Imaging and diagnostics of turbulent methane-air premixed flames by acetone-OH simultaneous PLIF

A strategy of diagnostics of ultra-lean combustion based on acetone-OH simultaneous PLIF is presented. Acetone seeded in the fuel flow and combustion-generated OH work for a marker of \ldunburned\rd and \ldburnt\rd zones, respectively. Since acetone and OH does not coexist when the proper combustion takes place, the signal \ldvalley\rd (dark zone) between acetone and OH fluorescence can be detected, which corresponds to flame zone; representative of the combustion status. System required for current imaging technique is one-laser and one-detector combination with \ldturned\rd band-pass filter. Transmittance characteristics of the filter and acetone-seeding rate are key issues to attain clear imaging, and we found that there is proper combination of them for that purpose. Imaging demonstration for the turbulent premixed flames shows the usefulness and applicability of this scheme on complex flame diagnostics: unique flame broken flame structure (\ldunburned\rd or \ldburnt\rd islands exist separately) are clearly obtained by this approach.