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

Abstract

Results of an experimental study of the application of frequency-modulated UV laser absorption spectroscopy to 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 profiles of the R 1 (7) and R 1 (11) , respectively). Temperature and OH mole fraction were determined by a best fit of 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 ( ‫ס‬ 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 ‫%01ע‬ in the current work) diagnostic approach for in situ measurements of temperature and OH mole fractions in combustion synthesis flames.

Combustion Synthesis and Characterization of Nanocrystalline Tin and Tin Oxide (SnOx, x= 0–2) Particles

“…Based on previous characterization studies of the MEDB including in situ temperature measurements using laser absorption spectroscopy and thermocouple measurements, 32,34 the maximum temperature of the primary flame, T ad , can be estimated using adiabatic equilibrium calculations and the known equivalence ratio and level of argon dilution of the primary flame (for calculation details, please see Donovan et al 34 ). The calculated values for T ad are provided in Table I as an indication of the magnitude of the changes in the primary flame temperatures examined in the study.…”

“…The temperature profile used in the model is a polynomial fit to a measured temperature profile of the primary flame system when the secondary fuel tube was not used for particle synthesis. Additional details of the model, including the chemical reaction mechanism used, are provided in Donovan et al 34 Again, the chemical kinetics model does not include the effects of the secondary flame, including any chemistry associated with the TMT. As seen in Fig.…”

“…Previously, we had obtained good agreement between one-dimensional premixed modeling of the primary flame (not including the effects of the secondary flame) and measured radical profiles by incorporating detailed chemical kinetics in the model simulations. 34 While the 1D premixed model does not accurately describe the mixing conditions in the first few millimeters above the burner surface, the results can be used to infer trends about the conditions of the primary flame system above (i.e., downstream of) the initial mixing region. Figure 8 shows the model results for the minor and major species of the primary flame for a typical stoichiometric condition.…”

“…Based on previous characterization studies of the MEDB including in situ temperature measurements using laser absorption spectroscopy and thermocouple measurements, 32,34 the maximum temperature of the primary flame, T ad , can be estimated using adiabatic equilibrium calculations and the known equivalence ratio and level of argon dilution of the primary flame (for calculation Fig. 3.…”

“…Typical X-ray diffraction patterns of as-produced SnO 2 , SnO, and Sn powders. The experimental conditions for each sample were as follow: SnO details, please see Donovan et al 34 ). The calculated values for T ad are provided in Table I as an indication of the magnitude of the changes in the primary flame temperatures examined in the study.…”