H_2o absorption spectroscopy for determination of temperature and H_2O mole fraction in high-temperature particle synthesis systems

Abstract

Water absorption spectroscopy has been successfully demonstrated as a sensitive and accurate means for in situ determination of temperature and H2O mole fraction in silica (SiO2) particle-forming flames. Frequency modulation of near-infrared emission from a semiconductor diode laser was used to obtain multiple line-shape profiles of H2O rovibrational (v1 + v3) transitions in the 7170-7185-cm(-1) region. Temperature was determined by the relative peak height ratios, and XH2O was determined by use of the line-shape profiles. Measurements were made in the multiphase regions of silane/hydrogen/oxygen/ argon flames to verify the applicability of the diagnostic approach to combustion synthesis systems with high particle loadings. A range of equivalence ratios was studied (phi = 0.47 - 2.15). The results were compared with flames where no silane was present and with adiabatic equilibrium calculations. The spectroscopic results for temperature were in good agreement with thermocouple measurements, and the qualitative trends as a function of the equivalence ratio were in good agreement with the equilibrium predictions. The determinations for water mole fraction were in good agreement with theoretical predictions but were sensitive to the spectroscopic model parameters used to describe collisional broadening. Water absorption spectroscopy has substantial potential as a valuable and practical technology for both research and production combustion synthesis facilities.

An experimental investigation of gas-phase combustion synthesis of SiO2 nanoparticles using a multi-element diffusion flame burner

“…However, the thermocouple measurements and the OH absorption spectroscopy measurements of temperature [31] confirm adiabatic behavior at fuel rich conditions. The systematically lower temperatures obtained using the H 2 O absorption spectroscopy are likely because of uncertainties in the collisional broadening data used in the spectroscopic model [29]. The improved agreement with adiabatic equilibrium calculations at fuel rich conditions is attributed to lower heat losses to the burner at Ͼ 1.0 because of the higher reactant flow rates.…”

“…Line-of-sight averaged temperatures were obtained in both particle forming and non-particle forming flames using differential absorption spectroscopy of the water vapor naturally present in the product gases. Details of the diagnostic approach are provided in [29,30]. Briefly, near infrared emission from a tunable semiconductor diode laser was rapidly modulated across several absorption line shapes of H 2 O spectra at ϳ1.39 m. The path-averaged temperature was determined using the relative peak heights of the absorption lines.…”

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

“…Details of the combustion synthesis facility are given in Torek [17] and Torek et al [8]. Briefly, the burner is a 25.4 mm square array of hypodermic fuel tubes and oxidizer channels (Fig.…”

“…Hanson [5] and Roth and Brandt [6,7] have demonstrated the ability to use rapid wavelength scanning absorption spectroscopy in the IR to measure gas concentrations (CO and CO 2 ) in carbonaceous particle-forming flames. Torek et al [8] used a scanning semiconductor diode laser in the IR to measure temperature and water concentrations in SiH 4 /H 2 /O 2 /Ar flames with high silica particle loadings. Zachariah and coworkers [9][10][11] have used laser-induced fluorescence (LIF) to make OH concentration measurements in ceramic particle-forming counterflow diffusion flames.…”

A Null Hypothesis for CO2

“…9 The calculations are described in detail in the related literature. [35][36][37][38][39][40][41] The absorption and emission spectra used in this work were calculated using Excel worksheets automated by using Excel VBA macros to cycle through the calculations. Most of the spectra were calculated from 200 to 2000 cm −1 using 0.01 cm −1 resolution for the spectral linewidths and 100m steps for the altitude.…”