Diode-laser-based sum-frequency generation of ultraviolet (UV) radiation at 313.5 nm was utilized for high-speed absorption measurements of OH mole fraction and temperature at rates up to 20 kHz. Sensor performance was characterized over a wide range of operating conditions in a 25.4 mm path-length, steady, C2H4–air diffusion flame through comparisons with coherent anti-Stokes Raman spectroscopy (CARS), planar laser-induced fluorescence (PLIF), and a two-dimensional numerical simulation with detailed chemical kinetics. Experimental uncertainties of 5% and 11% were achieved for measured temperatures and OH mole fractions, respectively, with standard deviations of <3% at 20 kHz and an OH detection limit of <1 part per million in a 1 m path length. After validation in a steady flame, high-speed diode-laser-based measurements of OH mole fraction and temperature were demonstrated for the first time in the unsteady exhaust of a liquid-fueled, swirl-stabilized combustor. Typical agreement of ∼5% was achieved with CARS temperature measurements at various fuel/air ratios, and sensor precision was sufficient to capture oscillations of temperature and OH mole fraction for potential use with multiparameter control strategies in combustors of practical interest.
© 2005 Optical Society of America
(120.1740) Instrumentation, measurement, and metrology : Combustion diagnostics
(280.2470) Remote sensing and sensors : Flames
(300.1030) Spectroscopy : Absorption
(300.6260) Spectroscopy : Spectroscopy, diode lasers
(300.6540) Spectroscopy : Spectroscopy, ultraviolet
Terrence R. Meyer, Sukesh Roy, Thomas N. Anderson, Joseph D. Miller, Viswanath R. Katta, Robert P. Lucht, and James R. Gord, "Measurements of OH mole fraction and temperature up to 20 kHz by using a diode-laser-based UV absorption sensor," Appl. Opt. 44, 6729-6740 (2005)