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Modeling of turbulent multi-stream combustion for integrating CO₂ capture on gas turbines

MEGEP (Mécanique, Energétique, Génie civil & Procédés)

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This thesis investigates turbulent combustion modeling in multi-stream burners featuring exhaust-gas recirculation (EGR). This work takes place within the European Transition program, aiming to understand how EGR affects flame stability in gas turbine burners, to permit efficient integration with CO₂ capture systems. Recirculated gases are simulated with pure CO₂ dilution, which, when present in fresh gases, lowers the flame temperature and intensity, modifying the burner operability range. Simulating these combined effects is a numerical challenge that this thesis tries to address. 

An enhanced version of the Thickened Flame (TF) model for Large Eddy Simulation (LES) is proposed, which relies on a reference-free flame sensor formulation. It builds on the Generic Flame Sensor proposed by Rochette et al. (2020), extending its robustness and capabilities to properly feed the turbulent combustion model parameters. This revision of the flame sensor called the ridge sensor, uses geometrical analysis to locate the flame, by exploiting characteristics of specific source terms found inside a flame. It exploits Lagrangian sensors to gather statistics in the neighborhood of the flame front. As a result, the need for pre-tabulation is removed, avoiding the associated challenges of accurately building and accessing look-up tables. However, handling millions of Lagrangian particles in massively parallel computational domains is expensive. 

Specific attention to the algorithmic implementation of the model was made, so that the over-cost of the Lagrangian procedure is not prohibitive. Depending on the configuration studied, the R-TF model (Ridge – Thickened Flame model) exhibits over-costs on 3D turbulent flames between 4-15%, compared to the standard modeling approach using look-up tables. The implementation of the model is systematically validated using canonical configurations, and ultimately compared to a state-of-the-art modeling approach specialized in stratified multi-fuel combustion modeling (called MF-TF for Multi-Fuel Thickened Flame model). The configuration experimentally studied at Cardiff University features an ammonia/hydrogen/air swirled burner, subject to preferential diffusion effects, on which MF-TF model assesses its capabilities. Results show that R-TF performs at least as well as MF-TF. Finally, the R-TF model is used to simulate a semi-industrial burner (SIB), whose geometry is provided by Baker Hughes and which is experimentally studied at the University of Florence (UNIFI). It operates at atmospheric pressure and three operating points are investigated: a non-reactive one, a reactive one with no dilution which serves as a baseline, and a CO₂ diluted one to investigate effects of dilution on flame stabilization.

Jury

Ronan VICQUELIN	CentraleSupelec / EM2C	Reviewer
Olivier COLIN	IFPEN	Reviewer
Bruno RENOU	INSA / CORIA	Examiner
Antonio ANDREINI	University of Florence	Invited
Eleonore RIBER	Cerfacs	Thesis supervisor
Thomas JARAVEL	Cerfacs	Thesis co-supervisor