CO2 laser welding

CO2 laser welding

Welding of steel with a CO2 laser recorded at 500 fps. CAVILUX is used as a light source. Process light is eliminated and features such as key hole and liquid melt pool can be seen.

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NdYAG laser welding

NdYAG welding

Visualization of NdYAG laser welding of steel with Cavitar’s CAVILUX Smart illumination laser – front illumination. Video taken at 1260 frames per second.

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Formation of shockwaves in gel

Creation of shockwaves during the creation of cavitation in gel with shadowgraph imaging , camera shutter 250 ns, 500.000 fps. Left video taken with cw metal halide lamp. Right video taken with CAVILUX Smart laser illumination with a 20 ns illumination pulse. Video material by Prof. Umemura and Prof. Yoshizawa, Tohoku University, Japan in co-operation with Nobby Tech Ltd.

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Fuel Injection Measurements with CAVILUX Smart Diode Laser

Oil spray

Author: Prof. Dr.-Ing. Reinhold Kneer

Description

The form of a fluid jet is highly determined by the collapse of the jet near the nozzle. This phenomenon is also known as primary collapse. Based on this knowledge various experimental, numerical and theoretical studies about the primary collapse have been performed worldwide in the past. However, especially under the conditions in diesel engines the mechanisms of the collapse have not been sufficiently understood. This lack of understanding originates in the lack of established data about form, size and velocity of the fragments in liquid jets. Motivated by the belief that the spatial resolutions that have been reached in current literature are too small to visualize the smallest of fluid structures but there are possibilities to improve the situation. The Institute of Heat and Mass Transfer (WSA) of the RWTH Aachen University has recently developed a new double-pulse backlight microscope [1]. The images that have been acquired with this measurement method contain information about primary fluid structures with a special resolution that has not been reached so far.

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The double-pulse back illumination microscopy creates photographic images of the area of interest of the primary collapse with high special resolution and at the same time low motion blur at two different times during the injection. Amongst other settings this is enabled with the use of a pulsed light source (CAVILUX Smart by the company Cavitar Ltd.). The light source emits the two short light pulses (pulse duration: 10 ns) within short time (1 μs). In addition the light is monochromatic and incoherent which is a major advantage in microscopic imaging. The microscopic optic in its current development state is able to visualize the area of the primary collapse of diesel jets with 600 nm/pixel and a special resolution of 2 μm. Based on the acquired double images not only the size, form and amount of primary fluid structures can be identified with appropriate analysis tools but also the velocity can be measured.

[1] Reddemann, M. A., Mathieu, F., Kneer, R. (2013) Transmitted light microscopy for visualizing the turbulent primary breakup of a microscale liquid jet, Experiments Fluids, 54(11).

About the author

Prof. Dr.-Ing. Reinhold Kneer
RWTH Aachen University, Institute of Heat and Mass Transfer

Augustinerbach 6
D-52056 Aachen
GERMANY

Tel. (0241) 80-95400
FAX (0241) 80-92145

RWTH Aachen logo
RWTH Aachen WSA logo

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Fuel Injection in Diesel Jet

Fuel injection

The target is to monitor fuel injection and to measure soot concentration inside a diesel jet during the combustion.

Frame rate: 25.000 fps

Laser pulse length: 800 ns

Working distance: ~ 500 mm

Camera optics: 100 Macro Carl Zeiss

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MAG Welding

MAG welding

 

Visualization of MAG arc welding with Cavitar’s CAVILUX illumination laser – front illumination. Video taken at 2.000 frames per second.

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