20 kHz CH2O and OH PLIF with stereo PIV.

ABSTRACT

Planar laser-induced fluorescence (PLIF) of hydroxyl (OH) and formaldehyde (CH2O) radicals was performed alongside stereo particle image velocimetry (PIV) at a 20 kHz repetition rate in a highly turbulent Bunsen flame. A dual-pulse burst-mode laser generated envelopes of 532 nm pulse pairs for PIV as well as a pair of 355 nm pulses, the first of which was used for CH2O PLIF. A diode-pumped solid-state NdYAG/dye laser system produced the excitation beam for the OH PLIF. The combined diagnostics produced simultaneous, temporally resolved two-dimensional fields of OH and CH2O and two-dimensional, three-component velocity fields, facilitating the observation of the interaction of fluid dynamics with flame fronts and preheat layers. The high-fidelity data acquired surpass the previous state of the art and demonstrate dual-pulse burst-mode laser technology with the ability to provide pulse pairs at both 532 and 355 nm with sufficient energy for scattering and fluorescence measurement at 20 kHz.