Publications

Radiative fraction and optical thickness in large-scale hydrogen-jet fires

MOLINA OCHOA, Alejandro N.; Schefer, Robert W.; Houf, William G.

The radiative characteristics of large-scale (visible length 1.4-9.1 m) hydrogen jet flames that simulate an accidental leak from a high-pressure hydrogen container were compared with previous experimental and theoretical results for laboratory-scale non-sooting flames. The comparison shows that correlations of radiative heat fraction with global residence time need to account for the differences in thermal emittance of combustion gases for different fuels. This correction was found to be particularly important when hydrogen flames were compared to flames with CO2 as a product specie. Measurements of the radiative heat fraction for CO/H2, CH 4 and H2 flames collapse onto one line when plotted against the logarithm of a characteristic residence time weighted by a factor that accounts for differences in the radiative characteristics of combustion gases. The radiative fraction of large-scale jet flames was found to be smaller than that predicted by the correlation obtained for laboratory-scale flames. This was explained by an increase in optical thickness as the flame size increases.