PhD defense - M. Porta

Development, verification and validation of LES tools to study
combustion noise and combustion-acoustics-turbulence interaction

Delivered by INP Toulouse
Speciality: Fluid dynamics

June 6, 2007 - CERFACS

In the last years, constraints on pollutants emissions for gas turbines have become more and more severe. In order to fulfill these requirements, gas turbines manufacturers developed combustion systems operating at very lean regimes. Unfortunately, burners working under these conditions can exhibit strong thermo-acoustical instabilities leading to serious damages or even to the complete destruction of the combustion system.

Large Eddy Simulation (LES) is nowadays considered as the most promising CFD tool for the study of combustion instabilities. Its intrinsic unsteadiness and the capability of directly solving the motion of the largest vortices and acoustic waves propagation, enable LES to analyze the strong interactions between turbulence, chemical species mixing, acoustics and chemical reactions, which are the primary sources of combustion instabilities.

However, the exact precision and the limitations of LES remain to be determined in particular for the prediction of combustion noise and self-excited combustion instabilities.

Therefore, in this work the ability of the LES code AVBP of CERFACS to accurately compute simple configurations involving only one physical phenomenon (turbulence, acoustics or combustion) is firstly veri?ed. Reactive and non-reactive academical test cases, for which the analytical solutions are known, are presented putting special emphasis on the influence of the numerical discretization and on its interaction with boundary conditions. Then, having gained confidence in the LES tool, the results obtained from a self-excited computation of a lab-scale burner are shown.

B. Nkonga	Associate professor - University of Bordeaux I	Referee
J. Réveillon	Professor - University of Rouen	Referee
J. Kok	Associate professor - University of Twente	Member
S. Ducruix	Researcher - EM2C, Paris	Member
F. Nicoud	Professor - University of Montpellier II	Member
T. Poinsot	Senior researcher - IMFT, Toulouse	Advisor