OH concentration measurements by resonant holographic interferometry and comparison with direct numerical simulations

We apply a novel laser diagnostic technique - Resonant Holographic Interfer ometry (RHI) to measure the concentration of hydroxyl radical (similar to 2 000 ppm) in a co-flow diffusion flame of diluted hydrogen and air stabilize d on a Wolfhard-Parker burner. This methodology is based upon the dispersio n of light of frequency close to an electronic transition of a target molec ule. The two-color setup utilized in RHI provides a two-dimensional distrib ution of the target species concentration and quantitative information can be obtained from the interferogram without requiring any calibration. To pr ovide independent flame data for comparison, a two-dimensional numerical si mulation was performed taking into account the effects of detailed chemical kinetics and transport phenomena. In spite of a number of simplifying assu mptions made in the simulation, computational and experimental results are in good agreement with respect to the magnitude and width of the region whe re OH is found. We do observe a difference of approximately 1 mm in the fla me position due to the simplifying assumptions made in the simulation. The comparison between the experimental and numerical results clearly demonstra ted the potential of RHI in flame diagnostics.