Candle diffusion flames combustion products

The formation of carbon black in a candle flame was the subject of a series of lectures in the 1860s by Michael Faraday at the Royal Institution in London (23). Faraday described the nature of the diffusion flame, the products of combustion, the decomposition of the paraffin wax to form hydrogen and carbon, the luminosity of the flame because of incandescent carbon particles, and the destmctive oxidation of the carbon by the air surrounding the flame. Since Faraday s time, many theories have been proposed to account for carbon formation in a diffusion flame, but controversy still exists regarding the mechanism (24). 

A flame is a gas rendered luminous by emission of energy produced by chemical reaction. In a stationary flame (for example a candle flame or gas stove flame) unburned fuel and air flow into the flame front as combustion products flow away from the flame front. A stationary flame may be from either premixed fuel and air, as observed in a Bunsen burner with the air hole open, or by diffusion of air into the combustion zone, as for a Bunsen burner with the air hole closed. 

A common type of fire or flame is a laminar flame, meaning that the flame has definable layers or regions. Within the laminar category, there are two familiar examples a candle and a Bunsen burner, shown in Figures 9.20 and 9.21. In a Bunsen burner, gaseous methane is mixed with air and injected into the combustion zone. Hot gaseous products diffuse away, while atmospheric oxygen... 

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