Flame Fundamentals Fundamentals I... · 2018-04-09 · Flame Fundamentals KAUST CISS 2018 April 1, 2018 Kaoru MARUTA, Institute of Fluid Science, IFS Tohoku University, Sendai, Japan

Flame Fundamentals

KAUST CISS 2018

April 1, 2018

Kaoru MARUTA,

Institute of Fluid Science, IFS

Tohoku University, Sendai, Japan

KAUST SS 2018

Kaoru MARUTA

2

KAUST SS 2018

Kaoru MARUTA

Tohoku University, Sendai, Japan

• City of Trees, 300

km north of Tokyo

• Found as third

university in Japan

on 1907

• Mission statements

-Research first

-Open doors

-Practice-oriented

R&E

Tokyo

Sendai

3

KAUST SS 2018

Kaoru MARUTA

• Kaoru Maruta, Professor

Institute of Fluid Science

(IFS), Tohoku University

• 1993 -1999

IFS, Tohoku Univ.

• 1999 Akita Pref. U.

Visit: USC, UCB

• 2002-Present

IFS Tohoku U.

IFS: 25 laboratories, 30 Faculties,Fluid-related research instituteMolecules, Rarefied, FD, Combustion, Plasma, SW, Bio- & Med Flow, Energy, Aerospace

Microgravity experiments at 10 sec, 490 m freefall, droptower in JapanCounterflow flame, flammability limit mechanism, Radiative extinction2010- Comprehensive limitAirplane, will be in Space

High Temperature Air Combustion Tech. (HiCOT), mild combustionFurnace, Reformer, Incinerator2011- High Temp. Oxy. Comb.

Microscale combustion, MicrocombustionMicrocombustor for heat sourceMicro flow reactor with controlled temperature profileKinetics study, super lean E/G combustion

Acknowledgements to collaborators:

• Professor Emeritus Takashi Niioka, Tohoku Univ.

• Professor Yiguang Ju, Princeton Univ.

• Professor Sergey Minaev, Far Eastern Federal Univ.

• Dr. Roman Fursenko, ITAM, SB RAS

• Professor Nam IL Kim, KAIST

• Professor Takeshi Yokomori, Keio Univ.

• Professor Hisashi Nakamura, Tohoku Univ.

• Mr. Susumu Hasegawa, Mr. Takuya Tezuka, Tohoku Univ.

• All other collaboration researchers, postdocs, and students

4

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Prof. Niioka

Prof. Ju

Prof. Minaev

Prof. Nakamura Mr. Hasegawa Mr. Tezuka Prof. Yokomori

Prof. N.I. Kim

Dr. Fursenko

Contents of Flame Fundamentals

• Part 1 Flame basics

• Part 2 Flammability limits

• Part 3 Flames under extreme conditions

5

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Part 1: Flame basics

• Introduction

• S-curve

• Premixed flame

• Non-premixed flame

• Flame characteristics

6

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Flame classification

• Premixed and non-premixed

(diffusion) flames

• Laminar and turbulent flames

*: www.nasa.gov

*

*

7

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Premixed and non-premixed flame

Non-premixed flame Premixed flame

(Diffusion flame)

8

FOF + O

**: Energy dynamics laboratory

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Fuel + Air (oxidizer)

Stabilized and propagation flames 9

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10Laminar and turbulent premixed flames

Turbulent premixed flame (Schlieren image)

Laminar flame(Direct photo)

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11Combustion in practical devices

• Turbulent combustion

• Reciprocating engines

Premixed combustion in Otto-

cycle engine (Spark-Ignited

engine, Gasoline engine)

Auto-ignited non-premixed (or

partially premixed) combustion in

Diesel engine (Compression

ignition engine)

• Gas turbine engine

Different types of GT, Premixed

and non-premixed combustion

• Furnace, incinerator

Mostly non-premixed, specific

combustion-mode (Mild

combustion)

The Jet Engine, Rolls-Royce, 1992

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World first micro-G exp. (1954) Kumagai

High

speed

com

bu

stion

researchComb. Inst. 1954

12Science and technology developments and combustion research

1950

2020

2000

1900

Steam engine, IC engines Otto, Diesel

Manned powered flight

WW II

Ford Model T, mass production Prop plane

Jet engine

Laser, invention・・・

Applications

Computer, Invention・

DevelopmentSpread

Super computing

Ro

ckets, V-II, V

osto

k, Saturn

V…

….

Periodic table(1869)Dmitri Mendeleev

ElectronAtom, Molecule,Proton, Neutron,

Elementary particles

First Comb. Symp. 1928

Third, 1948

Co

mb

ustio

n th

eory (A

symp

totic an

alysis……

)

Co

mp

utatio

ns

Laser diagn

ostics

Stud

y on

Co

mb

ustio

n Lim

its(M

inin

g safety)

Microgravity experiments (drop tower,

airplane, space shuttle,

IIS)

The Chemical History of a Candle (1861) Michael Faraday

Chemical kineticsHydrogen, hydrocarbon, PAH

Quantum chemistry, Ab initio

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• Introduction

• S-curve

• Premixed flame



13

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14

Stable solution

Stable solution

Unstable solution

• Time scales of

transport and chemical

reaction

• Extensively applicable

to various phenomena,

e.g., candle flame,

burner flame,

counterflow flame,

supersonic combustion,

etc.

S-curve (Fendell curve)

IgnitionExtinction

Damköhler number, D

𝑇 𝑚𝑎𝑥

(

𝑚…

)

𝐷 =𝐹𝑙𝑜𝑤 𝑟𝑒𝑠𝑖𝑑𝑒𝑛𝑐𝑒 𝑡𝑖𝑚𝑒

𝐶ℎ𝑒𝑚𝑖𝑐𝑎𝑙 𝑡𝑖𝑚𝑒

Liñán, A., Acta Astro. 1(7) 1007 (1974).

Fendell, F.E., J. Fluid Mech. 21(2) 281 (1965).

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15Chemical reactor and combustion

• Ignition

• Combustion

• Extinction

CSTR

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16Analogy between combustor and reactor

Batch CSTR

The Modal Shop, Inc., 2017

Meere et al., J. Eng. Math. 44: 57, 2002.

ST

RCM

GT

The Jet Engine, Rolls-Royce, 1992

Dagaut, ICFD 2016

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Time scales of reactive fluids 17

1 s

10-2s

10-4s

10-6s

10-8s

10-10s

Flow time

Transport timeMolecularTurbulent

NO formation

Product formation H2O

Radical formation H

Radical formation H2O2

quasi-steady state?

Radiation transferquasi-steady state

Chemical time Physical time

DNS Time-step

Physical interest

?

Ju, ICFD, 2008

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Time scales of chemical reactions

Lu et al., Prog. Energ. Comb. Sci. 35: 192 (2009).

18

• Distributions of ignition time scale (Residence time @1 ms, 2000 K）

• Pico-sec～milli-sec or even longer

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Seeking for “ideal” ignition phenomena 19

The Modal Shop, Inc., 2017

Meere et al., J. Eng. Math. 44: 57, 2002.

http://c3.nuigalway.ie

ST

RCM

High Purity

Photolysis Shock

Tube (NASA Tube), Stanford Univ.

Kinetics Shock

Tube (KST),

Stanford Univ.

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Seeking for “ideal” flames 20

?• Difficult to establish ideal

(probably one-dimensional,

adiabatic) flames without

influences of external factors

• Detailed data from ideal flames

are essential for establishing

computational tools, precise

kinetics, etc.

?

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21Chemical kinetics modeling

Homogeneous rector

0D model

Senkin, 1988

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• Introduction

• S-curve

• Premixed flame



22

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Fuel + Air

Flash back

Blow off

Bunsen flame

Flame propagation, laminar burning velocity, flame

quench, extinction, blow off, flame structure

23

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24

- Flame is interface separating unburned and

burned gases, thermodynamic equlibrium

- Transport in preheat

zone, diffusion

processes of mass and

heat

- Reaction sheet, source

of heat and sink of

reactant

- If Le =1, Y and T profiles

are mirror images

- Preheat and

Reaction zones

(Rankine-Hugoniot Relations,

→ detonation and deflagration waves)

Law, C.K., Combustion Physics, 2006.

Laminar premixed flame (Deflagration wave) KAUST SS 2018

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1-D steady propagating flame

Continuity

PREMIX, CHEMKIN

Forward rate

coefficient

25

Energy

Species

Equation of state

Governing equation for steady, isobaric, adiabatic one-dimensional flame propagation

For further details, refer, e.g., Poinsot, Theor. Num. Comb.

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26

! GRI-Mech Version 3.0 7/30/99 CHEMKIN-II format

! See README30 file at anonymous FTP site unix.sri.com, directory gri;

! WorldWideWeb home page http://www.me.berkeley.edu/gri_mech/ or

! through http://www.gri.org , under 'Basic Research',

! for additional information, contacts, and disclaimer

ELEMENTS

O H C N AR

END

SPECIES

H2 H O O2 OH H2O HO2 H2O2

C CH CH2 CH2(S) CH3 CH4 CO CO2

HCO CH2O CH2OH CH3O CH3OH C2H C2H2 C2H3

C2H4 C2H5 C2H6 HCCO CH2CO HCCOH N NH

NH2 NH3 NNH NO NO2 N2O HNO CN

HCN H2CN HCNN HCNO HOCN HNCO NCO N2

AR C3H7 C3H8 CH2CHO CH3CHO

END

!THERMO

! Insert GRI-Mech thermodynamics here or use in default file

!END

REACTIONS

2O+M<=>O2+M 1.200E+17 -1.000 .00

H2/ 2.40/ H2O/15.40/ CH4/ 2.00/ CO/ 1.75/ CO2/ 3.60/ C2H6/ 3.00/ AR/ .83/

O+H+M<=>OH+M 5.000E+17 -1.000 .00

H2/2.00/ H2O/6.00/ CH4/2.00/ CO/1.50/ CO2/2.00/ C2H6/3.00/ AR/ .70/

O+H2<=>H+OH 3.870E+04 2.700 6260.00

O+HO2<=>OH+O2 2.000E+13 .000 .00

O+H2O2<=>OH+HO2 9.630E+06 2.000 4000.00

O+CH<=>H+CO 5.700E+13 .000 .00

O+CH2<=>H+HCO 8.000E+13 .000 .00

O+CH2(S)<=>H2+CO 1.500E+13 .000 .00

O+CH2(S)<=>H+HCO 1.500E+13 .000 .00

O+CH3<=>H+CH2O 5.060E+13 .000 .00

O+CH4<=>OH+CH3 1.020E+09 1.500 8600.00

O+CO(+M)<=>CO2(+M) 1.800E+10 .000 2385.00

LOW/ 6.020E+14 .000 3000.00/

H2/2.00/ O2/6.00/ H2O/6.00/ CH4/2.00/ CO/1.50/ CO2/3.50/ C2H6/3.00/ AR/ .50/

O+HCO<=>OH+CO 3.000E+13 .000 .00

O+HCO<=>H+CO2 3.000E+13 .000 .00

O+CH2O<=>OH+HCO 3.900E+13 .000 3540.00

O+CH2OH<=>OH+CH2O 1.000E+13 .000 .00

O+CH3O<=>OH+CH2O 1.000E+13 .000 .00

O+CH3OH<=>OH+CH2OH 3.880E+05 2.500 3100.00

O+CH3OH<=>OH+CH3O 1.300E+05 2.500 5000.00

O+C2H<=>CH+CO 5.000E+13 .000 .00

O+C2H2<=>H+HCCO 1.350E+07 2.000 1900.00

O+C2H2<=>OH+C2H 4.600E+19 -1.410 28950.00

O+C2H2<=>CO+CH2 6.940E+06 2.000 1900.00

O+C2H3<=>H+CH2CO 3.000E+13 .000 .00

O+C2H4<=>CH3+HCO 1.250E+07 1.830 220.00

O+C2H5<=>CH3+CH2O 2.240E+13 .000 .00

O+C2H6<=>OH+C2H5 8.980E+07 1.920 5690.00

O+HCCO<=>H+2CO 1.000E+14 .000 .00

O+CH2CO<=>OH+HCCO 1.000E+13 .000 8000.00

O+CH2CO<=>CH2+CO2 1.750E+12 .000 1350.00

GRI-Mech 3.0 (1999)

53 species

327 reactions

+Transport dataThermodynamic data

GRI-Mech 3.0, <http://www.me.berkeley.edu/gri_mech/>.

Cont’d

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Example of reaction path, methane oxidation 27

Reactant

Product

Inte

rme

dia

tes

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Laminar burning velocity and burning flux

Laminar flame speed, SL Laminar burning flux, r SL

28

Figures: Law, C.K., Combustion Physics, 2006.

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Structure of laminar one-dimensional premixed flame

0

500

1000

1500

2000

0.000

0.050

0.100

0.150

0.200

0.250

0 0.05 0.1 0.15 0.2x, cm

Tem

pe

ratu

re, K

Mo

le f

ract

ion

, -

CH4/air, f = 1

O2

CH4

Temperature

H2O

CO2

CO

29

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Approximate analysis, Mallard-Le Chatelier, 1880’s

• Region of conduction（ZONE I）and region of burning（ZONE II）

• Intuitive recognition for reaction zone thickness, laminar burning velocity

30

Glassman, Combustion, 1987.

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31

Delete

Incoming flow speed = reaction rate

Temperature increase of unburned gas is due to conduction heat from reaction zone

Delete

: overall one-step reaction

Pressure dependence of SL

Glassman, Combustion, 1987.

Approximate analysis, Mallard-Le Chatelier, 1880’sKAUST SS 2018

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Laminar flames with different inert gas

• Thermal diffusivities of Ar and

N2 approximately equal

• Since Ar is monoatomic gas, its

specific heat is lower than N2.

• Since heat release is the same,

flame temperature, Tf, Ar > Tf, N2

• Ar and He are both

monoatomic and thus their

flame temperatures are equal,

however, thermal diffusivity of

He is much larger than Ar.

Consequently, SL of He case is

much larger than Ar.

Clingman et al., Symp. (Int.) Combust. 4, 310, (1953).

32

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33Simplification of governing equations

Zeldovich, Williams, Clavin,

Liñán, Matalon,

Poinsot, T., Theoretical and

Numerical Combustion, 3rd eds.

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35Simplification leads to “master equation” of LPF

Y = YF YF1 θ =

Cp T − T1)

QYF1 =

T − T1

T2 − T1

YF1

∕ CpT2 −T1

ρ1sLdYFdx

=d

dxρD

dYFdx

+ 𝜔𝐹

ρ1Cp sL

dT

d𝑥=d

dx𝜆dT

dx−Q 𝜔𝐹

ρ1sLd Y+ 𝜃

dx=d

dx𝜆d Y+ 𝜃

dx

𝜃 + Y = 1

ρ1sLd𝜃dx

=ddx

𝜆

𝐶𝑝

d𝜃dx

−B1 T1 + 𝜃 T2 − T1

𝛽1𝜌 1 − 𝜃 exp −

Ta1

T1+θ T2−T1

𝜔T

Scaled variables

If Le = 1 𝐷 =𝜆

𝜌𝐶𝑝

Only one variable left: reduced temperature, progress variable

Chemical enthalpy + sensible enthalpy = Constant

Spalding, D.B., Proc. Roy. Soc.

London. Ser. A 240(1220) 83 (1957).

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T. Poinsot, Princeton SS Lecture note, 2015.

36Flame characteristics and related topics

• Laminar burning velocity

• Adiabatic flame temperature

• Flame stretch

• Flame quench

• Flammability limits

• Quenching diameter

• Excess enthalpy combustion

• Flame instability

• Mild combustion

• Micro-scale combustion

37Adiabatic one-dimensional premixed flame

• Ideal flame is hard to realize because…

• Effect of heat loss

• Effect of flow non-uniformity

• Effect of wall (Thermal and chemical)

• Intrinsic flame instabilities

• Thus, measurement of laminar burning velocity needs various ideas & technique

• Laminar burning velocity → (eigenvalue of the governing equations) essential for chemical time determination, kinetics developments, etc.

Adiabatic (1-D planar flame)X

T

Non-adiabatic (1-D planar flame)

T

X

? ?

Adiabatic 1D planar premixed flame

Lowry, W., et al., J. Eng. Gas Turb. Power 133: 091501 (2011).

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Laminar burning velocity, methane-air flame

(1),(4),(7) Chamber (2) Flat flame (3) Propagating tube (5),(6) Burner flame

(7)

38

Equivalence ratio, f

Lam

inar

burn

ing

velo

city,

cm

/s Methane-air, 0.1 MPa

Fundamentals of Combustion Phenomena, Ohm. 2001 in Japanese.

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Variation of measured laminar flame speeds

Egolfopoulos et al., Prog. Energ. Combust. Sci. 43 (2014) 36.

39

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40Measurements of laminar burning velocity

• Burner method

• Flat flame

• Outwardly propagating

spherical flame

• Counterflow flames

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Bunsen flame and laminar burning velocity

• Flame propagate to flow

stream with angle a

• Laminar burning velocity could

be obtained from a and

41

Kobayashi lab., TOHOKU U.

Flame front

Mixture


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𝑆𝑢 = 𝑈𝑢 sin 𝛼

𝑈𝑢

Burner stabilized flat flame

• Flame is stabilized above porous material where flow velocity profile is flat

• Once flame is stabilized, local flow velocity could be equal to laminar burning velocity

• Effect of heat loss from flame to porous material could not be ignored

• Effect of buoyancy is significant at low flow velocity

42

Figure: Law, C.K., Combustion Physics, 2006.

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Modern flat flame burner

• Effect of heat loss to the burner plate could be canceled

• High fidelity measurement of laminar burning velocity by flat flame is enabled

L.P.H. de Goey et al., Eindhoven TU, 2011-

43

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Counterflow premixed twin flames

• One dimensional flame

• No conductive heat loss

• Flow could be

characterized by an

unique parameter

– stretch rate

淀み面

火炎面

x

混合気

燃料

酸化剤＋

44

Flame fronts

Stagnation

plane

Mixture

(Fuel +

Oxidizer)

Commonly used basic flame geometry,

general characterization of flame

→ Flame stretch!

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Counterflow premixed flame and laminar burning velocity

Egolfopoulos et al., Prog. Energ. Combust. Sci. 43 (2014) 36.

45

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Flame stretch and Lewis number effect

• Lewis number: ratio

of mass and thermal

diffusions

With the increase of stretch

rate, flame temperature

increases if Le < 1 and

decreases if Le > 1

46


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𝐿𝑒 =𝛼

𝐷𝛼 =

𝜆

𝜌𝐶𝑝where

• Local minimum of axial velocity profile corresponds to burning velocity at given stretch rate

• Linear extrapolation to zero stretch rate provides stretch-free laminar burning velocity of given mixture

Law, Symp. (Int.) Combust. 22, 1381, (1988).

47Counterflow premixed flame and laminar burning velocityKAUST SS 2018

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Outwardly propagating spherical flame

• If a quiescent mixture is

ignited, outwardly

propagating spherical

flame is observed

• When the size of the

spherical flame is small,

effect of the pressure

increase can be negligible

• Laminar burning velocity

can be measured if the

effect of flame stretch is

considered

• Applicable to high pressure

CH4/air, f=0.65

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• Estimating relative flame

speed Su to the mixture from

nominal flame velocity Sb

• Density ratio was estimated

from temperature ratio

• Need to consider the effects

of other factors, in particular,

effect of flame radius

49Outwardly propagating spherical flame

Commonly used basic flame geometry

Simple but essential flame physics involved

Flame front

Burned gas

Mixture

Need to consider the effects of other factors,

e.g., ignition energy, stretch rate, etc.

→ Flame stretch!

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Stretch rate

• Effects of flow non-

uniformity, flame

curvature, and flame/flow

unsteadiness can be

described by the single

parameter

• Three factors for flame

stretch are aerodynamic

strain, flame curvature

and flame motion

Flame stretch rate

50

Law, C.K., Combustion Physics, 2006.Chung and Law, CNF 55(1), 123-125, 1984.

Matalon, CST 31(3-4), 169-181, 1983.

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Examples of stretched flames 51


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52Determination of laminar burning velocity by linear extrapolation

𝑘 =2

𝑅𝑓

𝑑𝑅𝑓

𝑑𝑡

Figure: Law, C.K., Combustion Physics, 2006.

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53

0.0 1.0 2.0 3.0 4.0 5.00.0

1.0

2.0

3.0

4.0

5.0

6.0

Time after Ignition t [ms]

Mean

Fla

me R

ad

ius

rm

[m

m]

H2/N2/AIRP0 =0.101MPa

T0 =298K

SL0 =25cm/s

:0.3, 11.4:0.5, 11.4

:H2

D =0.1mm

W =0.5mm

:0.7, 11.4:0.9, 16.2

f

:1.2, 193.6

Ei[mJ]

0 5 10 150.0

0.5

1.0

1.5

2.0

2.5

3.0

Mean Flame Radius rf [mm]

SL

l /

SL∞

[-]

H2/N2/AIR

P0=0.101MPa

T0=298K

SL0=25cm/s 0.3

0.50.70.9

f

1.0

Ei =53 mJ (f=1.0) Ei =35 mJ (f=0.9) Ei =11 mJ (f=0.3,0.5,0.7)

Ei =194 mJ (f=1.2)

1.2 D[mm] 0.1 1.2 W[mm] 0.5, 4

For Meso rf < 5 mm

forf =0.3 -0.9

forf=1.0 forf=1.2

Meso Macro

Derivation of LBV from outwardly propagating spherical flame

Theoretical prediction Experimental results

Chen, Burke, Ju, PCI 33, 1219 (2011). Nakahara, M., et al., PCI 34, 703 (2013).

Figures: courtesy of Prof. Nakahara of Ehime U.

𝑘 =2

𝑅𝑓

𝑑𝑅𝑓

𝑑𝑡

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54

Figures: Ju, Y., Princeton SS, 2017.

Chen, Burke, Ju, PCI 33, 2011.

Derivation of LBV from outwardly propagating spherical flameKAUST SS 2018

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Spherical propagating flame at high pressure conditions

Burke et al., Combust. Flame, 156-4, 2009, 771.

55

Lead to realize comprehensive H2/O2 kineticsBurke, M.P., et al., Int. J. Chem. Kinet. 44(7) 444 (2012).

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• Introduction

• S-curve

• Premixed flame



56

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Non-premixed flames

• Fuel and oxidizer initially

spatially separated

• If subsequent mixing is

not sufficiently fast, the

mixing and reaction occur

in thin reaction zone

• Fuel and oxidizer are

mainly transported

thorough diffusion

processes

57


FuelOxidizer

Temperature

FO

Mixing

layer

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Non-premixed flames

• a. Typical configuration of

non-premixed flame

• b. Fuel and oxidizer are

transported through

diffusion (+ convection).

Since reactions occur at

finite rate and reaction zone

thickness is finite, some

reactants are leaked

• c. Reaction of non-premixed

flame often regarded as

infinitely fast and thus

reaction zone is regarded

as a sheet and no leakage

of reactants from there

58


a.

b.

c.

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Counterflow non-premixed flames


established in

counterflow field or in

forward stagnation

region in front of a

porous cylinder

(Tsuji burner)

• one-dimensional

stretched flame for basic

flame study, structure,

extinction limits, etc.

http://yoshidaweb.web.fc2.com

59


Tsuji burner

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Energy Dynamics Lab. Tohoku U.

Structure of counterflow non-premixed flame

Stretch rate, 56 sec-1

Temperature and species concentration profiles were measured.

Contribute to the development of computational code, e.g., CHEMKIN.

Tsuji, Yamaoka, Symp. (Int.) Combust. 13, 723, 1971.

Tsuji, H., Prog. Energ. Combust. Sci. 8(2), 93, 1982.

60

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61

Non-premixed flame of methane and air

stabilized in a forward stagnation region

in front of a porous cylinder

Tsuji burner

Prof. Tsuji

Droplet combustion

• One of the representative

fundamental non-premixed

flames

• The world’s first scientific

experiments conducted

under microgravity (1950’s)

by Seiichiro Kumagai of

Univ. of Tokyo

• Find D2-law

• And…then

62

Isoda, Kumagai, Symp. (Int.) on Combust. 7, 523 (1958).

Kumagai, Isoda, Symp. (Int.) Combust. 6. 726 (1957).

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Droplet combustion in Space

• Droplet combustion has been extensively contributed to the understandings of spray combustion to date

• Finally, cool burning flames of free droplet observed in International Space Station (ISS) in 2008-2009 (Prof. F.A. Williams of UCSD & collaborators)

63

http://jacobsschool.ucsd.edu/news/news_releases/release.sfe?id=1548

https://www.youtube.com/watch?v=BxxqCLxxY3M

Nayagam, V., et al., Combust. Flame 162(5) 2140 (2015).

Nayagam, V., et al., Combust. Flame 159(12): 3583 (2012).

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http://jacobsschool.ucsd.edu/news/news_releases/release.sfe?id=1548

https://www.youtube.com/watch?v=BxxqCLxxY3M


• Introduction

• S-curve

• Premixed flame



64

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65Flame characteristics

• Flame quench

• Flammability limits

• Quenching diameter


• Flame instability

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0

0.5

1

0 0.2 0.4

Heat loss parameter, l

Bu

rnin

g ve

loci

ty p

aram

eter

, μ

𝜇2 ln 𝜇2 = − 𝑙

1 𝑒

1 𝑒

Theory of flame quench, thermal

Adiabatic (1-D planar flame)X

T

Non-adiabatic (1-D planar flame)

T

X

20

2 p

d T dTmc q L

dx dx

Flow direction

66

Adiabatic 1D planar premixed flame

Non-adiabatic 1D planar premixed flame

Zel’dovich, Y.B., Zhurn. Eksp. Teoret. Fiz. 11, 159 (1941).

Spalding, D.B., Proc. Royal Soc., Ser. A 240(1220) 83 (1957).

Clavin, P., Acta Astronautica 3(3): 223 (1976).

Williams, F.A., Combustion Theory, 1985.

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67

• Mixture is only

flammable within a

certain range of the

equivalence ratio

• What is the mechanism

of fundamental

flammability limits?

Equivalence ratio← Fuel lean Fuel rich →

Lam

inar

bu

rnin

g ve

loci

ty (

cm/s

)

Fundamental flammability limitsKAUST SS 2018

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68Flame quench and fundamental flammability limit

Burning velocity against mixture ratio.

a, experimental findings;

b, prediction of all theories neglecting heat losses;

c, prediction of present theory, taking account of heat losses;

d, prediction of Weinberg's theory, neglecting heat losses and radicle-

generation other than branching reaction.


What is the loss mechanism?

The question of a long time; solved by microgravity experiments in 1990’s.Part 2

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Quenching diameter

• Determined from the

ratio of heat generation

and heat loss

• Analogy with

flammability limit

2

2 2( ) ( 4)( )

4( ) ( )

p f u f

f

f f u

c T T dHeat lossH Nu d

Heat generation d h T T

2q fd e Nu

69

Part 3

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70Excess enthalpy combustion

Weinberg, F.J., Symp. (Int.) Combust. 15(1) 1 (1975).

a. Ordinary combustion

1→2→3→4→5

b. Excess enthalpy combustion

1→1’→2’→3’→3’’→4→5

T

X

12

34 5

1’2’

3’ 3’’

Adiabatic flame temp.

Ambient temperature

Weinberg, F.J., Combustion temperatures: The

future ?, Nature 233, 239 (1971).

• Higher maximum temperature than adiabatic flame temperature

• Wider flammability limits

• Fuels with low calorific values applicable Part 3

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71

Flame instability

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Spherical flames under intrinsic instabilities

• Not all spherically

propagating flames

are ideal

• Some are wrinkled

and cracked due to

intrinsic instability

• Diffusive-thermal

instability

• Hydrodynamic

instability54 mm

Law, C.K., Combustion Physics, 2006.

72

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• Hydrodynamic instability

Flame instabilities, phenomenology

Williams, Combustion Theory, 1985.

73

• Diffusive-thermal instability

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Joulin and Clavin, Combust. Flame 35, 139 (1979).Clavin, PECS 11, 1 (1985).

Sivashinsky, Acta Astronaut. 4, 1177 (1977).

Sivashinsky, Annu. Rev. Fluid Mech. 15, 179 (1983).

SABATHIER et al., Prog. Aeronaut.

Astronaut. 76, 246 (1981).

Theory

74

End of Part 1

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1Part 2: Flammability limit

• History

• Theory and experiment

• Counterflow flames

• Flame ball

• Toward comprehensive

combustion limit theory

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2History of study on combustion limits

Flammability limit

theory (Planar flame)

Low speed

counterflow flame

Flame ball

Flame ball was predictedBasic limit theory presented1950

The world first experiment

in microgravity (Kumagai)

Requirement for fire safety in coal mines1800

1990

2000

Drop tower（NASA, JAMIC)

Space experiments

2010

Large variations on

combustion limit study

Unified combustion limit theory

Lean burn

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3Flammability limit theory (1940’s-)

Concept of flammability limit for one-dimensional planar flame

Zel’dovich, Y.B., Zhurn. Eksp. Teoret. Fiz. 11, 159 (1941).


Clavin, P., Acta Astronautica 3(3): 223 (1976).

Williams, F.A., Combustion Theory, 1985.

0

0.5

1

0 0.2 0.4

Heat loss parameter, l

Bu

rnin

g v

elo

city p

ara

me

ter,

μ

𝜇2 ln 𝜇2 = − 𝑙

1 𝑒

1 𝑒

20

2 p

d T dTmc q L

dx dx

• Flammability limit

may be induced by

a certain heat loss

• What is loss

mechanism?

• Conduction loss?

Radiative loss? If

adiabatic, no limit?

What is the mechanism of fundamental flammability limit?

• Fact: mixture is only

flammable within a certain

range of equivalence ratio

• Loss mechanism?

4

Equivalence ratio← Fuel lean Fuel rich →

La

min

ar

bu

rnin

g v

elo

city (

cm

/s)


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×

5Conventional methods of combustion limit study

Constant volume

chamber

Propagation

tube

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6

COWARD, H.F. and JONES, G.W., Limits of Flammability of Gases and vapors, BUREAU OF MINES Bulletin 503, (1952).

Fire safety in mines, “standard” propagation tube

H2-air

• Flame propagation tube, Bureau of Mines, US

• Flammability limits significantly differ in the

upward and downward propagating H2-air flames

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7

COWARD and JONES, BUREAU OF MINES Bulletin 503, (1952).

CH4-airExperiments by propagation tube

• Flammability limits of the upward and

downward propagating flames not

significantly differ as hydrogen but still

significant effects of the tube directions

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8

Self Extinguishing Flames (SEFs) in microgravity

Ronney, P.D., Combust. Flame 62(2) 121 (1985).

Ronney, P.D. and Wachman, H.Y., Combust. Flame 62(2) 107 (1985).

• Self extinguishing flames

(SEFs) were observed in

microgravity

• Effect of ignition energy,

flame curvature and

radiative loss were

discussed

• SEFs could be

interpreted through

counterflow flames under

microgravity

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9Low-speed counterflow flames under microgravity

Fuel concentration at

extinction

Fla

me s

tretc

h r

ate-Heat losses

-Buoyancy

-Flame stretch

-Wall effect

-Curvature

淀み面

火炎面

x

混合気

燃料

酸化剤＋

Flame

Stagnation plane

Mixture

(Fuel +

Oxidizer)

Maruta, K., et al., Symp. Int. Combust. 26, 1283 (1996).

Maruta, K., et al., Japanese Symp. Combust. 33, 137 (1995).

Law, Egolfopoulos, Symp. Int. Combust. 23, 413 (1990).

Concept

Microgravity experiments

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Microgravity experiments at drop tower

10 seconds microgravity

during 490 meters free fall,

facility closed on 2003.

10

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11Counterflow flame experiments in the ten-second drop tower, CH4/air

Counterflow twin flames at small stretch rates under microgravity (mid 90’s)

Maruta et al., International Symposium on Combustion 26, (1996).

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Results of microgravity experiments

C-shaped curve for CH4 (unexpected!)

and monotonic curve for C3H8

12

0

10

20

30

0.45 0.5 0.55　　当量比（燃料の濃度）

火炎伸長率（速度に関するパラメータ）［1/s]

微小重力場実験

メタン／空気プロパン／空気

Flammability limits of

planar flames

C3H8/air

CH4/air


Fla

me s

tretc

h r

ate

[1/s

ec]

Equivalence ratio

Flammable

Non-

flammable

Flammable

Non-

flammable

Maruta, Yoshida, Ju, Niioka, Symp. Int. Combust. 26, 1283 (1996).

Maruta, et al., Japanese Symp. Combust. 33, 137 (1995).

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Ju, Guo, Maruta, J. Fluid Mech. 342 (1997)

Maruta et al., Int. Symp. Combust. 27 (1998)

13

淀み面

火炎面

x

混合気

燃料

酸化剤＋

Flame

Stagnation plane

Mixture

(Fuel +

Oxidizer)

Mass diffusion

Thermal diffusion

Experimental C-shaped extinction curve and comprehensive “G-curve”

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Maruta, Ju, Honda, Niioka, Symp. Int. Combust. 27, 2611 (1998)

14

Another extinction limit

appeared when radiative heat

loss is considered


Guo, Ju, Maruta, Niioka, Liu, Combust. Flame 109(4) 639 (1997).

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Another extinction limit

appeared when radiative heat

loss is considered

Despite low flame temperature,

volume effect makes the role

of radiative heat loss dominant


Guo, Ju, Maruta, Niioka, Liu, Combust. Flame 109(4) 639 (1997).

𝑟𝑓 = −𝐿

𝐿

𝑞𝑟𝑑𝑦 −𝐿

𝐿

𝑘=1

𝐾𝐾

ℎ𝑘𝜔𝑘𝑀𝑘𝑑𝑦

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If equivalence ratio was

changed, island responses with

different size were appeared





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Flame separation distance


Ju, Guo, Maruta, J. Fluid Mech. 342 (1997).

Buckmaster, J., Combust. Theory Model. 1(1): 1 (1997).Non-adiabatic (counterflow twin flames)

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Effects of Lewis number on extinction curves

G- to K-shaped transformation

19

Lewis number

Le = 0.67

Le = 1.0

Le = 1.25

Le = 1.43

Le = 1.82

Le = a/D

Ju, Guo, Maruta, Niioka, Combust. Flame 113, 603 (1998).

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Flammability limits of planar flames obtained but sublimit mixture is flammable …

20

Le = 1.0 Le = 1.43

0

10

20

30

0.45 0.5 0.55　　当量比（燃料の濃度）

火炎伸長率（速度に関するパラメータ）［1/s]

微小重力場実験

メタン／空気プロパン／空気C3H8/air

CH4/air


Fla

me s

tretc

h r

ate

[1/s

ec]

Equivalence ratio

Flammable

Non-

flammable

Flammable

Non-

flammable

• Limit of planar flame

≠ “flammability limit”

• Definition?

Maruta, Yoshida, Ju, Niioka, Symp. Int. Combust. 26, 1283 (1996).

Maruta, et al., Japanese Symp. Combust. 33, 137 (1995).

Ju, Guo, Maruta, Niioka, Combust. Flame 113, 603 (1998).

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21Peculiar flame in microgravity: Flame ball

Zel’dovich predicted （1944) stationary spherical flame only

sustained by heat and mass transports in molecular diffusions

and reaction without any convective flows

Flame ball

Flame ball （Predicted theoretically at first in 1940’s）

Zel’dovich

Mathematical analysis indicated that it is unstable

but radiative heat loss was not considered

Zeldovich, Y.B., Theory of Combustion and Detonation, NN Semenov, 71, 1944.

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22Flame ball solution, adiabatic

Flame ball

Zeldovich, Y.B., Theory of Combustion and Detonation, NN Semenov, 71, 1944.

0 =1

𝑟2𝑑

𝑑𝑟𝑟2𝑑𝑇

𝑑𝑟+ B exp −𝜃/2𝑇∗ 𝛿 𝑛 −

1

𝜃𝐹

0 =1

Le

1

𝑟2𝑑

𝑑𝑟𝑟2𝑑𝑌

𝑑𝑟− B exp −𝜃/2𝑇∗ 𝛿 𝑛

F = θR02Cp f

λQ, θ=

ECp

RQ

𝑑

𝑑𝑟𝑟2

𝑑

𝑑𝑟𝑇 +

1

Le𝑌 = 0

𝑇 +1

Le𝑌 = 𝑇𝑖 +

1

Le𝑌𝑖

𝑇𝑏 = 𝑇𝑖 +1

Le𝑇𝑎 − 𝑇𝑖 𝑅𝑧 =

𝑌𝑖𝜆 exp 𝜃/2𝑇𝑏

Le 𝐵𝐶𝑝

r < 1 T = T𝑏, Y = 0

r > 1 T = Ti +YiLe

1r

, Y = Yi 1 −1r

Deshaies, Joulin, Combust. Sci. Technol. 37, 99 (1984).

Buckmaster, Weeratunga, Combust. Sci. Technol. 35, 287 (1983).

• Stationary spherical

flame sustained by heat

and mass diffusions

• Stable only if radiative

heat loss exists

Discovery of flame ball

Ronney（1990) Observation of spherical flames

in microgravity experiments at 2.2 sec drop tower

Ronney（1993) Observation of the flames in

aircraft experiments, longer time microgravity

duration but with severe gravity fluctuations

Three essentials: microgravity, low Lewis number,

vicinity of flammability limits

Ronney（USC）+ Tohoku (1996) collaboration at

Japanese 10 sec drop tower (JAMIC)

steady and stable flame balls observed

Space experiments in the Shuttle, 1997 STS-

83/MSL-1, STS-94/MSL-1R, and 2003 STS-107

Ronney

23

Buckmaster, Joulin, Ronney, Combust. Flame 79, 381 (1990).

Ronney, Combust. Flame 82, 1 (1990).

Ronney, Symp. Int. Combust. 27, 2485 (1998).

Abid, M., et al., Combust. Flame 116, 348 (1999).

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Flame ball in aircraft, KC-135 24

Ronney, early 90’s

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25

Flame ball, drop tower in Japan

Microgravity experiments at 10 sec drop tower （～10-4G）

Late 90’s, USC + Tohoku, Combustion and Flame 116, 348 (1999).

26

Flame ball in Space Shuttle

Experiments in the Space Shuttle (STS-107, Ronney, 2003)

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27

Regime of flame ball and planar flame

Wu, M.-S., et al., Combust. Flame 116(3) 387 (1999).

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(a) (b)

Flammable regions of H2-air

counterflow premixed flame.

Point K is the flammability limit

of a planar premixed flame.

Guo et al., Combust. Theor. Model. 4, 459 (2000).

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28

Estimation of lean flammability limits by computations

• Radiative heat transfer

considered in energy

equation

• Case of heat loss only

(optically thin model)

• Case of heat reabsorption

(Grey, SNB, etc.)

Ju et al., Symp.(Int.) Combust. 27, 1998, 2619

Low-speed Counterflow Flame Experiments

under Microgravity for Constructing

Comprehensive Combustion Limit Theory

Kaoru MARUTA1,2

Collaborators: T. Okuno1, T. Akiba1, H. Nakamura1, T. Tezuka1, S. Hasegawa1, R.

Fursenko3, S. S. MINAEV2, M. Katsuta4, M. Kikuchi4

1: Tohoku Univ., 2: FEFU, 3: SB RAS, 4: JAXA

KAUST SS, 1 April 2018

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30Low-speed counterflow flame experiments in microgravity for comprehensive

combustion limit theory (2010-)

Constructing comprehensive combustion limit theory

which covers both conventional flames and flame ball

based on low speed counterflow flames under microgravity

Counterflow

flames Flame ball

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31Hypothesis for unified combustion limit theory

・If long and high quality microgravity condition is available,

counterflow flames with extremely low speed can be realized.

It enables flow condition close to stationary mixture for FB.

・Using heavy dilution gases, mixtures with low Lewis numbers

can be realized. (CH4/O2/N2 -> e.g., CH4/O2/Xe or Kr, CH4/O2/CO2)

淀み面

火炎面

x

混合気

燃料

酸化剤＋

FlameMixture

(Fuel +

Oxidizer)

Extremely low

speed flows +

Possible to observe both ordinary flame and flame ball?

Long and high

quality microgravity

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32Preliminary computations

GRI-Mech 3.0[1] without reactions of N (37 species, 221 reactions)

[1] http://www.me.berkeley.edu/gri_mech.

[2] Moore, Physical Chemistry, Tokyo Kagaku Dojin (1974).

[3] Ohno, Quantum Physical Chemistry, University of Tokyo Press (1989).

[4] NIST Chemistry Webbook (http://webbook.nist.gov/chemistry/).

• Collision: value of Ar in GRI-Mech 3.0

• Transport: Data of Moore[2] (Kr polarity: Ohno[3])

• Thermodynamic: NIST Chemistry Webbook[4]

Mixtures

Chemical kinetics

Fuel lean CH4/O2/Xe (Le ~ 0.5)

Fuel lean CH4/O2/Kr (Le ~ 0.7)

Pressure： 1.0 atm

Dilution ratio: fraction of O2 / fraction of inert = 0.141

(Fuel leanCH4/Air : Le ~ 1)

Xe and Kr parameters:

http://www.me.berkeley.edu/gri_mech

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L 𝑇 =1

𝑐𝑝

𝜕

𝜕𝜒𝜆𝜕𝑇

𝜕𝜒−1

𝑐𝑝

𝐾=1

𝐾

𝜌 𝑌k𝑉k𝑐𝑝k𝜕𝑇

𝜕𝜒−1

𝑐𝑝

𝐾=1

𝐾

𝜔kℎk𝑊k −1

𝑐𝑝𝑞𝑟𝑎𝑑

33Computations: counterflow flame

Premix based flame code[1]

･ Optically thin radiation model[1]

･ Domain: 10 cm

Energy equation

Radiation term

-5 5

Flame

Mixture Mixture

T

0

YreactantYreactant

Flame

Location, x (cm)

[1] Takase, K., et al., Combust. Flame 160, 1235 (2013).

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0 =1

𝑐𝑝

𝜕

𝜕𝑟𝜆Α

𝜕𝑇

𝜕𝑟−Α

𝑐𝑝

𝐾=1

𝐾

𝜌 𝑌k𝑉k𝑐𝑝k𝜕𝑇

𝜕𝑟−Α

𝑐𝑝

𝐾=1

𝐾

𝜔kℎk𝑊k −Α

𝑐𝑝𝑞𝑟𝑎𝑑

Premix based code

･Optically thin radiation model[1]

･Domain radius: 100 cm

･Definition of flame ball radius: peak of heat release rate

Energy equation

(A=4pr2)

Radiation term

Gas temperature T

rT

1

Reaction zoneBurned gas Unburned gas

T* :Burned gas temperature

T0 :Unburned gas temperature

Fuel fraction Y

rY

11

T0

T*

Reactants

Products＋Heat

34Computations: flame ball

Takase, K., et al., Combust. Flame 160, 1235 (2013).

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35C-shaped extinction curve: counterflow flames

.2 constX

XZ

Inert

O

CH4/O2/Xe mixture

CH4/O2/Kr mixture

OTM

300 K, 1.0 atm

0.141

0.1

1

10

100

1000

0.3 0.4 0.5 0.6S

tret

ch r

ate

at

exti

nct

ion

lim

it (

1/s

)

Equivalence ratio

Kr

Xe

Flammable

region

Radiative extinction

f = 0.37 f = 0.41

・C-shaped extinction curves both for Xe and Kr flames

・Flammable region: Xe flames (Le~0.5) > Kr flames (Le~0.7)


Radius of flame balls

.2 constX

XZ

Inert

O

CH4/O2/Xe mixture

CH4/O2/Kr mixture

OTM

300 K, 1.0 atm

0.141

0

0.1

0.2

0.3

0.3 0.4 0.5 0.6F

lam

e b

all

ra

diu

s (c

m)

Equivalence ratio

Kr

Xe

f = 0.34 f = 0.45

・Flame radius: Xe flames (Le ~ 0.5) > Kr flames (Le ~ 0.7)

・ER at limits: Xe flames (f = 0.34) < Kr flames (f = 0.45)

36


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0.1

1

10

100

1000

0

0.1

0.2

0.3

0.3 0.4 0.5 0.6

Str

etch

ra

te a

t ex

tin

ctio

n lim

it (

1/s

)

Fla

me

ba

ll r

ad

ius

(cm

)

Equivalence ratio

Flame ball Counterflow

.2 constX

XZ

Inert

O

CH4/O2/Xe mixture

OTM

T0=300 K, 1.0 atm

0.141

0.34 0.37

Counterflow flame and flame ball

Possible experimental procedure can be made by the diagram

37


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38Microgravity experiments by aircraftKAUST SS 2018

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Establish counterflow flames in microgravity

↓Quasi-steadily reduction of fuel

concentration in the mixture

Apparatus and experimental procedure

Counterflow

burner

8mm

VCR

Settling

chamber

Mass flow controllers

Notebook

PC

Oxidant

FuelIgniter

D/A A/Dconverter

and

(a) 対向流予混合火炎用

0.2

0.3

0.4

0.5

0.6

0.7

0 5 10 15 20

Eq

uiv

ale

nce

ra

tio

Time (s)

U Ud d

Premixed flames Flow

L

39


Okuno et al., Combust. Flame 172, 13 (2016).

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40

© 2004 Diamond Air Service Inc. All rights reserved.

Parabolic

motion

Experiment in cabin Outside view

Microgravity experiment by airplane, MU-300KAUST SS 2018

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41Result (Twin flames -> ball-like flame)Equivalence ratio gradually decreased (Kr case)

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1150

1200

1250

1300

1350

1400

0.3 0.4 0.5

Ma

xim

um

tem

per

atu

re (

K)

Equivalence ratio

Tmax_Counterflow_3.2s-1 (K)

Tmax_Flameball (K)

対向流平面火炎 (伸長率3.2 s-1)

Flame ball

42Flame transition: mechanism

Maximum temperature:

Experiment (CH4/O2/Xe)

Counterflow flames < Flame ball

Computation (CH4/O2/Xe)

Stretch rate: 3.2 s-1

.2 constX

XZ

Inert

O

OTM

T0=300 K, 1.0 atm

0.141

10.85 s

Extinction of

planar flame

10.89 s

Formation of

ball-like flame

(f = 0.46)

11.39 s

Disappeared in

next moment

10.89 s

Extinction of

planar flame

10.93 s

Formation of

ball-like flame

(ER ~ 0.45)

Counterflow flames

Flame ball

Stretch rate: 3.2 s-1


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43Result (Xe cellular flames)Stretch rate 2.5 (1/s), ER：0.58→0.3

44Sporadic cellular flames by 3D computations

Contour of C=0.15 (top) and concentration distributions in z=0 (bottom) for Le=0.3;

(a) h=0, a=0.067, (b) h=0.6, a=0.033 (c) h=0.8, a=0.033.

Fursenko et al., Combust. Flame 162, 1712 (2015).

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Unified combustion limit theory? 45

Regime diagram of flame transitions 46

0.3 0.4 0.5 0.6 0.7 0.8 0.90.01

0.1

1

10

100 1D limit

Planar flame

Wrinkled flame

Sporadic flame

Transition to ext.

Extinction

S4 S3

S2 S1

(a)

(b)

(c)

a

(1/s)

φ

Numerical prediction by diffusive-thermal model

CH4/O2/Xe

Equivalence ratio

Str

etch

rat

e


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0.3 0.4 0.5 0.6 0.7 0.8 0.90.01

0.1

1

10

100 1D limit

Planar flame

Wrinkled flame

Sporadic flame

Transition to ext.

Extinction

S4 S3

S2 S1

(a)

(b)

(c)

a

(1/s)

φ

CH4/O2/Xe


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CH4/O2/Xe

Equivalence ratio

Str

etch

rat

e

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49Flame structures (f = 0.42)

• Computations by 3D

thermo-diffusive model

• Flame structure of

counterflow flame, flame

ball and sporadic flames

are compared

• Temperature profiles

showed sporadic flame is

an intermediate mode of

combustion between

counterflow flame and

flame ball 0

0.2

0.4

0.6

0.8

1

1.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

-20 -15 -10 -5 0

Tem

per

ature

(-)

Fu

el c

on

centr

atio

n (

-)

Location (-)

SporadicFlame

Counterflow planar flame

Flame ball

Okuno et al., Combust. Flame, accepted

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50Summary

• Study on flammability limits was initiated due to safety

requirements and enormous amount of experimental data

obtained

• Scientific studies which were trying to clarify fundamental

limit mechanism have been conducted but data are with

large and unacceptable uncertainties

• Theory and experiments under microgravity significantly

contributed the understandings on fundamental limit

mechanisms (counterflow flame, flame ball, sporadic flame)

• Fundamental flammability limit mechanism is radiative heat

loss and this induced rich varieties of near-limit flame

phenomena with Lewis number effects

• Still many unknowns and open questions to be solved

51

End of Part 2

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Part 3: Flames under extreme conditions

• Flame quench


• Mild combustion

• Microcombustion (microscale combustion)

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Quenching diameter

• Determined from the

ratio of heat generation

and heat loss

• Analogy with

flammability limit

2

2 2( ) ( 4)( )

4( ) ( )

p f u f

f

f f u



2q fd e Nu

2

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Quenching diameter

• Spalding theory and microgravity

experiments suggest the flammability

limits are not an flame property but a

heat loss induced flame event

• What happen if heat loss is insulated,

compensated by heat recirculation or

high-temperature wall …

2

2 2( ) ( 4)( )

4( ) ( )

p f u f

f

f f u



2q fd e Nu

3

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4Flame in small channel

Length and time scales: L=(DT)1/2,T=L2/D Non-dimensional numbers: Kn, Pe, Da, Bi, Fo, Le …

Channel diameter

Wall thickness

Flame thickness

Effective radius

Mean free pathQuenching diameteretc….

Time scalesResidence timeReaction timeDiffusion time in solid/gasetc…

Heat recirculation Heat loss…

Fresh mixture

Burned gas

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5

Takeno, Sato, Combust. Sci. Technol. 20, 73 (1979). Ju, Choi, Combust. Flame 133, 483 (2003).

Hanamura, Echigo & Zhdanok, Int. JHMT 36, 3201 (1993).

Hoffmann et al., Combust. Flame 111, 32 (1997).

Wood, S. and Harris, A.T., Porous burners for

lean-burn applications, PECS 34, 667 (2008).

Excess enthalpy combustion

• Essential heat transfer condition for excess enthalpy combustion could be attained not only in Swiss roll geometry but also in radiant emitter and receiver, porous media, small channel, etc.

• Fundamental studies of EEC have been conducted

• Super-adiabatic combustion, super-lean combustion available

Kim, N.I., et al., Combust. Flame 141, 229 (2005).

Ronney, 3D Swiss roll

(2001).

Maruta,

Microcombustor (2005).

Echigo, Porous media (1990’s).

Weinberg (1972).

Ronney, P.D., Combust. Flame 135, 421 (2003).

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Exergy loss during combustion process

6

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Combustion device

Mixture Burned gas

Yoshida et al., Exergy engineering, Kyoritu, 1999, in Japanese.

Higher inlet and outlet temperatures preferable

Comprehensive understanding is challenging due to various conditions and parameters

Exergy loss during combustion process

Inlet temperature

Outlet temperature

Inlet temperatureOutlet temperature

7

Lo

ss o

f e

xe

rgy r

ate

, %

Lo

ss o

f e

xe

rgy r

ate

, %

Tsutsumi, Clean

Coal Day, 2010

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8

Exergy (or availability)

Exergy efficiencySecond law efficiency

Ratio of effective work to total exergy

max Carnot01Q

H

H H

TE Q

TL Q

flow 1 0 0 1 0 JE H H T S S T

he

rma

l e

ne

rgy,

Q

Exe

rgy,

E

Anergy

Reversible process

Exergy loss, Llost

Irreversible process

Work, L

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Normal combustion

802.3kJ

Exergy efficiency of normal combustion 9

ηH： Ratio of the utilized thermal

energy to the heat generation

ηE： Ratio of the utilized exergy to

the fuel exergy

ηE heat： Ratio of the utilized exergy to

the total exergy

Yoshizawa, J Combust. Soc. Japan 50, 2008

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AB

E

C

D

Exergy efficiency of excess enthalpy combustion

Combustion with

heat recirculation

10




the fuel exergy


the total exergy


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11Adiabatic, non-adiabatic & excess enthalpy flames

X

T

T

T

• We have made

scientific discussion

on adiabatic and

non-adiabatic

flames

• Third status is

excess enthalpy

flames and it would

be better for higher

thermal efficiency

Adiabatic

Non-adiabatic

Excess

enthalpy

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High Temperature Air Combustion Technology Project(HiCOT)

12

HiCOT test furnace by NFK Co. Ltd.

-Major industrial companies (IHI, JFE, Kobelco, Chiyoda, NFK, etc),

Major universities (Hokkaido, Tohoku, Tokyo, Toyohashi, Osaka pref.)

and National institute (AIST)

- Fundamentals phase in early 90’s and development phase till 2004

- Mild combustion, Flameless combustion

-Fundamental phase 1991-1999

-Development phase 1999-2004,

Budget: 50 million USD for 5 yr

By METI

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13

CO2 reduction up to 30％Extremely low NOx

emissions No combustion

noise Downsizing

High temperature air combustion technology (Concept and technical merits)

Oxygen concentration (%) Distance

HiCOT Distance

Conventional combustion

Tem

p.

Tem

p.

Tair < 600 ˚CTair > 800 ˚C

Conventional combustion

New combustion regime

Unstable combustion

regime

High Temp combustion

Dilu

ted

air

tem

per

atu

re (

˚C) Diluted air temperature and combustion mode

FOF

FOF

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R

N F K

“A” Burner

“B” Burner

Fuel

Fan

4-way

Valve

Exhaust

1100oC

1200oC

1200oC

200oC

20oC

Fuel1100oC

1200oC

Periodic Switching in

every 30 sec

A pair of

Regenerator

High Temperature Air Combustion Technology(Flameless combustion, Mild combustion)

14

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Ceramic Honeycombs for Regenerator Media

Square Type Cylindrical Type

R

N F K

15

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Air Temperature= 1080ºC

Air Ratio, =1.3

Air Temperature= 600ºC

Air Ratio, =2.0

HiCOTNon-HiCOT

R

NFK

16High Temperature Air Combustion Technology(Flameless combustion, Mild combustion)

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17

17

Exergy efficiency of excess enthalpy combustion

Combustion with

heat recirculation




the fuel exergy


the total exergy


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Typical configuration of

HICOT flame

Hot airHot air

Fuel jet

Fujimori et al., PCI 27, 1998

High speed fuel jet lifted flame

Advantage of lifted flame (Neither Premixed nor Diffusion flames)

18

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Achievements of HiCOT project

-Up to 1200 conventional furnaces converted into HiCOT furnaces

-Around 10 HiCOT incineration furnaces and steam reformers

(0.1 billion USD/furnace) in sales contracts in the world

-HiCOT coal boiler

19

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Microcombustion study

20

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21

Microcombustion study 1

Swiss roll combustor for

heat sources

Micro flow reactor with

controlled temperature profile

Heat recirculation for realizing small flame

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P roducts

R e a cta nts

C om bus tion

volum e

1 6 00 1 20 0 40 0 3 00 K5 0 0

14 0 0 60 0 50 07 001 6 0 0

Combustion

room

Fuel + Air

Exhaust gas

Exhaust gas

Fuel + air

Principle of Swiss roll microcombustor 22

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100 60~85

40~15

100 63.4

36.6

Heating by microcombustor

Heating by electric resistive heater

Total loss during power

generation and transmission loss

Heat recirculation

Usable for heating

Usable for heating

Primary energy

（Fossil fuel）

Exhaust

loss

Energy saving by microcombustor 23

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24Swiss roll microcombustor as heat sources

Disk-type heaters: D = 64, 46, 26, 20 mm

Surface temperature: 650 - 1250K

Temperature controllability: within 1 K at 1173K

Thermal efficiency as a heater: up to 85% 100W-1kW for various industrial heating, heat source for TE, TPV…..

Kim et al., CNF 141 (2005)Kim et al., PCI 31 (2007)

../../../../PrevDocuments/研究/研究広報/マイクロコンバスタTG/新燃焼技術.mpg

../../../../PrevDocuments/研究/研究広報/マイクロコンバスタTG/新燃焼技術.mpg

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Possible application of microcombustors (Proto-type industrial heating furnace)

70 % reduction of fuel consumption

• Baking and drying food

• Drying for painting

• Thermal treatment of glass panel, polymer film

and material with low melting point

Specification

Length 7 m

Width 0.9 m

Temperature Max 400℃

Control 3 zone

Number of

heaters68

Bed speed 0.6m～12m/min

25

×68

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26

Microcombustion study 2

Swiss roll combustor for

heat sources

Micro flow reactor with

controlled temperature profile

For fundamental kinetics studies

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Micro flow reactor with a controlled temperature profile

27

Stationary wall-temperature profile

Diameter of tube < conventional quenching diameter

Gas phase temperature dominated by wall temperature profile

Laminar flow and constant pressure

T

xoTest section xo

TmaxT

xoTest section xo

Tmax

dd

T

Mixture

Room temp

Tmax = 1300 K

d < Quenching

diameter

External heat source

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Premixture

Flame behaviors in a meso-scale channel with a prescribed temperature profile

Normal flame

Oscillatory flame

High velocity region

Weak flame

Low velocity region

Intermediate velocity region

28

Maruta et al., PCI 30 (2005).

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29Three kinds of flame responses

(1) Normal flame

(3) Weak flame

(2) Oscillatory flame

V=50cm/s

V=20cm/s

V=0.2cm/s-12 -10 -8 -6 -4 -2 0 2 4 6 8 10

0

20

40

60

80

100

120

= 1.0

Normal flame

FREI

Estimated points

of ignition

Location (mm)

Mean f

low

velo

city (

cm

/s)

400

600

800

1000

1200

1400

1600

Wa

ll Te

mp

era

ture

, Tw (K

)Ignition

Extinction

Tw

Flow

Normal flame, oscillatory flame, weak flame

CH4/air

Maruta et al., PCI 30 (2005)

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30Theoretical S-shaped response

V

v

Stable

xStable

v

Unstable

Flow

Two stable and one unstable solutions were predicted theoretically

Minaev et al., Combust. Theory Model. (2007)

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31

Stable branch

Stable branch: weak flame

Unstable branch

timeChemical

time residense Flowa D

• Normal flame:

preheated premixed

flame

• Oscillatory flame:

flames with

repetitive extinction

and ignition, FREI

• Weak flame: stable

weak flame which

represent ignition

Analogy between S-curve and conventional Fendell-curve

Da: Damköhler number

Max

imu

m t

emp

erat

ure

Ign

itio

n

Exti

nct

ion

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32Lower limit of weak flames identified

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

0

5

10

15

20

25

30

Tem

pera

ture

diffe

rence (

K)

Mean flow velocity (cm/s)

= 1.2

= 1.0

= 0.85

= 0.6

Tg - Tw

At V = 0.2 cm/s, Tw = 1225 K, Tg-Tw< 2 K

Extremely small temperature increase near the limit

Flame position close to the ignition point

Lowest flame temperature → ignition temperature

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.00

10

20

30

Tem

pera

ture

diffe

rence (

K)

Mean flow velocity (cm/s)

Tg-T

w

Experiment

Computation

Tsuboi et al., PCI 31 (2009).

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33Limit mechanism

Species dissipation at low velocity region significantly

larger than that at higher velocity region

Lower limit of weak flame by diffusive dissipation

5.0 5.5 6.0 6.5 7.0 7.5 8.0-1.0x10

-3

-5.0x10-4

0.0

5.0x10-4

1.0x10-3

1.5x10-3

2.0x10-3

Flu

x (

g/c

m2s)

Location (cm)

OH flux (Vm=134cm/s)

Diffusion

Convection

4.0 4.5 5.0 5.5 6.0 6.5 7.0-1.2x10

-6

-1.0x10-6

-8.0x10-7

-6.0x10-7

-4.0x10-7

-2.0x10-7

0.0

2.0x10-7

4.0x10-7

Flu

x (

g/c

m2s)

Location (cm)

OH flux (Vm=1.82cm/s)

Diffusion

Convection

V =134 cm/s V =1.8 cm/s

OH flux by convection & diffusion

Tsuboi et al., PCI 31 (2009).

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34Three flames are utilized for:

(1) Normal flame

(3) Weak flame

(2) Oscillatory flame

Measurements of laminar burning

velocity of highly preheated mixtures

Investigations of non-linear dynamics of

given fuels

Investigations of ignition relevant

properties of various fuels, validation

and modifications of kinetics,

particularly at low temperature

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35Triple weak flames, n-heptane

U = 3 cm/s

Triple stationary weak flames observed

Weak flame location insensitive to flow velocity

= 1

Yamamoto et al., PCI 33

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Code PREMIX-based

Reaction scheme: n-heptane, reduced mechanism from LLNL

(159 species, 1540 steps)

Conditions: Stoichiometric gaseous n-heptane/air mixture

Experimental wall temperature profile was provided as Tw(x)

Gas-phase energy equation

Heat transfer with the wall

Flame position: Peaks of heat-release-rate (HRR) [W/cm3] profile

Computation (one-dimensional)

Seiser et al., PCI 28 (2000)

36

Μ𝑑𝑇

𝑑𝜒−1

𝑐𝑝

𝑑

𝑑𝜒𝜆Α

𝑑𝑇

𝑑𝜒+Α

𝑐𝑝

𝐾=1

𝐾

𝜌𝑌k𝑉k𝑐𝑝k𝑑𝑇

𝑑𝜒+Α

𝑐𝑝

𝐾=1

𝐾

𝜔kℎk𝑊k −Α

𝑐𝑝

4𝜆𝑁𝑢

𝑑2𝑇𝑤 − 𝑇 = 0

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U = 3 cm/s

Three-stage heat releases

Computational


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U = 3 cm/s

Three-stage heat releases


Computational


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300

400

500

600

700

800

900

1000

1100

1200

1300

0

5

10

15

20

25

3.5 4 4.5 5 5.5 6

Wa

ll t

em

pera

ture

[K

]

Mo

le f

ra

cti

on

[%

]

x [cm]

O2

CO2

CH2O×10 CO

CH4×20

n-C7H16×10

H2O2×10

Tw

U = 2.0 cm/s

Computational species profiles 39

Three peaks of heat release rateYamamoto et al., PCI 33

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300

400

500

600

700

800

900

1000

1100

1200

1300

0

5

10

15

20

25

3.5 4 4.5 5 5.5 6

Wa

ll t

em

pera

ture

[K

]

Mo

le f

ra

cti

on

[%

]

x [cm]

O2

CO2

CH2O×10 CO

CH4×20

n-C7H16×10

H2O2×10

Tw

LTO: CH2O, H2O2, CO, CH4 produced

U = 2.0 cm/s

Computational species profiles

First HRR peak

40


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300

400

500

600

700

800

900

1000

1100

1200

1300

0

5

10

15

20

25

3.5 4 4.5 5 5.5 6

Wa

ll t

em

pera

ture

[K

]

Mo

le f

ra

cti

on

[%

]

x [cm]

O2

CO2

CH2O×10 CO

CH4×20

n-C7H16×10

H2O2×10

Tw

U = 2.0 cm/s

CH2O + OH ⇒ HCO + H2O

H2O2 (+M) ⇒ 2OH (+M) HCO + O2⇒ CO + HO2


Partial oxidations:

Second HRR peak

41


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300

400

500

600

700

800

900

1000

1100

1200

1300

0

5

10

15

20

25

3.5 4 4.5 5 5.5 6

Wa

ll t

em

pera

ture

[K

]

Mo

le f

ra

cti

on

[%

]

x [cm]

O2

CO2

CH2O×10 CO

CH4×20

n-C7H16×10

H2O2×10

Tw

U = 2.0 cm/s

Full oxidations: CO + OH ⇒ CO2 + H


Third HRR peak

42


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0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

0

5

10

15

20

25

300 500 700 900 1100 1300

Ma

ss c

on

cen

tra

tio

n o

f C

H2O

[%

]

Vo

lum

etr

ic c

on

cen

tra

tio

n [

%]

Wall temperature [K]

O2

CO2

CH2O

CO

CH4×20

300

400

500

600

700

800

900

1000

1100

1200

1300

0

5

10

15

20

25

3.5 4 4.5 5 5.5 6

Wa

ll t

em

pera

ture

[K

]

Mo

le f

ra

cti

on

[%

]

x [cm]

O2

CO2

CH2O×10 CO

CH4×20

n-C7H16×10

H2O2×10

Tw

Measurement by GC

Measurements and computations

Three-stage oxidation process was

confirmed by gas sampling experiment

(U = 2.0 cm/s)

Computations

43


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44Interpretation of triple weak flames

Conventional two-stage ignition converted into steady,

three-stage, spatially-separated weak flames in MFR

Cool flame

Hot flame

Hea

t re

leas

e ra

te

time

Flow direction

PRF0

PRF20

PRF50

PRF100

700 800 900 1000 1100 1200Wall temperature (experiment) [K]

-1.5 -1.0 -0.5 0 0.5Location [cm]

Flow direction

PRF0

PRF20

PRF50

PRF100


-1.5 -1.0 -0.5 0 0.5Location [cm]

n-heptane/air = 1

1 mm

Ignition in

RCM and ST

(transient)

Cool flame Separated hot flames

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45MFR applied for gasoline PRF

n-heptane + iso-octane (PRF)

Appearances of multiple weak flames

represent Research Octane Number

Flow direction

PRF0

PRF20

PRF50

PRF100


-1.5 -1.0 -0.5 0 0.5Location [cm]

= 1U0 = 2 cm/s

Flow direction

PRF0

PRF20

PRF50

PRF100


-1.5 -1.0 -0.5 0 0.5Location [cm]

1 mm

Hori, et al., CNF 2012

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U=1.2 cm/sec

Weak flames at different RON

Significant LTO in smaller RON

Weak flame behaviors reproduced

46

Computation

Hori, et al., CNF 2012

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Flow direction

PRF0

PRF20

PRF50

PRF100

700 800 900 1000 1100 1200

Wall temperature (experiment) [K]

-1.5 -1.0 -0.5 0 0.5Location [cm]

(a)

(d)

Flow direction

700 800 900 1000 1100 1200Wall temperature (K)

2 mm

120

Flow direction

PRF0

PRF20

PRF50

PRF100

700 800 900 1000 1100 1200

Wall temperature (experiment) [K]

-1.5 -1.0 -0.5 0 0.5Location [cm]

methanetoluene

propane

ethane

n-heptane, PRF 0

iso-octane, PRF 100n-butane

PRF 50

PRF 20

120

112

108

100

94

50

20

0

RON

Weak flame appearances for various RON

Weak flame locations: monotonic function of RON

Second weak flame: visible when RON < 100

First weak flame: visible when RON < 20

P = 1 atm

47

Hori et al., CNF 159, 2012.Hori et al., PCI 34, 2013.Kamada et al., CNF 161, 2014.

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Structure of a separated cool flame in MFR 48

0

0.1

0.2

0.3

0.4

0

0.05

0.1

0.15

0.2

0.25

5 6 7 8 9 10 11 12 13M

ole

fra

ctio

n (

-)

HR

R (

J/s/

cm3)

1st flame

nC7H16×10

O2

H2O2×10

CH2O×10

CO×10

CO2×10

(cool flame)

KUCRS mech. Location (cm)

600 700650 600550

Wall Temperature [K]

Tatsumi et al., Heat Transfer Symposium 2017.Tatsumi et al., TFEC9, 2017.

Vertical MFR

Small temperature gradient

Symmetry & higher resolution

KUCRS mech.

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49Structure of a cool flame, computation

600 700650 600550

Conditions : nC7H16/air, f = 1, P = 1 (atm), V = 2 (cm/s), Exposure time 30 (minutes)

Wall temperature (K)

0

0.2

0.4

0.6

0

0.01

0.02

5 6 7 8 9 10 11 12 13 HR

R (

J/s/

cm3)

0

0.2

0.4

0.6

0

0.01

0.02

5 6 7 8 9 10 11 12 13

Mo

le f

ract

ion (

-)

Location (cm)

00.6

00.02

KUCRS mech.

LLNL mech.

nC7H16

H2O2CH2O

nC7H16 H2O2

CH2O

Tatsumi et al., Heat Transfer Symposium 2017.Tatsumi et al., TFEC9, 2017.

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50Reaction paths in a cool flame

RH

R

ROO

QOOH

OOQOOH

OQ-HOOH Cyclic ethers

Aldehydes + ester or ketone group

Alkenes + ester or ketone group

CH2O, H2O2

R : C7H15

Q : C7H14

Q-H : C7H13

(Ketohydroperoxide)

OQ-HO

← OH

← O2

→ OH

→ OH← OH

← O2

→ OH

Radical branching path

Radical propagation path

CO, CO2Tatsumi et al., TFEC9, 2017.

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56PRFs, ultra lean, higher resolution

Vertical-type reactorGrajetzki, et al., 36 Symp, WIPP. 2016.Grajetzki, et al., COMODIA, 2017.

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57CH4, ultra lean and Xe dilution

Okuno et al., PCI 36.

Conducted for analyzing

microgravity experiments

on interaction between

flameball and

counterflow flames

Fuel: CH4; O2/Inert = 0.141; = 0.3

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LIF for CH2O and OH applied 58

Shimizu et al., Energ. & Fuels 31, 2017.

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59LIF of CH2O & OH and Chemiluminescence methane/air

Shimizu et al., Energ. & Fuels 31, 2017.

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Soot and PAH formations at temperature below 1400 K

60

CH4 CH3

CH2O

HCO

CO

CO2

CH3O

C2H6

C2H3

C2H2

C2H4

C2H5

CH2CHO

CH2COHCCO

+ CH3(+M)

+H

+OH

+ CH3

+ HO2

+O

+OH

+H

+O

+ HO2

+O2

+O2

+(M)

+H2O

+OH

+HO2

+O2

+(M)

+OH

+H

+ CH3

+O

+OH

+H

+CH3

+O

+(M)

+O2

+(M)

+O2

+O2

+H

+OH

+(M)+O

+O

+ HO2

Dubey et al., CNF 174, 2017.

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Soot and PAH formations at temperature below 1400 K

61

Dubey et al., CNF 174, 2017.

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62Effect of radical quenching at wall

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

0.045

0.05

0.7 0.8 0.9 1 1.1 1.2 1.3

Mo

le f

ract

ion

[-]

φ

Inert wall

Quench wall

Experiment

Inert wall (computation)

Quench wall (computation)

Experiment

• CO mole fraction of burned gas:

Quench case > Inert case

• Experimental results agree with Inert case

→ radical quenching effect negligible

Inert: GRI3.0Quench: GRI 3.0 + Raimondeau

CH4/air; = 1; d = 1.5 mm, 1 atm

Kizaki, et al., PCI 35 (2015).

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63Quantitative measurement of wall chemical effect

Quartz plate Coated plate

20 mm

Thermocouple hole

• 100 nm-thick thin films on quartz plate

Metal: Sputtering/Arc plasma gun

Al2O3: Atomic Layer Deposition

Saiki, Fan & Suzuki,

Combust. Flame

(2015).

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Micro flow reactor with controlled temperature profile

64

Micro flow reactor with controlled temperature profile

would be a new platform for study on chemical kinetics

particularly for low temperature conditions

Acknowledgements

IHI, IIC, HONDA R&D, MAZDA

IHI, NEDO, HITACHI, TOKYO GAS, JSPS, JST

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Applications of MFR for future

By MEMS(?) MFROn board combustion controlOn board fuel reformingEfficient engines with higher fuel flexibility

Fuel reforming for reaction controlChemical reaction control designing

MEMS MFR+ECU

65

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66

Let us work together for tomorrow through clean combustion science & technology!

Thank you very much!

67

End of Part 3

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