Determining Total Radiative Intensity in Combustion Gases Using an Optical Measurement

A method is presented whereby spectral radiation measurements made in a combustion flue gas can be used with a spectral gas absorption model to calculate gas temperature, H2O concentration, CO2 concentration, and total radiation intensity for the gas. Measured spectral intensities from a natural gas-air flame in a 150 kWth furnace were used in conjunction with a spectral gas absorption model to calculate gas temperature and H2O concentration. The measured spectral intensities matched spectral intensities predicted by a one-dimensional intensity model when peaks were shifted and convolved to account for FTIR biases. On the basis of a successful prediction of intensities in the measured range of 1.709–2.128 μm, the calibrated intensity model was used to predict intensities for various wavelength bands including H2O and CO2 relative contributions. The total intensity for a wavelength range of 1–50 μm for the conditions studied was 10 659 W/m2/sr, with an equivalent total gas emissivity of 0.163.