Two-photon laser-induced fluorescence of sodium in multiphase combustion

• DOI: 10.1364/ao.392710
• Publication Date: 2020-05-19T20:04:07Z
• Authors: Keke Zhu; Stuart J. Barkley; Chloe E. Dedic; Travis R. Sippel; James B. Michael
• Keywords: Photon Counting

Alkali metals are prevalent in coal combustion, biomass thermal conversion to fuels, and energetic material have applications as dopants for combustion diagnostics plasma-based control. Recently, the dynamic control of propellant burning rate pyrotechnic luminosity been demonstrated through combined microwave field radiation incorporation alkali dopants. Understanding distribution within flame is essential predicting field–flame interaction. However, multiphase environment exhibits significant particle scattering, broadband emission background, high optical density, which complicate measurements. Here, multiple two-photon laser-induced fluorescence (LIF) schemes atomic sodium were compared gas-phase flames sodium-doped solid combustion. For Na LIF scheme, a equation model incorporating fluorescence, amplified spontaneous emission, ionization shows good agreement with experimental characterization flame. The technique was then extended flames, characterized by strong scattering. 3s–3d excitation achieved better signal-to-noise ratio <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>∼</mml:mo> </mml:mrow> <mml:mn>100</mml:mn> </mml:math> allowed imaging gradients at surface.