Mvel et al. (7th ICHS) Ignition of - - PowerPoint PPT Presentation

Ignition of hydrogen-air mixtures under volumetric expansion

• R. Mévela,b, J. Melguizo-Gavilanesc and D. Davidenkod

7th International Conference on Hydrogen Safety - Hamburg, GER

a Center for Combustion Energy b Department of Automotive Engineering, Tsinghua University c California Institute of Technology (GALCIT) d The French Aeropace Lab - ONERA Monday September 11, 2017

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Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 1 / 29

Introduction

• utlines

1

Introduction

2

Methodology and calculation procedure

3

Results and discussion

4

Conclusion

Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 2 / 29

Introduction Importance of unsteadiness

Formation of expansion waves

SW-obstacle SW diffraction

Expansions can be formed in complex pipelines Important for shock ignition and industrial safety

Simulations by Prof. H. Hornung

Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 3 / 29

Introduction Importance of unsteadiness

Re-initiation behind a decaying shock wave (1) Detonation direct initiation

2-D images 1-D simulations

t = 6.5 µs t = 9.0 µs t 16.6 s t 14.4 s

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 20 40 60 80 100 120 140 160

Shock pressure p/p

ZND

Distance 3 2 1

Bach et al., 1969 Ng and Lee, 2003

SW velocity decreases much below DCJ before re-initiation occurs

Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 4 / 29

Introduction Importance of unsteadiness

Re-initiation behind a decaying shock wave (2) Detonation diffraction

2-D simulations Velocity along the axis

xa Da/DCJ 100 150 200 250 0.4 0.5 0.6 0.7 0.8 0.9 1.0 4.15 3.75 3.5 2.5 3.0 1.0 2.0

SW velocity decreases much below DCJ before re-initiation occurs

Results from Arienti and Shepherd, 2005

Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 5 / 29

Introduction Importance of unsteadiness

Reaction in expanding flows (1) Lagrangian particles

Particle path Temperature profile

60 120 350

r

~ 300 100 140

t

~ 1 2 3 4 5 6 7 8 9 10 500 80 40 400 450 62D 27 5 . C9/22:6CCC 1/:0725 51 /916,70/1/016/:0725://79/09/6CCC 1/:0725 51:

4 120

t

~ 100 60 2 6

T

~ 1 2 3 4 5 6 7 8 9 10 140 160 80 40 62D 27 5 . C9/22:6CCC 1/:0725 51 /916,70/1/016/:0725://79/09/6CCC 1/:0725 51:

As the SW decays, ignition delay-time increases and the reaction is eventually quenched

Results from Eckett et al., 2000

Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 6 / 29

Introduction Importance of unsteadiness

Reaction in expanding flows (2) Ignition dynamics

Particle path Energy equation analysis

yw t 50 100 150 200 10 20 30 40 50 10 1 11 12 13 14 –10 10 20 30 40 a)

Chemical energy release vs unsteadiness

Results from Arienti and Shepherd, 2005

Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 7 / 29

Introduction Importance of unsteadiness

Previous work on reacting expanding flows Lundstrom and Oppenheim, Eckett et al., Arienti and Shepherd, Radulescu and Maxwell

0.2 0.5 1.0 2.0 5.0 10.0 20.0

t

103 101

∼

105 107 10-1

T ∼

a) c) e) b) d) f)

1-step chemical models were used

Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 8 / 29

Introduction Goals of the study

Purpose of the study Investigate the effect of volumetric expansion on the chemical kinetics of hydrogen-air mixtures Approach

Chemistry : detailed reaction model Flow : simple reactor model to describe expansion Scope : perform detailed kinetics analyses

Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 9 / 29

Methodology and calculation procedure

• utlines

1

Introduction

2

Methodology and calculation procedure

3

Results and discussion

4

Conclusion

Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 10 / 29

Methodology and calculation procedure

Problem definition Specific volume behind a decaying SW

t = 0 t > 0 t = tf Us (t = 0) = DCJ PvN,TvN Ps,Ts Ps, f , Ts,f vvN vs vs,f Us (t > 0) < DCJ Us (t = tf ) = Ucrit

s

Po, To Po, To Po, To Us Us Us

Gas expands behind SW as time progresses

Chemical reactions do not take place at constant pressure or volume... cooling needs to be considered

Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 11 / 29

Methodology and calculation procedure

Mathematical formulation (1) Three forms for the rate of SW velocity decrease

Linear : US(t) = DCJ −αt Exponential : US(t) = DCJ exp(−βt) Power law : US(t∗) = DCJ (t∗)−δ

α, β, and δ are adjusted so that ∆T/τ through isentropic expansion is the same

Linear : α(∆T) = DCJ −US(∆T) Exponential : β(∆T) = ln(DCJ/US(∆T)) Power law : δ(∆T) = ln(DCJ/US(∆T))

ln(2)

Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 12 / 29

Methodology and calculation procedure

Mathematical formulation (2) Final time of simulation

Linear : tf,Lin =

DCJ−Ucrit

S

α(∆T)

Exponential : tf,Exp =

ln(DCJ/Ucrit

S

) β(∆T)

Power law : t∗

f,Pw =

• DCJ

Ucrit

S

1/δ(∆T)

When SW becomes an acoustic wave (M ∼ 1)

Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 13 / 29

Methodology and calculation procedure

Calculation procedure Numerical routine including the following steps

Calculate DCJ Calculate PvN and TvN for US = DCJ Calculate τTh at PvN and TvN using a CP reactor Calculate PS(∆T) using the isentropic relationship for a given ∆T Calculate the corresponding US(∆T) Calculate the shock decay rates coefficients : α, β and δ Calculate tf (or t∗

f ) for all decay rates

Construct time vector in the range [0, tf ] Calculate shock velocity, US, corresponding to each element of the time vector Calculate PS(t) corresponding to each value of US(t) Calculate specific volume, ν, starting from PvN and TvN, and considering an isentropic expansion Calculate τTh with the volume vs. time option (VTIM)

Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 14 / 29

Results and discussion

• utlines

1

Introduction

2

Methodology and calculation procedure

3

Results and discussion

4

Conclusion

Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 15 / 29

Results and discussion Reaction model

Reaction model validation (1) Shock tube data

5 6 7 8 9 10

(1.104/T5) (K-1)

100 1000

D elay tim e (µs)

Φ = 1 ; XAr = 0,955 ; P5 = 101 kPa Φ = 1,03 ; XAr = 0,9847 ; P5 = 101 kPa Φ = 1,47 ; XAr = 0,955 ; P5 = 101 kPa

Petersen 2003

5 6 7 8 9

(1.104/T5) (K-1)

10 100 1000

Delay tim e (µs)

Φ = 1 ; XAr = 0,9925 ; P5 = 375 kPa Φ = 0,5 ; XAr = 0,98 ; P5 = 375 kPa

Hidaka

2 4 6 8 10 12

(1.104/T5) (K-1)

1E-011 1E-010 1E-009 1E-008 1E-007 1E-006 1E-005 0.0001

Delay*[O 2] (m ol.s.dm -3)

Φ = 2 ; XAr = 0,9 ; P5 = 507 kPa Φ = 0,25 ; XAr = 0,97 ; P5 = 101 kPa Φ = 1 ; XAr = 0,94 ; P5 = 101 kPa

Skinner-Schott

Good agreement

Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 16 / 29

Results and discussion Reaction model

Reaction model validation (2) Jet-stirred reactor data

900 1000 1100

Tem perature (K)

0.005 0.01 0.015 0.02 0.025

M ole fraction

XH2 XO2 XH2 = 0,0115 XO2 = 0,024 XH2O = 0,1 P = 100 kPa Φ = 0,2

Dagaut

800 900 1000 1100 1200

Tem perature (K)

0.004 0.008 0.012

M ole fraction

XH2 XH2O XH2 = 0,0108 XO2 = 0,027 P = 100 kPa Φ = 0,2

Dagaut

Good agreement

Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 17 / 29

Results and discussion Reaction model

Reaction model validation (3) Flow reactor data

0.1 0.2 0.3

Time (s)

0.2 0.4 0.6 0.8 1

M ole fraction (* 100)

XH2 = 0,0095 XO2 = 0,0046 P = 300 kPa T = 934 K ∆t = 0,123 s XH2 XO2 XH2O

Yetter et al.

0.1 0.2 0.3

Time (s)

0.4 0.8 1.2

M ole fraction (* 100)

XH2 = 0,0101 XO2 = 0,0052 P = 349 kPa T = 933 K ∆t = -0,02178 s XH2 XO2 XH2O

Yetter et al.

Reasonable agreement

Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 18 / 29

Results and discussion Ignition delay-time under volumetric expansion

Effect of expansion on the ignition dynamics Cooling rate 0-250 K/τ

Temperature profiles Thermicity profiles

10-1 100 101 102 Time (µs) 1000 1500 2000 2500 3000 3500

Temperature (K)

CP L 60 K/τTh L 140 K/τTh L 160 K/τTh E 60 K/τTh E 140 K/τTh E 160 K/τTh P 120 K/τTh P 160 K/τTh P 220 K/τTh

10-1 100 101 102

Time (ms)

1000 2000 3000 4000 5000 6000 7000 Thermicity (1/µs)

CP L 60 K/τTh L 140 K/τTh L 160 K/τTh E 60 K/τTh E 140 K/τTh E 160 K/τTh P 120 K/τTh P 160 K/τTh P 220 K/τTh

As cooling rate is increased τ increases and σmax decreases

Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 19 / 29

Results and discussion Ignition delay-time under volumetric expansion

Effect of expansion on τ P1 = 10-1000 kPa and Cooling rate 0-250 K/τ

Linear decay Exponential decay Power law decay

200 400 600 800 1000 Initial pressure (kPa) 10-1 100 101 102 τTh (µs) CP 20 K/τTh 40 K/τTh 60 K/τTh 80 K/τTh 100 K/τTh 120 K/τTh 140 K/τTh 160 K/τTh 170 K/τTh 200 400 600 800 1000 Initial pressure (kPa) 10-1 100 101 102 τTh (µs) CP 20 K/τTh 40 K/τTh 60 K/τTh 80 K/τTh 100 K/τTh 120 K/τTh 140 K/τTh 160 K/τTh 190 K/τTh 200 400 600 800 1000 Initial pressure (kPa) 10-1 100 101 102 τTh (µs) CP 120 K/τTh 130 K/τTh 160 K/τTh 180 K/τTh 200 K/τTh 220 K/τTh 230 K/τTh

Highest sensitivity to quenching for P1 = 500-800 kPa Lowest sensitivity to quenching for P1 < 100 kPa

Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 20 / 29

Results and discussion Ignition delay-time under volumetric expansion

Variation of CP τ along isentropes Effect of initial pressure

Low pressure range High pressure range

(Exponential decay) (Linear decay)

1 2 3 4 5 6 7 8

Normalized time (-)

10-2 100 102 104 106 108 1010 τTh (µs)

P0=20 kPa P0=101 kPa P0=202 kPa

1 2 3 4 5

Normalized time (-)

10-1 100 101 102 103 104 τTh (µs)

P0=303 kPa P0=659 kPa P0=1013 kPa

140 K/τTh 100 K/τTh

At LP, 2nd explosion limit is located at lower T At HP, delay-time decreases as P increases

Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 21 / 29

Results and discussion Thermo-chemistry dynamics at near-critical conditions

Species profiles Power law decay rate

Sub-critical Near-critical Super-critical

100 Time (µs) 10-6 10-5 10-4 10-3 10-2 10-1 Mole fraction H H2 O O2 OH HO2 H2O2 H2O 10-1 100 101 Time (µs) 10-6 10-5 10-4 10-3 10-2 10-1 Mole fraction H H2 O O2 OH HO2 H2O2 H2O 100 Time (µs) 10-6 10-5 10-4 10-3 10-2 10-1 Mole fraction H H2 O O2 OH HO2 H2O2 H2O

200 K/τ 225 K/τ 230 K/τ

At 225 K/τ, runaway just before final time At 230 K/τ, no significant consumption of reactants

Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 22 / 29

Results and discussion Thermo-chemistry dynamics at near-critical conditions

Energy release Chemical energy vs Cooling (expansion)

Sub-critical Near-critical Super-critical

2 4 6 8 10 Time (µs)

• 8
• 6
• 4
• 2

2 4 6 8 10 Energy release rate (MJ/cm3.s) Expansion cooling Chemical energy Net energy release rate 2 4 6 8 10 Time (µs)

• 8
• 6
• 4
• 2

2 4 6 8 10 Energy release rate (MJ/cm3.s) Expansion cooling Chemical energy Net energy release rate 2 4 6 8 10 Time (µs)

• 8
• 6
• 4
• 2

2 4 6 8 10 Energy release rate (MJ/cm3.s) Expansion cooling Chemical energy Net energy release rate

200 K/τ 225 K/τ 230 K/τ

At 225 K/τ, weak energy release at longer time At 230 K/τ, no significant energy release

Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 23 / 29

Results and discussion Thermo-chemistry dynamics at near-critical conditions

Energy release per reaction Focus on chemical energy release

Sub-critical Near-critical Super-critical

2 4 6 8 10 Time (µs)

• 3
• 2
• 1

1 2 3 4 5 Energy release rate (MJ/cm3.s) H+O2=O+OH H+O2(+M)=HO2(+M) OH+H2=H2O+H OH+H+M=H2O+M 2 4 6 8 10 Time (µs)

• 0.1
• 0.05

0.05 0.1 0.15 0.2 Energy release rate (MJ/cm3.s) H+O2=O+OH H+O2(+M)=HO2(+M) OH+H2=H2O+H OH+H+M=H2O+M H+O+M=OH+M 2 4 6 8 10 Time (µs)

• 0.01

0.01 0.02 0.03 0.04 0.05 Energy release rate (MJ/cm3.s) H+O2=O+OH H+O2(+M)=HO2(+M) OH+H2=H2O+H HO2+H=OH+OH

200 K/τ 225 K/τ 230 K/τ

At ≤ 225 K/τ : Induction : H+O2(+M) = HO2(+M) Exothermic : OH+H2 = H2O+H and OH+H(+M) = H2O(+M) At > 225 K/τ : No switch to branching chemistry

Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 24 / 29

Results and discussion Thermo-chemistry dynamics at near-critical conditions

Rate of production Analysis for OH radical

Sub-critical Near-critical Super-critical

2 4 6 8 10 Time (µs)

• 60
• 50
• 40
• 30
• 20
• 10

10 20 30 40 Rate of production (mol/cm3.s) H+O2=O+OH O+H2=H+OH HO2+H=OH+OH OH+H2=H2O+H 2 4 6 8 10 Time (µs)

• 2.5
• 2
• 1.5
• 1
• 0.5

0.5 1 1.5 Rate of production (mol/cm3.s) H+O2=O+OH O+H2=H+OH HO2+H=OH+OH OH+H2=H2O+H 2 4 6 8 10 Time (µs)

• 0.4
• 0.3
• 0.2
• 0.1

0.1 0.2 0.3 Rate of production (mol/cm3.s) H+O2=O+OH O+H2=H+OH HO2+H=OH+OH OH+H2=H2O+H

200 K/τ 225 K/τ 230 K/τ

At ≤ 225 K/τ : Double inversion between linear chain and chain branching At > 225 K/τ : Single inversion between linear chain and chain branching

Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 25 / 29

Results and discussion Thermo-chemistry dynamics at near-critical conditions

Sensitivity coefficient on OH Evolution as a function of cooling rate

50 100 150 200 250 Cooling rate (K/τTh)

• 300
• 200
• 100

100 200 300 400 500

Sensitivity coefficient (-)

O+H2=H+OH H+O2=O+OH H+O2(+M)=HO2(+M) HO2+H=OH+OH

Increasing sensitivity and competition between linear chain and chain branching

Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 26 / 29

Conclusion

• utlines

1

Introduction

2

Methodology and calculation procedure

3

Results and discussion

4

Conclusion

Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 27 / 29

Conclusion

Conclusion Study of chemical kinetics of hydrogen-air mixtures under volumetric expansion

Power law decay is the least efficient at quenching the reaction Intermediate pressure (P1 = 500-800 kPa) are the most sensitive to quenching Low pressure (P1 < 100 kPa) are the least sensitive to quenching Complex response to expansion is due to the extended second explosion limit

Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 28 / 29

Conclusion

Acknowledgments

Thank you for your attention Questions ?

t > 0

CJ

Ps,Ts P vs Us (t > 0) < DCJ Po, To Us

10-1 100 101 102 Time (µs) 1000 1500 2000 2500 3000 3500

Temperature (K)

CP L 60 K/τTh L 140 K/τTh L 160 K/τTh E 60 K/τTh E 140 K/τTh E 160 K/τTh P 120 K/τTh P 160 K/τTh P 220 K/τTh

Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 29 / 29