Demonstration of temperature and OH mole fraction diagnostic in SiH 4/H 2/O 2/Ar flames using narrow-line UV OH absorption spectroscopy

Abstract

Results of an experimental study of the application of frequency-modulated UV laser absorption spectroscopyto silica (SiO2) particle-forming flames (SiH4/H2/O2/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 R1(7) and R1(11) transitions in the A2Σ+«X2IIi (0,0) band of the OH spectrum (vo=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.