diffusion flame

Diffusion flames are a type of flame where the fuel and oxidizer are not mixed before entering the combustion zone. Instead, molecular or turbulent diffusion is responsible for mixing these components within the flame itself. These flames are common in industrial applications, such as furnaces, and are often turbulent.1

The chemistry of diffusion flames is less understood than premixed flames, with their behavior often explained more by physics and thermodynamics due to the diffusion-driven mixing process. Examples of diffusion flames include those from candles, liquid droplets, and many propellants. The theory of flame propagation involves either heat conduction or diffusion, where heat or reactive molecules move from the flame front to unburned fuel and air, causing ignition and self-propagation.12