An Experimental Study on Measurement of OH Radical Concentration in Flame by Laser Absorption Spectroscopy of Near-Infrared Region

As primary carrier of chain branching and propagation reactions, OH (Hydroxyl) radical is one of the most important species in hydrocarbon combustion environment. However, it is no easy to measure the OH radicals concentration in the flame, because it has short duration time, big fluctuation and rapid reaction characteristics. Nevertheless, it is important to measure OH radicals precisely because OH radicals in fames are closely related to combustion efficiency and pollutant emission. To overcome the OH radical concentration measurement in the rapid chemical reaction, TDLAS (Tunable Diode Laser Absorption Spectroscopy) can be a very attractive analysis technique for measuring the concentration of certain species in a gaseous mixture in the flame. In this study, an optical absorption region of OH radical was selected in the near infrared laser (6419 cm(-1)) to measure OH radical quantitatively in flame. Unfortunately, Most of the light absorption signals of OH radical are interfered by the absorption signals of H2O. So, the OH radical concentration should be calculated after excluding the contribution of H2O absorption from united absorption signal of OH and H2O.