FGM with REDx: chemically reactive dimensionality extension

Abstract

We propose a new approach to improve the accuracy of flamelet-generated manifolds (FGMs) method by extending the manifolds with additional chemically reactive degrees of freedom. Following the ideas of intrinsic low-dimensional manifold, the dimensionality of the FGM is increased by performing a local time-scale analysis of the chemical source term. A few slow characteristic directions of the reaction kinetics are used to extend the FGM, while the remaining reaction groups, characterised by fast time-scales, are assumed in steady state. The introduced method for FGM REactive Dimensionality extension is abbreviated as FGM-REDx. It is tested in one-dimensional simulations reproducing an expansion of burnt gases in an aero-engine stator. This process is characterised by a rapid change of enthalpy and pressure, altering, among others, the chemistry of pollutants CO and NO. The primary focus was on the assessment of the FGM's capability to predict the pollutants emissions. The rates of physical/thermodynamic perturbations turned out to be severe enough for the chemical species composition to go off the flamelet. The FGM extended with one additional chemically reactive dimension has been generated and successfully applied to the test cases, yielding a high accuracy gain over the standard FGM.

Keywords:

• flame modelling
• reduced chemistry
• prediction of emissions
• flamelet-generated manifolds (FGM)
• additional chemical time-scales

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Denis V. Efimov  http://orcid.org/0000-0002-2875-2146

Philip de Goey  http://orcid.org/0000-0001-6625-3113

Jeroen A. van Oijen  http://orcid.org/0000-0002-4283-2898

Additional information

Funding

The authors thank European Union's Seventh Framework Programme (FP7/2007-2013) for the Clean Sky Joint Technology Initiative under project DREAMCODE grant 620143 for supporting this research.