Synopsis of recent LII research activities as presented on the 4th International Workshop on LII: Laser-Induced Incandescence: Quantitative Interpretation, Modeling, Application

(1)

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(2)

FOURTH INTERNATIONAL WORKSHOP AND MEETING ON

LASER-INDUCED INCANDESCENCE: QUANTITATIVE INTERPRETATION,

MODELING, APPLICATION

April 2010, Varenna, Lecco, Italy

Supported from

Accordo di Programma MSE/CNR per l’Attività di

Ricerca di Sistema

ITALIAN SECTION OF THE COMBUSTION INSTITUTE

Synopsis of recent LII

research activities as

presented on the 4th

international workshop on LII

K.P. Geigle, K.A. Thomson, G.J. Smallwood, G. Zizak

Inst it ut e f or Chemical Process and Environment al TechnologyInst it ut e f or Chemical Process

(3)

LII_workshop_2010_IEA.ppt > July 2010

and Environment al Technology

Folie 2

Introduction

International LII community first met in 2005

Typically representing about 10 research groups world-wide Goal is a deeper understanding of the process of laser-induced incandescence

for more accurate determination of particle concentrations and sizes inside and post-combustion

soot and non-soot

through regular intensive exchange of experience

for improved application to relevant / industrial processes Developing LII for technical application

Has been key contributor to the IEA nanoparticulate diagnostics collaborative task

(4)

Folie 3

2010 LII Workshop Structure

Session 1 - Soot properties and LII signal in standard flames

optical properties

Session 2 - LII models and validation

cancelled due to limited air traffic

Session 3 - Extending LII

combining LII with other techniques

comparing LII to other techniques such as SMPS, PIMS, fluorescence

nascent soot particles

Session 4 - LII under various conditions

high/low pressure conditions

turbulent and technical flames, engines environmental applications

(5)

Folie 4

Session 1 -

Soot properties and LII signal in standard

flames

We know/assume that laser-heated soot particles emit LII signal even if the laser pulse modifies the particles

Question: how much are optical soot properties changed and how significant is the influence on the precision for particle sizes or soot concentrations?

(6)

MonteCarlo Uncertainty Results

_{Total uncertainty is on the order of 8 ‐}

_%

(7)

Folie 6

Determination of optical soot properties

Using extinction and scattering measurements for soot sampled from flames operated with different liquid fuels

(8)

De te rminatio n o f the re frac tive inde x wave le ng th de pe nde nc e o f Die se l and Die ste r so o t b y e xtinc tio n spe c tra analy sis.

J. YO N,W o o rkksho p LII, Ita ly, 19/04/10

7

Expe rime ntal Se tup

Soot t h e r m oph or e t ic de posit ion on TEM gr ids 0 50000 100000 150000 200000 250000 300000 0 200 400 600 800 1000 1200 1400 Dm (nm) dN ( N /c m 3 ) -500 0 500 1000 1500 2000 2500 3000 0 0.2 0.4 0.6 0.8 1 1.2 longueur d'onde (µm) I FPS soot sa m plin g

a n d dilu t ion D iffu sion D r y e r

D ie se l Or D ie se l ( 7 0 % ) + Est e r ( 3 0 % ) ( in volu m e ) Spe ct r a l Tr a n sm ission Opt ica l be n ch Plu s sca t t e r in g 9 2 m m Piston MET grid

Soot size dist r ibu t ion ( SM PS)

TEOM

( m a ss fr a ct ion)

2

Se con d Appr oa ch : w it h ligh t sca t t e r in g

Setup allows for detailed study of morphology and its influence on the optical properties

(9)

4th_{International Discussion Meeting and Workshop on}

Laser-Induced Incandescence: Quantitative interpretation, modelling, application April 18-20, 2010, Varenna, Italy

8

no laser

- TEM sampling in flame exhaust

- Monitoring LII signal emission in sampling pipe after different number of LII pulses

Soot properties during the LII process

The LII process is non-intrusive with respect to the total flame

What is the influence on the soot particles?

(10)

9

high fluence ~ 350 m J/ cm

2 0 2 4 6 8 10 12 0,0 0,1 0,2 0,3 0,4 Laser fluence = 350 mJ/cm2 Pos 1 Pos 2 Pos 3 LII intensity [a.u.] # laser pulses 530 nm 700 nm

- High fluence is typically used for soot concentration mapping; LII signal is „proportional“ to f_v

- Soot is emitting LII signal before or during getting destroyed

- Accumulating laser pulses results in decreasing signal

(11)

10

low fluence ~ 130 m J/ cm

2 0 2 4 6 8 10 12 0,0 0,2 0,4 0,6 0,8 1,0 700 nm POS1 POS2 POS3 L II in te n s ity [a .u .] # laser pulses 530 nm Laser fluence = 130 mJ/cm2

- Intermediate fluence is frequently used for particle sizing

- Moderate changes of soot morphology (T_peak < T_sub)

- Accumulating laser pulses results in increasing signal Æ T_peak in-creases with number of pulses; due to morphological changes allowing for better absorption?

(12)

Folie 11

Optical Properties of Soot – What happens during the

LII laser pulse?

Heat particles with IR pulse and study their absorptive behaviour continuously with any desired wavelength (cw)

Pipe is flushed with soot from a quenched flame White (pulsed) LII emission is visible in picture

(13)

Folie 12

Session 3 -

Combining LII with other diagnostics

Scattering Extinction TEM

(14)

13

Wide or multi angle scattering and LII

• Angle range 10°-170°

• Applied to various flames

• Applied to SiO

₂

and SnO

₂

pyrolysis flames

• For the characterization of

aggregates

Contributions by:

H. Oltmann et al., University Bremen O. Link et al., NRC Ottawa

D

_f

:fractal dimension

σ

_g

:distribution width

(15)

14

Combination of different diagnostics

9 LII/extinction

>

f

_v

9+Three-angle scattering

>

R

_g

, d

_p

9 TEM

>

D

_f

, K

_f

, R

_g

, d

_p

9 What about d

_p

derived from LII?

Premixed rich C₂H₄/air flame : Φ=2.34

(16)

15 mirror Monochromator photomultiplier prism lens burner laser oscilloscope

Two color LII set-up

Multi-angle scattering/TEM

Extinction

• Good agreement of TEM with optically determined parameters

– Primary particle diameter

• Good agreement of 2C LII with extinction (at 1064 nm)

(17)

16

Simultaneous LII/scattering

16 Excitation 532 nm. LII & scattering data collected at 35 & 145 degrees in separate experiments Detection : 450 nm Δλ=50 nm 780 nm Δλ=40 nm and 532 nm 35º detection package (collection optics, beam separation optics, and detectors) Nd:YAG laser head and doubler (532 nm) ½ wave plates & thin film polarizer rectangular aperture aperture imaging lens measurement location light collection lenses coupled to fiber beam dump

Laminar C

₂

H

₄

diffusion flame

42 mm HAB excitation

(18)

Folie 17

Combining LII with other diagnostics

Time of flight mass spectrometry

To determine species leaving the soot surface when intermediate to high fluence LII pulses are employed

So far, only assumptions or theoretical considerations are available Neutral species of type C₃ to C₁₀ are considered in LII models

Used pulsed UV laser fluences are known to be low enough not to fragment molecular and particular species

Used pulsed IR laser is in the fluence range typical for LII (much higher fluence, but photons of much lower energy)

(19)

Folie 18 He C₂H₄ + O₂ Low pressure burner (100 mbar) Quartz nozzle Inlet system IR-Laser 1064 nm and UV Laser 193 nm Re-TOF analyzer Flame as soot generator. C/O = 1

Experimental Set-Up - PIMS

Ion source < 10-5 _mbar

Small ionic C_n (n up to 18) clusters found with pulsed IR excitation, even without needing high energy UV photons

(20)

Session D - LII under various conditions

Î Making use of an optically accessible engine

Î Pure soot luminosity measurement (line of sight) was not sufficient to correlate

with exhaust gas measurements when studying the influence of EGR

Î LII allowed for qualitative and spatially resolved monitoring of soot fields over

whole combustion cycle and for different EGR rates quartz

glass ring

piston with

quartz glass crown

max: 1500 min: 0 no EG R 40 % EG R

-2°CA 3°CA 10°CA

LS-Pos.: 1

Examples of soot distributions during operation

(21)

20 1 2 A 0 B C D

Results

CR/AEE3-Sh | 16/07/2010 | © Robert Bosch GmbH 2010. All rights reserved, also regarding any disposal, exploitation, reproduction, editing, distribution, as well as in the event of applications for industrial property rights.

left: no EGR, SZ = 0,1 FSN*

right: 40% EGR, SZ = 0,4 FSN*

LII Signal

0 [counts] 1500

* thermodynamic engine

Soot Distribution at 35°CA

(22)

Folie 21

LII in ultra high vacuum

Negligible collisions of LII heated soot with ambient molecules Æ very long decay times on the order of 10s to 100s of µs (!) Æ lack of efficient particle cooling mechanisms

Æ high detection sensitivity, allowing for studying single aggregates here: aged soot from particle generator

New ultra-vacuum system has been designed

Includes aerodynamic lens to bring particles into vacuum chamber CW Fiber laser for particle heating

2-colour pyrometric detection

(23)

Adopt or optimize existing diagnostics

0 0.54 ppm 112 mm 405 mm 112 mm 405 mm

2D-LII Soot concentration

500 1000 1500 2000 2500 0 50 100 num ber of ev ent s [ N = 1193 of 1200] temperature [K] HAB = 250 mm, r = 0 mm Tmean = 1685 K Tpro = 1642 K Trange (90%)

Peak in single shot images: 4-5 ppm

To compare with candle: 1-2 ppm

(24)

Adopt or optimize existing diagnostics

To date, PIV is not applied to sooting flames, despite the usefulness of this information Æ challenging task

Data set is already being used by our CFD colleagues

(25)

Folie 24

Summary

Framework of the presentation was insufficient to cover all topics in detail Æ rather some snapshots were shown indicating ongoing research

Application of a variety of different complementary diagnostics supporting the understanding of LII and sooting flames

Diagnostics development

Synergies in the LII workshop community due to regular exchange of experts in the field

Contributions to appear in near future Applied Physics B issue for those interested in more details

(26)

(27)

Folie 26

Scattering/extinction measurements for soot particle formation and growth in a shock tube

S. De Iuliis, G. Zizak, CNR-IENI, Italy, and N. Chaumeix, M. Idir, C.E. Paillard, CNRS-ICARE and Universitè d'Orléans, France

Investigation of soot optical properties by spectral line-of-sight attenuation

Kevin Thomson, Francesca Migliorini, Greg Smallwood, National Research Council, Canada, and Klaus-Peter Geigle, DLR, Germany

Investigation of diesel soot emissions during transient engine operation using in-cylinder pyrometry

Patrick Kirchen, Peter Obrecht, Konstantinos Boulouchos, ETH Zurich, Switzerland

Complementary diagnostics for monitoring soot formation in fundamental flames by PIMS and LII and application of soot diagnostics to technical combustion

Klaus Peter Geigle, Jochen Zerbs, Horst-Henning Grotheer, Joachim Happold, DLR, Germany

Progress on the design and construction of a high vacuum LII system using an aerodynamic lens

Douglas Greenhalgh, Vivien Beyer, Heriot-Watt University, UK

Issues with applying LII to the measurement of nonvolatile particulate emissions

Greg Smallwood, Kevin Thomson, David Snelling, Fengshan Liu, National Research Council, Canada

Characterization of silica and titania nanoparticles synthesized in a spray flame reactor

F. Cignoli, S. Maffi, C. Bellomunno, S. De Iuliis, G. Zizak, CNR-IENI, Italy

Small-Angle X-Ray and Laser Light Scattering from Fractal-Like Soot Clusters

S. di Stasio Italy

Vacuum LII; New Directions for a Sensitive Nanoparticle Measurement Technology

D. Greenhalgh, UK

Advanced Diagnostics for Nano-Sized Particles Produced in Flames

A. D’Alessio, A. D’Anna, P. Minutolo, and L. A. Sgro, Italy

An Analytical Approach to the Detailed Analysis of Carbon Particulate Matter

A. Ciajolo, R. Barbella, A. Tregrossi, B. Apicella, and M. Alfè, Italy

Nanoparticles Characterization in the Cylinder and in the Exhaust of Internal Combustion Engines

B. M. Vaglieco, Italy

Characterization of Titania Nanoparticles Synthesized in a Flame

C. Bellomunno, F. Cignoli, S. De Iuliis, S. Maffi, and G. Zizak, Italy

In-situ Characterization of Particle Formation Processes with Subnanometer Structural Resolution on Nanoparticles and Soot (Size, Structure and Dynamics) Using X-ray Scattering Techniques

F. Ossler, S. Canton, J. Larsson, Sweden

Detection of Fluorescent Nanoparticles in Flames with Femtosecond Laser-Induced Fluorescence Anisotropy

A. Bruno, F. Ossler, C. de Lisio, P. Minutolo, N. Spinelli, A. D’Alessio, Italy/Sweden

Recent IEA papers

In red: groups

regularly contributing

to LII workshops

2009

(28)

Folie 27

Laser-induced incandescence for particle size and

soot volume fraction

dt

dT

C

r

⋅

−

π

3

σ

3 4 Internal energy l abs

W

K

r

⋅

+

π

2 Absorption

)

(

4 r

2

Λ

T

−

T

₀

−

π

Heat transfer

dt

dm

M

H

_V

⋅

Δ

−

Vaporisation 2 4 0 4

4 )

(

T

r

SB

π

σ

ε

⋅

−

⋅

−

Radiation

Oxidation Annealing Others

~ Soot concentration

(29)

28

Soot Volume Fraction Results

Instantaneous measurements via 2D-AC-LII Averaged 2D-AC-LII measurements

Comparing to 2D-LOSA measurements (Trottier et al)

_{These experiments}

served as starting point

for determining

experimental

uncertainty

_{Not detailed here}

(30)

Folie 29

Supporting soot modellers

Simple, well defined flame

Technically relevant features (high turbulence) Bundle of precise non-intrusive diagnostics …

(31)

Adopt or optimize existing diagnostics

0 0.54 ppm 112 mm 405 mm 112 mm 405 mm

2D-LII Soot concentration

500 1000 1500 2000 2500 0 50 100 num ber of ev ent s [ N = 1193 of 1200] temperature [K] HAB = 250 mm, r = 0 mm Tmean = 1685 K Tpro = 1642 K Trange (90%)

Peak in single shot images: 4-5 ppm

To compare with candle: 1-2 ppm

(32)

Folie 31

Results- Particle Phase (500 - 100.000 amu): Delay

Striking new feature: new particle mode (N) around 3000 u (i.e. approx. 1.5 nm)

A and B mostly destroyed by IR (2 mJ/mm²) B more than A

IR residues are mostly charged

Additional UV yields no signal enhancement not shown in plot

B A N IR Ionization Source UV Ionization Source IR generated C-Clusters Interpretation so far: complete graphite layers

Synopsis of recent LII research activities as presented on the 4th International Workshop on LII: Laser-Induced Incandescence: Quantitative Interpretation, Modeling, Application

Synopsis of recent LII

research activities as

presented on the 4th

international workshop on LII

Introduction

2010 LII Workshop Structure

Session 1 -

Soot properties and LII signal in standard

flames

Monte­Carlo Uncertainty Results



Total uncertainty is on the order of 8 ‐

%

Determination of optical soot properties

2

2

no laser

Soot properties during the LII process

The LII process is non-intrusive with respect to the total flame

What is the influence on the soot particles?

high fluence ~ 350 m J/ cm

low fluence ~ 130 m J/ cm

Optical Properties of Soot – What happens during the

LII laser pulse?

Session 3 -

Combining LII with other diagnostics

Wide or multi angle scattering and LII

•

Angle range 10°-170°

•

Applied to various flames

•

Applied to SiO

and SnO

pyrolysis flames

•

For the characterization of

aggregates

D

:fractal dimension

σ

:distribution width

Combination of different diagnostics

9 LII/extinction

>

f

9+Three-angle scattering

>

R

, d

9 TEM

>

D

, K

, R

, d

9 What about d

derived from LII?

Simultaneous LII/scattering

Laminar C

H

diffusion flame

Combining LII with other diagnostics

Experimental Set-Up - PIMS

Session D - LII under various conditions

Results

Soot Distribution at 35°CA

LII in ultra high vacuum

Adopt or optimize existing diagnostics

Adopt or optimize existing diagnostics

Summary

Recent IEA papers

In red: groups

regularly contributing

to LII workshops

2009

Laser-induced incandescence for particle size and

soot volume fraction

dt

MonteCarlo Uncertainty Results

_{Total uncertainty is on the order of 8 ‐}

_%

_{These experiments}

_{Not detailed here}