Energy & Fuels, Vol.34, No.12, 16572-16584, 2020
Automatic Construction of REDIM Reduced Chemistry with a Detailed Transport and Its Application to CH4 Counterflow Flames
Extinction limits are important quantities of counterflow diffusion flames. An accurate prediction of extinction limits is necessary for the design of engineering combustion devices involving flame quenching. In this work, the reaction-diffusion manifold (REDIM) reduced chemistry with a detailed transport model is applied for the numerical investigation of extinction limits of counterflow diffusion flames. Unlike other tabulated flamelet models where very detailed information about a particular combustion system is required, the REDIM reduced chemistry can be generated based on the detailed reaction mechanisms, requiring only a minimal additional knowledge of the considered combustion system. Recently, an automatic generation of the REDIM has been introduced and tested for premixed flames. This newly developed algorithm starts with a 1D reduced model, and any higher dimension of the REDIM reduced model can be constructed automatically without any additional information. Such an algorithm largely simplifies the generation of the REDIM reduced chemistry. The focus of this work is to apply this newly developed algorithm for the construction of two-dimensional (2D) and three-dimensional (3D) REDIMs for counterflow diffusion flames. It is shown how 2D and 3D REDIM reduced chemistry can be generated automatically in a generic way according to a hierarchical concept. An oxygen-enriched MILD combustion system CH4/CO2 versus the O-2/CO2 counterflow diffusion flame, whose extinction strain rates had been measured experimentally, is selected as an illustrative example for discussion and validation. The relative errors of predicted extinction strain rates using a 3D REDIM are much less than the experimental uncertainty and the differences using different detailed chemical mechanisms.