Liñán diffusion flame theory is a theory developed by Amable Liñán in 1974 to explain the diffusion flame structure using activation energy asymptotics and Damköhler number asymptotics. Liñán used counterflowing jets of fuel and oxidizer to study the diffusion flame structure, analyzing for the entire range of Damköhler number. His theory predicted four different types of flame structure as follows,
* Nearly-frozen ignition regime, where deviations from the frozen flow conditions are small (no reaction sheet exist in this regime),
* Partial burning regime, where both fuel and oxidizer cross the reaction zone and enter into the frozen flow on other side,
* Premixed flame regime, where only one of the reactants cross the reaction zone, in which case, reaction zone separates a frozen flow region from a near-equilibrium region,
* Near-equilibrium diffusion-controlled regime, is a thin reaction zone, separating two near-equilibrium region.