Further Development of a High Pulse-Energy LED at 4 kHz for Volumetric Particle Tracking Velocimetry and a Demonstration Using 32 Such LED Units

Abstract

In 2022, we reported at the 20th Lisbon symposium on the development of 460 nm LED specifically designed for illumination in volumetric Particle Tracking Velocimetry (PTV). At that time, our pulsed LED unit emitted light with a 6 ◦ divergence beam and a top-hat power cross section, producing 20 µ s pulses at a 4 kHz repetition rate and a 0.15 mJ pulse energy. Since then, we have been improving the efficiency of this LED. Currently, our LED unit emits a beam with similar specifications but with a pulse energy up to 0.65 mJ , which is 4.3 times more than the previous LED unit. We improved the efficiency of the electrical driver by further decreasing the footprint of the SMD circuitry and by using higher quality electronic components. Additionally, we replaced the aluminium pin fin heat sink with a copper pin fin heat sink and we characterized the thermal dissipation. Using SolidWorks, we integrated the electric driver, the copper heat sink and the collimating optics into a compact mechanical casing. These improvements resulted in an LED unit with greater overall efficiency, a larger pulse energy and a volume footprint that is half the the size of the previous design. Furthermore, we constructed four batteries of these LEDs, with each battery containing eight LED units. Here, we report on our improvements to the LED unit and our considerations in its development. Additionally, we describe preliminary results of a 3D-PTV experiment with Helium Filled Soap Bubbles (HFSB), which were illuminated by the four LED batteries.