COMBUSTION DIAGNOSTICS – LIF
Dr. Jimmy Olofsson
SLIDE 1 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Outline
• Why combustion diagnostics?
• Molecular spectroscopy in brief
• Combustion LIF system
• Time-resolved Combustion LIF
• Coffee break
• Applications
• Related Techniques
SLIDE 2 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Why combustion diagnostics?
SLIDE 3 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Benefits of analysing combustion
Combustion related applications:
• Transportation
• Electrical power production
• Heating
Combustion analysis can be used for
economic as well as environmental
benefits by:
• Optimizing fuel economy
• Improving performance and reliability
• Reducing pollutant emissions
SLIDE 4 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Benefits of using lasers for
combustion diagnostics
Laser-based measurements techniques can provide information on
species concentrations, temperature fields, flow velocities etc. and the
measurements often have the following properties:
•
•
•
•
•
•
Non-intrusive
High spatial resolution
High temporal resolution
High sensitivity
Species selective
2D measurements
SLIDE 5 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Combustion diagnostic techniques
Combustion
Radicals - LIF
Soot LII
Combined
Measurements
Fuel
Tracer LIF
Rayleigh
Temperature
SLIDE 6 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Molecular spectroscopy
in brief
SLIDE 7 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Combustion species
• Gas with chemical reactions
• Production of radicals
• Qualitative concentration of radical
- OH
- CH
- NO
- etc
• Concentration of larger molecules/tracers
- Formaldehyde
- Acetone
- etc
SLIDE 8 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Laser-Induced Fluorescence
Excited Molecule
Photon
Fluorescence
Emission
Excited State
• Species selective measurements
(OH, formaldehyde, fuel tracers, etc.)
Ground State
Absorption
SLIDE 9 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Molecular energy states: Electronic
ee-
SLIDE 10 | JIMMY OLOFSSON | 2013
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Molecular energy states:
Vibrational and Rotational
SLIDE 11 | JIMMY OLOFSSON | 2013
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OH absorption spectrum
Several absorption lines around 283 nm
• Air Wavelengths
Excitation in UV
Wavelength (Å)
SLIDE 12 | JIMMY OLOFSSON | 2013
A Nova Instruments company
OH absorption spectrum
Two narrow absorbtion regions within 100 nm range
0.05
~283 nm
O–H
Optical Density
0.04
0.03
0.02
0.01
0.00
240
260
280
300
320
340
360
Wavelength (nm)
SLIDE 13 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Temperature dependence
Choose a peak with for which the fluorescence is independent of temperature
in the measured temperature range
SLIDE 14 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Acetone absorption spectrum
Larger molecules have wider absorption range
0.05
Optical Density
0.04
0.03
0.02
0.01
0.00
240
260
280
300
320
340
360
Wavelength (nm)
SLIDE 15 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Selection of excitation wavelength
• To excite atoms or diatomic
molecules the laser wavelength must
be precisely tuned to match
molecular energy transition.
• Larger molecules, such as Acetone,
3-pentanone or Formaldehyde, have
many more close-lying states,
effectively making a wide continuous
absorption band. Therefore, any
wavelength within the absorption
band can be used to excite the
molecule.
SLIDE 16 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Laser-Induced Fluorescence
Laser
line
Bandpass
filter
Normalised
intensity
1,0
0,8
Fluorescence
spectrum
Absorption
spectrum
0,6
Detected
LIF
0,4
Residual
laser light
0,2
0
200
250
300
350
400
450
500
550
600
Wavelength
l /nm
SLIDE 17 | JIMMY OLOFSSON | 2013
A Nova Instruments company
SLIDE 18 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Combustion LIF system
SLIDE 19 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Combustion LIF system
Image
Intensifier
UV Camera
Lens
CCD
Camera
Optical
Filter
Nd:YAG Laser
Burner
Sheet
Optics
SLIDE 20 | JIMMY OLOFSSON | 2013
Dye Laser
A Nova Instruments company
Standard Nd:YAG pumped dye laser
1090 mm
Nd:YAG laser
• Single cavity 10 Hz
• Wavelengths: 1064 nm, 532 nm,
355 nm, 266 nm
• Pulse length ~10 ns
• Pulse energy 400 mJ @ 532 nm
3ω/4ω
2ω
Nd:YAG laser
Dye laser
Tuneable dye laser
• Tunability range of fundamental:
380-750 nm
• UV extension down to 200 nm
• Line width: 0.8 cm-1
laser UV
• Narrow band option: 0.08 cm-1 Dye
beams or
266nm or
355nm
250 mm
744 mm
250 mm
Beam combining output bench
840 mm
SLIDE 21 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Tuneable dye laser oscillator
Dye Laser
1.
2.
3.
Tuning mirror
Grazing incidence grating
Beam expander prism
(NBP Option)
SLIDE 22 | JIMMY OLOFSSON | 2013
4.
5.
6.
Flowing dye cell
High reflectivity mirror
Focusing lens
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Tuning curves for laser dyes
SLIDE 23 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Species and excitation wavelengths
Our refecence species which we use
during the lab training
Species
Excitation
wavelength
Laser pulse
energy
Process
Type of dye
OH
283 nm
25 mJ
Doubling
Rh590
CH
389 nm
28 mJ
Mixing
Rh610+Rh640
CO
230 nm
13 mJ
Mixing after
doubling
Rh610
NO
226 nm
4.5 mJ
Mixing after
doubling
RH590+Rh610
SLIDE 24 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Light sheet forming optics
• Quartz optics for UV/visible transmission
• Parallel light sheet
- Better control of reflections
- Enhanced energy distribution
Sheet height adjuster
Beam waist adjuster
Standard mount
Holder & fixation system
SLIDE 25 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Detecting Laser-Induced Fluorescence
Image
Intensifier
UV Camera
Lens
Spectral
Filter
CCD
Camera
• Sensitive, high-resolution CCD
camera
• Image intensifier
- Amplifies the incoming light
- Converts UV fluorescence to
visible light detectable by the CCD
camera
- Allows gated detection with very
short time gates, to minimise
detection of natural flame
emission
• UV camera lens required for detection
of UV fluorescence
• Spectral filter to eliminate detection of
scattered laser light and flame
emission
SLIDE 26 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Optical filters
• Interference filters are used to
transmitt only in the wavelength
interval of the fluorescence from the
molecular species of interest,
typically some few 10 nm
• All other wavelengths should ideally
be blocket by the filter
SLIDE 27 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Combustion LIF: Software and timing
•
Synchronization unit
•
Analog Input option. Includes the A/D board and
software add-on
•
Software:
-
DynamicStudio acquisition and processing
software
-
Software add-ons for tracer LIF and
combustion LIF
SLIDE 28 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Laser control from the software
Nd:YAG laser
• Automatic detecion
• Auto activation at
Preview/Acquisition
• Q-switch activation/de-activation
during Preview/Acquisition
• Interlock messages displayed in
Log
Tuneable Dye laser
• Wavelength set
• Wavelength fine-tune buttons
• Wavelength scan
• Output wavelength calculated
from fundamental depending on
frequency conversion scheme
SLIDE 29 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Time-resolved Combustion LIF
SLIDE 30 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Framing rate requirements
• Heat release event in combustion engine
running at 1200 rpm.
• The main heat release occurs within ~5CAD
out of the entire 360CAD engine cycle.
• Resolution used in the study: 0.5CAD
• This corresponds to a 14kHz
Time-resolved Formaldehyde LIF
EXAMPLE
J.Olofsson et al SAE 2005
SLIDE 31 | JIMMY OLOFSSON | 2013
A Nova Instruments company
High-speed Nd:YLF laser
Output pulse energy (527 nm) vs repetition rate (single cavity laser)
SLIDE 32 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Pumping of dye lasers
Pulse separation: 75 µs
Rep. Rate: 13kHz
Pumping of a dye laser with high
repetition rate causes two major
problems:
•
•
Decrease in pulse energy
Deterioration of beam profile
SLIDE 33 | JIMMY OLOFSSON | 2013
A Nova Instruments company
TR C-LIF: YAG-based pump lasers
IS Series
HD Series
• Repetition rate up to 10kHz
• Repetition rate up to 10kHz
• Pulse length: ~10ns
• Pulse length: ~10ns
• Pulse energy @ 4kHz: 8mJ
• Pulse energy @ 10kHz: 12mJ
• Pulse energy @ 5kHz: 20mJ
SLIDE 34 | JIMMY OLOFSSON | 2013
A Nova Instruments company
TR C-LIF: Dye laser
Example:
Pumping with 12W @ 1kHz => 12mJ / pulse
Dye: Rhodamine 6G (~570nm) gives 3.3mJ /
pulse
Frequency doubling to ~283nm for OH LIF is
estimated to give ~0.5mJ / pulse
This should be compared with the
corresponding ~20mJ / pulse achieved by the
standard 10Hz system!
SLIDE 35 | JIMMY OLOFSSON | 2013
A Nova Instruments company
TR C-LIF: SpeedSense camera series
Model example
SpeedSense v711
Maximum fps at
full res.
7500 at
1280 x 800
Resolution at
10kHz (example)
1280 x 600
Resolution at
15kHz (example)
896 x 544
SLIDE 36 | JIMMY OLOFSSON | 2013
A Nova Instruments company
TR C-LIF: Image intensifiers
Model
H Series
9138A1178
L Series
9138A1180
Maximum
repetition rate
200 kHz
100 kHz
Minimum gate
time
10 ns
40 ns
Diameter
(input/output)
24 mm
25 mm
Photocathode
material
Multialkali
S20
(as
Multialkali)
P46
P46
Phosphor
screen
material
SLIDE 37 | JIMMY OLOFSSON | 2013
A Nova Instruments company
SLIDE 38 | JIMMY OLOFSSON | 2013
A Nova Instruments company
COMBUSTION DIAGNOSTICS – APPLICATIONS
Dr. Jimmy Olofsson
SLIDE 39 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Scalar imaging applications
Gaseous flows
Gaseous flows
(non reactive)
(reactive)
Mixing and heat transfer
Pre- / Post-combustion
Combustion
Nd:YAG Laser
Image intensifier unit
Tuneable Dye Laser
Liquid flows
SLIDE 40 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Fuel Tracer-LIF
Two different approaches to fuel visualization
• ”Real” fuels
- Real engine conditions
- Unknown fluorescent
properties (temperature,
pressure, quenching etc.)
• Non-fluorescing reference fuel
with added fluorescent tracer
- Well-known fluorescent
properties
- Allows for quantification
- Further from real engine
conditions
SLIDE 41 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Fluorescent tracer spectra
• Acetone fluorescence spectrum
• Formaldehyde fluorescence spectrum
- A: in a flame
- B: in an engine
SLIDE 42 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Application example 1
SLIDE 43 | JIMMY OLOFSSON | 2013
A Nova Instruments company
How to acheive homogeneous Acetone
concentration for calibration
Example:
Quantification of fuel vapour in constant pressure vessel using liquid fuel
“Iso-octane was used as substitute of
real gasoline in PLIF experiment and
10% acetone was added in as tracer.”
…
“To get a homogeneous mixture, a
small amount of fuel was injected into
vessel. Waited about 30 seconds for
vaporization, then, recorded 100 LIF
signal images. After averaged the
images and subtracted the background,
the result gave the relationship
between current equivalence ratio and
the LIF signal.”
Tsinghua University
Beijing, China
SLIDE 44 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Tracer-LIF calibration
SLIDE 45 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Application example 2
SLIDE 46 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Formaldehyde visualization in an
HCCI engine
Homogeneous Charge Compression Ignition Engine
Advantages
• Lower NOx levels and less soot formation
compared to the Diesel engine
• Higher part load efficiency compared to the
SI engine
For some fuels
formaldehyde is formed in
the cool-flame region
Disadvantage
• Difficult to control ignition timing
J.Olofsson et al SAE 2005
SLIDE 47 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Formaldehyde LIF in an engine
High-speed
laser
Field-of-view
Wavelength: 355 nm
Fuel: N-Heptane
J.Olofsson et al SAE 2005
SLIDE 48 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Cycle-resolved
Formaldehyde consumption
Single-cycle-resolved formaldehyde
fluorescence imaged with a time separation
of ~70 µs (0.5 CAD).
J.Olofsson et al SAE 2005
SLIDE 49 | JIMMY OLOFSSON | 2013
A Nova Instruments company
SLIDE 50 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Fluorescence spectra diatomic radicals
• OH radical
SLIDE 51 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Application example 3
SLIDE 52 | JIMMY OLOFSSON | 2013
A Nova Instruments company
PIV/PLIF investigation of two-phase
vortex-flame interactions
• Study of two-phase vortex-flame
interaction in a counterflow burner
• Local flame extinction events
• PIV for flow velocity field measurements
giving the local strain rates
• PLIF of CH (389.5 nm) for diffusion flame
front location and flame extinction zones
Investigation done in collaboration between École Centrale
Paris, France, Innovative Scientific Solutions, and WrightPatterson Air Force Base, OH, USA
SLIDE 53 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Simultaneous CH PLIF and PIV
By courtesy of
École Centrale Paris, France, Innovative Scientific Solutions, and Wright-Patterson Air Force Base,
OH, USA
SLIDE 54 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Application example 4
SLIDE 55 | JIMMY OLOFSSON | 2013
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Combined OH LIF, fuel tracer LIF and PIV
SLIDE 56 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Combined OH LIF, fuel tracer LIF and PIV
• Local flame extinction
events
OH radical
• Create a data base of
measurement data
• Data used for model
comparison
Flow
velocity field
Fuel tracer / Acetone
Simultaneous flow field (PIV), fuel (tracer-LIF) (blue) and OH (LIF) (green)
visualisation in a turbulent atmospheric flame. Courtesy of R. Collin and P. Petersson,
Division of Combustion Physics, Lund University, Sweden.
SLIDE 57 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Simultaneous PIV and TR OH LIF
local flame extinction
Air&Burnt
OH
OH: Intermediate
combustion product in
hydrocarbon combustion.
Flame front marker.
Time-resolved OH LIF at
2.5kHz framing rate
OH
Coflow
Burnt
Unburnt: Methane&Air
Lund University P.Petersson and J.Olofsson
SLIDE 58 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Multi-dye laser cluster
J.Olofsson
SLIDE 59 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Application example 5
SLIDE 60 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Combined TR PIV and TR OH LIF
with Lund University, Sweden
Planar Laser-Induced
Fluorescence (PLIF) system
Diode pumped Nd:YAG laser
is used to pump a high
repetition rate dye laser.
The emitted 283 nm laser
pulses excites OH radicals in
the flame –> imaged on an
intensified high-speed
camera.
Combined with high repetition
rate Nd:YLF laser for
simultaneous TR PIV.
SLIDE 61 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Flow field and flame front at 4 kHz
Lund University P.Petersson and J.Olofsson
SLIDE 62 | JIMMY OLOFSSON | 2013
A Nova Instruments company
COMBUSTION DIAGNOSTICS – RELATED TECHNIQUES
Dr. Jimmy Olofsson
SLIDE 63 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Laser-Induced Incandescence
SLIDE 64 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Soot in combustion
• Soot is a hazardous pollutant
emission
• Soot is related to incomplete
combustion which has an impact on
combustor performance
SLIDE 65 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Laser-Indusced Incancescence
LII intensity (a.u.)
• Soot particles are heated up by laser radiation
• The increased particle temperature results in increased emission of
Plank radiation
Size decreases
0
100
200
300
400
500
Time (ns)
SLIDE 66 | JIMMY OLOFSSON | 2013
A Nova Instruments company
LII measurement systems
Image
Intensifier
SLIDE 67 | JIMMY OLOFSSON | 2013
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Application example 6
SLIDE 68 | JIMMY OLOFSSON | 2013
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Laser diagnostics in an IC engine
SLIDE 69 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Quantitative LII
Soot-volume-fraction in a Diesel engine
Soot volume fration (ppm)
• Soot formation at
different EGR rates
• Soot formation at
different piston bowl
geometries
Work done by H. Bladh et al, at Combustion Physics, Lund
University, Sweden
SLIDE 70 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Rayleigh Thermometry
SLIDE 71 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Rayleigh Thermometry
• The Rayleigh signal is dependent
on:
- Laser intensity
- Scattering cross section
- Number density
• If species composition and
pressure are known in the gas the
gas temperature can be
determined from imaging of the
Rayleigh scattering.
SLIDE 72 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Required data sets for
Rayleigh Thermometry
Measurement image
Reference image
SLIDE 73 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Results of Rayleigh Thermometry
analysis
Mean: 1350 K
RMS: 106
Mean: 1120 K
RMS: 61,3
Mean: 295 K
RMS: 12,2
SLIDE 74 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Rayleigh Thermometry results
Takes into account:
• Scattering cross-section
• Pressure
• Laser pulse energy
SLIDE 75 | JIMMY OLOFSSON | 2013
A Nova Instruments company
Thank you for your attention!
DANTEC
D Y N A M I C S
SLIDE 76 | JIMMY OLOFSSON | 2013
A Nova Instruments company