PhD, Gas turbines system simulation : modelling of the impact of mixing and dilution on combustion and pollutant emissions

This PhD aims to investigate the physical phenomena governing combustion dynamics related to transient operating conditions in gas turbines and formalize this understanding in a model suitable for system simulation approaches. To achieve this goal, an axial description of turbulence and combustion physics will be integrated in the model in order to account for temperature and composition gradients, which directly impact heat release and pollutant emissions. This development will be based on LES simulations of an academic and/or industrial aeronautic combustor, taking advantage of the IFPEN 15-year experience in the domain of 3D CFD model formal reduction to 0D approaches.

Description

The actual context in aeronautics aims to drastically reduce fuel consumption and pollutant emissions (ACARE targets 2020 and 2050). It is expected to reach these ambitious targets both by optimizing the current engine architectures and introducing breakthrough technologies, the latter being generally more complex than the former; accordingly, it seems essential to increase dynamism and flexibility of gas turbines design process. Numerical simulation, because of its reduced cost, effectiveness and capability to gather and summarize knowledge, favors tighter communication and more constructive interactions between the different professions; in particular, system simulation (SS) stands out for its capability to deal with complex multi-physics phenomena appearing at the interface of different disciplines. The SS state of the art for aeronautics gas turbines consists in using simple modeling approaches for combustion and pollutant emissions. IFPEN, in order to anticipate the evolution of the design approaches, developed a phenomenological approach to combustion modeling, aiming to account for the combustion dynamics related to transient operating conditions. This approach includes the relevant physics structuring the flame, coming from our experience in LES modeling, the reference numerical tool in the domain. However, some assumptions such as the macroscopic description of the mixture composition and the temperature field within the combustion chamber do not allow to describe with a convenient level of details the thermochemistry of the flame in the spatial domain, leading to approximations on the estimations of the flame length, thermal exchanges, and post-flame chemistry kinetics. This PhD aims to investigate the mixing and dilution phenomena in gas turbines and formalize this understanding in a model suitable for SS approaches. To achieve this goal, an axial description of turbulence and combustion physics will be integrated in the model in order to account for temperature and composition gradients, which directly impact heat release and pollutant emissions. This development will be based on LES simulations of an academic and/or industrial aeronautic combustor, taking advantage of the IFPEN 15-year experience in the domain of 3D CFD model formal reduction to 0D approaches.

Nr of positions available : 1