Skeletal Reaction Models for Methane Combustion

TL;DR

This paper introduces a novel local-sensitivity-analysis technique using the f-OTD method to develop skeletal reaction models for methane combustion, accurately simplifying complex chemistry while maintaining predictive performance.

Contribution

It presents a new sensitivity analysis approach with the f-OTD method to generate and evaluate skeletal reaction models for methane combustion.

Findings

Skeletal models with 24+ species replicate FFCM-1 results accurately.

The f-OTD based sensitivity analysis effectively identifies key species.

Models perform well in predicting ignition delay, flame speed, and extinction.

Abstract

A local-sensitivity-analysis technique is employed to generate new skeletal reaction models for methane combustion from the foundational fuel chemistry model (FFCM-1). The sensitivities of the thermo-chemical variables with respect to the reaction rates are computed via the forced-optimally time dependent (f-OTD) methodology. In this methodology, the large sensitivity matrix containing all local sensitivities is modeled as a product of two low-rank time-dependent matrices. The evolution equations of these matrices are derived from the governing equations of the system. The modeled sensitivities are computed for the auto-ignition of methane at atmospheric and high pressures with different sets of initial temperatures, and equivalence ratios. These sensitivities are then analyzed to rank the most important (sensitive) species. A series of skeletal models with different number of species and levels of accuracy in reproducing the FFCM-1 results are suggested. The performances of the generated models are compared against FFCM-1 in predicting the ignition delay, the laminar flame speed, and the flame extinction. The results of this comparative assessment suggest the skeletal models with 24 and more species generate the FFCM-1 results with an excellent accuracy.