TOMOGRAPHIC ANALYSIS OF CO ABSORPTION IN A LOW-PRESSURE FLAME

Tomographic analysis is used to provide a correction to low-pressure s toichiometric premixed CH4/O-2 flame temperatures measured with tunabl e diode laser absorption spectroscopy employing CO two-line thermometr y. It is shown that flame temperatures measured with line-of-sight-bas ed two-line thermometry are always too low and that the correction to the observed temperature is a nonlinear function of the height above t he burner surface. It is also shown that, at a given height in the fla me, a constant temperature across the flame does not imply that vibrat ional populations are constant and that, at low pressures (<20 Torr), the flame spreads radially beyond the burner diameter and so may no lo nger be approximated by a one-dimensional model.