Preheat zone: Negligibly small heat release

(Figure 23.1)

• Certain chemical reactions take place in this zone

Reaction zone:

• most of the chemical energy is released in the form of heat
• Decomposition of fuel takes place, leading to intermediate radical formation
• Reaction zone is very thin as compared to the preheat zone.
• Temperature gradient and concentration gradient are high.

Recombination zone:

• CO₂ and H₂O are formed;
• No heat release in this zone