SprayMaster

Spray Imaging Systems

for
Quantitative Spray Analysis
 Vision for Sprays

SprayMaster is a complete family of imaging systems for state-of-the-art

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spray characterization. The innovative measurement techniques applied in

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the SprayMaster systems provide new insights into even complex spray

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processes and permit cost effective and efficient development of smarter

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spray systems.

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ay V

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Planar measurements are performed on (laser) light sheets with excellent

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spatial and temporal resolution. The unique combination of different laser
imaging techniques allows multi-parameter measurements with nearly the
same system setup.

SprayMaster systems are easy to operate, fast and efficient measurement

tools suitable for R&D as well as quality control applications.
LaVision is committed to their customers. We work in close cooperation
with our customers to solve their specific needs with innovative solutions.
Integrated turn-key spray imaging systems with unique capabilities are
our speciality.

Temporal evolution of a pulsed spray: time sequence of the global spray mass distribution

SprayMaster Combustion
Applications 4Oil burners
4Automotive sprays (diesel and gasoline)
4Gas turbines

Coating and Additives

4Painting
4Insulation and encapsulation

Treatment
4Humidification and misting
4Washing and cleaning
4Fire protection (sprinkler systems)
4Agriculture

Production & Processing

4Drying and cooling
4Foam and dust control

2
 Processes &
Quantities

The major task of a spraying application is the conversion of a liquid This complex multi-stage spray formation process has to be optimized
fluid into fine droplets having a designated size range and distribution. for each desired application. For example, for coating, painting and
The processes involved are the breakup of the liquid structures wetting processes the interaction of the spray with a surface is important,
into droplets followed by further atomization into smaller droplets. while in combustion spray penetration, evaporation and fuel-air mixing
Eventually the fluid may evaporate and mix with the surrounding gas. are essential process parameters without generating liquid films on
combustion chamber walls.

Spray Visualization Laser Sheet Imaging

SLIPI
Liquid sheet
Spray Formation
Atomization

Primary breakups
Void

Hollow Rupture
inner

E. Kristensson, ILASS-Europe 2013

region
Droplet Transport

Secondary
Spray Region

breakups Large
droplets

Small
droplets

Evaporation
Spray-Surface Interaction Film Formation

As this spray formation takes place in a millisecond time scale and in a

Advantages of laser sheet imaging:
millimeter spatial range, diagnostics for spraying applications require high
spatial and temporal resolution without disturbing the spray process. This
4Instantaneous visualization of (transient) sprays
is best achieved by using optical diagnostics based on laser sheet imaging.
4Excellent spatial and temporal resolution
4Non-intrusive in-situ spray characterization
Laser imaging can be applied from macroscopic to microscopic
4Versatile technology supporting multi-parameter spray
measurements
measurements, from qualitative to quantitative spray characterization,
from planar to 3D imaging and from single-shot to high-speed imaging.

3
 Spray
Characterization

Spray Imaging
Overview
4Multi-phase
flow fields
4Mass flux
4Spray geometry
4Cone angle
4Patternation

4Local drop size

4Drop velocity
4Planar droplet sizing 4Mass transfer
4Sauter Mean Diameter D32

4For dense sprays

4Mass distribution
4Liquid/vapor phases 4Mie or LIF
4Liquid temperature
4With LIF tracers

Spray propagation: high-speed imaging at several kHz

4
 Systems &
Techniques

LaVision‘s SprayMaster systems enable the user to measure accurate and The accurate timing of (laser) spray imaging is under control of the
precise spray data from nearly all types of sprays including continuous SprayMaster system enabling variable exposure times for continuous
sprays, periodic pulsed or transient sprays. sprays, automatic phase scans for periodic sprays and precise high-speed
recordings for transient spray phenomena.
Its inspex versions based on backlights or light sheets are designed for
routine measurements of spray geometry and patternation. A customized Structured Laser Illumination Planar Imaging (SLIPI) applying spatially
Graphical User Interface (GUI) supporting remote system control is a modulated laser sheets is a novel laser imaging technique reducing
favorable feature for quality control applications. effectively multiple scattering in dense spray imaging.

SprayMaster systems using laser sheet imaging measure instantaneous

SprayMaster main performance features:
liquid (vapor) spray mass distributions and planar droplet size (D32) maps
as well as spray flow fields utilizing the PIV technique.
4Integrated and modular spray imaging systems
4Comprehensive spray imaging analysis software (DaVis)
Large scale imaging using extended backlight or sheet illumination as well
4Complete hardware control, accurate signal calibration
as high resolution imaging of single µm-droplets are supported.
4Robust system designs for industrial spray testing

Spray Spray Imaging Product

Illumination
Parameter Techniqu(s) (Application)
Geometry Mie Global-Illumination
SprayMaster inspex
Shape Shadowgraphy Back-Illumination
(Quality Control)
Patternation Mie Light Sheet
Mass Distribution LIF Geo
SprayMaster Spray inspection
Planar Droplet Sizing LIF/Mie Laser Sheet D32
(R&D)
Phase Separation LIEF LIEF

Flow Fields PIV FlowMaster

Laser Sheet
MassFlux LIF*PIV SprayMaster Flux

SLIPI Structured Laser

Dense Spray Imaging SprayMaster SLIPI
Sheet
Shadowgraphy Back-Illumination
Laser sheet imaging Local Droplet Sizing ParticleMaster Structured laser sheet
IMI Laser Sheet

Mie Mie scattering is elastic light scattering caused by surface LIF*PIV LIF*Mie allows planar mass flux measurements perpendicular
interaction. The wavelength is not changed. The signal strength to the laser sheet plane.
is proportional to the surface area of the droplet.
SLIPI Structured Laser Illumination Planar Imaging (SLIPI) is using
LIF Laser Induced Fluorescence (LIF) is a two step process spatially modulated laser sheets for Mie or LIF in combination
involving absorption of laser light and subsequent emission at with special image processing routines to reduce the effects of
a different wavelength. Thus, its signal scales with the droplet multiple scattering in dense sprays.
volume or (vapor) mass concentration.
Shadow Shadowgraphy and Interferometric Mie Imaging (IMI, applied
LIEF Phase-sensitive LIF emissions of so called exciplex tracers IMI on laser sheets) measure the size of single droplets in a local
are used to investigate liquid/vapor transitions and, therefore, probe volume of the spray. Both techniques are used for
evaporation processes in general. absolute size calibation of D32 size maps.

LIF/Mie LIF/Mie image ratios provide planar droplet size distributions

in terms of Sauter Mean Diameter (SMD) or D32 droplet size
maps which have to be calibrated for absolute size information.

5
 SprayMaster inspex

Contactless optical spray quality control

The SprayMaster inspex is a cost effective way of quantitatively measuring
the spray pattern in very short measurement times with high reproducibility.
It is the ideal testing tool for personal care, beauty & fragrance products,
home care and similar sprays.
The number of tested samples per day can be significantly increased by a
highly integrated measurement and data generation procedure.
The prealigned setup for a widely adjustable measurement plane reduces
setup and product change time to a minimum.
All types of aerosol, non-aerosol and powder sprays, generated from
spray pumps or pressurized containers are tested by a contactless optical
method simply using a sheet of light.

State-of-the art objective testing method

The optical spray patternation method is independent of the spray
formulation: water, alcohol or oil based liquids, low- and high-viscosity,
transparent and opaque, powders, all will be measured with the identical
system.
Computer based processing of spray images captured by the integrated
camera removes any subjectivity arising from a human tester. This
guarantees repeatable, operator independent results in a fraction of the
time needed by manual or semi-automated testing methods.

The flexible design of the SprayMaster inspex system makes it ideally

suited for routine spray characterization, from R&D applications through
to product quality control and batch testing.

6
 Quality Control

SprayMaster inspex components Optical spray pattern analysis

The SprayMaster inspex system makes use of flexible optical light guides. The contactless radial cut of a spray replaces the conventional testing
The light source is located outside the spray region or testing compartment. paper or mechanical patternation by a thin sheet of light. The camera
This removes any electrical parts of the illumination from the spray. captures the intersection of a light sheet with the spray plume at a defined
4Eye-safe illumination from flash or LED lamps plane and immediately generates a spray pattern image from it.
4Unique light sheet generation from fiber optics
4Versatile setup
Compact cameras
A choice of compact cameras and lenses provides a small size and fixed
setup. Watertight enclosures and protective air purge reduce contamination Spray
outline
from the spray product to a minimum.
Spray centroid
Orifice axis
Optical spray plume analysis
In contrast to paper testing methods, optical spray analysis can take place
in the direction of the spray propagation as well.
Either a light sheet will be projected coplanar to the spray plume, or a Equivalent
Largest & circle
full field backlight illuminates the projection of the spray plume onto the
smallest
camera.
radius
Both configurations capture a direct image of the spray cone and measure
the cone angle and its main axis direction.
Measured properties of the spray pattern
Spray outline: based on an objective and repeatable automated
algorithm
Spray area: total spray area covered by the outlined part of the spray
pattern
Centroid: automated detection of the spray center position and its
location relative to the mechanical spray axis
Spray diameter: the equivalence diameter represents a circle of the same
area as the spray pattern
Circularity: shortest and largest extension of the spray pattern show how
good the pattern matches to a circle
Pattern shape: an angular profile of spray density shows the portion of
spray propagating into a certain direction and reflects the uniformity of
the spray pattern

Time-resolved spray evolution

Using fast framing cameras, the SprayMaster inspex
can record the spray stroke in slow motion. This
allows a detailed time resolved analysis of every stage
of the spray. The very first breakup and the spray end
can show a behavior different from the average spray
plume, with impact to the overall spray quality.

7
 SprayMaster inspex

SprayMaster inspex for fuel sprays

The SprayMaster inspex is designed as a universal and easily applicable
tool for the measurement of fuel spray geometry.
Spray cone size, shape and evolution is directly imaged either with
standard or slow-motion cameras. A fast optical shutter or strobe light
illumination freeze any motion and reveals crisp still standing images from
any stage of the spray plume development.
The system can be universally applied to all types of fuel sprays, like
Diesel, port fuel or direct injection gasoline, or gas turbine injector sprays.
Spray test chambers can be equipped with the eye-safe non-laser optical
SprayMaster inspex testing system. Unique optics, designed by LaVision,
generates thin light sheets without using lasers. Global illumination is Image courtesy of Sonplas GmbH
provided by backlighting or flash lights.

Multi-hole GDI spray pattern with centroid, 50% and 80% mass circle

Time-resolved high-speed measurements

A SprayMaster inspex system based on high-speed cameras and
appropriate illumination allows recording multiple spray strokes within a
very short time.

In a quality testing environment, high-speed cameras quickly generate

return on investment resulting from a large number of tests which can
be performed within a short period of time. A few 10 spray strokes are
sufficient to capture all information about the spray development with a
good statistical relevance.

The benefits of using high-speed cameras are:

4Individual spray strokes are fully time-resolved
High-speed recording of a Diesel spray 4Stability information about the spray cone development
4Drastically reduced number of spray shots allows a higher number
of investigated spray conditions
4Longer operation time and shorter total setup time due to reduced
contamination of the spray testing chamber

8
 Fuel Sprays

Axial spray cuts: plume geometry and propagation

Axial cuts are aligned with the spray propagation direction. Measurements
are achieved using light sheets, global lighting or backlighting. Spray cone
angles are measured directly from images using one of these methods:
4At a given distance from the orifice (single or multiple planes)
4By interpolation of the spray rim
4By integration of the spray plume
4Bend angle (deviation from orifice axis) and both half angles indicate
the symmetry and direction of the spray plume

Additional measures are:

4Tip penetration represents the propagation of the spray, when
plotted over time
4An angular plot shows the uniformity of the spray

Radial spray cuts: spray patternation Multi-hole injectors

Radial cuts are derived from a light sheet in cross section with the spray For Diesel injectors and multi-hole gasoline injectors it is necessary to get
axis. The result of this layout is comparable to mechanical patternators. detailed information about the stability and uniformity of each single spray
Measured values are: cone. Time resolved measurements of individual spray strokes allows
4The spray pattern area and its equivalent diameter comparing the shot-to-shot stability.
4Mass circle diameters according to SAE definition Each cone of a multihole/multi cone spray is processed individually to
4Centroid position based on spray image intensity present information about uniform spray evolution.
4Largest and shortest radius to the pattern rim
4Plots about radial and angular spray distribution reveal the
structural characteristics of spray plumes

digital camera
Engine internal spray measurements
LaVision provides optical access to a running engine using endoscopes
and illumination probes for the camera and lighting. camera endoscope
The EngineMaster inspex is a direct upgrade from a SprayMaster inspex
to be synchronized and operated on engine test beds.
These systems visualize the fuel spray directly inside the engine with
minimum modifications. light
source engine illumination unit
sealing
sleeves

engine synchronization unit

crank angle encoder

9
 Laser Imaging in Sprays
Droplet Sizing Systems

Based on imaging shadow projections of droplets the method of

ParticleMaster Shadow
Shadowgraphy is applied in a small volume at a desired position within
a spray (local). Quantitative absolute results are obtained and a range of
lightsources from pulsed LEDs to lasers can be used as backlight source.
A long distance microscope assures a safe working distance at a high
magnification to even detect very small droplets.
4Droplet size and velocity incl. correlations
4Drop shape (eccentricity)
4Statistics, histograms (D10, D32, DV50)

Raw image Detected droplets Particle size histogram

The approach with interferometric Mie Imaging (IMI) is recommendable

ParticleMaster IMI
for scarce sprays and uses a laser light sheet thus observing a larger
area than Shadowgraphy. From defocused imaging in forward scattering
direction interference fringe patterns are recorded which contain the
information about droplet size in the fringe frequency.
4Droplet size and velocity
4Size/velocity correlation
4Statistics, histograms (D10, D32, DV50)

Compressed fringe patterns

Standard circular fringe patterns for denser sprays

An instantaneous global droplet size map is obtained from the LIF/Mie

SprayMaster D32
technique where simultaneously a fluorescence signal (propotional
to droplet volume) and a Mie signal (proportional to surface area) are
recorded and divided by each other. This gives the Sauter Mean Diameter
(SMD, D32) from a single laser pulse (fluorescent tracer required).

LIF = volume Mie = surface D32

10
 Laser Imaging
in Sprays

The Laser Induced Fluorescence (LIF) signal is proportional to the droplet

SprayMaster LIF
mass and, therefore, contains a different information from what can be
observed with purely Mie scattered light, which is proportional to the
surface of the droplet. In combination with PIV the mass flux can be
derived.

Liquid mass distribution

Laser Induced Exciplex Fluorescence (LIEF) allows simultaneous

SprayMaster Exciplex
visualization of the two phases. Due to the special LIF tracers the signals
from the liquid and the vapor phase can be spectrally separated by optical
filters.

Liquid phase Vapor phase

FlowMaster Velocity field measurements using Particle Image Velocimetry (PIV) are
well established in fluid mechanics and can be applied to spray droplets
or the surrounding air (with additional seeding). The double-pulse laser
of a FlowMaster system is an excellent basis for upgrades to many other
techniques.
Meas. Sci. Technol. 25 095204
Zhang et al, 2014,

2-phase flow field of spray

droplets and ambient air

11
 Laser Imaging
in Fuel Sprays

In-cylinder spray imaging

Fuel sprays determine to a large extend the fuel/air mixing process in e. g. IC- Max
engines and gas turbines and, thus, the quality of the combustion process
itself. Laser imaging provides useful information about the fuel concentration

Time Development
distribution, evaporation and, finally, maps of fuel/air mixture ratios.

Fuel Concentration
Min

DI-gasoline injection

Exciplex Monomer
Fluorescence t= 1000 µs Fluorescence

Nowadays laser imaging is a routinely used measurement tool for the

investigation of fuel sprays in high pressure test cells or directly inside
the combustion chamber. Keyhole imaging can be realized using laser and
liquid phase vapor phase
camera endoscopes, respectively.
Vaporizing fuel spray
Laser spray imaging offers an efficient analytical method for spray
characterization replacing old “trial and error” approaches and provides
useful data for the validation of CFD models.

Image courtesy of TU-Munich

liquid fuel vapor fuel

Mie PLIF

Jet fuel distribution in a gas turbine combustor

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 Advanced
Solutions

Novel technique for imaging in dense sprays

Structured Laser Illumination Planar Imaging (SLIPI) reduces multiple is maintained for singly scattered light. When the stripe-like phase
light scattering applying laser imaging in dense sprays. SLIPI is shifted images are combined correctly, the resulting SLIPI image
based on spatially modulated laser sheets for Mie or LIF imaging. shows higher image contrast and reveals inner spray structures,
While multiply scattered light loses the modulation information, it which are hidden when using conventional planar laser imaging.

hollow cone
revealed

Structured laser sheet Conventional SLIPI

Image courtesy of E. Berrocal and E. Kristensson, Lund University

3D spray flow field

Most sprays show turbulent droplet motion and, therefore, are
3-dimensional (3D) in nature. While 2D laser sheet imaging cannot resolve
3D flow structures, tomographic reconstruction techniques using multiple
camera views of the illuminated spray volume are capable to capture
instantaneously complex spray structures in all three dimensions.

From such time-correlated 3D spray images the

instantaneous 3D droplet flow field is derived
together with its 3D vortex structure enabling 3D
spray characterization in all details.

13
 SprayMaster
Software

SprayMaster software packages

SprayMaster software packages are designed for a wide range of spray
imaging applications, including spray patternation, plume geometry,
planar droplet size distribution, and evaporation.

Spray geometry analysis

This basic spray package extracts spray geometry information from
backlight and light sheet spray images and replaces conventional
patternation by an optical measurement.
Measured values for axial and radial light sheet cuts are:
spray angle at interpolated rim or at a fixed distance, bend angle, tip
penetration, front angle, cone diameter, cone symmetry, centroid position,
angular and radial profiles of spray density and more.
Analysis of multi-hole injectors (e.g. automotive fuel sprays) reveals
individual spray cone information. SprayMaster Geometry dialog

Spray geometry dialog Synchronized spray recording

The SprayMaster Geometry package allows to arrange results LaVision‘s unique Programmable Timing Unit PTU X allows very flexible
presentations defined by the operator. Multiple windows can be arranged triggering and timing schemes for low-speed and high-speed systems.
together in a view according to individual needs. If more space is needed Scanning is the automated variation of the measurement time with respect
on the screen, information can be spread over multiple tabs. Integrated to the spray injection. The PTU X can be triggered by the spray driver
screenshots and movie generation allow to achieve reportable results with system, by a light barrier, or it can generate injection triggers on its own.
a minimum of user interaction. Multiple injections typical for modern automotive injectors are generated,
and the illumination and camera system is automatically synchronized to
it.

14
 SprayMaster
Software

SprayMaster LIF
The SprayMaster LIF package includes all tools to process laser based
images. Its main features are:
4Background subtraction removes stray light
4Sheet correction compensates laser sheet inhomogeneities
4White image correction removes influence of the optics to the image
brightness
4Distortion correction and mapping: the so-called de-warping removes
any distortion from optics, de-skews images recorded from
perspective angles and maps images together from several cameras
with sub-pixel precision

SprayMaster D32
The spatial distribution of the Sauter Mean Diameter (SMD, D32) is
measured from planar laser imaging using a ratiometric approach of LIF
and Mie scattering. The SprayMaster D32 package allows to record this
information from one or two cameras, matches the images together and
reveals a planar D32 map.
4Ratiometric approach to calculate global Sauter-Mean-Diameter
maps from LIF and Mie image pairs
4Calibration procedure add absolute droplet size using e. g. the
ParticleMaster systems

SprayMaster Exciplex SprayMaster software customization

Liquid-Vapor separation is obtained by planar laser imaging using Exciplex Based on the standard off-the-shelf functionality, the SprayMaster
tracers. The SprayMaster Exciplex package supports all image processing software is the ideal platform to build a highly optimized spray analysis
steps to separate phase images properly. system tailored to your needs. It can be integrated into an existing spray
4Liquid-vapor separation from Exciplex LIF images testing environment, e.g. for automated batch testing. Customization of a
4Removes image cross-talk from overlapping LIF emissions SprayMaster system can be implemented at different levels:
4Ratiometric approach for liquid/vapor ratio 4Optimized user interface
4Streamlined to an existing workflow
4Automated storage of result data, images and reports
4Remote control for automated and unattended operation

LaVision‘s customized SprayMaster systems reduce the operation costs

of a spray testing facility and improve the objectivity of measured spray
properties. The benefits are:
4Higher testing volume
4Reliable and repeatable results
4Traceability of testing procedures

15
 Related Product Information

LaVisionUK Ltd LaVision GmbH LaVision Inc.

2 Minton Place / Victoria Road Anna-Vandenhoeck-Ring 19 211 W. Michigan Ave. / Suite 100
Bicester / Oxon / OX26 6QB / United Kingdom 37081 Göttingen / Germany Ypsilanti, MI 48197 / USA
E-Mail: sales@lavisionuk.com E-Mail: info@lavision.com E-Mail: sales@lavisioninc.com
www.lavisionUK.com www.lavision.com www.lavision.com
Phone: +44-(0)-870-997-6532 Tel.: +49-(0)5 51-9004-0 Phone: (734) 485 - 0913
Fax: +44-(0)-870-762-6252 Fax: +49-(0)551-9004-100 Fax: (240) 465 - 4306
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