Demonstration of temperature and OH mole fraction diagnostic in SiH4/H2/O2/Ar flames using narrow-line UV OH absorption spectroscopy

Results of an experimental study of the application of frequency-modulated UV laser absorption spectroscopyto silica (SiO 2 ) particle-forming flames (SiH 4 /H 2 /O 2 /Ar) are presented. An argon-ion pumped ring-dye laser system in the rapid wavelength scanning configuration was used to obtain multiple line shape prifoles of the R 1 (7) and R 1 (11) transitions in the A 2 Σ + «X 2 II i (0,0) band of the OH spectrum ( v o =32,625,547 and 32,625.072 cm −1 , respectively). Temperature and OH mole fraction were determined by a best fit a convolved Voigt absorption profile to the data. Measurements were made in the multiphase regions of silane/hydrogen/oxygen/argon flames, verifying the applicability of the diagnostic approach to combustion synthesis systems. Absorption measurements were taken over a range of particle environments found at increasing heights above the burner surface (5–20 mm) and equivalence ratios ( φ =1.0 and 1.2). The experimental data were compared with thermocouple measurements, equilibrium, and one-dimensional modeling simulations. The results of the study successfully demonstrate OH UV absorption spectroscopy as a highly sensitive and accurate (uncertainties less than±10% in the current work) diagnostic approach for in situ measurements of temperature and Oh mole fractions in combustion synthesis flames.