Christopher GRUNBOK, Boris LEONOV, Richard MILES
DOI Number: N/A
Conference number: HiSST-2025-022
In this work, the authors present the development of a new approach to sodium planar laser-induced fluorescence (PLIF). The approach is a LIF scheme which excites the 3s-4p transition of sodium near 330 nm and detects fluorescence from the intermediate 3d-3p transition at 819 nm. The 3s-4p transition avoids optical thickness effects typically encountered with the sodium D-lines near 589 nm, and fluorescence from the 3d-3p transition is an intermediate excited state transition, which helps avoid self-trapping effects. This non-resonant scheme allows the use of simple long-pass filters to block both the 330-nm excitation laser light and the naturally occurring 589-nm emission from sodium in the
targeted hypersonic and high enthalpy environments. This work demonstrates the use of this LIF scheme for planar imaging initially at a laser repetition rate of 30 Hz, and subsequently 250 kHz, in a benchtop sodium-seeded flame. The 250-kHz repetition rate is sufficient to capture dynamic phenomena in hypersonic and high enthalpy environments of interest, where sodium occurs nearly ubiquitously. Future work includes deployment of this approach in these environments to image flow fields within boundary or shear layers, post-shock environments, or combustion reaction/product zones.