High temperature gas diagnostics by spectral remote sensing

Abstract

The usefulness of spectral emission measurements in determining line-of-sight temperature and/or concentration distributions in high temperature gaseous systems is investigated. An analytical model was constructed which relates the emitted spectral intensity to the local temperature and radiating species concentration within the gas. The mathematical statement of the model leads to a series of integral equations, one for each frequency at which data are taken. The profiles within the gas are determined by inverting these integral equations through the use of a parameter estimation inversion technique. In addition to a series of analytical experiments, experimental verification study was conducted in which gas temperatures varying from 700 to 1350 K over a 25 cm path were produced in an electrically heated furnace. The gas consisted of CO 2 N 2 mixtures whose relative mole fractions could be varied with the total pressure remaining constant at 1 atm. Temperature profiles determined by inversion agreed with profiles based on a combination of predictions and independent thermocouple measurements with an average error of less than 3% (using the independently measured CO 2 partial pressure).