Laser induced fluorescence measurements of radical concentrations in hydrogen–hydrocarbon hybrid gas fuel flames

Laser Induced Fluorescence (LIF) measurements of OH, CH and CN radical concentrations in hydrogen–natural gas hybrid fuel diffusion flames at Re=150 are presented. Radial concentration profiles of these radicals in the near-burner region (7 mm above the burner) for different mixtures of hydrogen–natural gas are reported. The OH radical concentration profile shows a peak on the stoichiometric contour for all three mixtures (100%, 80–20% and 65–35% by volume of hydrogen–natural gas). The OH radical concentration decreases with the increase of natural gas content in the mixture. The peaks of relative CH radical concentration-profiles do not coincide with the temperature maxima, but appear on the fuel side of the stoichiometric contour. As expected, CH concentration also increases with the increase of natural gas concentration in the mixture. The CN radical concentration profile has a peak close to the flame edge on the air side of the stoichiometric contour. Similar to the CH radical, CN radical concentration also increases with the increase of natural gas content in the hybrid fuel.