Method of invariant grid for model reduction of hydrogen combustion

TL;DR

This paper introduces the Method of Invariant Grid (MIG) for model reduction in hydrogen combustion, effectively approximating the slow invariant manifold to simplify complex kinetic systems while maintaining accuracy.

Contribution

The work applies MIG to a realistic hydrogen-air combustion system, constructing and refining invariant grids based on thermodynamic Lyapunov functions for improved model reduction.

Findings

Invariant grids accurately replicate detailed kinetics.

MIG effectively reduces model complexity.

Reduced models show excellent agreement with full kinetics.

Abstract

The Method of Invariant Grid (MIG) is a model reduction technique based on the concept of slow invariant manifold (SIM), which approximates the SIM by a set of nodes in the concentration space (invariant grid). In the present work, the MIG is applied to a realistic combustion system: An adiabatic constant volume reactor with H2-air at stoichiometric proportions. By considering the thermodynamic Lyapunov function of the detailed kinetic system, the notion of the quasi-equilibrium manifold (QEM) is adopted as an initial approximation to the SIM. One- and two-dimensional discrete approximations of the QEM (quasi-equilibrium grids) are constructed and refined via the MIG to obtain the corresponding invariant grids. The invariant grids are tabulated and used to integrate the reduced system. Excellent agreements between the reduced and detailed kinetics is demonstrated.