Near-kHz 3D tracer-based LIF imaging of a co-flow jet using toluene

Abstract

This work demonstrates tracer-based, high-repetition-rate planar (15 kHz) and three-dimensional (940 Hz) laser-induced fluorescence imaging. An off-the-shelf, pulsed, frequency-quadrupled Nd:YAG laser at 266 nm is used as the excitation light source, and a high-frame-rate intensified relay optic with a slow P46 phosphor coupled to a CMOS camera is used to image the fluorescence. Four different tracers are investigated (3-pentanone, acetone, anisole, and toluene) and relative signal levels are measured in the potential core of a laminar co-flow jet. Resulting SNR values range from 6 to 44 for the different tracers, and relative signal levels and SNR for each tracer are provided as an engineering-basis for tracer-based imaging diagnostic design. It was found that signal levels from anisole (relative to toluene) are about ten times less than suggested by other literature, owing to uncertainty in the reported absorption cross sections. Using toluene as a tracer and a custom-made piezo-actuated steering optic to scan the laser sheet, 3D LIF imaging at 940 Hz is demonstrated by visualizing a co-flow jet mixing with ambient air.

Single-shot volumetric laser induced fluorescence (VLIF) measurements in turbulent flows seeded with iodine

“…One possible approach of such extension is a scanning PLIF (planar laser induced fluorescence) technique, in which the excitation laser sheet used in the PLIF technique was scanned across multiple spatial locations sequentially, and then the 2D measurements obtained at these locations were stacked together to form a 3D measurement [12][13][14][15][16]. Even though this approach was conceptually straightforward and has been explored earlier [12,17], it is not trivial to obtain quantitative measurements with sufficient temporal and spatial resolution.…”

“…Even though this approach was conceptually straightforward and has been explored earlier [12,17], it is not trivial to obtain quantitative measurements with sufficient temporal and spatial resolution. Even with the latest advancement in high repetition rate lasers, high frame rate cameras, and the corresponding optics and electronics, measurements following the scanning approach have been limited to a temporal resolution of 1 kHz and a spatial resolution on the order of 1 mm in the direction of the scanning [14][15][16]. Higher spatiotemporal resolutions are desired or required for many flows of practical interest [18].…”

From ignition to stable combustion in a cavity flameholder studied via 3D tomographic chemiluminescence at 20 kHz

“…Progress to extend PLIF and PIV techniques for high-speed 3D measurements has also been reported. Examples include the PLIF measurements at several locations by scanning the excitation laser sheet at ~ 1 kHz [19,20], and 3D three-component velocity measurements by combining PIV with tomography [21][22][23].…”

3D flame topography and curvature measurements at 5 kHz on a premixed turbulent Bunsen flame

“…Approaches in the first category involve the scanning of a planar technique to obtain a series of 2D measurements sequentially, and these 2D measurements can then be combined to form an effectively instantaneous volumetric measurement when the scanning is performed rapidly. Demonstrations have been performed to obtain 3D measurements by the scanning of the laser sheet for PLIF [11][12][13] , planar Mie scattering [14] , and planar laser-induced incandescence [15] . With current high-repetition-rate lasers and scanning technologies, 3D measurements with temporal resolution near 1 kHz and a spatial resolution on the order of 1 mm in the direction http of scanning [11][12][13] are feasible.…”

“…Demonstrations have been performed to obtain 3D measurements by the scanning of the laser sheet for PLIF [11][12][13] , planar Mie scattering [14] , and planar laser-induced incandescence [15] . With current high-repetition-rate lasers and scanning technologies, 3D measurements with temporal resolution near 1 kHz and a spatial resolution on the order of 1 mm in the direction http of scanning [11][12][13] are feasible. Multiple lasers can potentially be used to improve the temporal and spatial resolution at the cost of complexity and capital investment [15] .…”