Thermo-chemical manifold reduction for tabulated chemistry modeling. Temperature and dilution constraints for smooth combustion reactors

Tabulated chemistry methods are viable solutions to represent the thermo-chemical pattern in combustion systems with internal recirculation. However, the identification of adequate controlling variables for these systems is important. In addition to mixture fraction and progress variable, an internal dilution and a heat loss parameter must be considered, leading to a four-dimensional thermo-chemical manifold, with an inherent increase of computational costs. In this study, a novel tabulation procedure was proposed to represent such comprehensive manifold taking into account the primary role of the internal recirculation on system reactivity. A reduction of the thermo-chemical manifold was carried out by exploiting active interconnections between experiments and computations and embedding physical and process constraints based on measurable quantities obtained from experiments. These constrains are related to minimum ignition and maximum attainable process temperatures, heat loss through the surroundings and recirculation rate. The reliability of the proposed approach was assessed by comparing the reduced manifolds to the measured data for a cyclonic burner operating under massive internal dilution levels with pure methane as the fuel and N/O mixture as the oxidizer.