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Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
ディーゼル燃焼場におけるすす粒子生成過程と Time-Resolved LII による
火炎中すす粒子計測
学術フロンティア「次世代ゼロエミッション・エネルギー変換システム」技術セミナー「エンジン排気微粒子の健康影響と計測技術および生成・排出過程」
1.背景&研究目的2.化学反応動力学によるすす生成過程の解析3.LIIによる燃焼火炎場のすす粒子測定
同志社大学大学院 工学研究科 千田 二郎2006.3.13
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Emission reduction approachesMore regulation on particle matter emission from diesel engine is gradually conducted
Recently…
Regulation on particulate matter emissions from diesel vehicles
-Aftertreatment technologiesDPF
-Combustion MethodHCCIMK CombustionLow temp. rich combustion
-Fuel modificationOxgenated fuels Biodiesel fuels
-Improving atomizationand turbulent mixing
High pressure fuel injectionsmall orifice nozzle
Recent Research Attempts against the Emission Regulation
JAPAN
EU
USA
0
0.05
0.10
0.15
0.20
0.25
1998 20102000 2002 2004 2006 2008
PM [
g/kW
h]
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
(D. B. Kittelson, J. Aerosol Sci, Vol.29, No.5/6, pp.575-588, 1998)
Typical particle diameter distribution
Mass weighting Number weighting
Nucleimode
NanoparticlesDp<50nm
Ultra fine particlesDp<100nm
Fine particlesDp<2.5mm
PM10Dp<10mm
Accumulationmode
Coarsemode
0.001 0.010 1.0000.100 10.000Diameter [ m]
Nor
mal
ized
con
cent
ratio
n dC
/Cto
tal/d
logD
p
Nanoparticles (dp<50nm)ex.) Soot, SOF
→ Serious health damageLung cancerbreathing problem
due to low mass concentration→Nanoparticles is unregulated
High number concentration
Investigate soot formation characteristic focused on soot volume fraction and particle diameterin diesel spray flame Investigate effects of various parameters on particulate characteristics
Objectives
Back ground of this study
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Soot Formation Processes in Detailed Model
Rea
ctio
n tim
e (a
few
milli
seco
nds)
Gas phase reaction
(2) Primary particle formation
(1) Initial PAH formation
Nucleation
PAH growth
Surface growthCoagulation
Agglomeration
(3) Soot particle formation
Fuel O2
H2
H2OCO2
SootModel
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Conceptual Model of Diesel Jet Flame(Dec, SAE Paper 970873, 1997)
Temporal sequence of auto-ignition & premixed combustion phase
Chemiluminescenceemission region
Auto-ignition
PAH & soot formation
Diffusion flame
Flesh oxygen entrainment
Lift-off lengthRich fuel / air
mixture st=20~30%Products of rich combustion
CO, UHC & particulates
NOx
CO2 & H2O
Soot concentrationHighLow
0 10 20
Scale
Quasi-steady combustion phase
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Fuel droplets
Fuel vapor
OH formingregion
Air entrainment
Soot precursor(PAHs)
Soot growth regionLarge diameter
Low number densityT=2000-2100K
=0.7-1.0
Young sootSmall diameter
High number density
Soot oxidation regionT=2200-2400K
High concentrationof OH
Head vortex
Conceptual model of diesel combustionby Aizawa/Kosaka/Kamimoto in TIT
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
fuel: n-heptane, Tamb=900[K], amb=16.2[kg/m3], Xo2=17%, Pinj=70[MPa]D
ista
nce
from
noz
zle
[mm
]20
40
80
60
10020
40
80
60
100
(167) (14) (4) (4) (6)
1.4ms 2.0msTASI= 2.5ms 3.0ms 4.0ms
dp
fv
Low HighSoot volume fraction: fvParticle diameter: dp [nm] 1000
Distribution of soot volume fraction and soot particle diameter in diesel jet flame obtained by Time-resolved LII
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
7
6
5
4
3
2
1
01000 1400 1800 2200 2600 3000
Temperature [K]
Equi
vale
nce
ratio
1%5%10%15%
20%
25%
Soot
5000ppmNO
Low temp. rich combustion [Akihama et al., SAE Paper 2001-01-0655]
MK combustion[Kimura et al., SAE
Paper 2001-01-0200]
500ppm
HCCI
Desirable path[Kamimoto et al.,
SAE Paper 880423]
Combustion Mode in Φ- T Map
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
含酸素燃料を用いた無煙ディーゼル燃焼法の化学反応論的解析
- Detailed Chemical Kinetic Modelingof Smokeless Diesel Combustion
with Oxygenated Fuels –
北村・伊藤ら
非定常噴霧燃焼場のすす粒子生成挙動の解析
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Oxygen Impact on Particulate Emissions
(Miyamoto et al., Int. J. Engine Research, 1-1, pp.71-85, 2000)
Main OxygenateDGM: [CH3OCH2CH2]2O
Operating Conditionall = 1.0
EGR ratio: 30 vol%
Bosc
h sm
oke
[%]
80
60
40
20
032 34 36 38 40
Oxygen content in fuel [% by mass]
Using highly oxygenated fuel1. Stoichiometric2. Non-sootingcombustion can be realized!!
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
First aromatic ring formation
C2H3+C2H2 [C4H5]#
C4H4 n-C4H3+H-H2
C2H2
n-C4H5+ C2H2
+H-H2
+H
High temperature route
Low temperature route
C3H3+C3H3 c-C6H6 CC
H
+C2H2
-H+H-H2
+C2H2
-H+H
CC
H
-H+C2H2
HACA reaction sequenceRing-ring condensation
+
+H -H2
+C2H2
-H+H
Combination of resonantly stabilized radicals
+ -H2
+ -H2
Reaction Model of Soot Formation
Step.1 Gas Phase Chemistry
n-Heptane fuel
DME fuelDMM fuelMeOH fuel
MB fuel
Fuel chemistryHACA reaction sequence
Ring-ring condensation
Combination of resonantly stabilized radicals
PAH growth chemistry
Particle inception
Particle coagulation
Surface growth and oxidation
PAH condensation
HH2C2H2
O2 OH
Step.2 Soot Formation Model
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Chemkin-Ⅲ SENKINコード低温酸化・高温酸化・熱分解~7環PAH生成モデル
・n-ヘプタン反応モデル—Curranらのモデル・MarinovらのPAH生成モデル(C4以下の低級炭化水素から
4環芳香族までの分子成長反応・CurranらのDMEモデル、Marinovらのエタノールモデル・Fisherらのメチルブタノエート酸化反応モデル・Dalyらのジメトキシメタン酸化反応モデル
すす粒子生成モデルはFrenklachらのモーメント法による
粒子生成モデル・HACAメカニズム-芳香族環への水素引抜き-アセチレン付加反応・FrenklachらのPAH生成モデル
Gas Phase Chemistry – 素反応モデル
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Expression of soot yield, particle diameter and soot volume fraction
ini
1MSY mSoot yield・・・・・・・・・・・・
1/3
c 1soot
soot 0
M6md MParticle diameter・・・・・・
3soot
v 0dF M6Soot volume fraction・・・
0soot MNParticle number・・・・・・・
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
10
7.5
5
2.5
0 10.75
0.50.25
01400 1600 1800 2000 2200
Shock tube experiments (Kellerer’s)
1.2ms0.9ms0.5ms0.3ms0.1ms
Calculations 1.2ms
0.9ms0.5ms0.3ms
0.1ms
Fv [ppm
]F v
[ppm
]
Temperature [K]
Model Validation I: Temperature Dependence of Soot Formation
(fuel: benzene, =5, p=3 MPa, reaction time: t=0.1~1.2 ms)
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Model Validation II: Pressure Dependence of Fv, dsoot, Nsoot
0 1 2 3 4 5 6 7Pressure [MPa]
43210
dsoot [nm
]Shock tube experiments (Kellerer’s)
Exp. (Fv x 1/6)Model
86420
Nso
otx
1012
[par
ticle
s/cm
3 ]
2.01.51.00.5
0
F v[p
pm]
Exp. (dsoot x 1/8)Model
Exp. (Nsoot x 10)Model
(fuel: toluene, =5, T=1600 K, p=3 MPa, reaction time: t=1.5 ms)
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
5
4
3
2
1
0
Equi
vale
nce
ratio
1000 1500 2000 2500Temperature [K]
Particle diameter
Calculations5nm
40nm
Model Validation III: Sooting Limit on EquivalenceRatio - Temperature Diagram
(fuel: toluene, p=0.5 MPa, reaction time: t=4.0 ms)
Calculations
9x1012/cm3
1x1012/cm3
Particle number density
1%5%
10%
15%
20%
Calculations
Soot yield
Experiments= Wang , et al.
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Fuel Consumption Process in n-Heptaneand DME Reactions (T=900 K, p=8 MPa, =4)
(a) n-Heptane (C7H16) reactions
0.4
0.3
0.2
0
0.5
500 100 150
N2H2
CO
CH4
C2C3
Aldehydes
Time [ s]
0.1
O2
n-C7H16
H2O
CO2
H2O2
AromaticsC4
100015002000
Inte
grat
ed m
olar
frac
tion
of
gas-
phas
e sp
ecie
sTe
mp.
[K]
(b) DME (CH3OCH3) reaction
100015002000
0.6
0.5
0.4
0.3
0.2
0.1
0
Time [ s]
Tem
p. [K
]
N2 H2
CO
CH4
AldehydesO2
H2O
CO2
H2O2
CH3OCH3 C2
0 20 60 10040 80
Inte
grat
ed m
olar
frac
tion
of
gas-
phas
e sp
ecie
s
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Chemical Role of Oxygenated Fuels on PAH Suppression
これまでの含酸素燃料の基礎解析によると、PAH生成およびその前駆物質であるC2,C3などの低級炭化水素生成
の抑制特性として、燃料構造が影響する。
① 主要反応生成物が重要アセチレン、エチレンなどの多環化物質は促進アルデヒド類は抑制に働く
② 酸素原子に由来するOHラジカルによる酸化分子成長反応を抑制
③ アルデヒド類はHCOラジカルを介して水素原子を生成ベンゼン前駆体のプロパルギルラジカルの水素引き抜きベンゼン生成を抑制
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Oxygenated Fuels Examined
Oxygenates(Code name)
Oxygen content[% by mass]Molecular equation
Methanol(MeOH) CH3OH 50
Dimethyl ether(DME)
34.8
Dimethoxy methane(DMM) 42.1
31.4Methyl butanoate
(MB)
CH3OCH2OCH3
CH3OCH3
CH3(CH2)2(CO)OCH3
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Effect of Fuel Type on PAH Formation
(p=10 MPa, [C]=4.21x1019~1.26x1020 atoms/cm3 ,reaction time: t= 3ms, isometric pyrolysis reaction)
50
40
30
20
10
01000 1500 2000 2500
Initial temperature [K]
PAH
yie
ld [C
PA
H/C
fuel
%] n-Heptane
MBDMEDMMMeOH
(a) PAH yield (1000 ~ 2400 K)
50
40
30
20
10
00 20 40 60Oxygen content [% by mass]
PYm
ax[%
]
10 30 50
n-Heptane
MB
DME
DMM MeOH
(b) PAH yield (bell peak temp.)
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
*すす生成のベル型温度依存性・低温域では熱分解による低級不飽和炭化水素の生成が遅れ、PHA抑制・高温域では分子成長反応の逆反応であるPAHの分解可能が促進
ギブス生成自由エネルギの観点でも、1500K以上ではPAHよりアセチレン
などの低級不飽和炭化水素が安定
*ベル型分布のリーン側での低温側シフト(外部酸素)・燃料の酸化反応の寄与度が増加し、初期に900K程度の低温でも酸化後の
平衡温度が1600-1700Kに達する
*ディーゼル噴霧火炎内部でのすす生成の推定・低燃料噴射圧力条件:低い空気導入率
最大PAH生成温度域は1700K程度の高温噴霧外縁部の拡散火炎近傍ですす生成
・高燃料噴射圧力条件:高い空気導入率噴霧内部の当量比4程度の希薄な領域で900-1000KでPAH最大生成
噴霧中心部で活発なすす生成が生じる
Chemical Role of Molecular Oxygen and Oxygenate on PAH Suppression
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Particle Number Density Map as a Function of and T for Three Fuels
765432101300 1700 2100 2300
Temperature [K]
Equi
vale
nce
ratio
(a) Benzene reactions
3x1013
/cm3
3x1012/cm3
765432101300 1700 2100 2300
Temperature [K]
Equi
vale
nce
ratio
(b) n-Heptane reactions
3x1013/cm3
3x1012/cm3
765432101300 1700 2100 2300
Temperature [K]
Equi
vale
nce
ratio
(c) DME reactions
9x1012/cm3
3x1012/cm3
(P=6 MPa, reaction time: t=2 ms)
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
(P=6 MPa, reaction time: t=2ms)
5nm 40nm
80nm
100nm
120nm765432101300 1700 2100 2300
Temperature [K]
Equi
vale
nce
ratio
(a) Benzene reactions
5nm40nm
80nm
765432101300 1700 2100 2300
Temperature [K]
Equi
vale
nce
ratio
(b) n-Heptane reactions
5nm
40nm
765432101300 1700 2100 2300
Temperature [K]
Equi
vale
nce
ratio
(c) DME reactions
Particle Number Density Map as a Function of φ and T for Three Fuels
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Variation of Soot Formation Limits among Different Type of Fuels on -T Diagram
(defined as 1% soot yield)
Temperature [K]
7
6
5
3
4
2
1
01300 1700 2100 2500
Equi
vale
nce
ratio
C/O
atomic ratio
2.5
2.0
1.5
1.0
0.5
0.0
benz.
0.0
2.0
1.5
1.0
0.5
n-hep.
0.0
1.0
0.5
DME
n-Heptane
DME
Benzene
Low temp. limitLow temp. limit
Critical equivalence ratioCritical equivalence ratio
High temp. lim
it
High temp. lim
it
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Conclusions
詳細な0次元すす反応動力学モデルにより,粒子径・粒子数を考慮したすす生成の当量比-温度マップ解析および燃料組成がすす生成特性
に及ぼす影響の検討を行ない,以下に示す知見を得た.
すす生成の当量比-温度依存性は燃料成分の影響を強く受
ける.特に,含酸素燃料では最大すす生成収率の大幅な低下やすす生成領域の大幅な縮小化が可能となる.
すす体積分率のベルピーク温度よりも低温側では,小粒径・高数密度・高PAH濃度の粒子が,逆に高温側では,大粒径・低数密度・低PAH濃度の粒子が生成される.
上記に起因して,すす排出重量の低減に加え,微小すす粒子数および未燃PAH濃度を同時に低減するには,当量比-温度マップ上におけるすす生成半島の低温側より,燃料希薄側の利用が望まれる.
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
turbikin
iii f
YY,
*
Yi : current concentrationYi
*: equilibrium concentrationkin,i : kinetic timescaleturb : turbulent timescale~k/
f : delay coefficient
ikin
iiikin
YY,
*
,
Production rate of species i
Kinetic controlled production rateof species i
dtY
dtYY iii
Yi : current concentrationYi
‘ : concentration after CHEMKIN cal.dt : numerical time-step
dtY
YYi
iiikin
*
,
*Assumptions
0*
,,
f
fuelkinikin
Y iffii
ffkin
YYYYY
dtYY
)/(
)/(*
New species at the current time-step
dtf
YYYdtYY
turbkin
iffi
ni
ni
)/(1
iturbkin
kin Yf
Turbulence chemistry interaction model(Kong et al. SAE paper 2001-01-1026)
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Temporal change of distribution of flame temperature(fuel: n-heptane, Tamb=900[K], amb=16.2[kg/m3], pinj=70[MPa], tinj=2.65[ms])
120
30
60
90
0D
ista
nce
from
noz
zle
orifi
ce [m
m]
120
30
60
90
0
Dis
tanc
e fro
m n
ozzl
e or
ifice
[mm
]
0.2msTASI = 0.6ms 0.7ms 0.8ms 1.0ms 1.2ms 1.4ms
1.5msTASI = 2.0ms 2.5ms 3.0ms 4.0ms 5.0ms 6.0ms
Temperature [K] 2800900
temperature
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Temporal change of equivalence ratio in jet(fuel: n-heptane, Tamb=900[K], amb=16.2[kg/m3], pinj=70[MPa], tinj=2.65[ms])
[-] 0
fai120
30
60
90
0
Dis
tanc
e fro
m n
ozzl
e or
ifice
[mm
]
120
30
60
90
0
Dis
tanc
e fro
m n
ozzl
e or
ifice
[mm
]
0.2msTASI = 0.6ms 0.7ms 0.8ms 1.0ms 1.2ms 1.4ms
1.5msTASI = 2.0ms 2.5ms 3.0ms 4.0ms 5.0ms 6.0ms
1 2 3 4 5 6 7
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
naphthalene masss fraction [ppm] 4000
Distribution of naphthalene mass fraction and soot volume fraction(fuel: n-heptane, Tamb=900[K], amb=16.2[kg/m3], pinj=70[MPa], tinj=2.65[ms])
soot volume fraction
200soot volume fraction [ppm]
120
30
60
90
0D
ista
nce
from
noz
zle
orifi
ce [m
m]
120
30
60
90
0
Dis
tanc
e fro
m n
ozzl
e or
ifice
[mm
]
0.7msTASI = 1.0ms 1.5ms 2.0ms 2.5ms 3.0ms 4.0ms
0.7msTASI = 1.0ms 1.5ms 2.0ms 2.5ms 3.0ms 4.0ms
naphthalene mass fraction
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Soot volume fraction and soot particle diameterin a combusting diesel jet
Soot measurement
Laser-Induced Incandescence
Soot volume fraction : fv
Time-resolved LII
Soot particle diameter : dp
Soot Measurement Scheme
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Soot particle temperature increases rapidlyby high energy laser
Soot
Radiation
Laser sheet
Laser-Induced Incandescence (LII)
In addition, LII signal intensity vf
Soot incandescence (LII signal) irradiates→Visualization of soot distribution
Principle of LII
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Advantage of LII for soot diagnostics
Fundamental properties of LII
Fv∝Np・dp3
Application of LII to diesel engine
L.A.Melton
A.C.Eckbreth
J.E.Dec
Numerical analyze of LII
LII signal intensity increase with increasing laser power
Decrease in soot diameter due to soot vaporization
LII signal intensity is proportional to soot volume fraction
Lack of scattering influence due to droplet or cylinder wall
Previous Study about Laser Induced Incandescence
Spray and Combustion Science Laboratory, DOSHISHA University
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
2 4 44 ( )rad flameq a T T
( )8 mabs
aEQ
220
50
2 4[exp( ) 1]LII p
em em
c hS N ahc kT
3 154 / 3emLII p p p p vS N d N d f
At maximum temperature of soot particle (by Melton#)
LII signal (SLII)
(# L. A. Melton, APPLIED OPTICS, Vol.23, No.13, pp.2201-2208, 1984)
Theoretical Equations
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
LII signal decay after laser incident depends on particle diameter.
LII signal ratio at two different times also depends on particle diameter.
Temporal change in LII signal decay after laser incident(LII signal ratio at two different timing, etc)
Numerical simulation
(L. A. Melton, APPLIED OPTICS, Vol.23, No.13, pp.2201-2208, 1984)as well as Melton’s method
0 10 20 30 40 50Time after laser incident [ns]
10-3
10-1
10-2
10-0
LII s
igna
l [N
orm
aliz
ed] Increasing diameter
20, 40, 60, 80100, 150, 300nm
Time-Resolved LII
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Laser-Induced Incandescence (LII)法の原理
CCD camerawith I.I.(Ⅰ)
Band pass filter
Cylindrical lens(f=1000mm)
Nd:YAG Laser (532nm)
Notch filter
Cylindrical lens(f=25, 100mm)
radiation
Soot
LIIの光学系の例
レーザ光により熱せられたすす粒子からのふく射光を検出することですす濃度を測定する. レーザ光
シグナル強度∝すす体積濃度
燃料液滴や壁面等の散乱光の影響を受けにくい.
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Ratio of black body radiation at 4500K anthat at 2200K
Wavelength [nm]200 1000600 800
Inte
nsity
400100
102
106
108
104
S/N
Wavelength [nm]200 1000600 800
Inte
nsity
400100
102
106
108
104
Wavelength [nm]200 1000600 800
Inte
nsity
400100
102
106
108
104
S/N
Ratio of black body radiation at 4500K and that at 2200K
短波長ほどS/N比が高い.
LII信号強度 ∝ Npdp3+154nm/ 長波長ほど体積濃度に比例
短波長ほどLII信号強度そのものも低い
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
LIIシグナル強度に及ぼすレーザ強度の影響
Laser fluence [J/cm2]0.4 1.60.8 1.20.60 0.20
300
400
600
500
700
200
100
LII s
igna
l [a.
u.]
1.41.0
Plateau region
Premixed burner ( =2.3, HAB=12mm)
Laser fluence [J/cm2]0.4 1.60.8 1.20.60 0.20
300
400
600
500
700
200
100
LII s
igna
l [a.
u.]
1.41.0
Plateau region
Premixed burner ( =2.3, HAB=12mm)
Laser fluence [J/cm2]0.4 1.60.8 1.20.60 0.20
300
400
600
500
700
200
100
LII s
igna
l [a.
u.]
1.41.0
Plateau region
Premixed burner ( =2.3, HAB=12mm)
ある程度のレーザ強度以上ではLIIシグナル強度は飽和する.レーザシート光の強度ムラやすすによるレーザ強度の減衰の影響を受け難い.
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
LIIを用いたすす粒子径の計測:Time-Resolved LII (TIRE-LII)
0 10 20 30 40 50Time after laser incident [ns]
10-3
10-1
10-2
10-0
LII s
igna
l [N
orm
aliz
ed] Increasing diameter
20, 40, 60, 80100, 150, 300nm
レーザ照射後のLIIシグナル強度の時間履歴は粒子直径に依存する.
異なる2時期でのLIIシグナル強度比
から粒子直径を算出できる.
Laser pulse
ディーゼル燃焼場 → 高温,高圧
粒子径が既知の粒子を用いた検定実験が困難.
: 単一球形粒子仮定
LIIシグナルの時間変化を数値予測 0 20 40 60 80 1000.0
0.1
0.2
0.3
0.4
Particle diameter [nm]
LII s
igna
l rat
io
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
change ofinternal energy
Absorption
Thermal radiation
Vaporization
Heat transfer
Energy balance equation
absorbed laser energy
heat transfer loss
heat loss soot
evaporation
internal energy change
heat loss thermal radiation
Mass conservation equation
(Stefan Will, et al, APPLIED OPTICS, Vol.37, No.24, pp.5647-5658, 1998)
2 2 3( ) 0
44 ( ) 03
vabs t rad s s
s
H dM dTQ a q a T T q a CW dt dt
2 24 42s v
v
dM da RTa adt dt W
Power balance of a laser-heated soot particle
Kabs
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Time after laser incident [ns]0 10 20 30 40 50
2000
4500
4000
3500
3000
2500Tem
pera
ture
[K]
0
100
80
60
40
20
Diam
eter [nm]
すす粒子の温度および粒子径変化(初期粒径: 50nm,粒子初期温度: 2200K,レーザ強度: 0.92J/cm2)
Temperature
Diameter
Laser pulse
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Time after laser incident [ns]0 10 20 30 40 50
100
10-1
10-2
10-3Nor
mal
ized
LII
sign
al in
tens
ity
LIIシグナル強度の時間履歴(初期粒径: 50nm,粒子初期温度: 2200K,雰囲気圧力:4.1MPa,レーザ強度: 0.92J/cm2)
Laser pulse
LII signal
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
LII signal decay for various particle sizes
Pamb=4.1MPa, Laser fluence=0.92J/cm2, Tflame=2200K
increasing diameter20, 40, 60, 80,
100,150, 300nm
100
Time after laser incident [ns]
Nor
mal
ized
LII
sign
al
10 20 30 40 50
10-1
10-2
10-3
0
Laser pulse
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
LII signal decay for various particle sizes
Pamb=4.1MPa, Laser fluence=0.92J/cm2, Tflame=2200K
increasing diameter20, 40, 60, 80,
100,150, 300nm
100
Time after laser incident [ns]
Nor
mal
ized
LII
sign
al
10 20 30 40 50
10-1
10-2
10-3
promptLII
0
Laser pulse
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
LII signal decay for various particle sizes
Pamb=4.1MPa, Laser fluence=0.92J/cm2, Tflame=2200K
increasing diameter20, 40, 60, 80,
100,150, 300nm
100
Time after laser incident [ns]
Nor
mal
ized
LII
sign
al
100 20 30 40 50
10-1
10-2
10-3
delayLIILaser pulse
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Particle diameter [nm]25 15075 1000
LII s
igna
l rat
io r
50
0.5
0.2
0.1
0
0.3
0.4
125
Pamb=4.1MPa, Laser fluence=0.67J/cm2, Tflame=2200K
first
second
SSr
LII signal ratio of first and second gate versusparticle diameter
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Time-Resolved LIIによるすす粒子径の決定法
promptLII (raw image) delayLII (raw image)
1) delayLIIpromptLII
Diameter distributionシグナル比を算出
2) From signal ratioto diameter
0 20 40 60 80 1000.0
0.1
0.2
0.3
0.4
Particle diameter [nm]
LII s
igna
l rat
io
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
increasing ambient pressure0.1, 1.0, 2.0, 3.0,
4.0, 5.0MPa
100 20 30 40 50Time after laser incident [ns]
100
LII s
igna
l [no
rmal
ized
]
10-1
10-2
10-3
大気圧場では,LIIシグナルの減衰は緩慢である.
大気圧バーナやエンジン排気中のPM粒径を計測する場合はレーザ照射後数百ns後のシグナルを用いるのが一般的.
LIIシグナルの時間履歴に及ぼす雰囲気圧力の影響
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Schematic diagram of experimental system
C2H2O2 N2
ECD-U2
Amp
Timing control unit
Amp
P
P.C
Injector
Vacuum pump
Sparkplug
Stirrer
Pressuretransducer
Mixingtank
Pressure gauge
Stirrer
Pressure pick up
Spark plugIntakeExhaust
Pressure gauge
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
CCD camera with I.I.(Ⅰ) Half mirror
Combustion vessel
Nd:YAG Laser ( =532 nm)
CCD camera with I.I.(Ⅱ)
Notch filter ( =532nm, 3nm FWHM)
Short pass filter ( =450nm)
Pin-hole
Convex lens (f=800mm)
Cylindrical lens (f=100mm)
Optical measurement system for Time-resolved LII
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Property of test fuel
Fuel:N-heptane
Density at 298K [kg/m3]
Lower calorific value [MJ/kg]
Boiling point [K]
Kinematic viscosity [mm2/s]
Cetane number
Stoichiometric A/F [kg/kg]
680
372
0.584
47.8
56
15.1
軽油 すす生成量が多過ぎる. レーザ光の減衰が著しく,またシート光とカメラまでのすすにより,LIIシグナルも大幅に減衰する.
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Experimental condition
Ambient gas temperature Tamb [K]
Injection pressure drop Pinj [MPa]
Ambient gas density amb [kg/m3]
Ambient oxygen concentration XO2 [%]
Set injection duration tinj [ms]
Injection quantity Qinj [mg]
900
16.2
17, 21
70
2.65
18.3
Nozzle orifice diameter d [mm] 0.2
40
3.2
100
2.1
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
0.52(1.30ms)0.4(1.00ms) 0.44(1.10ms)
dp
fv
fv and dp distribution (Pinj=70MPa)
dp [nm]
0 20 40 60 80 100<
fv
low high
Dis
tanc
e fro
mno
zzle
[mm
] 40
50
60
70
Dis
tanc
e fro
mno
zzle
[mm
] 40
50
60
70TASI*=
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
0.6(1.50ms) 0.72(1.80ms) 0.8(2.00ms)
dp
fv
fv and dp distribution (Pinj=70MPa)D
ista
nce
from
nozz
le [m
m] 40
50
60
70
Dis
tanc
e fro
mno
zzle
[mm
] 40
50
60
70TASI*=
dp [nm]
0 20 40 60 80 100<
fv
low high
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
0.92(2.30ms)
dp
fv
1.12(2.80ms) 1.2(3.00ms)
fv and dp distribution (Pinj=70MPa)
Dis
tanc
e fro
mno
zzle
[mm
] 40
50
60
70
Dis
tanc
e fro
mno
zzle
[mm
] 40
50
60
70TASI*=
dp [nm]
0 20 40 60 80 100<
fv
low high
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
燃料噴射圧力の影響 (上段: pinj=40MPa,下段:100MPa)
0.4 0.44 0.52 0.6 0.72
0.8 0.92 1.12 1.2 1.32
No image
Dis
tanc
e fro
mno
zzle
[mm
] 40
50
60
70Dis
tanc
e fro
mno
zzle
[mm
] 40
50
60
70
TASI*=
* TASI*= tinj / tinj
dp [nm]
0 20 40 60 80 100<
dp [nm]
0 20 40 60 80 100<
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
雰囲気酸素濃度の影響 (上段:Xo2 =21%,下段:17%)
0.4 0.44 0.52 0.6 0.72
0.8 0.92 1.12 1.2 1.32
No image
Dis
tanc
e fro
mno
zzle
[mm
] 40
50
60
70Dis
tanc
e fro
mno
zzle
[mm
] 40
50
60
70
TASI*=
* TASI*= tinj / tinj
dp [nm]
0 20 40 60 80 100<
dp [nm]
0 20 40 60 80 100<
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Conclusion
すす生成開始直後は,生成領域の全域を10~20nm程度の小さな粒子が占め,拡散的燃焼期間への移行に伴い,噴霧外縁付近から大粒子へと成長する.
上流側で生成された小粒径のすすは下流に向かうに従い,凝集や表面反応により成長し,大粒子化する.
噴射圧力が増加するに従い,大粒子径のすすが生成し始める位置は下流へと遷移し,その時期は噴射時期後半へと移行する.
.
大粒子径のすすは噴霧外縁付近に多く分布し,噴霧中心軸付近は小さなすす粒子で占められる.
雰囲気酸素濃度の低下は,噴霧火炎内部で生成されるすす粒子の成長を抑制し,すすの小粒径化をもたらす.
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Ambient gas temperature Tamb [K]
Fuel
Injection pressure drop Pinj [MPa]
Ambient gas density amb [kg/m3]
Ambient oxygen concentration XO2 [%]
Injection duration tinj [ms]
Injection quantity Qinj [mg]
n-Heptane
900
16.2
13
70
2.5
18.3
Nozzle orifice diameter d [mm] 0.2
800 1200
17 21
Experimental conditions
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
fuel: n-heptane, Tamb=900[K], amb=16.2[kg/m3], Xo2=21%, Pinj=70[MPa]D
ista
nce
from
noz
zle
[mm
]20
40
80
60
10020
40
80
60
100
(1071) (54) (21) (9) (5)
1.0ms 1.2msTASI= 1.3ms 1.5ms 1.8ms
dp
fv
Low HighSoot volume fraction: fvParticle diameter: dp [nm] 1000
Rat
e of
hea
t rel
ease
[kJ/
s]
200
800
400
2 8 12Time after start of injection [ms]
0
0
104 6
400
1000
800
0
Cum
ulat
ive
heat
rele
ase
[J]
Injection duration
600
200
600
Rat
e of
hea
t rel
ease
[kJ/
s]
200
800
400
2 8 12Time after start of injection [ms]
0
0
104 6
400
1000
800
0
Cum
ulat
ive
heat
rele
ase
[J]
Injection duration
600
200
600
Distribution of soot volume fraction and soot particle diameter in diesel jet flame obtained by Time-resolved LII
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Dis
tanc
e fro
m n
ozzl
e [m
m]
20
40
80
60
10020
40
80
60
100
(3) (3) (4) (4) (14)
2.0ms 2.5msTASI= 3.0ms 3.5ms 4.0ms
dp
fv
fuel: n-heptane, Tamb=900[K], amb=16.2[kg/m3], Xo2=21%, Pinj=70[MPa]
Low HighSoot volume fraction: fvParticle diameter: dp [nm] 1000
Distribution of soot volume fraction and soot particle diameter in diesel jet flame obtained by Time-resolved LII
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
fuel: n-heptane, amb=16.2[kg/m3], Xo2=21%, Pinj=70[MPa]
Dis
tanc
e fro
m n
ozzl
e [m
m]
20
40
80
60
100
20
40
80
60
100
(117) (126) (38) (245)
TASI= 2.5ms 3.0ms 3.4ms 4.0ms
dp
fv
Low HighSoot volume fraction: fvParticle diameter: dp [nm] 1000
Tamb=800[K]
(10) (1) (1) (7)
0.5ms 1.0ms 2.0ms 3.5ms
Tamb=1200[K]
dp
fv
Rat
e of
hea
t rel
ease
[kJ/
s]
300
1500
600
2 8 12Time after start of injection [ms]
0
0
104 6
400
1000
800
0
Cum
ulat
ive
heat
rele
ase
[J]
Injection duration
1200
200
600900
Rat
e of
hea
t rel
ease
[kJ/
s]
300
1500
600
2 8 12Time after start of injection [ms]
0
0
104 6
400
1000
800
0
Cum
ulat
ive
heat
rele
ase
[J]
Injection duration
1200
200
600900
Tamb=800K
Rat
e of
hea
t rel
ease
[kJ/
s]100
400
200
2 8 12Time after start of injection [ms]
0
0
104 6
400
1000
800
0
Cum
ulat
ive
heat
rele
ase
[J]
Injection duration
300
200
600
Rat
e of
hea
t rel
ease
[kJ/
s]100
400
200
2 8 12Time after start of injection [ms]
0
0
104 6
400
1000
800
0
Cum
ulat
ive
heat
rele
ase
[J]
Injection duration
300
200
600
Tamb=1200K
Distribution of soot volume fraction and soot particlediameter in diesel jet flame obtained by Time-resolved LII
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
fuel: n-heptane, Tamb=900[K], amb=16.2[kg/m3], Xo2=13%, Pinj=70[MPa]
Dis
tanc
e fro
m n
ozzl
e [m
m]
20
40
80
60
10020
40
80
60
100
(152) (135) (34) (23) (10)
2.0ms 2.5msTASI= 3.0ms 3.5ms 4.5ms
dp
fv
Low HighSoot volume fraction: fvParticle diameter: dp [nm] 1000
Rat
e of
hea
t rel
ease
[kJ/
s]
100
400
200
2 8 12Time after start of injection [ms]
0
0
104 6
400
1000
800
0
Cum
ulat
ive
heat
rele
ase
[J]
Injection duration
300
200
600
Rat
e of
hea
t rel
ease
[kJ/
s]
100
400
200
2 8 12Time after start of injection [ms]
0
0
104 6
400
1000
800
0
Cum
ulat
ive
heat
rele
ase
[J]
Injection duration
300
200
600
Xo2=13%
Distribution of soot volume fraction and soot particle diameter in diesel jet flame obtained by Time-resolved LII
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Are
a-av
erag
ed f v
0
200
400
600
800
0
20
40
60
80
100
0 1.0 4.02.0 3.0
Are
a-av
erag
ed d
p[n
m]
Time after start of injection [TASI*]
1200K900K800K
Are
a-av
erag
ed f v
0
200
400
600
800
0
20
40
60
80
100
Are
a-av
erag
ed d
p[n
m]
0 1.0 4.02.0 3.0Time after start of injection [TASI*]
7.05.0 6.0
21%17%13%
Integrated LII intensity and characteristicparticle diameter
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
(1) 予混合的燃焼期間の終盤に生成した微小なすす粒子は
燃焼の進行とともに噴霧下流部へ拡がり,噴霧先端・外縁部で大粒子径のすすが高濃度で分布する.
(2) 雰囲気温度の低下に伴い,大幅にすす濃度が減少し,粒子径もLIIシグナルが検出される全期間において微小とな
る.
(3) 雰囲気酸素濃度が低下すると,噴霧火炎が肥大化するこ
とにより,すす生成領域が拡大する.また,雰囲気酸素濃度の低下に伴い,すす粒子の生成・成長が緩慢となることで,粒子径およびすす濃度はともに減少する.
Conclusions
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Flame temperature [K]20001800 2100 2200 2300 24001900
Pamb=4.1MPa, Laser fluence=0.67J/cm2
0.2
0
-0.2
-0.4
0.4d p
/dp
[-]
10nm50nm80nm
dp@2200K
Effect of flame temperature on calculated diameter
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
0.50 0.60 0.70 0.80Laser fluence [J/cm2]
2.5
2.0
1.5
1.0
0.5
0
-0.5
d p/d
p[-]
Pamb=4.1MPa, Tflame=2200K
10nm50nm80nm
Effect of laser fluence on calculated diameter
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
TASI=0.8ms, g=1.45, Dg=7
0
1.0
0.8
Par
ticle
dis
tribu
tion
[Nor
mal
ized
]
0.4
0.6
0.2
Particle diameter [nm]0 20 40 60 80
ExperimentLog-normal
Log-normal fitting of soot particle
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
-0.6
0.4
0.2
d p/D
TIR
E
-0.2
0
-0.4
D10 D20 D30 D32
D43 D63
g=1.6
Dg=10, DTIRE=19.6nmDg=15, DTIRE=29.2nmDg=20, DTIRE=39.1nmDg=25, DTIRE=48.4nm
Relative error of Dmn to DTIRE
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
0 20 40 60 80 100 120 140Particle diameter [nm]
0
0.02
0.04
0.06
0.08
Pro
porti
on [-
]
0.5ms(0.21)0.8ms(0.34)1.0ms(0.43)
2.0ms(0.85)1.5ms(0.64)
2.5ms(1.06)
3.5ms(1.49)3.0ms(1.28)
TASI(TASI*)2.03, 0.452.50, 0.452.80, 0.453.40, 0.455.90, 0.456.00, 0.456.00, 0.459.21, 0.45
Temporal changes in particle size distribution forn-heptane
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
0.5ms(0.15)0.7ms(0.20)1.0ms(0.30)
2.3ms(0.70)1.7ms(0.50)
3.3ms(1.00)
4.0ms(1.20)3.6ms(1.10)
TASI(TASI*)1.50, 0.451.55, 0.451.80, 0.451.90, 0.452.00, 0.452.30, 0.452.40, 0.453.00, 0.45
0 20 40 60 80 100 120 140Particle diameter [nm]
0
0.02
0.04
0.06
0.08
Pro
porti
on [-
]
Temporal changes in particle size distribution for DGE
Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –
Time-Resolved LIIの問題点
検査領域中(画像ピクセル中)に粒度分布が存在する場合.見積もられる平均粒子径は概ねD32と一致するが,粒度分布によって若干異なる.
下図のように凝集体の構造が異なる場合,算出される粒子径 ???
point contact
・
loose structure
・
point contact
・ point contact
・
loose structure
・ loose structure
・
compact・
dense structure
・
compact・ compact・
dense structure
・ dense structure
・
p ppn
A A
App = primary particle surface
pA “enwrapped”surface of the agglomerate
as equivalent diameter
measured diameter=
mean primary particle diameter
measured diameter=
mean primary particle diameter
measured diameter=
“heat transfer diameter”measured diameter
=“heat transfer diameter”
より定量的な結果を得るには噴霧火炎内部の局所的な温度情報が必要とされる.