Ji is the diffusion flux of species i, which arises due to concentration gradients and differs in both laminar and turbulent flows.
This model provides with the exact solution for laminar flames but gives inaccurate solution for turbulent flames, in which turbulence highly affects the chemistry reaction rates, due to highly non-linear Arrhenius chemical kinetics.
In the non-premixed flames, turbulence slowly mixes the fuel and oxidizer into the reaction zones where they burn quickly.
The EDC model attempts to incorporate the significance of fine structures in a turbulent reacting flow in which combustion is important.
EDC has been proven efficient without the need for changing the constants for a great variety of premixed and diffusion controlled combustion problems, both where the chemical kinetics is faster than the overall fine structure mixing as well as in cases where the chemical kinetics has a dominating influence.