Flame turbulences recorded at 1 kHz using planar laser induced fluorescence upon hot band excitation of OH radicals

Abstract

Laser-induced fluorescence (LIF) in flames is excited by a diode-pumped all-solid-state disk laser system which operates at a pulse repetition rate of 1 kHz and a tunable wavelength around 1030 nm. The laser fundamental is converted to 343 nm and used to excite into the hot band transition $A^2\Sigma^{+}(v^{\prime}=0)\gets{X}^{2}{\Pi}(v^{\prime\prime}=1)$ of OH radicals in H₂/O₂ diffusion flames of an industrial burner and in the premixed flame of a microburner. The OH radical emission around 308 nm is resolved spectrally and spatially using a light-sheet technique. Imaging of the planar LIF (PLIF) by a gated camera visualizes the turbulent flame behavior on the millisecond time scale without averaging. To our knowledge this is the first time that an all-solid-state laser providing at the same time a kHz repetition rate as well as pulse energies of up to 5.5 mJ is available for PLIF observation of OH radicals.