Nitric Oxide Measurement Study. Volume III, Comparison of Optical and Probe Methods.

Abstract : Nitric oxide (NO was measured in the exhaust of three different combustion systems by in situ ultraviolet absorption and by chemiluminescent analysis after gas sampling with several probe designs. The three combustion systems were: (1) a flat flame burner fueled with CH4/N2/O2; (2) a research swirl burner fueled with C3H8/air; and, (3) a modified FT12 combustor operated on Jet A/air. Each combustion system was run at several different conditions so that probe and optical measurements could be obtained over a wide range of exhaust environments encompassing products from lean, stoichiometric, and rich flames, laminar to turbulent flows, and temperatures at centerline from 600 K to 1800 K. The results obtained with the metallic, water-cooled probes of different designs (all expansion-type) agreed with the optical results to within 25%. Some small losses of NO (10-15%) were observed in a lean methane flame at 1800 K with an uncooled stainless steel probe, but under fuel-rich conditions up to 80% NO destruction was observed. Experimental facilities are described, previous results are discussed, and a summary of the major findings of this study is given. (Author)