Diode-Laser Absorption Sensor System for Measurements of Combustion Pollutants

摘要

A diode-laser sensor system has been applied to measure the concentrations of NO, N2O, CO, and CO2 in combustion gases using absorption spectroscopy and fast extraction-sampling techniques. Measured survey spectra of the NO 3v band (R branch) and H2O lines from the v2 + v3 band in the spectral region from 5556/cm to 5562/cm were recorded and compared to calculated spectra to select optimum transitions for NO detection. Similarly, measured survey spectra of the N2O 3v3 band from 6535/cm to 6600/cm were used to identify optimum transitions for N2O detection. High resolution NO absorption measurements were recorded in a fast-flow multipass cell containing probe- sampled combustion gases to determine NO concentrations in a laminar, premixed CH4/air flame, seeded with NH3. For fuel-rich conditions, the fraction of NH3 converted to NO decreased with increasing equivalence ratio. In additional experiments, CO and CO2 absorption measurements were used to determine species concentrations above a laminar, premixed CH4/air flame. Good agreement was found between measured CO and CO2 concentrations and calculated chemical equilibrium values.