2-meccanismi di formazione degli inquinanti e diagnostiche ...wpage.unina.it/anddanna/capri/capri...

Meccanismi di formazione degli inquinanti e diagnostiche in situ per la caratterizzazione delle polveri

Andrea D’Anna

Dipartimento di Ingegneria ChimicaUniversità “Federico II”, Napoli

Patrizia Minutolo

Istituto di Ricerche sulla CombustioneCNE, Napoli

Inquinanti primari da processi di combustione

monossido di carbonio (CO)

ossidi di azoto (NOx)

ossidi di zolfo (SOx)

idrocarburi incombusti (Volatile Organic Compounds – VOC)

benzene ed Idrocarburi Policiclici Aromatici (IPA o PAH)

diossine e furani

fasi condensate e composti particellari organici

particolato inorganico

Il contributo dei processi di combustione

CnH2n+2 + (3n+1)/2O2 nCO2 + (n+1)H2O

miscelazione dei reagenti a livello molecolare(condizioni ideali)

CH CH3

CH2CH2

CHCH

CH2

CH

CH2CH

O2

COCO2

CH2

CH2

0 ms

1 ms

10 ms

100 ms

nei sistemi di combustione reali la mancata miscelazione a livello molecolare favorisce reazioni di crescita molecolare rispetto a reazioni di ossidazione

Meccanismo di ossidazione del metano

ΦΦΦΦ = 1.0 ΦΦΦΦ > 1.0(C/O)

(C/O)st

ΦΦΦΦ =


Gassosi

Liquidi

Solidi

Premiscelati

Diffusivi

Laminare

Turbolento

combustibili sistemi di combustione

Combustione controllata dalla diffusioneΦΦΦΦ = 1ΦΦΦΦ > 1 ΦΦΦΦ < 1

prodotti di combustione ricca

prodotti di combustione povera

CH CH3

CH2CH2

CHCH

CH2

CH

CH2CH

O2

COCO2

CH2

CH2

PREMIXEDFUEL + OXIDIZER

BURNER

FLAME ZONE

POST FLAME ZONE

0 ms

1 ms

10 ms

100 ms

CH CH3

CH2CH2

CHCH

CH2

CH

CH2CH

O2

COCO2

CH2

CH2

CH CH3

CH2CH2

CHCH

CH2

CH

CH2CH

O2

COCO2

CH2

CH2


BURNER

FLAME ZONE

POST FLAME ZONE


BURNER

FLAME ZONE

POST FLAME ZONE

0 ms

1 ms

10 ms

100 ms

0 ms

1 ms

10 ms

100 ms

Combustione premiscelata

Fiamma premiscelata (metano)

Φ = 1.0

Rapporto di equivalenza

φφφφ = (C/O)/(C/O)stoich

Ossidazione in condizioni stechiometriche

Formazione di CO2 e H2O


fiamma premiscelata ricca (metano)

fiamma particle-emitting!

Ossidazione in condizioni ricche (di combustibile)

Formazione di CO e H2

Crescita molecolare (formazione di composti con peso molecolare maggiore di quello del combustibile alimentato)



O2

0.00

0.05

0.10

0.15

0.20

0.25

0 0.2 0.4 0.6

Mol

e fr

actio

n

CO & CO2

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

Mol

e fr

actio

n

C2H2

0.0E+00

4.0E-03

8.0E-03

1.2E-02

1.6E-02

2.0E-02

0 0.2 0.4 0.6Distance from burner surface

Mol

e fr

actio

n

n-Heptane

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

0.040

0 0.2 0.4 0.6

Mol

e fr

actio

n

H2 & H2O

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

Mol

e fr

actio

n

CH4

0.0E+00

4.0E-03

8.0E-03

1.2E-02

1.6E-02

2.0E-02


Mol

e fr

actio

n

FuelO2

0.00

0.05

0.10

0.15

0.20

0.25

0 0.2 0.4 0.6

Mol

e fr

actio

n

CO & CO2

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

Mol

e fr

actio

n

C2H2

0.0E+00

4.0E-03

8.0E-03

1.2E-02

1.6E-02

2.0E-02


Mol

e fr

actio

n

n-Heptane

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

0.040

0 0.2 0.4 0.6

Mol

e fr

actio

n

H2 & H2O

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

Mol

e fr

actio

n

CH4

0.0E+00

4.0E-03

8.0E-03

1.2E-02

1.6E-02

2.0E-02


Mol

e fr

actio

n

Fueln-Heptane

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

0.040

0 0.2 0.4 0.6

Mol

e fr

actio

n

H2 & H2O

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

Mol

e fr

actio

n

CH4

0.0E+00

4.0E-03

8.0E-03

1.2E-02

1.6E-02

2.0E-02


Mol

e fr

actio

n

n-Heptane

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

0.040

0 0.2 0.4 0.6

Mol

e fr

actio

n

H2 & H2O

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

Mol

e fr

actio

n

CH4

0.0E+00

4.0E-03

8.0E-03

1.2E-02

1.6E-02

2.0E-02


Mol

e fr

actio

n

Fuel


Φ = 2.0

1.E+09

1.E+10

1.E+11

1.E+12

1.E+13

1.E+14

1 10 100 1000

DP, nm

dN

/dL

OG

(DP)

1.E+09

1.E+10

1.E+11

1.E+12

1.E+13

1 10 100 1000

DP, nm

dN

/dL

OG

(DP)

1.E+09

1.E+10

1.E+11

1.E+12

1 10 100 1000

DP, nm

dN

/dL

OG

(DP)


Particolato

20 nm

1-2 nm

0.38 nm

10 nm

Particolato

C2H2 addition to C4 hydrocarbons(even-carbon-atom pathways)

n-C4H3 + C2H2 phenyln-C4H5 + C2H2 benzene + H

resonantly stabilized free radical combination(odd-carbon-atom pathways)

C3H3 + C3H3 phenyl + HC3H3 + C3H3 benzeneC5H5 + CH3 benzene + H + H

Formazione del benzene

multimulti--ring aromatic formationring aromatic formationCC22HH22 addition to aromatic rings (HACA mechanism)addition to aromatic rings (HACA mechanism)

Formazione degli IPA

- H2

.

.

+ C2H2

- H

CH

+ H

.CH

.

+ C2H2

- H

+ C2H2

- H

+ C2H2

- H

CH

+ C2H2- H

CH

- H2

+ H

- H2

..

.

+ C2H2

- H

CH

+ H

..CH

.

+ C2H2

- H

+ C2H2

- H

+ C2H2

- H

CHCH

+ C2H2- H

CHCH

- H2

+ H

multimulti--ring aromatic formationring aromatic formationresonantly stabilized free radical combination

+ - H2

. .

+ C3H3

- H2

H H

.

+ - H2

.

Formazione degli IPA

• crescita molecolare dei precursori

• nucleazione delle particelle

• coagulazione (coalescenza) dei nuclei

• addizione di composti dalla fase gassosa

• coagulazione (formazione di strutture a catena)

Formazione del particolato


OneOne--ringring

aromaticsaromatics

cyclizationcyclization

20 nm

20 20 –– 30 nm30 nm

1 1 –– 2 nm2 nm

OH

OHO CH3

3 3 –– 4 nm4 nm

OH

OH

O

CH3

OH

OH

O

CH3

OH

OH

O

CH3

3 3 –– 4 nm4 nm

molecular weight, time

C/H

1 1 –– 2 nm2 nm

growth by growth by

C2H2C2H2 coalescent coalescent

coagulationcoagulation

PCAH

AALH

growth by aromatic growth by aromatic

and aliphaticand aliphatic

OneOne--ringring

aromaticsaromatics

cyclizationcyclization

20 nm

20 20 –– 30 nm30 nm

20 nm20 nm20 nm

20 20 –– 30 nm30 nm

1 1 –– 2 nm2 nm

OH

OHO CH3

3 3 –– 4 nm4 nm

OH

OH

O

CH3

OH

OH

O

CH3

OH

OH

O

CH3

3 3 –– 4 nm4 nm

molecular weight, time

C/H

1 1 –– 2 nm2 nm

growth by growth by

C2H2C2H2 coalescent coalescent

coagulationcoagulation

PCAH

AALH

growth by aromatic growth by aromatic

and aliphaticand aliphatic

coagulazione di molecole/particelle

Formazione del particolato (coagulazione)


intermolecular potential between molecules

the interaction between two particles containing q molecules per unit volume

the overall interaction potential between two equal-sized particles is a function of the particle radius RP and the particle polarizability through the Hamackerconstant A

1 2

r

φ(r) = -φm[( )12 - 2( )6]rm rm

r rφ(r) = -φm[( )12 - 2( )6]rm rm

r r

U = ∫V1

dv1 ∫V2dv2q2φ(r)

V1 V2

r

dDp

-1.E-12

-9.E-13

-8.E-13

-7.E-13

-6.E-13

-5.E-13

-4.E-13

-3.E-13

-2.E-13

-1.E-13

0.E+00

0.90 0.95 1.00 1.05 1.10 1.15 1.20 1.25 1.30 1.35

d/Dp

U (

erg

)

Dp=2nm

Dp=4nm

Dp=8nm

Dp=16nm

kT @ 1600K

Ha=1E-13 erg

φ 0

A

p

dDp

dDp

-1.E-12

-9.E-13

-8.E-13

-7.E-13

-6.E-13

-5.E-13

-4.E-13

-3.E-13

-2.E-13

-1.E-13

0.E+00

0.90 0.95 1.00 1.05 1.10 1.15 1.20 1.25 1.30 1.35

d/Dp

U (

erg

)

Dp=2nm

Dp=4nm

Dp=8nm

Dp=16nm

kT @ 1600K

Ha=1E-13 erg

φ 0

AA

p


− φ0 /kTe (1+ φ0 /kT)N>φ0

N=

− φ0 /kTe− φ0 /kTe (1+ φ0 /kT)N>φ0

N=

−φ1 - e (1+φ)γ =−φ1 - e (1+φ)γ =

1.E-12

1.E-11

1.E-10

1.E-09

1.E-08

0.0E+00 5.0E-07 1.0E-06 1.5E-06 2.0E-06

Particle Diameter, cm

Co

agu

lati

on

Co

nst

ant,

cm

3 /s

aliphatic (A=1E-13)

benzene (A=5E-13)graphite(A=5E-12)

@ T=1800KGas Kinetic Limit


Fiamma a diffusione (flussi coassiali)

z=10mm z=30mm z=50mm

0.0E+00

1.0E-06

2.0E-06

3.0E-06

4.0E-06

5.0E-06

0 2 4 6 8 10r, mm

soo

t vo

lum

e fr

acti

on

0.0E+00

1.0E-06

2.0E-06

3.0E-06

4.0E-06

5.0E-06

nan

op

arti

cle

volu

me

frac

tio

n

300

600

900

1200

1500

1800

2100

tem

per

atu

re, K

0.0

10.0

20.0

30.0

40.0

50.0

0 2 4 6 8 10r, mm

d63

, nm

z=10mm z=30mm z=50mm

I0 I

0.0

0.5

1.0

1.5

volu

me

frac

tio

n (

pp

m)

0.0E+00

5.0E+12

1.0E+13

1.5E+13

2.0E+13

2 3 4 5 6 7 8z, mm

nu

mb

er c

on

cen

trat

ion

, cm

-3

0

5

10

15

20

d63, n

m

0.0E+00

2.0E-08

4.0E-08

6.0E-08

8.0E-08

1.0E-07

LIF

an

d L

II, c

m-1

sr-1

vis-transparent vis-absorbing

LIF 350nm+ LIF 440nm LII 550nm

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

0 0.2 0.4 0.6 0.8 1z, mm

mo

le f

ract

ion

400

1100

1800

2500

T, K

O2C2H2C2H4A1sumPAHsT(K)

pyrolysis zone

stagnation plane post-oxidation zone

soot formation zone

fuel oxy

Fiamma a diffusione (flussi contrapposti)

OH

OHO CH3

chemical growth(by C2H2)

coalescentcoagulation

chemical growth(by aromatics,

aliphatics, oxygen)

OH

OH

O

CH3

OH

OH

O

CH3

OH

OH

O

CH3

coalescentcoagulation

bassa concentrazionedi precursori

alta concentrazione diprecursori

Aromatic chemical growth

Ai + H ↔ Ai* + H2

Ai* + Aj ↔ Ai+j + H

Aromatic cluster formation

Ai + Aj ↔ Ai+j


Bruciatore domestico alimentato a metano

1.0E+03

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+08

1 10 100

Diametro, nm

dN

/dlo

gD

p, c

m-3

Bruciatore a Diffusione

Premiscelato foro

Premiscelato maglia

Aria

alimentazione stechiometrica

Microturbina per cogenerazione

diesel oil

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

dN

/dL

OG

(Dp

), c

m-3

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

1 10 100

Dp, nm

dN

/dL

OG

(Dp

), c

m-3

bio-diesel

Motori a combustione interna

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

1 10 100 1000 10000

dN

/dL

OG

(D),

cm

-3

ELPI 1500-50-r

1500-50-r

AFM

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

1 10 100 1000 10000Diametri, nm

dN

/dL

og

D, c

m-3

SMPS 1500-30Diesel MaricqELPI 1500-30-rAFM Diesel

benzina

diesel

10 nm

1.E+06

1.E+07

1.E+08

1.E+09

1.E+10

1.E+11

1.E+12

1.E+13

1.E+14

1.E+15

1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02

Dp, micron

N, #

/m3

Combustibili solidi: carbone e rifiuti


i processi di combustione possono contribuire alla formazione diparticolato ultrafine ed iperfine ed alla loro emissione in atmosfera

1.E+07

1.E+08

1.E+09

1.E+10

1.E+11

1.E+12

1.E+13

1 10 100 1000 10000

D, nm

dN

/dL

OG

(D),

cm

-3

PSD.10

PSD.11

PSD.12

PSD.13

Modello cinetico per la formazione del particolato

BIN1 BIN2 BIN3 BIN4

BIN2

BIN3

BIN4

BIN1

H/C=1

H/C=0

BIN1 BIN2 BIN3 BIN4

BIN2

BIN3

BIN4

BIN1

H/C=1

H/C=0H/C = 0

H/C = 1 H/C = 0.85

H/C = 0.35

H/C = 0.60

H/C = 0.10

8.85E13 T0.5 exp(-16,000/RT) nC2/3 H/C

8.85E13 T0.5 exp(-4,650/RT) nC2/3 H/C

6.00E14 T0.5 exp(-113,100/RT) nC H/C

8.00E12 T0.5 nC1/6Ri + Rj Ai+j

Ai == Ri + H

Ai + H,OH == Ri+j + H2,H2O


3.00E6 T1.787 exp(-3262/RT) nC0.616

2.00E13 T0.5 exp(-15,000/RT) nC1/6

Ri + C2H2 Ai + H

Ri + Aj Ai+j + H


8.85E13 T0.5 exp(-10,000/RT) nC2/3 H/C

6E14 T0.5 exp(-20,000/RT) nC H/C

Ri + H Ai + H2

Ri + H Ai + H + H2


3.00E12 T0.5 exp(-10600/RT) nC0.623

4.30E11 T0.5 exp(-8000/RT) nC2/3

2.00E13 T0.5 nC1/6 γ

Ai + OH Ai + HCO

Ri + O2 Ai + 2CO

Ai + Aj Ai+j


0.E+00

1.E-06

2.E-06

3.E-06

4.E-06

0 2 4 6 8 10 12 14 16

HAB, mm

Co

nce

ntr

atio

n, g

/cm

3

particulate

exp data Ciajolo et al., 19960.0

0.2

0.4

0.6

0.8

1.0

0 2 4 6 8 10 12 14 16

HAB, mm

H/C

rat

io

H-to-C


fuliggine

exp data Ciajolo et al., 1996

specie condensate


0.0E+00

1.0E-06

2.0E-06

3.0E-06

4.0E-06

0 2 4 6 8 10 12 14

HAB, mm

Co

nce

ntr

atio

n, g

/cm

3

0.0E+00

5.0E-07

1.0E-06

1.5E-06

2.0E-06

0 2 4 6 8 10 12 14

HAB, mm

Co

nce

ntr

atio

n, g

/cm

3

Φ = 2.4

0.00

0.33

0.66

1.00

0.00

0.33

0.66

1.00

0.00

0.33

0.66

1.00

0.00

0.33

0.66

1.00

0.00

0.33

0.66

1.00

0.00

0.33

0.66

1.00

1.0

1.2

1.6

2.1

2.5

3.1

4.0

5.0

6.3

7.9

10.0

12.6

15.9

20.0

25.2

31.8

40.0

50.5

63.6

80.1

101.

0

127.

2

160.

3

201.

9

254.

4

0.00

3.0 mm

3.5 mm

4.0 mm

4.5 mm

6.0 mm

15.0 mm

1.90E-07-2.00E-07

1.80E-07-1.90E-07

1.70E-07-1.80E-07

1.60E-07-1.70E-07

1.50E-07-1.60E-07

1.40E-07-1.50E-07

1.30E-07-1.40E-07

1.20E-07-1.30E-07

1.10E-07-1.20E-07

1.00E-07-1.10E-07

9.00E-08-1.00E-07

8.00E-08-9.00E-08

7.00E-08-8.00E-08

6.00E-08-7.00E-08

5.00E-08-6.00E-08

4.00E-08-5.00E-08

3.00E-08-4.00E-08

2.00E-08-3.00E-08

1.00E-08-2.00E-08

0.00E+00-1.00E-08

g/cm3

H/C

Dp, nm


Light Scat./Light ext.

DLS

AFMDMA

In situ Ex-situ On line

Sizing Methods for Ultrafine Particles

The color of the sky is caused by the scatteringof sunlight by the molecules of the atmosphere.

Iscatt~1/λ4

Violet-blu components of sunlightare scatterd more efficiently so the sky appears blue.

Light ScatteringLight Scattering

At sunset or sunrise, the sunlight we observehas traveled a longer path through the atmosphere. Therefore, a large amount of blue and violet light has been scattered and the light that is recieved by an observer is red.

Light Scattering Light Scattering -- ExtinctionExtinction

Rayleigh approximation: ππππd/λλλλ~0.1

incident light beam: Ei (t)=E0cosω0t

⇒ Induces oscillating dipole moment in the molecules/particles: p(t)= α Ei(t) α= polarizability

⇒ the oscillating dipoles radiate at the same frequency as the applied field.

( ) is Ir

I2

2

40

22 sin θλεαπθ =

• Extinction = Absorption + Scattering

• For small particles (d/λ < 0.1) absorption dominates.

• For large particles (d/λ > 0.1) scattering also contributes.

Beer-Lambert law:

I(λ, x)=I0 e -N σ(λ)x

0 x

ICCD Camera

PCDelay Generator

Lens

Lens

- -

Burner

Deuterium Lamp

Laser

62

2

2

4

4

2~1~

4 p

pVV dN

mmQ +

−= λπ

32

22

2~1~

Imp

p

oext dN

mmK

+−−=

λ

π

Scatt: Iscat(λ)=Qvv(λ)∆V∆ΩIo(λ)

Ext: IT=Ioexp(-KextL)

For isotropic spheres:

m = n-ik complex refractive index

6

3dNf V

π=

Light Scattering Light Scattering -- ExtinctionExtinction

1.E-8

1.E-7

1.E-6

1.E-5

1.E-4

0 5 10 15height above the burnerz, mm

Sca

t. c

oef

fici

ent,

cm

-1sr

-1

1.E-3

1.E-2

1.E-1

0 5 10 15

height above the burner z, mm

Ext

. co

effi

cien

t,cm

1

LS/LS/ExtExt –– exampleexample: : CC22HH44/air /air premixedpremixed flameflame

λ=266 nm

λ=532 nm

∑∑∑ ++=i

sootvvi

NOCvvi

gasvvvv iii

QQQQ ∑∑∑ ++=i i

sootexti i

NOCexti i

gasabsext KKKK

Qvv gas

Qvv flame

LS/LS/ExtExt --Gas Gas ContributionContribution

( ) ( )igasvvi i

gasvv nCTNQ ,λ∑= ( ) ( )TTNK ii i

gasabs ,λσ∑=

@λ=266 nm i=CO2, H2O

To estimate Qvv and Kabs is necessary to know for each specie i

Ni: Concentration

σi(λ,T): Light absorption cross section

Cvv(λ, ni) Light scattering cross section

T: Temperarure

LS/LS/ExtExt -- COCO22 contributioncontribution

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

200 220 240 260 280 300

wavelength, nm

Kab

s, c

m-1

C2H4/air

φ=1

CO2

0

20

40

60

80

100

120

1 1.2 1.4 1.6 1.8 2

φφφφ

% K

abs(

CO

2)/K

abs

Joutsenoja et al 2001

LS/LS/ExtExt –– exampleexample: : CC22HH44/air /air premixedpremixed flameflame

results

0

0.1

0.2

0.3

0.4

0.5

200 250 300 350 400

Wavelenght, nm

Kab

s, c

m-1

10-6

1010

1011

1012

1013

0 2 4 6 8 10

Num

ber

dens

ity N

, cm

-3

z, mm

Vol

ume

frac

tion

fvv

2.0 10-6

0.5 10-6

1.0 10-6

1.5 10-6

Mean

diameter

d, cm

0

010-8

10-7

Total (from Kabs(266))

soot (from Kabs(532))

sootNOC

Shortcomings

Gas

Fluorescence interference

Detection of small particles in presence of larger ones

Particles Refractive Index

Advantages

In situ measurement

Size and Concetration

Particles Refractive Index

Wavelength Dependence allows multi-species analysis

LS/LS/extext

Temperature

Species concentr.

( ) 336

i

6ii

i

3ii

2

2

22

2

23

vv

abs

d1

)),(m(fdN

dN

2)(m1)(m

2)(m1)(m

Im

Q)(K

−

λλ=

+λ−λπ

+λ−λλ−

=λλ

∑

∑

LS/LS/ExtExt -- advantagesadvantagesdependencedependence on on ParticlesParticles RefractiveRefractive IndexIndex

0.0

0.1

1.0

1.0 1.2 1.4 1.6 1.8 2.0n

k

d63=2.85λ=266 nm

Cecereet al., 2002

ikinm 09.035.1~ −=−=

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

1,E-01 1,E+00 1,E+01 1,E+02

Hydrodynamic Diameter [nm]

Num

ber

Dis

trib

utio

n F

unct

ion

D=2.78 nmIf particle size is known:

Particle refractive indexcan be measured

DynamicDynamic Light Scattering Light Scattering UsingUsing BrownianBrownian motiomotio toto MeasureMeasure SizeSize

Scattered light

Scatterers in solution (Brownian motion)

Laser at fo

ffo

incident laser

Doppler broadenedscattered light

∆f

0

∆f ~ 1 part in 1010 - 1015

In frequency domain

time

Scattered intensity Iaverage

In time domain

fluctuation in intensity are analysed by Its autocorrelation function

6B

K TD

Rπηπηπηπη====

DLSDLS–– exampleexample: ex: ex--situsitu

D=2.78 nmC/O = 0.77 z = 3.5mm

Normalized intensity correlation function

0

0,2

0,4

0,6

0,8

1

1,E-06 1,E-04 1,E-02 1,E+00 1,E+02 1,E+04 1,E+06

Lag time, ms

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

1,E-01 1,E+00 1,E+01 1,E+02

Hydrodynamic Diameter [nm]

Num

ber

Dis

trib

utio

n F

unct

ion

exhaust

H2Oin

out

H2O

condenser

water

bubblerWater cooled probe

StopperStopper

FiberFiber opticoptic

AutocorrelatorAutocorrelatorPMTsPMTs PADsPADs

GlanGlan ThompsonThompsonPrismPrism

LensLens

LensLens ArgonArgon--IonIonLaserLaser

BurnerBurner

PrismPrism

FlameFlameScattering Scattering

AngleAngle 5°5°

λλλλ=488nm488nm

DLSDLS–– exampleexample: in situ: in situ

d3TCk

D uB

πη=

Normalized Intensity Correlation Function

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

1,E-06 1,E-04 1,E-02 1,E+00 1,E+02 1,E+04 1,E+06

Lag time, ms

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

1,E+00 1,E+01 1,E+02Hydrodynamic Diameter [nm]

Num

ber

Dis

trib

utio

n F

unct

ion

D=11.19nm

FromFrom LS/LS/ExtExt DD6,36,3=15.5 nm=15.5 nm( )

( )r

T

T

rCu

λλ

−++= 25.1exp29.0864.01

Ethylene/air C/O=0.77 z=9.5 mm

In free molecule regime

At flame Temperature minimum detection size=10 nm

Difficult to analyse too diluted or too concentrated samples

Dust contamination of sample

In polydispersed sample cannotdetect very small amounts of the smaller mass species

Measure Distribution Function of: Diffusion coefficient and Hydrodinamic Size (the size of a spherical particle with the same diffusioncoefficient)

Size range 0.6nm-6 µµµµm (in liquid )

Does not require knowledge of particles refractive index

Can detect very small amounts of the higher mass species (<0.01% in many cases)

DLSDLS

AdvantagesAdvantages ShortcomingsShortcomings

Scanning Mobility Particle Scanning Mobility Particle SizerSizer (SMPS) (SMPS)

ionization efficiency

1,E-07

1,E-06

1,E-05

1,E-04

1,E-03

1,E-02

1,E-01

1,E+00

1 10 100

mobility diameter, nm

effi

cien

cy

d>10 nm

d<10 nm Z∝1/d2

(To account for diameter of gas molecule)

Range ~3–100 nm

TSI

Electrical Mobility ClassifierElectrical Mobility Classifier

d

CenZ

µπ3=

For a charged particle moving in

an electric field: Z =vsteady/E

=1

2* ln2 r

r

LV

qZ sh

p π

diffusion-efficiency

1,E-07

1,E-06

1,E-05

1,E-04

1,E-03

1,E-02

1,E-01

1,E+00

1 10 100

mobility diameter, nmef

fici

ency

DetectorsDetectors

Condensation Particle Counter Condensation Particle Counter -- Faraday cup electrometerFaraday cup electrometer

• wide range of concentrations(4-5 orders of magnitude).

•particle concentrations > 103-105 cm-3

•Ultra-fast response (~ 50 ms) •No nominal minimum size limit

even below 1 nm),

SamplingSampling

Temperature effect

Typical samplingsystem

Dilution

effect

dilution

ionization

1,E-07

1,E-06

1,E-05

1,E-04

1,E-03

1,E-02

1,E-01

1,E+00

1 10 100

mobility diameter, nm

effi

cien

cy

diffusionCPC

TOTAL

SMPSSMPS

AdvantagesAdvantages ShortcomingsShortcomings

Low efficiency @d<10 nm

-Ionization

-Diffusion losses

-CPC/electrometer sensitivity

-Sampling

Size Distribution Function

Size range 1-100 nm

Polydisperse sample

Not dependent on particle properties and composition

Real time measurements

Field measurement

SMPS SMPS –– exampleexamplepremixed Cpremixed C22HH44/air flames/air flames

AtomicAtomic Force Force MicroscopyMicroscopy

UsingUsing IntermolecularIntermolecular ForcesForces toto MeasureMeasure TopographicTopographic StructureStructure

Forces between the tip and the sample surface cause the cantilever to bend, or deflect.

A detector measures the cantilever deflection as the sample is scanned under the tip.

The measured cantilever deflections allow a computer to generate a map of surface topography

AFM AFM –– examplesexamples

Image of large soot particles

and agglomerates

Image of primary soot particles

And smaller nanoparticles

Image of small nanoparticles

AdvantagesAdvantages

3D Topological images Morphology

Single particle analysis

High resolution on z axis (Ǻ)

Good resolution on x, y axes (10Ǻ)

Pdf determination

ShortcomingsShortcomings

Substrate roughness

Tip artifacts

Detection of small particles in presence of larger ones

Sampling artifacts (size dependent adesion of particles on substrate)

many particle statistics for Pdf

AFM AFM

AFM AFM –– shortcomingsshortcomings

• Minutolo, P., D’Anna, A., D’Alessio, A., “On detection of nanoparticles below the sooting threshold”, Combust. Flame, 152:287-292 (2008).

• D’Anna, A., “Detailed kinetic modelling of particulate formation in laminar premixedflames of ethylene”, Energy & Fuels, 22(3):1610-1619 (2008).

• D’Anna, A., Commodo, M., Minutolo, P., “Particle Inception in a Laminar Premixed Benzene Flame”, Combust. Sci. Technol., 180(5):758-766 (2008).

• D’Anna, A., Sirignano, M., Commodo, M., Pagliara, R., Minutolo, P., “An experimental and modelling study of particulate formation in premixed flames burning methane”, Combust. Sci. Technol., 180(5):950-958 (2008).

• D’Anna, A, Kent, J.H., “A model of particulate and species formation applied to laminar, nonpremixed flames for three aliphatic-hydrocarbon fuels”, Combust. Flame, 152:573-587 (2008).

• C.A. Echavarria, A.F. Sarofim, J. Lighty, A. D’Anna “Modeling and Measurements of SizeDistribution in Premixed Ethylene and Benzene Flames” Proc. Combust. Inst. 32:705-711 (2009).

• A. D’Anna, M. Commodo, M. Sirignano, P. Minutolo, R. Pagliara, “Particle Formation in Opposed-Flow Diffusion Flames of Ethylene: an Experimental and Numerical Study” Proc. Combust. Inst. 32:793-801 (2009).

• A. D’Anna, “Combustion-formed Nanoparticles”, Proc. Combust. Inst. 32:593-613 (2009).

• M. Sirignao, J.H. Kent, A. D’Anna, “Detailed Modeling od Size Distribution Functions and Hydrogen Content in combustio-Formed Particles”, Combust. Flame (2009).

Bibliografia

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