Selection of the optimal combination of water vapor absorption lines for detection of temperature in combustion zones of mixing supersonic gas flows by diode laser absorption spectrometryстатья
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Аннотация:Determination of a gas medium temperature by diode laser absorption spectrometry (DLAS) is based on the measurement of integral intensity of an individual absorption line of a test molecule (generally water vapor molecule). In case of local thermodynamic equilibrium temperature is inferred from the ratio of the integral intensities of two lines with different low energy levels. For the temperature above 1500 K and total gas pressure above 1 atm the absorption lines are broadened and one cannot find isolated well resolved water vapor absorption lines within relatively narrow spectral interval of fast diode laser tuning range (about 3 cm-1). For diagnostics of a gas object in the case of high temperature and pressure DLAS technique can be realized with two DLs working in different spectral ranges with strong absorption lines.
In such situation the criteria of the optimal line selection differs significantly from the case of narrow lines. These criteria are discussed in the presentation. The software for selection the line pairs using the HITRAN-2012 and HITEMP databases is developed. The soft selects optimal pairs minimizing the error of temperature determination - Т/T basing on the attainable experimental error of line intensity measurement S. Two pairs of lines were selected – (1.392µ - 1.343µ) and (1.392µ - 1.339µ). Different algorithms of experimental data processing are discussed in the presentation