Spectra and temperatures of diffusion flames at high pressures to 1000 bar

Diffusion flames have been produced by injection of oxygen into homogeneous dense mixtures of methane or hydrogen with supercritical water or argon. The mixture temperatures were around 500°C, pressures were varied between 50 and 1000 bar. The fuel concentrations were 30 mole percent or lower. Flames appeared spontaneously. Apparatus and procedure are described. Diffusion flame photographs to 1000 bar are shown. Emission spectra from 275 to 600 nm were recorded with a grating spectrometer and 1024 channel diode array. Emission in the visible is not of black body character and does not permit pyrometric temperature measurement. Flame temperature determination was based on the intense rotational emission of OH-radicals in the near UV, produced by vibrational 0–0 and 1–0 transitions of the electronic A2Σ–X2∏ transition. The 0–0 band is near 306 nm. A fit program to determine rotational temperatures is developed which includes the influence of pressure broadening. The temperatures obtained for CH4 and H2 in supercritical water increase with pressure and reach 4000 to 4500 K at 1000 bar. Rotational temperatures obtained for dense argon environment are lower: 3000–3200 K. Adiabatic temperatures and calculated values for one-dimensional diffusion flames are given for comparison.

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