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

mailto:[email protected]

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


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


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:

28

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

31

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:


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


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


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 =−


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


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


),( 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


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.

soot and nanoparticulate optical measurements

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