Laser-diagnostic multi-species imaging in strongly swirling natural gas flames

Within the TECFLAM group a standard swirl burner is investigated, both expe rimentally using optical and probe measurements and by simulations using di fferent modeling attempts. The present study is focused on the laser-based investigation of the NO distribution within the reacting flow field of a st rongly swirling, confined 150-kW natural gas flame. Simultaneous quantitati ve measurements of NO- and OH-concentration fields by laser-induced fluores cence imaging (LIF) and temperature distribution (Rayleigh scattering) are performed. Mixing properties of the unburned gases are investigated for the isothermal and the combusting flow using tetrahydrothiophene (THT) as a ne w fluorescing tracer. These measurements show which areas are sufficiently mixed allowing for the application of planar Rayleigh thermometry. Areas wh ere THT-LIF interferes with OH-LIF detection are localized and omitted from data evaluation. The data is analyzed yielding global scalar fields for comparison with mode l simulations and correlations between the different measured scalars are i nvestigated showing an almost linear correlation of NO concentration and te mperature within the swirl flame whereas no apparent correlation between NO and OH concentration was found.