A method to extend flamelet manifolds for prediction of NOx and long time scale species with tabulated chemistry

Abstract

Numerical simulation is currently used to help design low NOx devices for aircraft engines. In order to improve the prediction of pollutant species, combustion models based on tabulated chemistry have been commonly used in recent years. However, the short time scales of usual flamelet manifolds can lead to errors concerning the NO prediction in post flame area, as shown in this paper. Thus, a new method is proposed to extend the manifold in order to describe the evolution of species with a long characteristic time. This method is tested in the framework of 0D-1D computations. The use of the extended manifold is shown to be necessary to correctly predict the evolution of NO concentration in burnt gases. As an example, the extended and classical manifolds were compared in the framework of 2D simulations of an industrial-like combustor, showing an evident difference on the NO levels predicted in the outlet section.

Experimental and numerical studies on the premixed syngas swirl flames in a model combustor

“…Ansys Fluent utilises the second approach to define NO x in the FGM model. Boucher et al[37] extracted NO reaction rate from the manifold at the given equivalence ratio based on t e second a roac from Van ijen's model at t e ma imum value of t e rogress variable. This implies a linear evolution of progress variable for mass fraction of NO x as the reaction rate is independent of the calculated NO x concentration.…”

Hybrid Eulerian-Lagrangian method for soot modelling applied to ethylene-air premixed flames

“…However, the modelling of heat losses as well as the consideration of combustion regimes and multiphase flow effects increase the complexity and thus the computational cost of such approaches. Also, the extension of tabulated chemistry to species having long evolution time scales, such as NO or soot, is an issue [21]. Alternatively, sectional methods can be used to characterize PAH growth [10,22,23] and combined with a reduced chemical mechanism for lighter species [24,25].…”