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www.iitk.ac.in/erl
Laser Diagnostic Techniques forEngine Research
IIT Kanpur
Kanpur, India (208016)
Dr. Avinash Kumar Agarwal,
Associate Professor,Engine Research Laboratory,
Department of Mechanical Engineering,Indian Institute of Technology Kanpur
Optical Diagnostics
Increasing Environmental problems - more stringent Emission Control Norms
Demand to minimize fuel consumption
Better understanding of in-cylinder processes required
To use optical diagnostic techniques to visualize the in-cylinder processes
Even the simulation results need to be verified experimentally using Optical
Diagnostic Techniques
Engine Research Laboratory, IIT Kanpur
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Very high non-steady pressure and temperature conditions; high mechanical and
thermal stresses
proper lubrication not possible, liner heating
Optical Access: Major Challenges
supporting structure should not block the optical access
requirement of a flat optical window
aberration due to unwanted scattering
maintaining realistic engine geometry
Engine Research Laboratory, IIT Kanpur
Optical Access
Optical access is usually obtained by:
Full Optical Access:
Transparent Piston Head, and
Endoscopic Access:
Optical Fiber based Endoscopic windows
Common Materials used:
Quartz
Sapphire
Engine Research Laboratory, IIT Kanpur
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Full Optical Access vs. Endoscopic Access
Full Optical Access:
The optical access is maximized to allow application of complex opticaldiagnostic techniques while maintaining minimum necessary operability of theengine or engine components
Full optical access allows a wide range of diagnostics to be applied
Endoscopic Access:
Full engine operability is maintained while optical access and diagnostictechniques are tailored to the diagnostic demand and the restraints of engineoperation
Engine Research Laboratory, IIT Kanpur
Endoscopic access puts the emphasis on organizing and extending realisticengine operation conditions
Full Optical Access
Transparent CylinderLiner
Engine Research Laboratory, IIT Kanpur
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Endoscopic Access Arrangement
Engine Research Laboratory, IIT Kanpur
Optical Diagnostic Techniques
Particle Image Velocimetry (PIV)
Scattering
Mie/Raman/Rayleigh Scattering
Self Emission Spectroscopy
LASER Induced Fluorescence (LIF)
Planar LASER Induced Fluorescence (PLIF)
LASER Induced Incandescence (LII)
Laser Holography
Laser Doppler Velocimetry
Engine Research Laboratory, IIT Kanpur
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Particle Image Velocimetry (PIV)for IC Engines
Engine Research Laboratory, IIT Kanpur
Technique Study flow of a Fluid.
The flow is illuminated with a double pulsed light sheet and the positions of a
large number of tracer particles are recorded with a photographic camera viewing
What is PIV?
.
Advantages of PIV
Non-intrusive into the flow field being studied.
2D or 3D full-field flow measurements can be made.
Instantaneous velocity fields are obtained.
Engine Research Laboratory, IIT Kanpur
Capability for studying multiphase flows.
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Single and multi-phase channel flows .
Steam bubble collapse
Flow around cylinders in a channel
PIV can be Used to Study:
u y p pe ows
Free surface experiments
Sprays
Heated cavity flows
Engine Research Laboratory, IIT Kanpur
PIV measures whole velocity fields by taking two images shortly after each other
and calculating the distance individual particles travelled within this time. From
the known time difference and the measured displacement the velocity is
calculated.
Principle of PIV
3-D PIV
based on the principle of stereoscopic imaging: two cameras capture the image of
the illuminated particles from different angles and then the images are digitally
combined to obtain a 3-D images.
Engine Research Laboratory, IIT Kanpur
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Seeding: The flow medium is seeded with particles, droplets or bubbles
Double Pulsed Laser: Two laser pulses illuminate these particles with short timedifference
Light Sheet Optics: Laser light is formed into a thin light plane guided into the
Components
flow medium
CCD Camera: A fast frame-transfer CCD captures two frames exposed by laser
pulses
Software: Calculates the velocities and makes Velocity Maps
Engine Research Laboratory, IIT Kanpur
Principle of Particle Image Velocimetry (PIV)
PIV is a technique for the measurement of instantaneous planar velocity fields.
Engine Research Laboratory, IIT Kanpur
Experimental Arrangement for PIV in a Wind Tunnel
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Particle Image Velocimetry (PIV)
Definition
An optical imaging technique to measure fluid orarticulate velocit vectors at man e . Thousands
points in a flow field simultaneously.
Measurements (2 or 3 components of velocity) usually
made in Planar slices of the flow field.
Engine Research Laboratory, IIT Kanpur
Accuracy and Spatial resolution
Comparable to LDV and HWA.
Particle Image Velocimetry
Engine Research Laboratory, IIT Kanpur
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PIV - Principle
Engine Research Laboratory, IIT Kanpur
Cross-correlation
Interrogation
region
Interrogation
region
particleparticledisplacementdisplacement
Cross-
correlation
frame 1
frame 2
Crosscorrelation
Vector fieldVector field
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Components Needed for PIV:
an illumination source
optical system for illuminating the testsection.
field
a system for image processing, particleidentification, particle tracking, andvector field cleaning
The laser is synchronized with thedi ital ima ers the laser li ht is
Engine Research Laboratory, IIT Kanpur
positioned to illuminate the test volume,the scattered light from the tracer
particles is recorded with the digitalcameras, and then image analysis isperformed.
General Aspects of PIV
Non-intrusive velocity measurementIndirect velocity measurement
Whole field technique
Velocity lag
Illumination
Duration of illumination pulse
Time delay between illumination pulses
Distribution of tracer particles in the flow
Density of images of tracer particles on the PIV recording
Low image density (PTV)
Medium image density
High image density (LSV)
Engine Research Laboratory, IIT Kanpur
Number of illumination per recording
Number of components of the velocity vector
Extension of observation volume
Extension in time
Size of interrogation area
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Light Source (LASER): Laser Material, Pump Source, MirrorArrangement
Schematic of a laser
Engine Research Laboratory, IIT Kanpur
Various Kinds of interactions between atoms and electromagnetic radiation
Three level laser system Four level laser system
Engine Research Laboratory, IIT Kanpur
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Particle Generation and Supply
For seeding gas flow: Air jets, condensation generator, atomizers, smoke
generators, Laskin nozzle generators.
Types Material Mean
Diameter (m)
Solid Polystyrene
Aluminum
Glass Sphere
Granules for synthetic
coating
10-100
2-7
10-100
10-500
Types Material Mean
Diameter
(m)
Solid Polystyrene
Aluminum
Magnesium
Glass micro-balloonsGranules for synthetic
coating
10-100
2-7
2-5
30-10010-50
1-10
Engine Research Laboratory, IIT Kanpur
Liquid Different oils 50-500
Gaseous Oxygen bubbles 50-1000
Dioctylphathalate
Smoke
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PIV Recording Techniques
Single frame/multi-exposure PIV Multi-frame/single exposure PIV
Types of CCD Camera
- Frame transfer CCD Interline transfer CCD Full-frame interline transfer CCD
POST-processing of PIV Data
Replacement of incorrect data
Engine Research Laboratory, IIT Kanpur
Analysis of the information Presentation and animation of the information
Study of IC Engine Charge Motion Using PIV :
Charge motion within a IC Engine has a Significant effect on:
Power Output
Fuel Efficiency
Exhaust Emissions
The combustion behavior of internal-combustion s ark-i nition SI en ines is
strongly dependent on:
The quality of the mixture processing, which in turn is affected by the motion of
the in-cylinder flow.
Fresh charge, and residual gas resulting from the former combustion cycle, have
to form a proper mixture.
In addition, a certain level of turbulence is required at the time of ignition to
erform an accelerated flame ro a ation and thereb a hi hl efficient
Engine Research Laboratory, IIT Kanpur
combustion.
Therefore, it is highly importance to collect detailed information on the in-
cylinder flow field and its temporal development during the combustion cycle. PIV
has proven to be a helpful tool in order to analyze the air-flow in the cylinder.
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Fluid motion within IC engine fundamentally affects
engine performance and emissions.
To analyze and optimize complex coupled processes
inside and between automotive components and
Engine Manufacturers aredeveloping more fuel
efficient, more refined andwhich produce lower amountof pollutants.
Introduction
or outer acoustic noise, including brake noise, and
the combustion analysis for diesel and gasoline
engines to further reduce fuel consumption and
pollution.
Deeper insight in modern engine combustion
concepts such as flow generation, fuel injection and
spray formation, atomization and mixing, ignition
Engine in-cylinder fluid
motion is known to
fundamentally affect the
combustion process.
It is important to understandcombustion phenomenon
Engine Research Laboratory, IIT Kanpur
and combustion, and formation and reduction of
pollutants.
The need for an non-intrusive measurement system.Laser Assisted Diagnostics is an important tool for
such measurements.
under different operatingconditions such as valve
deactivation, port injectionand variable injection timing.
Objective
PIV Is used to investigate the in-cylinder fluid motions and its interaction withpropagating flame in a production geometry pentroof multi-valve optical SIengine, fired using liquid fuel.
This allows mapping of the flame position and study of the fluid motion aheadof flame front.
Two color PIV is used to obtain full field instantaneous velocity data over planerregions within the combustion chamber with a spatial resolution of less than 1.5mm. Si oil seed burn in the flame front hence it is possible to distinguish theburnt and unburned re ion of the inc-c linder flow.
Engine Research Laboratory, IIT Kanpur
The flow structures distribution were obtained with both open and closed inletvalve injection timing under normal running and with a single inlet portdeactivated.
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Optical Engine
Bore mm 80Stroke mm 89Swept Volume cc 447 cc
Compression ratio (nominal) 10 : 1Inlet valve peak lift 70 BBDC
Exhaust valve peak lift 70ABDC
ng ne pee 1000 rpm
Salient Features
Single Cylinder Optical Engine
Pent-roof combustion Chamber
Production grade, four stroke, fourvalve per cylinder, Rover K series
Engine Research Laboratory, IIT Kanpur
Fused Silica Barrel
Extended Piston incorporating Fused
Silica Piston Crown Window.
Port injected with iso-octane and skipfired
Schematic of Experimental Facility
Average diameter of Sioil droplets seed: 1.4m
Large Scale Motion
,amplifier Nd:YAG laser,frequency doubled togenerate green light at532 nm. (Pulse duration10s)
Engine Research Laboratory, IIT Kanpur
Cycle to Cycle Variation
Small Scale Motion
Flame Convection
Flame Geometry
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Illustration of 3-D Motion Inferred from Planer Data
Engine Research Laboratory, IIT Kanpur
Measurement
Plane
340-380CAD
Normal Running Conditions
One Inlet Port Deactivated Condition
Measurement Conditions
Data acquisition in
Horizontal Plane
Horizontal light sheet located 2mm above the piston at TDC
Ignition timing 25BTDC
Start of Injection 10ATDC
amera mag ng o t e 45m rrorand through the piston window
Vertical Plane
Vertical light sheet falling on 45mirror and through the pistonwindow
Camera imaging in horizontallane close to iston at TDC
Engine Research Laboratory, IIT Kanpur
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Normal Operating Conditions
Engine Research Laboratory, IIT Kanpur
Normal Running 20 CAD BTDC
Engine Research Laboratory, IIT Kanpur
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Normal Running 10 CAD BTDC
Engine Research Laboratory, IIT Kanpur
Normal Running TDC
Engine Research Laboratory, IIT Kanpur
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Normal Running 10 CAD ATDC
Engine Research Laboratory, IIT Kanpur
Normal Running 10 CAD ATDC
Engine Research Laboratory, IIT Kanpur
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Inlet Port Deactivated Condition
Engine Research Laboratory, IIT Kanpur
Port Deactivated Condition 20 CAD BTDC
Engine Research Laboratory, IIT Kanpur
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Port Deactivated Condition 10 CAD BTDC
Engine Research Laboratory, IIT Kanpur
Port Deactivated Condition TDC
Engine Research Laboratory, IIT Kanpur
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Port Deactivated Condition 10 CAD ATDC
Engine Research Laboratory, IIT Kanpur
Port Deactivated Condition 20 CAD ATDC
Engine Research Laboratory, IIT Kanpur
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Scattering
Principle: When light interacts with matter different scattering processes can
happen simultaneously or exclusively depending on chemical and physical properties
of the scatterer. Therefore scattered light contains information about the material, it's
size and environmental conditions like temperature.
Mie imaging:
elastic scattering; same wavelength as the incident light; intensity is proportional to
the size of the scattering particles; for particles which are large compared to the
wavelength of the incident light.
Rayleigh imaging:
elastic scattering; same wavelength as the incident light; intensity is proportional to
the intensity of incident light, a material-dependant constant and the number density
of particles; for particles are small compared to the wavelength of the incident light.
Engine Research Laboratory, IIT Kanpur
aman mag ng:
inelastic scattering; shows a spectral response that is shifted from the laser line and
characteristic for the Raman active molecules; do not suffer from collisionquenching.
Applications
Mie Scattering :
particle analysis (size, shape, distribution)
flow analysis (velocity information PIV)
spray analysis (particle size distribution and spray geometry)
Rayleigh Scattering:
combustion processes
pollutant formation
total gas density
temperature fields
Engine Research Laboratory, IIT Kanpur
Raman Scattering: majority species concentrations
space and time-resolved
mixture fractions
local temperature
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Self Emission Spectroscopy
Principle:
During combustion many species get excited due to the high temperaturesinvolved, as their electrons come back to the ground state they emit light which
can be resolved to give the fingerprint spectra studying which the type and
The two-colour method relies on the measurement of the radiation intensity
from soot particles which are generated during combustion. The radiation
intensity can then be measured at two wavelengths.
Applications
Flame temperature, flame location & stability
Engine Research Laboratory, IIT Kanpur
Spatial Soot concentration
excited species distribution like OH*, CH*, C2*
on-set of ignition
Laser Induced Fluorescence (LIF)
Engine Research Laboratory, IIT Kanpur
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LASER Induced Fluorescence (LIF)Principle:
the species of interest is excited using a LASER light of specific wavelength.
the electrons move to a higher energy level, emits light at some characteristicwavelengths on returning, this is the fingerprint of the species.
the emission spectrum is specific for the molecule.
.
LIF signal is quite strong and can be filtered from the incident laser wavelength.
LIF signal is proportional to the volume of a liquid droplet, leads to a directmeasurement of the droplet size.
Engine Research Laboratory, IIT Kanpur
LIF and Scattering Spectra
Laser Induced Fluorescence (LIF)
Molecules/atoms are excited tohigher energy states.
Intensity of fluorescence is afunction of species concentration(number density), and the gastemperature and pressure.
Selective detection of NO is possibleeven in inhomogeneous combustionenvironments like in direct injectinggasoline and diesel engines.
This technique allows the effective
Fluorescence is linearly related tonumber density.
Spectral absorption regions arediscrete.
Fluorescence occurs atwavelengths laser wavelength.
suppress on o n er er ng s gna sdue to hot oxygen and partially burnedhydrocarbons.
With this technique, influence of laserbeam attenuation is minimized.
The LIF images represent the NOconcentration present in the planedefined by the position of the laserA chemiluminescence detector (CLD)
Engine Research Laboratory, IIT Kanpur
eam w ereas t e ex aust gasmeasurements represent averagedconcentrations after homogeneouslymixing the burned gases during theexpansion and exhaust stroke.
s use o con ro e n a econcentration during calibrationmeasurements and for additionalexhaust gas NOX concentrationmeasurements for the differentoperating conditions.
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LASER Induced Fluorescence (LIF)
Applications of LIF:
OH, NO, O2, CnHm, H2and H2O
Pollutant formation
. .
spray injection
liquid/gas transition
velocity fields
droplet size
Engine Research Laboratory, IIT Kanpur
LASER Induced Fluorescence (LIF)
PLIF:
Sheet of LASER light is used to excite; 2-D imaging
LIPF:
to avoid quenching short lived quantum states are excited and these
'predissociative' states are so fast that no collisions occur during their
lifetime
Engine Research Laboratory, IIT Kanpur
Tracer-LIF:
a medium is seeded with proper tracer material to make it visible or to
observe its mixing with other medium
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Case Studies of LIF
Optically Accessible DIGasoline Engine
Schematic of Laser-Based Imaging Setup
Engine Research Laboratory, IIT Kanpur
mag ng measuremen s ase on n-cy n er- orme orma e y e an 3-
pentanone as a fuel tracer under controlled auto-igniting (CAI) conditions.
Fuel consisting of 50% n-heptane and 50% iso-octane is used to ensure stable
auto-ignition while having the reduced compression ratio and temperature
typical of most optically accessible engines.
NO distribution in a DI diesel engine with PLN and CR injection System:
Pump-line-nozzle (PLN) system: it consists of a cam driven pump, a shortinjection line and an injection nozzle. The injection pressure increases from a lowlevel after start of injection.
Common-rail (CR) system: A constant rail pressure is provided.
Case Studies of LIF
Engine Research Laboratory, IIT Kanpur
Two different detection systems for recording 2-D images andspectroscopic data
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LIF to visualize the flash boiling effects on the development of GDIengine sprays:
LIF is used for spray characterization because of its possibility to differentiatebetween the liquid and the vapor phase.
LIF can be combined with a long distance microscope so it is possible to
Case Studies of LIF
the area nearby.
Flash boiling effect causes a rapid spray breakup into a mixture of vapor andsmall droplets.
Engine Research Laboratory, IIT Kanpur
Planer LIF
Engine Research Laboratory, IIT Kanpur
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What is Combustion PLIF?
Combustion PLIF tells us how the fuel is burning, byshowing the location of key species like OH, CH, NO,band CHO.
CO2 + H2O + N2OH
CH
OH
Soot (C2)
Engine Research Laboratory, IIT Kanpur
CHO
C3H8 + O2 + N2
What is Combustion PLIF?
We work with molecules, NOT particles
Species absorbs laser light, emits fluorescence
uorescence g s co ec e an ana yze
We examine the intensity of this light, and spatial variation Where does it exist in space?
It is possible to relate the image intensity to temperature orconcentration
Engine Research Laboratory, IIT Kanpur
Propane Flame:Where is the OH?
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How does PLIF work ?
A sheet of laser light illuminates a plane
A target species within the plane of the sheet absorbs light at the wavelengthof the laser, exciting the species to a higher energy state
The high energy state decays to a lower energy state, emitting a photon
The emitted photons are collected on a CCD array
Engine Research Laboratory, IIT Kanpur
e g ta mage s nterprete
Measurements with PLIF
Temperature or concentration
Heat transfer
Mass transfer
Mixing pH
Possible but not common Species measurement
Used to monitor chemical reaction intermediates
Engine Research Laboratory, IIT Kanpur
om us on, ame, an eng ne s u es Pressure
Requires calculations based on known temperature,concentration
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PLIF System Components
Illumination Subsystem - Laser (Mixture of Dye Laser & Nd:YAG
266/532 nm Lasers), Beam delivery, Light optics.
ave engt
Pulse energy
Repetition rate
Image Capture Subsystem CCD Camera, Intensified CCD Camera.
Capture the Fluorescence image and record them.
Analysis Subsystem
Engine Research Laboratory, IIT Kanpur
a cu ates an sp ays a two- mens ona sca ar e rom t e uorescence mage
field.
Planer LIF
A laser source, usually pulsed and tunablein wavelength, is used to form a thin lightsheet.
If the laser wavelength is resonant withan optical transition of a species, a
PLIF Imaging of Self-Ignition
Centers in SI Engine
absorbed. Absorbed photons may subsequently be
reemitted with a modified spectraldistribution.
The emitted light, known as fluorescence,is collected and imaged onto a solid-statearray camera.
The light detected by a camera dependson the concentration of the interrogated
Plan view into the combustion chamber,showing the self-ignition regions
Knock intensity is related to pressuretraces.
The pressure recorded during knockingoperation is non-uniform throughoutthe c linder
Engine Research Laboratory, IIT Kanpur
measurement volume and the local flowfield conditions.
This technique offers excellent temporalresolution (order of ns) and yieldsinformation along a thin (0.2 mm andbetter) 2-D plane.
. Analysis of such traces does not yield
any spatial information about the self-ignition process.
Thus, optical techniques (e.g. PLIF) areused to obtain spatially and temporallyresolved information.
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Experimental Engine Optical Setup
Engine Research Laboratory, IIT Kanpur
with Optical Access
chamber
PLIF Measurements in HCCI Engine
Engine Research Laboratory, IIT Kanpur
Scania D12 single cyl engine Bowditch type ScaniaD12 engine
Optical setup for measurementsin the Scania D12 engine
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Previously, it was impossible to decide about growth of structure. Also,
measurements did not reveal if new ignition kernels appeared during the
combustion event.
High speed imaging system reveal distributed gradual consumption of fuel or
.
The PLIF sequences shows a well-distributed gradual decay of fuel concentration
during the first stage of combustion.
During the later parts of the combustion process, the fuel concentration images
present much more structure, with distinct edges between islands of unburned
fuel and products.
Engine Research Laboratory, IIT Kanpur
Intensity histograms reveals that the transition from fuel to products in the HCCI
engine is a gradual process.
The engine configuration, laser sheet orientation and air/fuel ratio do not
influence the general results.
Laser Induced Incandescence (LII)
Engine Research Laboratory, IIT Kanpur
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LASER Induced Incandescence
Principle:
intense laser light sheet is used to illuminate and slice the (reactive) particle flow at
user defined locations.
the particles within the light sheet are heated up to the carbon evaporationtem erature > 000K .
the resultant incandescence (blackbody emission) of the heated particles isdetected with a fast shutter camera synchronized to the laser pulse.
appropriate filtering and time-gating of the LII emission assure accurate sootvolume fraction measurements.
Mechanism: It involves heating the particles using an intense laser pulse to theirsublimation temperature. A soot particle can absorb energy from the beam, which
Engine Research Laboratory, IIT Kanpur
. ,energy. If the energy absorption rate is sufficiently high, the temperature will riseto levels, where significant incandescence and vaporization can occur. Thesethermal radiation, when collected after an appropriate time delay is found to bedirectly proportional to the local mass concentration under specific controlledconditions.
LASER Induced Incandescence
A technique used for exhaust emissionmeasurements in engines.
Planar imaging of soot distributions insteady flames and diesel sprays.
LII gives a direct measure of the sootvolume fraction (elemental carbononly).
.However, sensitivity is limited only bythe size of the measurement volume.
Neither cooling nor dilution arerequired, and measurements can bemade either in situ or by continuoussampling through an external opticalcell.
The LII technique is capable of real-timemeasurements during transient vehicleo eration for o timizin soot emissions
Engine Research Laboratory, IIT Kanpur
performance. Also, this technique can be executed
with other laser-based techniques toobtain particle size and number densityinformation.
Ensemble-averaging for many enginecycles can be used to reconstruct cycle-resolved transient behavior. Sectional top view of optical cell for LII measurements
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Laser Holography
Engine Research Laboratory, IIT Kanpur
Sectional top view of optical cell for LII measurements
Principle of Holography Method
An object beam and a reference beam are required during recording.
In-line method: The object beam also serves as the reference beam. It is used for
droplet measurement. However, it is difficult to obtain a clear image in an area
.
Off-axis method: The reference beam and object beam take different optical
path.
Interference fringes on the holographic plate are recorded by adjusting the
difference of the optical path of object beam and reference beam. Reconstruction
beam is incident on the holographic plate to reproduce the spray image in the
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space. Enlarged photograph is taken using CCD camera and diameter of each
droplet is measured. Then the 3-Dimensional structure of the droplet is obtained.
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Experimental Setup
Optical Recording SystemPrincipal of Holography
Engine Research Laboratory, IIT Kanpur
Optical Reconstruction System
Laser Holography
To measure atomization: Laser holography method, Direct recording method,The PDPA method, and the Fraunhofer diffraction method.
The holography method is a 3-D measuring method, which utilizes the
interference of light. The Phase Doppler Particle Anemometry (PDPA) method
utilizes the Doppler signal of the droplets. The Fraunhofer diffraction method
obtains the distribution of the droplet diameter from the distribution of
diffracted light.
Laser holography method can
record the shape of each droplet in
the entire spray area and the spatial
distribution with one recording.
Engine Research Laboratory, IIT Kanpur
in high-density fields, long
analyzing period.
Measuring Methods of Spray Droplets
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Laser Doppler Velocimetry (LDV)
Engine Research Laboratory, IIT Kanpur
Laser light source
Light separation optics
Li ht transmittin o tics Li ht collectin
Major Components of LDV System
optics
Photo-detectors
Signal processing electronics
External data input devices
Com uter
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Software
Traversing system
Seed particles
Experimental Setup of LDVfor Diesel Spray Breakup
Length
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Laser Doppler Velocimetry (LDV)
Data at a single point. Offers flexibility.
It works in air or water. As micron-sized particles entrained
in a fluid pass through theintersection of two laser beams, the
Applications:Measurements of rotor tip vortices usingthree-component Laser DopplerVelocimetry.LDV measurements in a boundary layer.Survey of a wake field.
scattered light received from theparticles fluctuates in intensity.
The frequency of this fluctuation isequivalent to the Doppler shiftbetween the incident and scatteredlight, and is thus proportional to thecomponent of particle velocity.
The velocity direction can be fixed if
.Measurement of Diesel Spray BreakupLength
Diesel spray characteristics by laserDoppler signals:Spray tip penetration and spray breakuplength are simply obtained by measuringthe delay time of Doppler signals from
Engine Research Laboratory, IIT Kanpur
one o t e aser eams as afrequency slightly different from that
of the other. The frequency is measured usingdigital computers or photoncorrelators or spectral analyzers.
measuring point.Spray breakup length is estimated by
measuring the standard deviation of thedelay time of Doppler signals, whichindicates dispersion of the time frominjection start to Doppler signal rising.
Thermal Anemometry LDV
Comparison of Various Methods of Flow Measurements
Invasive method of measuring1, 2, or 3 components of velocity
using a heated wire or film sensor
Non-invasive method of measuring1, 2, or 3 components of velocity
using a laser technique
PIV Particle Diagnostics
Engine Research Laboratory, IIT Kanpur
Non-invasive method of measuring2 and 3 components of velocity in aplane using a double-pulsed laser
Non-invasive method of measuringParticle, droplet, or bubble sizeusing laser techniques
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Engine Research Laboratory, IIT Kanpur