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The environmental emergency has led to the development of new combustion technologies. In this context, flameless combustion (FC in this manuscript) offers the prospect of a less polluting and more efficient technology. In FC, combustion is strongly diluted with recirculated burnt gases. Consequently the oxygen content is reduced and temperature peaks are smoothed, yielding reduced heat release. These conditions dramatically reduce the conditions of NO pollutant formation and increase the efficiency of the combustion process. Being FC a relatively new technology, it still needs optimization and R&D, which can be expensive and time consuming. Potentially, CFD can reduce both the financial costs as well as the R&D projects length. The context in which this thesis is inserted is exactly the numerical modeling of FC, by using Large Eddy Smulations for its better prediction of the turbulent ternary mixing (fuel - burnt gases -air), compared to RANS. This work has been divided into two main parts. In the first, combustion in FC has been investigated by means of a new tabulated combustion model initially written in the context of the EC-KIAI project and developed and adapted to FC in this thesis. The model uses diluted homogeneous reactors DHR to simulate FC and it was developed to account for under adiabatic enthalpy losses and the ternary mixing typical of FC. The model was firstly validated on a non-premixed flame academical configuration called Flame D and subsequently on a real FC combustor from the work of Verissimo et al. The results obtained for these configurations are quite correct although some discrepancies in CO prediction are observed. In the second part of the thesis, the NO pollutant modeling in FC is investigated. With this aim, the Diffusion Flame - NO relaxation approach DF-NORA was developed. It consists in tabulating the NO relaxation towards equilibrium of the NO source term in a flamelet structure. As done in the first part, the model was first validated on Flame D and then employed in a real FC configuration. Results are quite satisfactory in both config- urations. The encouraging results obtained in this work open the possibility of applying the proposed developments to real industrial configurations in the future.