Analysis of the flamelet model for calculation of emissions of pollutants by combustors

Features of the simulation of the formation of pollutants—nitrogen oxides $(\mathrm{NO}_x)$ and carbon oxide $(\rm CO)$—in combustion are considered. The causes of a possible decrease in accuracy in the estimation of $\mathrm{NO}_x$ and $\rm CO$ emission in the context of the stationary flamelet model, which is caused by the nonequilibrium character of combustion, are analyzed. It is shown that, in the case of diffusion combustion of fuel in traditional chambers, the formation of $\mathrm{NO}_x$ and $\rm CO$ has a nonstationary character amplified by an additional factor, i.e., high gradients of the scalar dissipation of the recovered fuel concentration. A promising method for enhancing the flamelet model, which is connected with transfer to the model in the nonstationary formulation, is considered. By the example of combustion of methane as a model fuel for natural gas, it shown that the flamelet model in the nonstationary formulation favors enhanced accuracy when evaluating $\mathrm{NO}_x$ and $\rm CO$ emission.