Highly Rarefied Flames

All existing flames are divided into two classes those without premixing of the reactants and those in prepared mixtures. The first class comprises both diffusion flames intermixed by molecular diffusion (laminar diffusion flames) and by turbulent (eddy) diffusion (turbulent diffusion flames) and highly rarefied flames for which the admission and intermixing of reactants is realized either by diffusion, of by the Knudsen molecular flow (see [230]). 

These flames are sustained at very low pressures, usually 0.001 to 0.01 torr, and also at relatively low temperatures (200 to 300 °C). 

In another method the vapours of two reacting compounds are fed to the reaction zone in parallel streams. 

An example of flames intermediate between highly-rarefield flames of the diffusion type (p 0.01 torr) and the hot diffusion flames is the hydrogen sulfide flame in oxygen at several torr and at about 300 K [230]. 

Usual hot diffusion flames with a temperature of 1500—3000 K are observed at atmospheric or close to atmospheric pressures. A hot flame produced by means of two coaxial tubes (Fig. 57) is a simple model of this kind of flames. The fuel 

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An example of a consecutive reaction is that between sodium vapor and mercuric chloride vapor observed in highly rarefied flames (see Section II.6), i.e. 

The study of chemical reactions in highly-rarefied flames has proved to be of great value in the investigation of elementary reactions of free atoms and radicals. Highly-rarefied flames are specific in that they are sustained at very low... 

Reactions in Highly-Rarefied and Diffusion Flames Reaction M + X... 

E. N. Taran and V. I. Tverdokhlebov, Some electrical properties of a rarefied acetylene air flame with an admixture of alkali metal salts, High Temperature 4, 160-165 (1966). 

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