Absolute concentration measurements of OH* in an axisymmetric hydrogen-air premixed flame adjacent to a hot graphite model

Absolute concentration measurements of OH* in an axisymmetric hydrogen-air premixed flame adjacent to a hot graphite model

Absolute concentration of the chemiluminescent radical OH* was determined in an axisymmetric hydrogen-air premixed flame adjacent to a resistively-heated graphite surface. Two-dimensional images of the axisymmetric chemiluminescence from the excited-state of OH were recorded by an ICCD camera with a narrow-band filter at approximately 310 nm. A temperature of around 1800 K was achieved on the graphite surface using an electrical heating power of 5.5 kW. Surface temperatures were measured using a two-color ratio pyrometry (TCRP) technique. The line-of-sight-integrated chemiluminescent emissions that were imaged using the ICCD device were transformed to radial distributions through an Abel inversion method. A new method for calibration of the absolute number density of the radiating radical OH* is proposed based on the intensity ratio of the measured OH* chemiluminescence and the radiation emitted from the hot graphite surface. This is a convenient approach in the present work because adequate signal magnitudes from both these phenomena are acquired by the ICCD device simultaneously during testing.