Diffuusipalaminen

Diffuusipalaminen is a term used in fire science to describe combustion that is governed by diffusion of oxidizer into the fuel and diffusion of combustion products away from the reaction zone, rather than by rapid, well-mixed gas-phase reactions in a narrow flame front. The process yields a broad, diffuse heat release and is typical for porous or solid fuels where the reactive zone extends over a volume rather than a thin sheet. In solids and porous media, diffusion-controlled burning can manifest as smoldering, sustained at lower temperatures with little visible flame, and may persist after the external flame is removed.

Key factors influencing diffusipalaminen include porosity, pore size, moisture content, oxygen partial pressure, temperature, and thermal conductivity. When ignition occurs, the oxidation front moves slowly through the material as oxygen diffuses inward. In gas flames, diffusion flames are formed when fuel and oxidizer streams are separate, and the flame stabilizes at their interface.

Occurrence and relevance: diffusipalaminen is relevant in wildland fuels, coal and charcoal combustion, wood and textiles, and certain polymer burns. It poses fire safety concerns due to its hidden spread and potential for long-duration fires. In engineering, diffusion flames are exploited in diffusion-burner systems and in catalytic combustion where the reaction zone is spread out.

See also: diffusion flame, smoldering, porous media combustion, flame front.