Radiation from Flames

Abstract

As is well known, R. von Helmholtz found that the radiation from carbon monoxide flames was nearly 2.5 times as great as that from hydrogen flames. This appears to be generally interpreted as indicating that carbon dioxide radiates more powerfully than water vapour¹. But the opposite is the case; water vapour radiates twice as powerfully as carbon dioxide under similar conditions of temperature, etc^2,3. Helmholtz's results (which at first sight are all the more surprising because hydrogen-air flames are some 100° C. higher in temperature than carbon monoxide-air flames) would appear to be due to the more rapid cooling of the hot products surrounding the outer cone in the case of hydrogen flames than in the case of carbon monoxide flames, for Hartley⁴ has shown that the overwhelming proportion of the radiation from flames comes not from the interconal gases but from these hot products. It would appear that the more rapid the combustion the greater the turbulence in these products, and hence, owing to the more effective intermingling with the surrounding air, the more rapid the cooling.