In this study, a strategy was developed for in situ, non-intrusive, and quantitative measurement of the oxides of nitrogen (NO and NO₂) to describe emission characteristics in gas turbines. The linear calibration-free wavelength modulation spectroscopy (LCF-WMS) approach combined with the temperature profile-fitting strategy was utilized for trace NO and NO₂ concentration detection with broad spectral interference from gaseous water (H₂O). Transition lines near 1308 nm, 5238 nm, and 6250 nm were selected to investigate the H₂O, NO, and NO₂ generated from combustion. Experiments were performed under different equivalence ratios in a combustion exhaust tube, which was heated at 450–700 K, with an effective optical length of 1.57 m. Ultra-low NO_x emissions were captured by optical measurements under different equivalence ratios. The mole fractions of H₂O were in agreement with the theoretical values calculated using Chemkin. Herein, the uncertainty of the TDLAS measurements and the limitation of improving the relative precision are discussed in detail. The proposed strategy proved to be a promising combustion diagnostic technique for the quantitative measurement of low-absorbance trace NO and NO₂ with strong H₂O interference in real combustion gases.

The problem of yellow plume exists in most heavy-duty gas turbine units under start-up and low load conditions. How to suppress the yellow plume is a difficult problem in gas turbine power plants. It is judged that yellow plume is caused by the high NO₂ concentration in flue gas. From the point of view of mechanism research, this study analyzed the causes of yellow plume by numerical simulation combined with experimental research; obtained influence factors of the conversion of NO into NO₂; analyzed the degree of influence of these factors on the formation of yellow plume; verified the results through on-site measurement of a 6FA gas turbine unit; and finally proposed the countermeasures to suppress yellow plume from the gas turbine side and the heat recovery steam generator (HRSG) side.