SOLUTION SHEETLII System

Soot-volume-fraction measurements by Laser-Induced Incandescence

Quantitative soot-volume-fraction imaging
Combining the latest developments in laser and imaging technology with our userfriendly software, the Laser-Induced Incandescence (LII) system is a powerful tool forsoot diagnostics. With full control over data acquisition and analysis, the system offers
quantitative 2D imaging of soot-volume-fraction and carbon concentration, and is well
suited for applications in open laboratory flames as well as IC engines and industrialenvironments.

Key benefits•Non-intrusive imaging technique for measurements of soot volume fraction and carbon
concentration•

Compact yet powerful laser solution with excellent beam quality•

High sensitivity camera•

Advanced synchronization with temporal precision down to sub-nanoseconds•

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

Software module for calibration and processing data to gain direct information on sootvolume-fraction (in ppm) and carbon concentration equivalent (in mg/cm3)

Soot diagnostics for combustion applications
Soot is considered a hazardous pollutant emission and is typically the resultof incomplete combustion processes, and thus related directly to combustion
performance. Laser-Induced Incandescence (LII) is a laser-optical measurement
technique dedicated to soot diagnostics. LII can provide measurements of sootvolume fraction (e.g. in diesel engine exhaust) and even instantaneous images ofsoot distribution during formation inside a running IC engine.

The LII system in brief
Laser-Induced Incandescence data is obtained in a plane by illuminating the process
under investigation with a thin laser light sheet. The illuminated soot particles
absorb the light and are heated up by the laser excitation to very high temperatures.
As a consequence of the increased temperature, the soot particles emit increased
levels of black body (Planck) radiation or incandescence. The incandescence is thenrecorded by an intensified camera placed perpendicularly to the light sheet. As theincandescence intensity is related to the soot-volume-fraction, quantitative sootvolume fraction measurements can be made, with a proper calibration.

Overview of the different components, timing and data flow.

Laser light source
The Nd:YAG laser, optimized for 10 Hz repetition rate, is equipped with a temperaturestabilized 2nd harmonic generator which provides 430 mJ at 532 nm. The 2nd
harmonic unit comes with intelligent auto-tuning to maintain optimum phasematching and maintain maximum output energy over time. The laser is easy tooperate and does not require external water-cooling or other complex infrastructure.
Our robust Light Sheet Optics are included with the system and provide a parallellaser sheet for consistent light intensity. A parallel light sheet is required to assurethat the intensity distribution, over the laser sheet height, is the same over theobserved length of the Field-of-View. Light sheet dimensions are approx. 50 mm x0.1 mm (when used with a beam waist adjuster) with a working distance of 600 mm.
To ensure a secure working environment, laser alignment goggles and protective
goggles are available.
Cameras, Image Intensifiers and Lenses
The standard camera for Laser-Induced Incandescence is the HiSense Zyla camerafeaturing high sensitivity and low noise levels.
The image intensifiers are designed for UV, visible and near-IR applications using
a broadband Multialkali or S20 photocathode in order to cover a wide range of
combustion related applications. The units offer full control over gain and gate
time options ranging from continuous to ultra-fast, with a minimum gate time as
low as 3 ns depending on the model. Relay optics used to adapt the camera to theimage intensifier are also included.
We offer a wide range of camera lenses for visible light, together with an adapter
ring for fitting filters to the selected lens. Each system includes a lens to optimize
the magnification and field-of-view for the scope of the measurement along withthe option of an interference filter for Rayleigh Thermometry.
Page 2HiSense Zyla camera, image
intensifier unit and front lensThe camera and image intensifier are separate units, allowing for flexible useof the hardware. This solution is ideal for laboratories dealing with multiple
applications such as LII, Rayleigh Thermometry, LIF, PIV, microscopy andspectroscopy.
High Performance Synchronizer
Synchronization of laser pulses, cameras and image intensifiers is masteredby a High Performance Synchronizer, fully controlled via the DynamicStudiosoftware. The synchronizer is a multi-channel delay and signal generator with<= 1 ns 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 forsynchronization with external devices or events, two analog inputs with up
to 500 kHz sample rate, and four analog outputs. For further details, please
consult separate data sheet on “Imaging Synchronizers”.

High performance synchronizer

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. It features anadvanced plug-and-play based distributed system, making it easy to get fullcontrol over the hardware for image acquisition. Data acquisition and analysis
are supported within the same software, so there is no need to export the datafor post-processing.
The LII software add-on contains dedicated calibration and processing
routines. The LII routine offers quick and reliable calibration by simplyrecording a single set of LII images at well-known conditions. The calibration
sequence only requires specifying two distinct regions in the image set withknown soot levels; checking the scale option, ‘in ppm’ (linear-linear calibration)or ‘mg carbon/cm3 (log-log calibration); and completing the simple laser lightsheet information dialog. The result is an accurate calibration which can beused for direct transformation of LII images into ppm or carbon concentrationequivalent maps.
In the LII Processing, the calculation of soot-volume-fraction or carbonconcentration equivalent is performed based on the previously generated
calibration. With automatic compensation for laser energy and distribution
variations between pulses, the image processing is both simple and accurate.
To make image processing even more reliable for sooty combustion processes,
we have developed advanced algorithms which compensate for non-linear
absorption phenomena on individual soot maps. This High-Accuracy Module
enables data correction based on energy budget, local energy absorption
calculations and penetration lengths.
Boosting analysis capabilities with analysis sequences and MATLAB® LinkThe data analysis is further strengthened by the ability to define analysis
sequences and perform batch processing which makes quick work ofprocessing large data sets. And with the MATLAB Link in DynamicStudio, you
can tailor your analysis by calling up your personally designed MATLAB scripts
directly from DynamicStudio, allowing you to process the data directly in thedatabase without the need to export.

OptionPulse 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 ismounted between the laser output and the light-sheet optics.
Page 3

Soot-volume-fraction measurement in a sooting diffusion flame.

Technical specifications
Laser
Wavelength (nm)				532Pulse energy (mJ)				
430
Pulse duration (ns)			
~5Repetition rate (Hz)			
10

Light sheet optics
Wavelength range 			Light sheet height			

UV and visible
50 mm

Camera 					HiSense Zyla
Speed (fps) with frame grabber/with USB
49/40
Resolution (MP)				5.5Sensor resolution (pixels)			
2560 x 2160
Pixel size (µm)				
6.5
Lens mount				F-mount or C-mount

Image intensifiers*

H Series 18 mm

L Series 18 mm

Minimum gate time			

3 ns

Photocathode diameter 			

18 mm

Photo cathode material

Multialkali

S20

Phosphor screen				P43Camera attachment			

C-mount

Lens attachment				F-mount

Camera lenses and filters
Focal length and aperture		
50mm f/1.4, 85mm f/1.4, 100					mm f/2.0
Filter adapter		Adapter for 62 mm filter 							included
Lens mount				F mountHigh Performance Synchronizer
Time resolution				<= 1 ns
Synchronization outputs		

32, TTL

Synchronization inputs		

4, TTL

SoftwareDynamicStudio		Base package
LII Add-on

Data Sheet 0559_v1. Subject to change without notice. Copyright © 2019.
Dantec Dynamics. All Rights Reserved. www.dantecdynamics.com