Quantitative evaluation of wall chemical effect in hydrogen flame using two-photon absorption LIF

A premixed H₂/air flame with N₂ dilution (U_in = 533 cm/s, ? = 1) was formed in a quartz micro flow reactor with/without a 100-nm thick Inconel coating for the investigation of wall chemical effect of the metal surface. Two-dimensional distributions of OH radical, O atom and H atom in the hydrogen flame were measured via the planar laser induced fluorescence (PLIF) and two-photon absorption laser induced fluorescence (TALIF), respectively. It is found that the distributions of all these three main species in the hydrogen flame are significantly affected by the wall chemical effect. OH, O and H shift downstream in the Inconel-coated channel, and also their concentration becomes lower than those in the less-reactive quartz channel. Based on the measured distributions of OH, O and H over the Inconel surface, the initial sticking coefficients (S₀) of the radical quenching model are optimized. It is found that S₀ for Inconel are 0.4–0.5, 0.1–0.2 and < 0.05 for OH, O and H, respectively, showing different sticking coefficients for different species for the first time.