Towards a better assessment of Hydrogen Safety

Research Topics on Hydrogen Combustion:

Towards a better assessment of Hydrogen Safety

N. Chaumeix

Benevento, 21st of February 2012

1

ICARE – CNRS

Institut de Combustion, Aérothermique Réactivité et Environnement

1c, avenue de la Recherche Scientifique 45071 Orléans – Cedex 2 – France

Orléans Paris

ICARE is in Orléans, 125 km from Paris

Total staff : 110 35 Researchers

30 Engineers and technicians 30 PhD students and post-docs 15 Various trainees

Where is ICARE ?

Research domains of ICARE

Energy & Environment Propulsion & Space

• Combustion

• Chemical kinetics • Plasmas physics

• Fluid mechanics, turbulence • Two phase flows

• Supersonic, hypersonic flows • Ionized, rarefied flows

Application domains

• Aerospace propulsion

• Electric propulsion

• Liquid and solid propulsion

• Atmospheric reentry

• Atmospheric chemistry

• Energy production

• Alternative fuels, biofuels, hydrogen

• Pollutant emissions reductions

• Industrial risk prevention

Main cooperations

International co-operations: All EU countries, Russia, USA, Canada, China, Japon, Ukraine, Turkey, Argentine, etc

Research Areas @ ICARE

 3 main research fields:

 Combustion

• Chemical kinetics of reactive systems

• Dynamics of Combustion

 Atmospheric Reactivity

 Spatial Propulsion and Hypersonic Flows

 8 different Groups of Research

Explosions and Chemical Reactions behind

Shock and Detonation Waves Group

Research Activities of the S. W. Group

 Combustion Chemistry

 Elementary Reaction Rates involving O and H atoms

 Pollutant Formation from Gasoline Components

 Reduced Mechanim of soot precursors from kerosene fuel

 Soot Formation from fuels

• Diesel, Gasoline, kerosenes

 Soot Oxidation

• In engine conditions behind shock waves

• Particles Filter

Research Activities of the S. W. Group

 Flame and Explosions Dynamics

 Hypergolic limits of propellant agents

 Propellents for PDE

 DDT using hot jet ignition

 Laminar Flame properties and their instabilities

 Flame acceleration in obstructed areas

 Detonation criteria and industrial safety

 Solid Explosives and their thermal aging

Accidental explosion in the industrial context

Gas leak/production Distribution in the area

Gas proportion in the mixture equivalent to the flammability range

Sufficient energy provided (e.g. hot surface)

Ignition and propagation

Introduction

Fukushima Daichii 10

Introduction

 Prevention of Gas Explosion in a Nuclear Power Plant

 Need a good assessment of combustion properties according to

• initial temperature and pressure

 In the risk of explosion analysis

 Good knowledge of Combustion Properties of the combustible mixture:

• the flammability limits

• ignition energy,

• flame velocity, burning rates,

• energy release,

• Auto-ignition delay times

• Detonation cell size

11

Hydrogen Hazard in Nuclear Power Plants ?

Destruction of the Nuclear Power Plant Building

Rejet des produits radioactifs dans l'environnement

12

Context

 Mixtures involved in Pressurized Water Reactor

 Hydrogen – air – water vapor

 Lean

 Unstable

 Flame Acceleration Mechanism

 A. F. : turbulence + instabilities

 T.D.D. : shock focusing

 Insight in the different mechanisms involved in flame acceleration

13



 ^Model

Real

Identification of a Scenario

14

Flammability Limits

1 2 3 4 5 6 7 8 9 10 11 12

Pourcentage molaire en Hydrocarbure 0

1000 2000 3000 4000 5000

Pression (mm de Hg)

Ethane Propane Butane Pentane

Limites Inférieures Limites Supérieures

Minimum Ignition Energy

Combustion Regimes

 Deflagration : Ignition wave, propagation via Heat &

Mass Transfer

17

 Detonation : Coupling between a shock wave (|) and a reaction zone ()

Reaction zone

(burnt gas) (fresh gas)

Delay

(fresh gas) (burnt gas)

High P & T

État initial (gaz frais) Onde de combustion

État final (gaz brûlés)

Combustion regimes

Flame acceleration (turbulence, instabilities…)

DDT (shock focusing, local m explosion…)

Slow deflagration

Flame speed

18

Fast deflagration Detonation

LAMINAR PREMIXED FLAMES

Basic Properties

PART I – FLAMMABILITY LIMITS

20

Laser beam

Variable Attenuator Xenon Lamp

Beam trap

Pressure sensor

Mirror

Mirror

Screen

Photodiode 1 Photodiode

2

Photodiode 3 Knife

Fast video camera Spherical

Lens

Lens

Nd:YAG laser 1064 nm, 13 ns

10x telescope

Volume : 8L

4 Silica Windows

diameter= 250 mm

Experimental set-up: Flammability limits

21

E

= 80 mJ

Laser Ignition

Schlieren System

Flammability limits: methodology

t= 0 s t= 12 ms t=24 ms t=36 ms t=48 ms

0 1 2

Temps (s) 1

2 3 4 5

Pression absolue (bar)

Manip L085 Pressure Laser PAICC

Case 1: Mixture is flammable

After ignition, the flame

propagates upwardly in the vessel

Pressure increases slightly in the vessel

22

Flammability limits: methodology

t= 0 s t= 2,2 ms t=4,7 ms t=12 ms t=20 ms

-0.05 0 0.05 0.1 0.15 0.2

Temps (s) 0.5

1 1.5 2 2.5 3

Pression absolue (bar)

Manip L087 Pressure Laser

Case 2: Mixture is not flammable

After ignition, a combustion products kernel is formed and fades away quickly

Pressure remains constant in the vessel

23

Results – Lean Mixtures

24

2 limits observed

Downward Propagation Limit

Full Propagation

Image 40 Image 80 Image 120

Image 160

0 2 4 6 8 10

Time (s) 1

2 3 4

Absolute Pressure (bar) _0.09H

2 + 0.191O₂ + 0.719N₂ 100 kPa ; 30°C

P_AICC=3.93 bar

Image 10 Image 25 Image 35

Image 45

-2 0 2 4 6 8 10

Time (s)

1 1.2 1.4

Absolute Pressure (bar)

7% H₂ + 19.5% O₂ +73.5% N₂

Results – Dry mixtures H

/ Air – 1 bar

25

PART II - LAMINAR FLAME PROPERTIES

26

Flame Structure

T

T, concentration (unités arbitraires)

x

T

réactifs produits

Intermédiaires réactionnels

Etat final (gaz brûlés)

Etat initial (gaz frais) T





Laminar Flame Velocity

 Definition : unburned gas flow-rate normal to the flame front surface

 Implies that

 Constant flowrate

 Plane flame

 Negligible thickness

 In case of Outward Spherical Propagation

 Pressure Signal

 Flame Front Detection

28

Volume : 56 L

P

= 50 Bars

T

470 K

Central Ignition

4 Silica Windows

diameter=550 mm

Schlieren System

High Speed Numerical Camera

VHT

Spark Electrodes

Oscilloscope HT

High Voltage Source

Spherical Bomb

Current Probe

To the Camera

I High voltage probe /1000

Experimental Setup: Laminar study

29

Spatial flame speed determination

Electrodes

Burned gases

Fresh gases

Flame front

30

Outward Spherical Flame Front Propagation

31

 

 



 



 



 

 

 



 

 

 



 

 

 u

b b

u u

b b

b S b

L P

P T

T M

M dt

dP P

3 V r

S

Eschenbach & Agnew (1958) expression

• M : relative molar mass

• P, T : pressure and temperature

• r : flame radius

•  : gas expansion ratio

  ^s

L V

In the early stages of the flame propagation S

• t : time

• u : relative to unburned gas

• b : relative to burned gas



o

Spherical flame

o

Curvature and thickness negligible

o

Adiabatic process and isentropic compression

o

Chemical equilibrium behind the flame front

o

No dissociation or reactions in the fresh gas

o

Local deposit of the energy

Spatial flame speed determination

0 0.004 0.008 0.012 0.016

Time (s) 0

10 20 30 40 50

Radius (mm)

E.R. =1.05 E.R.=1.2 E.R.=0.85

^s

L

S V

Pressure remains constant

0 0.2 0.4 0.6

Time (s) -2

0 2 4 6

Overpressure(bar)

G222 + Air - MANIP 187 Equivalence ratio = 1.05 and

P_ini = 1 bar T= 363 K

-0.02 0 0.02 0.04

Time (s)

0 2 4

Overpressure (bar)

G222 + Air - MANIP 187 Equivalence ratio = 1.05 and

P_ini = 1 bar T= 363 K Pressure

Observation Window

t= 0.00033s t= 0.0025 s t= 0.0035 s

t= 0.00616s t= 0.009 s t= 0.01183s

V

= 0.8 %V

32

Unstretched velocity

f S

r 2 V

 







  V L

V _{s s} S _L ^  S _L  L  

 Finite flame thickness

 A uniform & well-defined stretch

 Visualisation of the flame propagation

o Laminar flame velocity versus stretch

o

Derive the laminar flame velocity at zero-stretch

33

Flame Stretch

Due to curvature :

Due to the strain ahead of te flame front:

Total Stretch rate :

u L

c

r

2 S





u g

S

r

2 u





u S s

c

r

2 V













u

: velocity of the fresh gas ahead of the flame r

: flame radius S

: stretched laminar flame speed

V

: stretched burning speed

Markstein Length, L et L’

 Clavin and Joulain expression :

 Burning Speed: V _s  V _s ⁰  L . 

Laminar Flame Speed:

 



 S ⁰ L . S _{L L}

S

° : vitesse laminaire de flamme étirée

V

° : vitesse spatiale de propagation de flamme étirée

 : rapport d’expansion des gaz L, L’ : Longueurs de Markstein



  L L

avec



 _S

L V

S

Methodology

Image 15

Image 25

Image 35

Image 45

Image 55

H

/Air à Φ=3,491 T

=30,7°C ;

P

=100 kPa V

= 15 000 i/s

100 200 300 400 500 -300

-200 -100 0 100 200 300 400 500

image 26

100 200 300 400 500 -300

-200 -100 0 100 200 300 400 500

0 0.001 0.002 0.003

Temps (s) 0

10 20 30 40

Rayon (mm)

R² = 0.9998

36

Methodology

 Equilibrium Calculations

 Providing the thermodynamic properties of the species involved

• H

, O

, N

, H

O, H, O, OH, HO

, H

O

, NO, NO

, N

O, …..

37

0 0.4 0.8

Time (s) 0

2 4 6 8

Absolute Pressure (bar)

0.333H₂ + 0.14O₂ + 0.527N₂ 100 kPa ; 30°C

 At constant Pressure

• Adiabatic Flamme Temperature, T

 At constant Volume

• Adiabatic Maximum Pressure, P

 Software COSILAB

 Species in the detailed

chemical kinetic mechanism

ini AICC

ini exp

max,

P P

P P





Experimental Conditions

 Mixture Composition

 H2 / Air

 Temperature domain

 25 – 150 °C

 Pressure Domain

 1 – 2.5 bar

 Low ignition Energy

  0.4 to 40 mJ

38

Flame Propagation – H ₂ + Air

Far from the limits – 1 bar- T

39

0 1 2 3 4 5

Rapport d'équivalence, 

0 100 200 300 400

V it es se d e fl am m e la m in ai re /( cm /s ) ^{H 2 /Air}

Egolfopoulos et al Lijima et Takeno Berman

Takahashi Aung et al Liu et al Raman Lamoureux cette étude

H ₂ /Air

Koroll et al Vagelopoulos Wu and Law Dowdy et al

Egolfopoulos et al Lijima et Takeno Berman

Takahashi Aung et al Liu et al Raman Lamoureux cette étude

H ₂ /Air

Koroll et al Vagelopoulos Wu and Law Dowdy et al

Egolfopoulos et al Lijima et Takeno Berman

Takahashi Aung et al Liu et al Raman Lamoureux cette étude

Markstein Length

0 1 2 3 4 5 6

Rapport d'équivalence, F -1x10^-3

-8x10^-4 -4x10^-4 0x10⁰ 4x10^-4 8x10^-4

Longueur de Markstein, L' (m)

Aung et al. (1997)

Davis and Searby (2002) Dowdy et al. (1990) ce travail

Prediction

Sun et al. (1999)

Combustion Parameters

0 1 2 3 4 5

Equivalence ratio,

1.0x10^-5 1.0x10^-4 1.0x10^-3 1.0x10^-2

Flame thickness,  (m)

^=D_(H2,mixt.)/SL^°

^=/SL^°

0 2 4 6

Equivalence ratio, 

0 40 80 120 160 200

Overall activation energy, Ea (kJ.mol-1)

Sun et al. (1999) Dorofeev (2001) This Work

PART III - FLAME ACCELERATION

42

3.3 m ; V= 65L



= 0.154 m 1.68 m ; V= 685L



= 0.738 m Dome T ube

Experimental set-up: ENACCEF

43

3.3 m ; V= 65L



= 0.154 m 1.68 m ; V= 685L



= 0.738 m



Ignition 

Electrical discharge between two electrodes

Obstacles

8, 11, 14 equidistant rings Blockage Ratio (BR)

of the rings BR = 0.6, 0.4, 0.33

(BR=1-(d/D)²) D

d

Dome T ube

Experimental set-up: ENACCEF

44

Equipment :

15 UV-Photomultipliers (PM)

 flame detection and speed measurement

8 pressure sensors (Chimie-Metal and Kistler)  pressure load measurement

 9 sampling locations at different positions  6 locations in the tube

 3 locations in the dome

Dome T ube

Experimental set-up: ENACCEF

45

Types of propagation – Full Propagation

-0 0.4 0.8 1.2 1.6 2

Time (s) 2

4 6

Pressure(bar)

G222_167 Pressure PAICC=6.3 Bar

2 regimes

If V

/ (Cs)

< 0.5 then: slow flame propagation

If V

/ (Cs)

≥ 0.5 then: Fast flame propagation

(C_s )_BURNED : Speed of sound in the burned gases

Position %G222 initial

%G222 final

0.277 6.5 0

0.527 6.5 0

1.277 6.5 0

2.139 6.5 0

2.877 6.5 0

3.341 6.5 0

Tube Dome

0 1 2 3 4

Position (m) 0

100 200 300 400

Mean Velocity (m/s)

6.5% G222 / Air M167 BR=0.3, 8 Obstacles

46 ^{0 1 2 3 4}

Position (m) 0

200 400 600

Mean Velocity (m/s)

G222 / Air, BR=0.3, 8 Obstacles 6.5%

7.6%

0,5*C_S,GB

Types of propagation - Partial propagation

Extinction

Post combustion chromatographic analyses report the initial mixture unburned outside the obstacle range

Turbulent mixing becomes much too important leading to extinction

(C_s )_BURNED : Speed of sound in the burned gases

Position %G222 initial

%G222 final 0.277 6.8 1.6 0.527 6.8 4.1 1.277 6.8 5.8 2.139 6.8 6.8 2.877 6.8 6.8 3.341 6.8 6.8

0 0.2 0.4 0.6 0.8

Time (s) 0

2 4 6 8

Pressure (bar)

Pressure M220

PAICC=6.97 bar Tube Dome

0,5*C_S,GB

0 1 2 3 4

Position (m) 0

100 200 300 400

Mean Velocity (m/s)

6.8% G222 / Air 8 Obstacles, BR=0.6

M220 Extinction

47

H2 - Air

48

0 1 2 3 4

distance from electrodes (m) 0

200 400 600

Flame speed (m/s)

13 % Uniform - BR=0,63 (Averaged) 10.5 % Uniform - BR=0,63 (Averaged)

0 1 2 3 4

distance from electrodes (m) 0

10 20 30 40 50

Flame speed (m/s)

13 % Uniform - Smooth tube (Averaged) 10.5 % Uniform - Smooth tube (Averaged)

Acceleration Criterion

49

-9 -8 -7 -6 -5 -4

(Le-1)

3.4 3.6 3.8 4 4.2 4.4



(0,130;0,00;3,76)

(0,130;0,20;3,76)

(0,130;0,30;3,76)

(0,130;0,40;3,76)

(0,110;0,00;3,76)

(0,105;0,00;3,76) (0,105;0,10;3,76)

E_a(kJ.mol^-1) = 224,14 -156,00 F + 47,15 F² - 4,16 F³ Flammes rapides

Flammes lentes Flammes coincées

(0,116;0,00;3,50) (0,122;0,00;3,25)

(0,128;0,00;3,00)

(0,119;0,07;3,00) (0,115;0,10;3,00)

(0,115;0,00;3,76)

 = 0.09 (Le-1) + 4.5

PART IV - DETONATION

50

 Detonation : Coupling between a shock wave (|) and a reaction zone ()

Delay

(fresh gas) (burnt gas)

High P & T

Figure 1 : Structure ZND de la détonation

51

Detonation

Cellular detonation wave structure

 In Case of Self-sustained Detonation

52

53

{H

/CH

/O

} mixture :



CH

/CH

+H

= 0.4, F =0.75; P1 = 10 kPa; T1 = 20°C



Velocity : D

= 1800 m.s

(D

= 2218  14 m.s

)



Von Neumann parameters:



T

= 1380 K and P

=250 kPa

Triple

points

Leading shock

Reaction zone



:

 : ignition delay time behind the leading shock

CORRELATION BETWEEN  AND 

λ = k* _i

IMPORTANCE of the cell size

 Critical Energy of Initiation

3 2

0

3      







 _{CJ i CJ}

c A P B D

E ^{B 425}

 Minimum tube diameter   d  

 Transmission from a tube  open space d _c   13 

 Minimum tube diameter with obstacles d  

 Run-up distance _{ 40}

TDD

 L

54

IMPORTANCE of the cell size

55

 Sensitivity to detonation

0.1 1 10 100 1000

Initial Pressure P

(kPa) 0.1

1 10 100

C el l w id th  ( m m )

C₂H₂/O₂F=2.5

C₂H₂/O₂F=1.0

C₂H₂/O₂ F=0.6 CH₄/O₂F=1.0

H₂/O₂ F=1.0 C₂H₄/O₂ F=1.0

C₃H₈/O₂F=1.0

C₂H₆/O₂F=1.0 C₇H₁₆/O₂F=1.0

Relation between  and  _i

56

 ₂ 

2 1 2 1

1 2

avec . .

i i CJ

CJ

CJ

i i

D v

v u u D u

D



 



   

  

 

λ = k* _i

Chemistry

Thermodynamics

0 0.2 0.4 0.6 0.8 1

CH₄/{CH₄+H₂}

0 20 40 60 80

Largeur de cellule (mm)

 : F=0,75 - P1=10 kPa

: F=1 - P₁=10 kPa

: F=1 - P1=20 kPa

 =  (D

- u)

0.0x10⁰ 2.0x10^-4 4.0x10^-4 6.0x10^-4

Temps (µs)

Unités arbitraires

x_CH4/(x_CH4+x_H2) = 0.4 ; F = 0.4 P₅ = 924 kPa ; T₅ = 1620 K Délai d'auto-inflammation

_infl. = 70,5 µs Onde de choc réfléchieOnde de choc incidente

Signal d'émission OH

Signal de pression

Detonation

Acquisition of Database –

Fundamental Properties

57

CONCLUSION

58

Laminar Flames

Wrinkled Flames

Turbulent Flame

Highly accelerated Flames

Detonation

Safety Analysis of Gas Explosions