Absorption of tunable, infrared, diode laser radiation has been used to measure nitric oxide (NO) in combustion gases. Measurements were made in the post flame gases of an atmospheric pressure flat flame burner doped with calibrated amounts of NO (100-2500 ppm) in order to simulate a range of combustion and exhaust gas conditions. Laser absorption measurements of NO were compared with measurements of NO obtained using probe sampling and chemiluminescent analysis. The laser absorption measurements were corrected for the effect or temperature nonuniformities along the optical path. In fuel lean flames, laser and probe determinations were in good agreement and, in addition, agreed with the amount of NO added to the combustion gases. In fuel rich flames, the laser and probe results also agreed, and indicated some decomposition of the added NO.
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