-- The 41st International Symposium on Combustion, or ISOC 2026, highlighted growing demand for measurement tools that can resolve the interaction among turbulent flow, species transport and chemical reactions in low-carbon combustion.
Research involving hydrogen, ammonia, sustainable aviation fuels and multicomponent alternative fuels is moving beyond conventional assessments of flame appearance, temperature and pressure. Scientists increasingly need to determine how shear layers, recirculation zones and transient vortices deform flame fronts, and how heat release, density variation and species diffusion feed back into the surrounding flow.
A High-speed Camera can record rapid flame motion, but imaging alone does not provide the complete relationship between velocity structures and reaction zones. High-speed particle image velocimetry combined with planar laser-induced fluorescence, known as PIV-PLIF, addresses this limitation by synchronizing flow-field measurements with species-sensitive fluorescence imaging.
At ISOC 2026, Revealer presented a high-speed PIV-PLIF measurement platform designed to place velocity and fluorescence data within the same temporal and spatial reference frame.
Why Combustion Research Requires Synchronized PIV-PLIF
Particle image velocimetry, or PIV, tracks the displacement of seeded particles illuminated by a laser sheet. The method provides velocity vectors and can support calculations of vorticity, shear rate, strain and recirculation structures. It does not, however, directly identify the location or intensity of a chemical reaction zone.
Planar laser-induced fluorescence, or PLIF, uses wavelength-selective excitation to image species or radicals such as OH, CH and NH. It can reveal flame fronts, reaction layers and intermediate-species distributions, but it does not independently measure the surrounding velocity field.
Conducting PIV and PLIF in separate experiments creates a fundamental problem. Turbulent combustion is unsteady and partly stochastic, so two measurements performed under nominally identical operating conditions may not represent the same instantaneous event.
A synchronized PIV-PLIF system must therefore do more than combine two instruments. The PIV and PLIF laser sheets must overlap in the measurement plane, the two imaging systems must share a calibrated coordinate framework, and the lasers, image intensifier and each High-speed Camera must operate from a common timing reference.
Only then can the velocity field and fluorescence distribution be assigned to the same instant and physical location.
Revealer PIV-PLIF Measurement Platform
The Revealer PIV-PLIF system integrates high-speed PIV and high-speed PLIF within a common optical, timing and data-processing architecture.
According to the supplied technical material, the system supports tunable excitation from 220 to 566 nanometers. The excitation wavelength can be selected for target radicals or intermediate species, including OH, CH and NH-related signals.
High-speed lasers, image intensification and synchronized High-speed Camera acquisition provide sampling rates of up to 10 kilohertz. This allows millisecond and submillisecond flame behavior to be followed as a continuous sequence rather than reconstructed from isolated measurements.
For spatial alignment, the PIV illumination sheet and PLIF excitation sheet are shaped into approximately 0.3- to 1-millimeter-thick light sheets. Beam combining and calibration are used to keep the two measurement planes as close to coincident as practical, reducing errors caused by sampling different flame volumes.
Weak fluorescence and strong combustion background radiation can limit PLIF image quality. The Revealer configuration can use narrowband filtering, short-gated exposure and an intensified imaging channel to improve fluorescence contrast.
Timing control coordinates the PIV double-pulse laser, the PLIF pump and tunable dye lasers, the image intensifier gate and the High-speed Camera exposure windows. The resulting PIV particle images and PLIF fluorescence frames can then be mapped, overlaid and analyzed as a synchronized dataset.
10 kHz High-Speed PIV-PLIF Combustion Experiment
In a combustion flow and chemical-reaction coupling experiment conducted at a national laboratory, researchers assembled a high-speed PIV-PLIF platform consisting of laser sources, High-speed Camera modules, synchronization hardware, data-processing components and a combustion test section.
The first stage established spatial coupling between the PIV and PLIF light sheets. Beam expansion and cylindrical optics formed collimated sheets that overlapped in the flame measurement region.
A shared calibration target was then recorded by both imaging channels. Lens distortion correction, coordinate transformation and spatial mapping placed the PIV velocity field and PLIF fluorescence field within the same physical coordinate system.
For temporal synchronization, High-speed Camera frame triggering served as the master timing reference. The researchers adjusted the PIV double-pulse interval, PLIF laser delay and image-intensifier gate so that the PIV channel captured usable particle displacement while the PLIF channel exposed during the valid fluorescence window.
The experiment acquired both image streams continuously at 10 kHz, with corresponding timestamps and frame numbers.
Correcting Laser-Energy and Light-Sheet Variations
PLIF image intensity is affected not only by species distribution but also by laser-pulse energy and spatial nonuniformity in the illumination sheet.
Pulse-to-pulse energy fluctuations can create apparent changes in fluorescence that do not represent actual changes in the flame. The experiment therefore monitored laser energy and aligned the energy record with the corresponding High-speed Camera frames.
The researchers also corrected the nonuniform intensity distribution across the laser sheet. These procedures made the fluorescence sequence more representative of the reaction zone’s actual spatial and temporal variation and improved its comparability with the PIV velocity data.
Such corrections are important because uncorrected PLIF intensity should not automatically be interpreted as an absolute radical concentration. Temperature, pressure, collisional quenching, laser energy and optical-system response can all affect the measured signal.
Coupled Images Reveal Vortex-Flame Interaction
After spatial registration and frame-by-frame synchronization, the PIV velocity field was overlaid with the PLIF fluorescence field.
The coupled results showed that stronger transient vortical structures in the local flow were associated with increased wrinkling, bending and localized deformation of the nearby flame front. The synchronized view also showed whether a vortex approached the reaction zone from the unburned region, interacted directly with the reaction layer or developed in the burned-gas region.
This relationship would be difficult to establish from PIV or PLIF alone. PIV identifies the motion and strength of flow structures, while PLIF identifies the corresponding reaction-zone topology. Synchronized PIV-PLIF connects the two.
Continuous high-speed sequences can also support extraction of vortex trajectories, flame-front curvature, local velocity gradients, fluorescence variation and the time delay between a flow disturbance and the resulting reaction-zone response.
Figure-Revealer PIV-PLIF coupled measurement showing a synchronized flame velocity field and OH fluorescence reaction zone, with transient vortices corresponding to flame-front wrinkling and bending.
From Parallel Imaging to Coupled Combustion Analysis
The value of high-speed PIV-PLIF is not limited to collecting two types of images at the same time. Its main contribution is the ability to establish a testable relationship among flow disturbance, species transport and chemical response.
For research areas emphasized at ISOC 2026, including turbulent combustion, low-carbon fuels and advanced diagnostics, the Revealer system provides a framework for studying flame stabilization and instability, ignition and extinction, swirling combustion, turbulent flame propagation and alternative-fuel reaction mechanisms.
By combining synchronized lasers, calibrated optical planes, image intensification and High-speed Camera acquisition, the Revealer PIV-PLIF platform moves combustion diagnostics from separate field measurements toward direct analysis of flow-reaction coupling.
Contact Info:
Name: Harrison Shawn
Email: Send Email
Organization: HF Agile Device Co., Ltd.
Website: http://www.revealerhighspeed.com
Release ID: 89199914
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