Resumen de Numerical studies of diffusion flames. Special emphasis on flamelet concept and soot formation
Combustion is one of the oldest energy sources. Nowadays, combustion processes cover a great part of the world-wide energy demands. Its comprehension in order to improve efficiency and to reduce pollutant formation, partially responsible of the global warming, is considered to be of great importance. Reactive flows of gases are affected by a great amount of phenomena, the governing equations of which are highly non-linear, strongly coupled and, only in the last decades, with the development of computers, the modelling of these equations has been possible. The main objective of this thesis consists in developing numerical tools potentially applicable to technological processes of interest able to solve and predict combustion processes of gases under laminar and turbulent regimes, with special emphasis on pollutant formation such as soot and NOx. With the numerical techniques employed here, the understanding of the mathematical formulation and combustion phenomena is aimed. The methodology is mainly based on multidimensional detailed calculations based on the resolution of Full Transport Equations (FTE) in the physical space, together with the application of simplified models based on the flamelet concept. In order to obtain a deeper understanding of the flamelet model, flamelet predictions have been compared against FTE calculations. This methodology allows to investigate the capabilities and limitations of the flamelet concept under laminar situations, taking advantage of the fact that the flamelet idea arises from laminar combustion. In chapter 3, Non-Interactive and Interactive flamelet models are compared between them and with FTE calculations for a coflow methane/air laminar diffusion flame. The Non-Interactive models under consideration are the Steady Flamelet Model (SFM), the Enthalpy Defect Flamelet Model (EDFM), and its extended versions to approach pollutants formation, the E-SFM and E-EDFM respectively.
