Quantitative frequency-scanning NO PLIF at 20~kHz measurement rates via the burst-mode 5th harmonic.

This Letter presents the first, to the best of our knowledge, use of the Nd:YAG fifth harmonic for quantitative absorption line broadening measurements via frequency-scanning planar laser-induced fluorescence (FS-PLIF). This measurement is performed in a combustion environment generated with an oxy-propane torch. Using a harmonic of the Nd:YAG for PLIF removes the need for complex wavelength conversion equipment and greatly simplifies the optical setup while providing higher pulse energies than other conventional systems. Frequency scanning is performed for measurement rates of up to 20 kHz with a 500 kHz laser repetition rate and an average pulse energy of 1.7 mJ at 213 nm. The measured average linewidth of absorption features equals 0.366 cm-1, corresponding to an estimated temperature of 2200 K. Predicted 2D temperature profiles show good agreement with CFD-simulated results.