SOLUTION SHEETLIF Systems for Combustion Diagnostics
Complete, modern and modular solutions
for planar LIF measurements

The complete solution for LIF measurements in combustion research
Designed as a complete, modern and modular imaging system for data acquisition andanalysis, our Combustion LIF system it is a unique tool for experimental diagnostics ofcombustion by means of planar Laser-induced Fluorescence (LIF).
By handling measurements of combustion radicals, pollutants, fuel tracers etc., thesystem is suitable for studies of a vast number of phenomena, such as fuel injections,
ignition phenomena and flame fronts, ultimately improving the understanding ofcombustion processes.

Key benefits•

Non-intrusive imaging technique for measurements of several combustion species•

Compact and integrated tunable pump and dye laser systems with improved laser
safety and excellent beam quality•

Wide range of high-sensitivity cameras and image intensifiers•

Advanced synchronization with temporal precision down to sub-nanoseconds•

Complete software platform for system set-up, data acquisition, data analysis andvisualization of results•

Dedicated software modules for LIF of combustion radicals and LIF of fuel tracers•

Fully compatible also with Dantec Dynamics’ PIV systems, for combined multiparameter measurements

Flexible planar LIF system for measurements of combustion
species
Dantec Dynamics’ combustion LIF system utilizes a non-intrusive (optical),
two-dimensional measurement method based on the laser-induced
fluorescence emissions of molecular species. The system enables theuser to select between number of species to study, ranging from flame
radicals such as OH and CH, and pollutants such as NO and CO, produced
during combustion, to larger combustion species or tracers seeded into
the process such as Formaldehyde and Acetone. This makes the systemvery versatile, and well suited for combustion research. The beam from asophisticated tunable laser source is shaped into a light-sheet illuminatinga thin planar section of the combustion process and exciting the selectedspecies. The subsequent fluorescence is recorded by an intensified camera,
creating a map of the species distribution in the illuminated plane. Throughuser-friendly hardware and software the user quickly gains full confidence
to operate the system. As the backbone of our systems, we have developed
the most comprehensive imaging software for optical diagnostics –DynamicStudio. From here you can easily control the measurement system
as well as perform advanced image data analysis, to extract valuable
information for a better understanding of the studied combustion process.
Naturally, velocity information from a PIV system can be integrated forfurther advanced analyses combining combustion chemistry and fluid
mechanics.

The Combustion LIF system solutions in brief
The system consists of a Nd:YAG pumped, state-of-the-art tunable dyelaser with light-sheet optics, a camera equipped with an image intensifier
for imaging UV fluorescence, advanced electronics for hardware synchronization and software for straightforward data acquisition and analysis.

Overview of the different components, timing and data flow.

Laser light sources
The Nd:YAG laser, optimized for 10 Hz repetition rate, is equipped with atemperature stabilized 2nd harmonic generator, providing 430 mJ at 532
nm. Optionally it can also include a 3rd or 4th harmonic for applications
such as tracer LIF or Formaldehyde (HCHO) LIF. All Nd:YAG harmonicscome with intelligent auto-tuning to maintain optimum phase matching
and thus maximum output energy, clearly improving the user experience.
The air/water heat exchanger for this laser does not require external
water-cooling.
Two modular tunable dye laser models are available; a compact system(the most compact on the market) and an advanced system with a larger
footprint but with unique features to benefit the user.
The compact system is an advantage when lab space and/or economy
is of importance, however it uses both 532 nm and 355 nm from theNd:YAG laser for pumping, depending on what species/wavelength range
is required.
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Simultaneous dual-species PLIF by
two synchronized systems, showing
the flame front and postflame gases (OH, top) and the pre-heat layer(CH2O, bottom) in a turbulent labflame.

The advanced system can reach all species by using 532 nm pumping only.
This makes it easier for the user as there is no need to switch pump laser
output when switching to a different dye laser wavelength. As only 532
nm pumping is required, this also facilitates the use of more stable longlived laser dyes, instead of the use of the more short-lived dyes normallyassociated with 355 nm pumping. For the user this means no need for
frequent replacement of the dye, and more time to focus on the research.
The two dye laser models have several features in common. They enable
operation across a very wide range of wavelengths, direct tuning from 420
to 740 nm with 2400 l/mm grating. (Can optionally be expanded to 900 nm,
with an additional 1800 l/mm grating.) The lasers feature:•Linewidth 0.06 cm-1 at 570 nm providing more efficient excitation ofnarrow absorption lines, and thus increased signal-to-noise ratio•

Main amplifier with Bethune cell providing superior circular beam
quality and thus improved image quality•

Digital wavelength selection making it easy for the user to control froma computer•

Automated crystal phase matching even through wavelength scanningand thus no need for the user to do manual adjustments

UV / visible parallel light sheet optics

The laser comes with UV extension. To gain the highest energy level
outputs possible, the dye laser is equipped with dedicated, modular
crystals optimized for UV light. The crystal to produce the wavelengths
for OH excitation is included, and crystals for species such as CH, NO andCO can be added at any time. The output is fine-tuned by scanning thewavelength from the software, and the crystal phase matching follows
automatically to maintain optimum energy throughout the scan. The
pump and dye lasers are fitted together, virtually forming a single laser
unit which makes it easier for the user and ensures the best possible
stability for maintaining alignment.
Dantec Dynamics’ optical devices used to form parallel UV light sheets areincluded with the system. Light sheet dimensions are approx. 50 mm x 0.1
mm (when used with a beam waist adjuster) with a working distance of600 mm.

HiSense Zyla camera, image intensifier and UV front lensTo ensure a secure working environment, UV and visible light - fromthe Nd:YAG laser to the location at which the light sheet is formed - isall shielded. Laser alignment goggles and protective goggles are alsoavailable for your safety.

Cameras, Image Intensifiers and Lenses
The cameras and the image intensifiers are separate units, thereby
allowing existing hardware systems to be upgraded to combustion
applications. This solution is ideal for laboratories dealing with multiple
applications such as PIV, LIF in liquid and gaseous phases including
combustion processes, microscopy and spectroscopy. Typically a camera
from our HiSense family is selected, featuring high sensitivity and low
noise levels.
The image intensifier units are designed for UV, visible and near-IR
applications using a broadband Multialkali or S20 photocathode in order
to cover a wide range of LIF applications of different species. The units
offer full control over gain and gate time options ranging from continuous
to ultra-fast, with a minimum gate time of down to 3 ns, depending on
the model. Relay optics used to adapt the camera to the image intensifier
unit is also included. (Please refer to the related Data Sheets for further
information about these cameras and image intensifiers)
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LIF imaging of CH showing the thin
flame front at the base of a turbulent
gas flame.

Two camera lenses (f=78 mm and f=100 mm) with optimized transmission
for UV light are available together with an adapter ring for fittinginterference filters to the selected lens. Interference filters are available formeasurements of tracers and combustion species.

Synchronizer
Synchronization between laser pulses, cameras and image intensifiers
is mastered by the High Performance Synchronizer, fully controlled via
the DynamicStudio software. The synchronizer is a multi-channel delay
and signal generator with <= 1ns resolution. The 32 output channels
are programmed independently; thereby offering comprehensive
synchronization and triggering facilities for highly demanding processes.
It also features four input channels for synchronization with external
devices or events.

The High Performance Synchronizer
dedicated for LIF applications.

User-friendly imaging software platform- Straightforward data analysis
The image acquisition system is based on DynamicStudio, a comprehensive and user-friendly software platform for imaging applications. Itfeatures an advanced plug-and-play based distributed system, making
it easy for the user to get full control over the hardware for image
acquisition. Data acquisition as well as analysis is supported within thesame software, so there is no need to export the data for continuing withthe analysis.
With easy access to numerous numerical methods and quick andaccurate calibration and processing methods, users will experience thebenefits of working with a truly integrated solution.
Numerical methods available with the software:•Calibration (Tracers)•Processing (Tracers)•Statistics on LIF images and scalar maps•

Re-sampling•

Reynolds flux

OH distribution in a Bunsen type
flame, including a cross-section intensity plot and the result of gradientdetection showing the main reactionzone.

The software features many automated options such as laser pulseenergy correction (on each individual LIF image), hardware calibrationand processing routines etc.
DynamicStudio also features an Image Processing Library (IPL), which
is a comprehensive “catalogue” of numerical methods, offering quick
access to image quality enhancement, image filtering and other moreadvanced numerical processing to work with LIF images. Processing isfully automated and includes macro-analysis capability (i.e. sequence ofprocessing methods).

Boosting analysis capabilities with analysis sequences
and MatLab® Link
The data analysis is further strengthened by the possibility of defining
analysis sequences and performing batch processing, which significantly
speeds up the way of working with large data sets. And with the MatLabLink in DynamicStudio, you can tailor your analysis by calling up yourpersonally designed MatLab scripts directly from DynamicStudio,
allowing you to process the data directly in the database without theneed of first exporting the data.
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Simultaneous control of multiple systems
The modular design of the systems allows the user to control several different
systems at the same time from one master computer. In this way, a Combustion
LIF system can be combined with a PIV system for simultaneous combustion
species measurements and flow velocity measurements. Or two LIF systems canbe combined to measure two species simultaneously. With data from all systems
collected in one database, perfectly synchronized (time-stamped) correlated
analyses and visualizations are made easy.

Additional options
Pulse energy monitor
A proven method of reaching higher accuracy is to measure the laser pulseto-pulse fluctuations by means of a Pulse Energy Monitor and subsequently
compensate for this during LIF image analysis. The Pulse Energy Monitor can bemounted between the laser output and the light-sheet optics. The photo sensor issensitive to UV (down to 200 nm), visible and IR (up to 1100 nm) laser light and canmonitor laser pulses with a repetition rate of up to 1 kHz. For recording the output
signal from the pulse energy monitor an analog input solution is also required.

Technical specifications
Pump laser

Second harmonic

Third harmonic

Fourth harmonic

Wavelength (nm)
Pulse energy (mJ)
Pulse duration (ns)
Repetition rate (Hz)532
430355 (optional)
230~510266 (optional)
100

Tunable dye lasers
Fundamental tuning range,
2400 l/mm grating
Linewidth
Enhanced tuning added 1800
l/mm grating option
UV extension unit
Required pump beams
Crystals for species typically
included

Tunable dye laser 1:
Compact model

Tunable dye laser 2:
Advanced & user-friendly
420-740 nm< 0.06 cm-1 at 570 nm
420-900 nm

Frequency doubling
Frequency doubling/tripling
532 nm & 355 nm
532 nm only
OH, CH, NO and CO (typically 220-266 nm & 275-400 nm)

Camera

HiSense Zyla

Speed (fps)Resolution (MP)Sensor resolution (pixels)
Pixel size (µm)

495.52560 x 2160
6.5

Image intensifiers
Minimum gate time
Photocathode diameter
Photo cathode material
Phosphor screen
SoftwareDynamicStudio

H Series 18 mm

L Series 18 mm
3 ns18 mm

Multialkali

S20
P43

Base package
Combustion LIF Add-on for DynamicStudioLiquid and Gas LIF Add-on for DynamicStudio

Solution Sheet 0551_v3. Subject to change without notice. Copyright © 2019.
Dantec Dynamics. All Rights Reserved. www.dantecdynamics.com