Non-linear simulations of combustion instabilities with a quasi-1D Navier-Stokes code

TL;DR

This paper presents a non-linear, quasi-1D Navier-Stokes simulation approach with a new heat release model to predict combustion instabilities in lean premixed flames, validated against experimental data.

Contribution

It introduces a novel phenomenological heat release model within a quasi-1D Navier-Stokes framework for attached flames, improving prediction accuracy of combustion instabilities.

Findings

Simulations accurately reproduce experimental frequencies.

Resonant acoustic mode amplitudes are well predicted.

The approach effectively models thermoacoustic instabilities.

Abstract

As lean premixed combustion systems are more susceptible to combustion instabilities than non-premixed systems, there is an increasing demand for improved numerical design tools that can predict the occurrence of combustion instabilities with high accuracy. The inherent non-linearities in combustion instabilities can be of crucial importance, and we here propose an approach in which the one-dimensional Navier-Stokes and scalar transport equations are solved for geometries of variable cross-section. The focus is on attached flames, and for this purpose a new phenomenological model for the unsteady heat release from a flame front is introduced. In the attached flame method (AFM) the heat release occurs over the full length of the flame. The non-linear code with the use of the AFM approach is validated against results from an experimental study of thermoacoustic instabilities in oxy-fuel flames by Ditaranto and Hals [Combustion and Flame, 146, 493-512 (2006)]. The numerical simulations are in accordance with the experimental measurements and both the frequencies and the amplitudes of the resonant acoustic pressure modes are reproduced with good accuracy.