Cerfacs Enter the world of high performance ...

Abstract :

Nowadays, more than 80% of the energy consumed on Earth is produced by burning fossil fuels. Alternative solutions to combustion are being developed but the specific constraints related to air transport do not make it possible to currently power engines without introducing a technological breakthrough. These findings explain the research activity to improve the knowledge and the control of combustion processes to design cleaner, and more efficient aeronautical engines. In this framework, Large Eddy Simulations (LES) have become a powerful tool to better understand combustion processes and pollutant emissions. This PhD thesis is part of this context and focuses on the models and numerical strategies to simulate with more accuracy turbulent gaseous and two-phase reacting flows in the combustion chamber of aeronautical engines.
First, a generic and self-adapting method for flame front detection and thickening has been developed for the TFLES model, and validated on several academic configurations of increasing complexity. This generic approach is then evaluated in the LES of a laboratory-scale burner and compared to the classical thickening method. Results show a more accurate thickening in post-flame regions.
Second, from the analysis of 1-D homogeneous laminar spray flames where the dispersed phase has a relative velocity compared to the carrier phase, two analytical formulations for the spray flame propagation speed have been proposed and validated. The agreement between the overall trend of both the measured/estimated spray flame speeds demonstrates that the model and its parameters correctly take into account the main physical mechanisms controlling laminar spray flames.
Finally, the state-of-the-art TFLES models were tested on complex turbulent gaseous and two-phase reacting configurations. The pros and cons of these models were investigated to contribute to the understanding of the mechanisms related to turbulent combustion, and to propose a LES modeling strategy to improve the fidelity of reactive simulations.

Jury :

Ronan VICQUELIN       Laboratoire EM2C – CNRS, Gif-sur-Yvette                Referee

Fabien HALTER            Université d'Orléans                                                   Referee

Denis VEYNANTE        Laboratoire EM2C – CNRS, Gif-sur-Yvette                 Member

Frédéric GRISCH         CORIA Rouen                                                             Member

Stéphane RICHARD     SHE SAFRAN Bordes                                                Industrial thesis Supervisor

Bénédicte CUENOT     CERFACS                                                                   Member

Thierry POINSOT         IMFT-CNRS  Toulouse                                                Advisor

Olivier VERMOREL      CERFACS                                                                   Co-advisor