Parametric Studies and Simulations of a Hydrogen Micromix Combustor

The use of hydrogen as an alternative fuel in the combustion chamber of an aircraft turbine engine would offer a practical solution to reducing levels of emissions which contribute to atmospheric pollution. In recent years various designs of the basic system component of such an engine have been proposed being described as the hydrogen micromix combustor. This technology requires the design and development of a safe mechanism for hydrogen combustion which avoids auto-ignition and flashback and permits the initial balance and mixing of a hydrogen-air mixture to produce thrust from the combustion of hundreds of miniature low temperature diffusion flames which produce extremely low levels of NOx. In this paper a potential geometry and typical operating conditions of such a micromix combustor has been selected for a critical examination of the numerical modelling with particular attention to the levels of NOx predicted. In particular the level of grid independence of the NOx modelling is assessed as well as the variations in NOx levels generated in the march towards steady state solutions for various numerical methods. Additionally, a series of parametric studies associated with modifications of the basic micromix combustor design are explored to verify both the consistency in the numerical methods adopted as well as assessing the impact of such modifications on the overall micromix combustor performance.