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1
Non interfering diagnostics for the study of thermofluidynamic processes in
ICEB. M. Vaglieco
Istituto Motori – CNR
Napoli, ITALY
Study of chemical and physical phenomena in internal combustion engine by non intrusive
techniques at high spatial (< micron) and temporal resolution (nanosecond)
Objective
CompressionIgnition
Diesel Engine Gasoline Engine HCCI Engine
SparkIgnition
Homogeneous ChargeCompression Ignition
Fuelinjector
NOsoot
Sparkplug
Flame frontNO
Hot Flame Low temperature combustion
Combustion
Engine parameters
Exhaust emissionsHC, O2, CO, CO2, NOXparticulate mass concentration
UV-IR analyzer and opacimeter
In-cylinder pressurequartz piezoelectric pressure transducer
CONVENTIONAL MEASUREMENTS
spark and injectioncurrent and voltage sensors
PiezoelectricPressure transducer
Determination of Start of Combustion
The heat release indicates : in the absolute minimum the overcoming of the first exothermic combustion reactions with respect to endothermic due to the evaporation of fuel injected
The variation of slope of pressurecurve
2
-10 0 10 20 30 40 50
Crank Angle Degree
0
10
20
30
40
50
Pre
ssur
e [b
ar]
GAS90
ST=13 CAD BTDC
ST=3 CAD BTDC
(d)
0 10 20 30 40
Crank Angle Degree
-1.2
-0.8
-0.4
0
0.4
0.8
1.2
knoc
k pr
essu
re [b
ar]
(d)
ST=13 CAD BTDC
Pressure measurements
•Non intrusive techniques
•High spatial and temporal resolution
Non interference on phenomena
Capability to follow stationary phenomena and to measure “in situ”
Interaction light-matter
Qualitative and quantitative characterization on transient phenomena in optically accessible combustion system
EXCITATIONOccurs when an electron in an atom is given energy causing it to jump to a higher orbit. This can happen through collisions or photon absorption (the photon absorption must exactly match the energy jump).
The excited atom usually de-excites in about 100 millionth of a second.The subsequent emitted radiation has an energy that matches that of the orbital change in the atom. This emitted radiation gives the characteristic colors of the element involved
Radio waves are produced byelectrons moving up and down an antenna
Visible light is produced byelectrons changing energy states in an atom
ELECTROMAGNETIC SPECTRUMEM WavesRadio WavesMicrowavesInfraredVisibleUltravioletX-raysGamma rays
SourcesVibrating chargesMolecular rotationsMolecular vibrationsAtomic vibrationsAtomic vibrationsAtomic vibrations Nuclear vibrations
Emission SpectraContinuous Emission Spectrum
Prism
Photographic Film
Slit
White LightSource
Emission Spectra of Hydrogen
Prism
Photographic Film
Film
Slit
Low DensityGlowing
Hydrogen Gas
Discrete Emission Spectrum
3
Discrete Absorption Spectrum
Absorption Spectraof Hydrogen
Prism
Photographic Film
Film
Slit
White LightSource
Discrete Emission Spectrum
Hydrogen Gas
ABSORPTION SPECTRA
•Frequencies of light that represent the correct energy jumps in the atom will be
absorbed.
•When the atom de-excites, it emits the same kinds of frequencies it absorbed.
•However, this emission is in all directions.
INCANDESCENCE
Electron transitions occur not only in the parent atom but in adjacent atoms as well
FLUORESCENCE
•Some materials that are excited by UV emit visible.
•These materials are referred to as fluorescent materials.PHOSPHORESCENCE
•Electrons get "stuck" in excited states in the atoms and de-excitation occurs at different times for different atoms.
•A continuous glow occurs for some time.
•Bioluminescence
MAGIC BOXMAGIC EYE
pros•non-intrusive method•simultaneous multispecies detection (spectroscopy)•differentiation at same wavelength (chemiluminescence)•cons•line-of-sight method• low signal/noise
UV-visible natural emission
Quartz window
UV mirror
Quartz window
UV mirrorhν
hν
hν
hν
h CFD and optical measurement are suitable tools for explanation of complicated combustion mechanism.
h If the other sub-models (spray,etc) are effective, recent CFD with detailed kinetics model is though to be robust or adaptable to the various combustion and emission description.
4
Commercial cylinder head
Common Rail InjectorConditioned
intake Air
section view
Coolant temperature control system
Non lubricated condition(Bronze-Teflon Ring)
Exhaust gas
Transparent diesel engine Transparent engine
13
13
2 Toroidal bowl optical access diameter = 34mm;Lateral window diameter =14mm
Lateral and Top Cross-Sections
upper edge ofbowl
edge of quartz window in bottom piston
upper edge ofbowl
edge of quartz window in bottom piston
FRONT VIEW
exhaust valve replaced by quartzwindow
injector
pressure transducer
upper edge ofbowl
TOP VIEWOUT IN
Optical Setup
Common Rail
Pump
PC
Unit Control
Electric Engine
UV-Mirror
Injector
Encoder
CCD
CCD
Digital imagingCCD camera 640x480 pixels - Minimum exposure time 10 μs
1cad=166.66μs @1000rpm
Common Rail
Pump
PC
Unit Control
Electric Engine
UV-Mirror
Injector
Encoder
CCD
CCD
Common Rail
Pump
PC
Unit Control
Electric Engine
UV-Mirror
Injector
Encoder
CCDCCD
CCDCCD
Digital imagingCCD camera 640x480 pixels - Minimum exposure time 10 μs
1cad=166.66μs @1000rpm
Acquisitionthrough pistoncrown window
CCD
DIGITAL IMAGINGof fuel spray and combustion phase
Pre+Main InjectionInj. Pressure 600 bar
-30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30crank angle [degree]
0
10
20
30
40
50
60
70
Com
bust
ion
Pres
sure
[bar
]
0
20
40
60
80
100
RO
HR
[kJ/
kg/C
AD]
0
10
20
Driv
e C
urre
nt [A
mpe
re]
Pre+M
PSOC Pre
PSOC M
-30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30crank angle [degree]
0
10
20
30
40
50
60
70
Com
bust
ion
Pres
sure
[bar
]
0
20
40
60
80
100
RO
HR
[kJ/
kg/C
AD
]
0
10
20D
rive
Cur
rent
[Am
pere
] M PSOC
Main Injection
Experiments vs ModellingPre
7.0 BTDC
6.5 BTDC
2.5 ATDC
3.5 ATDC
Main
Autoignition
R1) H + O2 = O + OH
R2) O + H2 = H + OH
R3) H2 + OH = H2O + H
H2 as fuel
Heywood, 1988
5
Autoignition phase of pre injection occurs during the first times of main injection
Spectra at Autoignition of Pre + Main
0
100000
200000
300000
400000
500000
Emis
sion
inte
nsity
[a.u
.]
220 250 280 310 340 370 400 430 460Wavelength [nm]
α
β
γ
OH
αβγ
0
100000
200000
300000
400000
500000
Emis
sion
inte
nsity
[a.u
.]
220 250 280 310 340 370 400 430 460Wavelength [nm]
α
β
γ
OH
αβγ
αβγ
1.5° BTDC=1.5°ASOCpre
OH
220 250 280 310 340 370 400 430 460
Wavelength [nm]
0
10000
20000
30000
40000
Em
issi
on in
tens
ity [a
.u.]
α
β
γOH
CH3° BTDC=SOCpre
220 250 280 310 340 370 400 430 460
Wavelength [nm]
0
100000
200000
300000
400000
Emis
sion
inte
nsity
[a.u
.]
α
β
γ
OH
CH2.4° BTDC=0.6°ASOCpre
α
βγ
α
βγ
Black body
• Brightness versus color curve for different temperatures
(measured in Kelvins)
0.0
0.1
0.1
0.2
0.2
0 500 1000
Wavelength (nm)
Rel
ativ
e E
nerg
y
Tf ∝
3° btdc
Visible FlameTemperature Soot
2500
Temperature scale [K]
1850 3000KL factor scale
0 15
Soot mass concentration[mg/m3]
0 44
Imaging, Temperature and Soot concentration1000 rpm - Pinj 600 bar
-10 0 10 20 30 40 50 60Crank angke [degree]
0
10
20
30
RO
HR
[kJ/
kg/C
AD
]
0
10
20
30
Curr
ent [
Am
pere
] 2° btdc
Visible FlameTemperature Soot
2500
Temperature scale [K]
1850 3000KL factor scale
0 15
Soot mass concentration[mg/m3]
0 44
Imaging, Temperature and Soot concentration1000 rpm - Pinj 600 bar
-10 0 10 20 30 40 50 60Crank angke [degree]
0
10
20
30
RO
HR
[kJ/
kg/C
AD
]
0
10
20
30
Curr
ent [
Am
pere
]
tdc
Visible FlameTemperature Soot
2500
Temperature scale [K]
1850 3000KL factor scale
0 15
Soot mass concentration[mg/m3]
0 44
Imaging, Temperature and Soot concentration1000 rpm - Pinj 600 bar
-10 0 10 20 30 40 50 60Crank angke [degree]
0
10
20
30
RO
HR
[kJ/
kg/C
AD
]
0
10
20
30
Curr
ent [
Am
pere
] 16° atdc
Visible FlameTemperature Soot
2500
Temperature scale [K]
1850 3000KL factor scale
0 15
Soot mass concentration[mg/m3]
0 44
Imaging, Temperature and Soot concentration1000 rpm - Pinj 600 bar
-10 0 10 20 30 40 50 60Crank angke [degree]
0
10
20
30
RO
HR
[kJ/
kg/C
AD
]
0
10
20
30
Curr
ent [
Am
pere
]
6
New concepts for diesel combustion
P. Pinchon at al., IFP – Thiesel 2004
Late injection
MK Concept Nissan Motors
HiMIcs HINO Motors
UNIBUS - PCI
PREDIC/MULDIC
HCCI Denbratt
Injections per cycle
1 4 2 3 (with 3 injectors) 5
Compression ratio 18:1 16:1 18:1 Varied
12:1 to 21:1 16.5:1 Varied 17:1 to 11.5:1
Displacement [cc] 488 - 622 2147 915 - 2000 2004 480
Fuel wall impingement
very limited yes yes yes yes
EGR rate [%] high low high high high
Load range limited large large very limited large
Test speed [rpm] 1200 - 2000 1000 - 1600 1000 1000 2000
Knock at high load
no no high high no
NOx very low low very low very low very low
Smoke very low low very low improved very low
Early injection
Engine speed: 1000rpm - Fuel amount: 8 mm3/stroke
Injection strategies
-40 -30 -20 -10 0 10 20 30 40crank angle [degree]
0
10
20
30
40
50
60
70
Com
bust
ion
Pres
sure
[bar
]
0
20
40
60
80
100
RO
HR
[kJ/
kg/C
AD]
0
10
20
Driv
e C
urre
nt [A
mpe
re]
Pinj = 600 bar
-80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40crank angle [degree]
0
10
20
30
40
50
60
Com
bust
ion
Pre
ssur
e [b
ar]
0
20
40
60
80
100
RO
HR
[kJ/
kg/C
AD
]
0
10
20
Driv
e C
urre
nt [A
mpe
re]
Pinj = 700 bar
CR HCCI
Pinj
[bar]Tin
[°C]
Pin
(abs) [bar]
Fuel [Kg/h]
BMEP [bar]
SOI Pilot
[°]
ET Pilot [μs]
SOI Pre [°]
ET Pre [μs]
SOI Main
[°]
ET Main [μs]
SOI Post
[°]
ET Post [μs]
SOI After
[°]
ET After [μs]
CR Pre+Main+Post 600 44 1.33 0.32 3.0 \ \ -9 400 -4 625 11 340 \ \
HCCI 700 35 1 0.30 2.4 -70 400 -60 400 -50 400 -40 400 -30 400
-70 -60 -50 -40 -30 -20 -10 0 10 20 30Crank angle [degree]
0
40
80
Rate
Of H
eat R
elea
se [k
J/kg
/CA
D]
0102030
Driv
e cu
rren
t [Am
pere
]
0 2 4 6 8 10 12 14 16Time ASOI [ms]
0
100
200
300
400
500
600
700
800
900
1000
Tem
pera
ture
[K]
Ignition delay LTR HTR
Heat release rate for HCCI68° btdc 58° btdc 48° btdc 38° btdc 28° btdc
I II III IV V
I II III IV V
0.5°ASOI
1.0°ASOI
1.5°ASOI
2.0°ASOI
-80 -70 -60 -50 -40 -30 -20Crank angle [degree]
0
5
10
15
20
Cyl
inde
r Pre
ssur
e [b
ar]
0
10
20
Driv
e C
urre
nt [A
mpe
re]
HCCI injection phase
ASOI = After Start Of Injection66° btdc 56° btdc 46° btdc 36° btdc 26° btdc
Pinj = 700 bar
Chemiluminescence Measurements
# 2008-01-0027
300 325 350 375 400 425 450 475 500Wavelength [nm]
0
2000
4000
6000
8000
10000
Em
issi
on in
tens
ity [a
.u.]
OH
CH
300 325 350 375 400 425 450 475 500Wavelength [nm]
0
500
1000
1500
2000
2500
3000
3500
Em
issi
on in
tens
ity [a
.u.]
γ
OH
CH
300 325 350 375 400 425 450 475 500Wavelength [nm]
0
500
1000
1500
2000
2500
3000
3500
Em
issi
on in
tens
ity [a
.u.]
αOH
CH
HCHOHCO
OH is the most important radical for driver the ignition process. It is producing by the decomposition of H2O2 at 1100 K (ref.
2001-01-2077) GAYDON
6° atdc
αβγ
β
-5 -2.5 0 2.5 5 7.5 10 12.5 15Crank angle [degree]
0
40
80
120
RO
HR
[kJ/
kg°]
SOI EOI SOC
300 325 350 375 400 425 450 475 500Wavelength [nm]
0
100000
200000
300000
400000
500000
Emis
sion
inte
nsity
[a.u
.]
β
HCOHCHO
OH
300 325 350 375 400 425 450 475 500Wavelength [nm]
0
20000
40000
60000
80000
Em
issi
on in
tens
ity [a
.u.]
αOH
300 325 350 375 400 425 450 475 500Wavelength [nm]
0
100000
200000
300000
400000
500000
Emis
sion
inte
nsity
[a.u
.]
γ
OH
Chemiluminescence Measurements
10° atdc
αβγ
-5 -2.5 0 2.5 5 7.5 10 12.5 15Crank angle [degree]
0
40
80
120
RO
HR
[kJ/
kg°]
SOI EOI SOC
7
10° atdc 12° atdc 14° atdc
Chemiluminescence MeasurementsIn the whole chamber
300 325 350 375 400 425 450 475 500Wavelength [nm]
0
20000
40000
60000
80000
Em
issi
on in
tens
ity [a
.u.]
300 325 350 375 400 425 450 475 500Wavelength [nm]
0
50000
100000
150000
200000
250000
300000
Em
issi
on in
tens
ity [a
.u.]
300 325 350 375 400 425 450 475 500Wavelength [nm]
0
20000
40000
60000
80000
100000
120000
Em
issi
on in
tens
ity [a
.u.]
-5 -2.5 0 2.5 5 7.5 10 12.5 15Crank angle [degree]
0
40
80
120
RO
HR
[kJ/
kg°]
SOI EOI SOC
OH radical is a good marker of LTC combustion process
HCCI vs CR visible combustion
13° BTDC 12° BTDC 10° BTDC 8° BTDC9° BTDC 7° BTDC11° BTDC
-15 -10 -5 0 5 10 15 20 25 30 35 40Crank angle [degree]
0
0.2
0.4
0.6
Mea
n K
L fa
ctor
for H
CC
I stra
tegy
0
20
40
60
Rat
e O
f Hea
t Rel
ease
[kJ/
kg/c
ad]
-15 -10 -5 0 5 10 15 20 25 30 35 40Crank angle [degree]
0
2
4
6
Mea
n K
L fa
ctor
for C
R s
trate
gies
0
20
40
60
Rat
e O
f Hea
t Rel
ease
[kJ/
kg/c
ad]
CRHCCI
3° BTDC TDC 4° ATDC 10° ATDC 15° ATDC 21° ATDC17° ATDC
1 10 100 1000diameter [nm]
1.0x100
1.0x104
1.0x108
1.0x1012
num
ber c
once
ntra
tion
[par
t*cm
-3]
40° ATDC52° ATDC66° ATDC
Exhaust particle size distribution
1 10 100 1000
1.0x100
1.0x101
1.0x102
1.0x103
1.0x104
1.0x105
1.0x106
1.0x107
1.0x108
1.0x109
Primary and secondaryparticles at exhaust
Electrical Low Pressure Impactor
Experimental method for exhaust characterization
SOOT
Nitrogen Oxides
OPACIMETER SMOKE METER CHEMICALANALYSIS
N% FSN DRYSOOT
SOF
OPACIMETER SMOKE METER CHEMICALANALYSIS
N% FSN DRYSOOT
SOF
PARTICULATEMASS
CONCENTRATION
EXTINCTION
VOLUME FRACTION
OPTICAL TECHNIQUE
SCATTERING
PARTICLE SIZE NUMBER
DISTRIBUTION
NUMBERCONCENTRATION
CHEMILUMINESCENCE ANALYSER
INFRARED ANALYSER
NUMBERCONCENTRATION
CHEMILUMINESCENCE ANALYSER
INFRARED ANALYSER
NUMBERCONCENTRATION
CHEMILUMINESCENCE ANALYSER
INFRARED ANALYSER
NUMBERCONCENTRATION
CHEMILUMINESCENCE ANALYSER
INFRARED ANALYSER
OPTICAL TECHNIQUE
OPTICAL TECHNIQUE
ABSORPTION CROSS
SECTION
ABSORPTION SPECTROSCOPY
OPTICAL TECHNIQUE
OPTICAL TECHNIQUE
ABSORPTION CROSS
SECTION
ABSORPTION SPECTROSCOPY
ABSORPTION CROSS
SECTION
ABSORPTION SPECTROSCOPY
Experimental Apparatus
in
Nd:YAG
1064nm
extinction
scattering
Gas analysers ELPI
DILUTER
Opacimeter
PLANO-CONVEX
LENS
Nd:YAG
BEAM SPLITTER
out
Spectrometer
ICCD
BICONVEX LENS
CDPF
Still plugvalve
PLANO-CONVEX
LENS
Pulsed nanosecond light source: laser
induced optical breakdown
EXTINCTION and SCATTERING SPECTRA
200 250 300 350 400 450 500 550wavelength [nm]
0.0x100
2.0x10-3
4.0x10-3
6.0x10-3
8.0x10-3
1.0x10-2
1.2x10-2
1.4x10-2
1.6x10-2
1.8x10-2
extin
ctio
n co
effic
ient
[cm
-1] NO
soot
1500rpm - 2bar
1500rpm - 5bar
200 250 300 350 400 450 500 550wavelength [nm]
0.0x100
2.0x10-3
4.0x10-3
6.0x10-3
8.0x10-3
1.0x10-2
1.2x10-2
1.4x10-2
1.6x10-2
1.8x10-2
extin
ctio
n co
effic
ient
[cm
-1] NO
soot
1500rpm - 2bar
1500rpm - 5bar
200 250 300 350 400 450 500 550wavelength [nm]
0.0x100
5.0x10-7
1.0x10-6
1.5x10-6
2.0x10-6
2.5x10-6
3.0x10-6
3.5x10-6
4.0x10-6
4.5x10-6
scat
terin
g co
effic
ient
[cm
-1 s
r-1]
1500rpm - 2bar
1500rpm - 5bar
200 250 300 350 400 450 500 550wavelength [nm]
0.0x100
5.0x10-7
1.0x10-6
1.5x10-6
2.0x10-6
2.5x10-6
3.0x10-6
3.5x10-6
4.0x10-6
4.5x10-6
scat
terin
g co
effic
ient
[cm
-1 s
r-1]
1500rpm - 2bar
1500rpm - 5bar
8
1 10 100 1000Diameter [nm]
0.0x100
1.0x1010
2.0x1010
3.0x1010
Num
ber C
once
ntra
tion
[#/c
m3 ] Discr = 11%
graphitic10 min
1 10 100 1000Diameter [nm]
0.0x100
1.0x104
2.0x104
3.0x104
Num
ber C
once
ntra
tion
[#/c
m3 ] Discr = 8%
soot15 min
1 10 100 1000Diameter [nm]
0.0x100
4.0x105
8.0x105
1.2x106
Num
ber C
once
ntra
tion
[#/c
m3 ]
Discr = 2%Soot & organic
35 min
0
40
80
120
160
200
0 10 20 30 40 50
Time [min]
Pres
sure
Dro
p [m
bar]
Regeneration
DOWNSTREAM
UPSTREAM
D= 20 nmsoot
t = 10 minD= 15 nmgraphitic-like
t = 35 min D2= 15 nm50% soot50% organic
D1= 30 nmsoot
t = 15 min D= 20 nmsoot
3000rpm-12bar
Transparent spark ignition engine
UV-45°
mirror
Abnormal combustionThe flame front may be started by hot surface either prior to or after spark ignition
Spark knockCan be controlled by the spark advance
Normal combustionThe combustion process startsat spark timings.The flame front moves across the combustion chamber in like-uniform manner.
Heywood J. B. - Internal Combustion Engine Fundamentals New York - McGraw-Hill 1988.
The knock is identified by intense pressure oscillations that arise around the maximum of pressure.
The frequencies of oscillations are typically higher than 5 kHz
-10 0 10 20 30 40 50 60 70CAD
0
20
40
60
Pre
ssur
e [b
ar]
12 22 32 42 52 62 72CAD ASOS
-1
0
1
knoc
k pr
essu
re [b
ar] 10 20 30 40 50 60
CAD
2000 rpm – 1400 mbarStart of Injection 130 CAD BTDC
Duration of injection 96 CADSpark 8 CAD BTDCHigh pass filter 5kHz
The knock is identified by intense pressure oscillations that arise around the maximum of pressure.
The frequencies of oscillations are typically higher than 5 kHz
29.6 CAD ASOS 30.4 CAD ASOS
2000 rpm – 1400 mbarStart of Injection 130 CAD BTDC
Duration of injection 96 CADSpark 8 CAD BTDC0
20000
31.6 CAD ASOS 33.6 CAD ASOS
34.0 CAD ASOS 34.4 CAD ASOS 36.0 CAD ASOS 36.4 CAD ASOS
12 22 32 42 52 62 72CAD ASOS
-1
0
1
knoc
k pr
essu
re [b
ar] 10 20 30 40 50 60
CAD
Knocking phase
Abnormal combustionA combustion process in which a flame front may be started by hot
surface either prior to or after spark ignition
Hot spots and Surface ignition
The hot spots correspond to very small centres of autoignitiondue to exothermic reactions.
In the same time of hot-spots appearancea flame front (ignition surface) starts from spark plug.
This flame is due to the thermal phase of knock (*)
(*)Maly, R.R.- 25th Symp.Int. on Combustion. Combustion Institute Ed. 1994.
9
33.6 CAD ASOS
Ignition surface
KnockHot-spots
DropletsHot-spots
KnockHot-spots
KnockHot-spots
Spark 8 CAD BTDC
[*] Witze, P. O. and Green, R. M.SAE Paper No. 970866, 1997.
Fuel films on cold walls do not fully vaporize during combustion, but instead accumulate over many cycles. [*]
As the engine warms, the lighter components of the film vaporize, leaving a film of increasingly heavy composition;
Eventually, the wall reaches a temperature where the film fully vaporizes.
Pool fire images of gasoline wall films duringa simulated cold start, observed through a
window in the piston [*].
Closed-valve injection Open-valve injection
Intake valves
[**] C. Arcoumanis et al.Int. J. Engine Research – Vol.1 n. 1, 2000.
Valve firingAbnormal combustion
46 CAD ASOS 70 CAD ASOS
0
120
Pool fire: soot concentrationKL
intake
exhaust
intake
exhaust
intake
exhaust