Diagnostic techniques (1/2)To investigate soot formation and growth in practical systems two
different kinds of diagnostic techniques can be applied.
Intrusive techniques (e.g. gravimetric analysis, Transmitted
Electron Microscope analysis (TEM), SMPS). Advantages: direct information of the system under study (TEM)
disadvantages: possible perturbation of the system (especially in
hostile combustion environment).
Example: during soot sampling for TEM analysis a strong perturbation can
result from a fast insertion of the probe in the flame. This last can also
produce non-controlled chemical effects.
88
Diagnostic techniques (2/2)
Non-intrusive techniques (optical as laser diagnostics).
Advantages: High spatial and temporal resolution
In-situ measurements
Remote measurements
No upper temperature limit
Disadvantages: Optical access needed
Complex experiments
Sometimes complex models for the interpretation
High cost
9
To develop and improve a suitable diagnostic tool for:
• Increasing the knowledge on soot formation (basic research) with
• high sensitivity (e.g. to detect very low soot concentration)
• dependence on the experimental conditions (e.g. temperature, pressure,
equivalence ratio)
• To perform easily measurements in industrial environment (for the
implementation of the set-up and to derive soot parameters from the
raw signals)
Aim of experimentalists
1010
Soot Diagnostic Techniques
Extinction (1D, 2D): fv, integral line-of-sight (easy
to perform in industrial application)
Extinction/Scattering: fv , dp, (multiple angles scattering to
derive the morphology)
Two-colour emission (point, 2D): fv and Tsoot (only soot temperature,
neglect the contribution of cold gas)
Laser Induced Incandescence (LII): fv and dp (interpretation of LII
signal still under study – LII workshop
Varenna Aprile 2010)
11
Point measurements
lens
diaphragm
detector
lens
Laser beamlens
Probe volume
Probe volume: interception of the laser beam and the image of the detector
slit in the flame. Diameter depends on the laser wavelength, the focal lens
and the beam diameter.
Laser trap
12
Line measurements
1-D detector diode array
Laser-beam mildly focused in the flame
The signal is collected from different probe volumes along the laser beam
and imaged onto pixels of a 1D detector
13
Two-dimensional measurements
2D detector - CCD camera
objective
Cylindrical lens
Laser sheet
Laser beam: from circular section to a vertical sheet using a cylindrical lens
Signal: from each measurements volume imaged on a 2D detector
14
EXTINCTION TECHNIQUE
1515
Extinction Technique
Homogeneous medium
LKIITR ext
L −=⎟⎟⎠
⎞⎜⎜⎝
⎛=
0
lnλ
where TRλ is the monochromatic transmittance and Kext is the extinction coefficient expressed in cm-1.
dzIKdI zextz −=
Beer-Lambert’s law
∫∫ −=L
ext
I
I z
z dzKIdIL
00
IL
L
zzz
1616
Extinction Technique
absscattabsscattpext KKCCNK +=+= )(
Np [#/cm3] is the particle number density
Cabs and Cscatt the cross sections for absorption and scattering.
In most practical cases, the scattering contribution can be assumed to be
negligible: Kext = Kabs.
λπ v
absfmEK )(6
=
In the Rayleigh regime: (particle size much smaller than the
wavelength of the incident radiation), the absorption coefficient can be
expressed as a function of fv as:
1<<λ
π pd
1717
Extinction Technique
The soot volume fraction, fv, can be expressed in terms of Np and dp, as:
ppv Ndf 3
6π
=
and by taking into account the transmittance, fv can be determined as:
)(6
ln0
mELII
f
L
v π
λ⎟⎟⎠
⎞⎜⎜⎝
⎛−
=
where E(m) is a function of the refractive index m (m = n - ik):
( ) 222222
2
4221Im
61)(
knkn
nkmmmE
++−=⎟⎟
⎠
⎞⎜⎜⎝
⎛
+−
=
1818
Typical experimental set-up for extinction
cw laser (at a given wavelength)
Focusing and collecting optic systems
Detector (working in the spectral region of the source)
Processing signal arrangment (+ mechanical chopper)
19
Typical extinction measurements
Each signal = average over a certain number of samples
Number of samples linked to the signal-to-noise ratio
1ppm =2 106 μg/m3
Clean air < 50 μg/m3
2020
Experimentally simple technique
Line-of–sight: average fv along the pathway of the medium, no spatial
resolution along the laser beam direction. Difficult to apply in non-
homogeneous distribution (e.g. turbulence flames)
To overcome the problem extension of the technique to 2D case
2D distribution of fv in a single measurement
Particular laser wavelength used, according to the experimental
conditions employed (in terms of the fuel, temperature and pressure)
Extinction: Main characteristics
2121
Local measurements can be derived in the case of axial-symmetric
geometry of the system:
• Chordal profiles of extinction measurements are carried out
• Applying the mathematical procedure local Kext and fv are
obtained.
Abel inversion procedure
Tomoghraphic deconvolution by 3-point
Abel inversion and iterative method for
self-absorption correction
C.J. Dasch, One-dimensional tomography: a comparison of Abel, onion-peeling, and filtered backprojection methods, Appl. Opt. 31, 1146-1152 (1992)
2222
Example of optical set-up for 2D measurements
Probe beam Probe+flame Ratio
2323
In laboratory flames, gas species (particularly PAH) exhibit strong
absorption spectra in UV-VIS, which can be competitive with soot
broad-band grey body absorption.
Dependence of absorption on laser wavelength
Absorption of the laser light by the species in the probe volume.
Each species (gas or solid phase) are characterized by a given spectrum
of absorption.
To measure fv care has to be taken in discriminating such contribution
from other “non-solid” species.
2424
Dependence of extinction on laser wavelengthExamples in two different reactors
0 2 4 6 8 10 12 140,00
0,05
0,10
0,15
0,20
0,25
0,30
0,35
0
20
40
60
80
100
120
140
160
1064 nm 632.8 nm
fv (p
pm)
HAB (mm)
LII
LII signal (a.u.)
-0.001 0.000 0.001 0.002 0.003 0.0040.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
f v (ppm
)time (s)
488 nm ext - T=2010K
810 nm ext - T=2010K
632.8 nm ext - T=2023 K
Premixed conditions
C2H4/Air Flame 2% C2H4/Ar – Shock Tube
Pyrolytic conditions
25
SCATTERING/EXTINCTION TECHNIQUE
26
Scattering/Extinction Technique
Light Scattering
Laser beam
(vertically polarized) Light Scattering
(vertically polarized)
Laser beam: Vertically polarized
Light scattering: vertically/horizontal polarized, same wavelength of
the laser beam
Dependence on the scattering angle of the scattering signal strictly
related to soot structure
Soot particles
27
ppppppp CVNII ΔΔ= θ0
Scattering/extinction Technique
pppppp CNK =
pp =polarization of source and detected signal
Np [cm-3], Kpp [cm-1], [cm2]pppC
for Np isolated primary particle /volume:
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In the Rayleigh regime: 1<<scatt
pdλπ
64
4
)(4 p
scatt
pVV dmFC
λπ
=
2
2
2
21)(
+−
=mmmF
64
4
)(4 p
scattppp dmFNK
λπ
=
abs
ppabs
dNmEK
λπ 32 )(
=
From Scattering From Extinction
absabsscattext KKKK ≅+=
LKIITR ext
L −=⎟⎟⎠
⎞⎜⎜⎝
⎛=
0
lnλ
3/1
2
3/14
)()(4
⎟⎟⎠
⎞⎜⎜⎝
⎛⎟⎟⎠
⎞⎜⎜⎝
⎛=
abs
vv
abs
scattp KmF
KmEdπλ
λ3
6
p
vp d
fNπ
=
29
Primary particle polydispersityIn the probe volume particles of different size
probability distribution function (PDF)
)ln(2
)ln(/ln(
21exp
)(
2
gp
g
mpp
p N
dd
dpσπ
σ ⎥⎥
⎦
⎤
⎢⎢
⎣
⎡
⎟⎟⎠
⎞⎜⎜⎝
⎛−
=
dpm = geomtric mean
σg = standard deviation
)/(1
0
0
)()(
)()(nm
pn
pp
pm
pp
mnp
ddddp
ddddpd
−
∞
∞
⎥⎥⎥⎥
⎦
⎤
⎢⎢⎢⎢
⎣
⎡
=
∫
∫
660
4
0
64
4)()()(
4)(
pPscatt
ppppscatt
a dNmFddddpNmFKvv ⎟⎟
⎠
⎞⎜⎜⎝
⎛=⎟⎟
⎠
⎞⎜⎜⎝
⎛= ∫
∞
λπ
λπ
3302
22
0
32
22
11Im)()(
11Im pP
extpppP
extabs dN
mmdddpdN
mmK
⎭⎬⎫
⎩⎨⎧
+−
−=⎭⎬⎫
⎩⎨⎧
+−
−= ∫∞
λπ
λπ
3/1
2
3/14
63 )()(4
⎟⎟⎠
⎞⎜⎜⎝
⎛⎟⎟⎠
⎞⎜⎜⎝
⎛==
abs
vv
ext
abs
KmFKmEdpdp
πλλ
30
What happens if primary particles are not isolated?(still in the Rayleigh regime)
)180()()(ϑ
ϑϑ−
=VV
VVVV C
CR
1)(
Dissymmetry ratio technique
• Single spheres in the Rayleigh regime =ϑVVR
No dependence on the scattering angle
• Linear chain up to fractal like structure: 1)( >ϑVVR
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Dependence of the scattering signal on the scattering angle
)(θα FIVV
)( Structure factorθF
S. di Stasio, P. Massoli, M. Lazzaro, J.Aerosol Sci. 27, 897-913 (1996)
32
Dissymmetry ratio vs Np for different soot structure
S. di Stasio, P. Massoli, M. Lazzaro, J.Aerosol Sci. 27, 897-913 (1996)
33
Idea: Depending on IVV vs θ, the morphology can be derived with a
choice of θ.
At higher Np a bending in the trend is detected.
Rvv(30°/150°) more sensitive than Rvv(45°/135°), more than Rvv(90°/150°)
Dissymmetry ratio technique
More regular the increasing of Rvv with Np, higher the sensitivity of Rvv
to the morphology. Rvv (10°/90°) is the most sensitive.
The choice of a number of angles allows to identify unambiguously soot
morphology and aggregation.
According to di Stasio: ….. the selection of three scattering angles is enough to yield such information.
34
Douce et al. Proc. C. I., 2000
Fractal-like behavior in flames
From TEM analysis in flames:
- PDF for Aggregates (lognormal with σ = 2.1)
- Radius of gyration Rg of each aggregate
-N primary particles, of diameter dp, in each
cluster.
fDgf dpRkN )/(=
According to the mass fractal approximation
Rg = the radius of gyration
Df = the fractal dimension
kf = constant fractal prefactor∑=i
ig rn
R 22 1
35
)(2g
pvv
avv qRSNCC =
2/sin4 θλπ
=q
)()( 20 g
pvva
mVV qRSNCNII ηθ =
Fractal-like approach + Rayleigh-Debye-Gans theory
Each primary particle acts as a dipole for scattering radiation.
The scattered field is given by the phase difference of the light
scattered from separate particles.
S(qRg) = structure fractor
Na = number of aggregates/volume
The scattering coefficient not related directly to dp
Dependence of Rg on dp
Parameters to be evaluated Df, Rg, dp, N
36
Fractal-like approach + Rayleigh-Debye-Gans theory
In literature: soot parameters are obtained by performing scattering
measurements at different scattering angles.
Different expression of the structure factor are proposed in theliterature, as for example
⎟⎟⎠
⎞⎜⎜⎝
⎛−=
3exp)(
22g
g
RqqRS
fDgg qRqRS )()( =
Guinier regime
Power law regime
122 <<gRq
122 >>gRq
From the first Eq. the radius of gyration can be derived
From the power law it can be obtained the fractal dimension
C.M. Sorensen, J. Cai, N. Lu, Langmuir 8, 2064-2069 (1992)
37
New approach: measurements performed at 3 angles (90°, q°, 180-q°)
where C1=8/(3Df), C2=2.5, C3=-1.52 and C4=1.02
Structure factor from Lin
C.M. Sorensen, J. Cai, N. Lu, Langmuir 8, 2064-2069 (1992)
8/4
1
2)(1)(fD
s
sgs qRCqRgS
−
=⎥⎦
⎤⎢⎣
⎡+= ∑
∫∞
=0
)( dNNpNm qq
dNNpqRSNNCII gap
vvp
VV )()()( 20 ∫=ηθ
Considering the lognormal PDF for the population of aggretes:
The scattering from a polydisperse aggregates:
38
∫∫=
dNNpN
dNNpqRSNqRS
gg
)(
)()()(
2
2
)()()( 22
gg qRSmdNNpqRSN =∫
New approach: measurements performed at 3 angles
Considering the definition for the average structure factor:
A mean value of the radius of gyration can be derived with the assumption:
)()( *gsg qRSqRS =
A new relationship S*(qRgs), describing the behavior of the integrated
polydisperse distribution, must be evaluated: this function has to be
written in terms of an averaged radius of gyration Rgs for scattering.
39
)/1(11 )/( Df
fgmgs kmdpRR ==
Different definitions for the average Rgs as:
New approach: measurements performed at 3 angles
Fixing:
- the structure factor (Lin et al.)
- definition of average Rg
- PDF, σ = 2.1
Building up:
)()()(
12
12
gmgm qRSm
dNNpqRSN=∫ Rgm1 =fixed, obtained with
Np=10 dp=25 nmNp=150 dp=10 nm
as a function of the wave vector q (the scattering angle).
40
New approach: measurements performed at 3 angles
0.000 0.005 0.010 0.015 0.020 0.0250.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Structure Factor (Rgm1=38.87 nm) Lin et al. dp=5 nm Nm=150 Lin et al. dp=25 nm Nm=10 Teng et al. dp=25 nm Nm=10
S(q
Rg)
q (μm-1)
This curve is fitted with a polynomial expression of the structure
factor as a function of Rgm1 :
414
33
21211
1*
)()1()()(11)(
gmgmgmgm qRPqRgmPqRPqRP
qRS++++
=
where P1, P2, P3, P4 are fitting parameters. This equation is satisfied
whatever is the radius of gyration.
41
New approach: measurements performed at 3 angles
Knowing the new polynomial expression for the structure factor,
Rgm1 is evaluated from two-angle scattering measurements.
Scattering signals at θ and 180°- θ, IVV,1 and IVV,2
Ratio of the two signals to derive RVV
)(
)(
)()(
)()()()(
),(12
*11
*
22
21
2,
1,
2
121
gm
gm
g
g
VV
VV
VV
VVVV RqS
RqS
dNNpNRqS
dNNpNRqSII
II
R ====∫∫
θθ
θθ
Rgm1 derived with a numerical inversion procedure
42
Rvv(20°/160°)
Rvv(45°/135°)
Rvv(30°/150°)
0 1 2 3 4 5 6 7 8 9 100
20
40
60
80
100
120
140
160
20°/160°
Rgm
1
IVV,1/IVV,2
30°/150°
45°/150°
vs IVV,1 /IVV,2
New approach
Considering Rvv(30°/150°) versus IVV,1/IVV,2 and fitting with a 6th order
polynomial equation, given by the analytical expression
∑=
=6
02,1,1 )/(
n
nVVVVngm IICR
: measurements performed at 3 angles
43
)()(4 1
*24
64
, gmascatt
Ppolvv qRSmNFdK λ
λπ
=
( )3/1
,1*
,3/14
30 )(
)90()(41⎥⎥⎦
⎤
⎢⎢⎣
⎡ °⎟⎟⎠
⎞⎜⎜⎝
⎛=
polabsgmn
polvv
ext
scatt
KqRSfmF
KmED
πλλ
π
f
f
Dgmf
Dp Rk
Dd1
3303 =−
New approach: measurements performed at 3 angles
scattering signal at 90°
Radius of gyration from scattering at 2 angles.
Other soot parameters: + extinction coefficient
31
2
, )( paext
polabs dmNmEKλπ
−= extinction coefficient
3130 pdmD =
3130 pdmD = + )/1(
11 )/( Dffpgm kmdR =
44
IVV(30°) IVV(150°) IVV(90°), Kvv
Rvv(30°/150°)
Rgm1
Kext
D30
TEM, Kf Dfdp
Structure factor: Lin relationship (Sorensen et al. 1999)
PDF for Na (Lognormal, σ = 2.1)
From Fractal-like approach 2 unknown parameters Df and Kf
TEM analysis: Df, Kf
-Validation of dp measurements
45
Scattering/Extinction Experimental Set-up
Scatt.+ emiss
ON
OFF
emiss
46
0.0 0.5 1.0 1.5 2.0 2.5 3.00
1
2
3
4
5
ln(N) =0.0208+1.6855 ln(RL/a)
ln(N
)
ln(RL/a)
Flame HAB, mm Df Kf dp, nm (TEM) dp, nm (opt.)A 14 1.68 6.3 24.7±3 22.5±2.5
Koylu et al. Comb.Flame 100, 621 (1995)
α
⎟⎠⎞
⎜⎝⎛=
aRkN L
L
f
f
D
g
LD
L
f
RR
kk
⎟⎟⎠
⎞⎜⎜⎝
⎛= 2
α
⎟⎟⎠
⎞⎜⎜⎝
⎛=
p
aa A
AkN
TEM measurements - Validation
47
Scattering/Extinction: Main characteristics
In industrial application the implementation of 90° scattering
coupled with extinction measurements could be enough to derive
information about soot size.
For the development of the mechanisms of soot formation and
growth it could be important to investigate soot morphology. In
this case scattering signal collected at different angles could be
needed. Anyway it is quite tricky and particular care is required
to perform such analysis both from an experimental point of
view, and for the procedure to retrieve soot parameters.
48
Two-colour emission technique
49
detectorflame
calibrated lamp
Two-colour emission technique
Comparison of the radiation emitted from soot in flame and that of a
calibrated lamp.
The optical set-up has to be the same, or differing of neutral
(independent of wavelength) components
50
The light intensity emitted from soot can be described as:
ληλλε ssBBvss TIfI ),(),(=
1exp
1),(2
51
−⎟⎟⎠
⎞⎜⎜⎝
⎛=
s
sBB
TC
CTI
λλ
λ
Two-colour emission technique
),( vs fλε is the soot emissivity
),( sBB TI λ is the spectral blackbody radiation intensity at Ts given by
the Planck’s law:
1=sε for a blackbody
1<sε dependence on the wavelength and soot volume fraction
For λ<800 and T<2500 K the Wien’s law holds:
⎟⎟⎠
⎞⎜⎜⎝
⎛−=
ssBB T
CCTIλλ
λ 251 exp),(
51
For a uniform soot layer of length L and fv, the emissivity is given by:
Kirchhoff’s lawAt thermodynamic equilibrium, the spectral radiancy of an emitter is
proportional to its spectral absorption coefficient (Havrodineau).
)exp(1),(0
LKIIf absVS −−=
Δ=λε
where Kabs is the absorption coefficient
)(36 mEKflabs
vabs π
λ==
As fv L/labs <<1 an expansion in the Taylor series of εs can be applied .
labs is the natural length of absorption: the thickness of pure soot
(fv=1) with a transmittance equals to 1/e
52
Two-colour emission technique
ληλλε LLBBLLL TITI ),(),(=
ληλλε ssBBvss TIfI ),(),(=
Light emitted from a calibrated lamp at TL
2
1
2
1
λ
λ
λ
λ
ηη
ηη
L
L
S
S =
1
12
2
2
1
2
)1
1
2
2
1
212
11),(
,()()(
)()(ln11
−
⎥⎦
⎤⎢⎣
⎡⎟⎟⎠
⎞⎜⎜⎝
⎛−+⎟⎟
⎠
⎞⎜⎜⎝
⎛⎟⎟⎠
⎞⎜⎜⎝
⎛−−=
λλλελε
λλ
λλ
λλ Labs
abs
LL
LL
L
L
S
SS T
cll
TT
II
IIcT
⎟⎟⎠
⎞⎜⎜⎝
⎛⎟⎟⎠
⎞⎜⎜⎝
⎛⎟⎟⎠
⎞⎜⎜⎝
⎛−−−−=
SLL
SLL
abs
TTc
II
TL
lfv 11exp
)()(
),(1ln 2
λλλ
λε
written for 2 wavelengths, λ1 and λ2
Light emitted from soot
53
red filter
blue filter
ND filter quartz
prism burnerUV lens
CCD
ribbon lampacquisition
heat absorbingfilter
Same distance quartz-lamp and burner/quartz
Same optical set-up to collect the radiation
Quartz plate is the difference in the optics:
for the flame ,the quartz transmittance has to be considered
for the lamp, the refrectivity has to be taken into account
plate
Example of two colour emission technique
F. Cignoli, S. De Iuliis, V. Manta, G. Zizak, Appl.Opt. 40(30), 5370-5378, 2001
Extinction: Main characteristics
The technique is simple and robust, without a laser
It allows to deliver a significant amount of data in a short time (Ts, fv)
Uncertainties due to “cold” soot regions in the flame, different
contribution to the overall radiation intensity.
Attention for focusing optical system, especially for wide width flames.
f # large enough: the regions beyond and before the focal length axis
give different contribution to the signal.
Integral technique. Only for axial symmetric geometry, local values of fv
e Ts are derived through inversion.
55
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.60.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.60.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
9.0 -- 10 8.0 -- 9.0 7.0 -- 8.0 6.0 -- 7.0 5.0 -- 6.0 4.0 -- 5.0 3.0 -- 4.0 2.0 -- 3.0 1.0 -- 2.0 0 -- 1.0
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.60.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
methane propane ethylene
2D two-color imaging of soot volume fraction
in diffusion flames
56
T (left) and fv (right) - Propane
2 4 6 8 10 12 14
0.87 -- 1.0 0.75 -- 0.87 0.62 -- 0.75 0.50 -- 0.62 0.37 -- 0.50 0.25 -- 0.37 0.12 -- 0.25 0 -- 0.12
4 12 10 8 6 4 2 14 12 10 8 6 4 22 4 6 8 10 12 1
16 14 12 10 8 6 4 22 4 6 8 10 12 14 1 2 4 6 8 10 12 14 166 14 12 10 8 6 4 2
1
1
2.1E3 -- 2.2E3 2E3 -- 2.1E3 1.9E3 -- 2E3 1.8E3 -- 1.9E3 1.7E3 -- 1.8E3 1.6E3 -- 1.7E3 1.5E3 -- 1.6E3
Application to a diesel engine
J.Vattulainen, V. Nummela, R. Hernberg, J. Kytola, Meas. Sci. Technol. 11, 103 (2000)
basic principle real implementation
58
Final remarks
The application of one or another diagnostic tool is related to:
- the information we are interested in- the environment where they have to be applied- the experimental conditions
Extinction and emission is almost a classical technique. Anyway,
attention has been taken for the application in some experimental
conditions.
Scattering/exinction technique is quite well assessed, a further
development would concern the morphology.
LII technique is still under study and many efforts are still needed to
gain a complete understanding of the physical phenomena involved.