Schafer, K.K.SchaferBrockmann, K.K.BrockmannHeland, J.J.HelandWiesen, P.P.WiesenJahn, C.C.JahnLegras, O.O.Legras2022-03-032022-03-032005https://publica.fraunhofer.de/handle/publica/20994810.1364/AO.44.0021892-s2.0-17644384029The detection limits for NO and NO2 in turbine exhausts by nonintrusive monitoring have to be improved. Multipass mode Fourier-transform infrared (FTIR) absorption spectrometry and use of a White mirror system were found from a sensitivity study with spectra simulations in the mid-infrared to be essential for the retrieval of NO2 abundances. A new White mirror system with a parallel infrared beam was developed and tested successfully with a commercial FTIR spectrometer in different turbine test beds. The minimum detection limits for a typical turbine plume of 50 cm in diameter are approximately 6 parts per million (ppm) for NO and 9 ppm for NO2 (as well 100 ppm for CO2 and 4 ppm for CO).en535journal article