Development and application of numerical methods for the simulation of advanced combustion processes within complex devices

The modern combustion research faces two major objectives, the optimization of the combustion efficiency and the reduction of pollutants according to the new emission standards. The current tendency is towards using lean and stratified burning conditions, where low emissions and improved performance can be achieved. Hence, it is desirable to predict the essential physical and thermochemical properties of such systems as accurately as possible. This promotes an increasing use of computational methodology, which enables a more detailed insight into the combustion physics and processes controlling the emission formation, as they are beyond the reach of the experimental techniques. Consequently, this work addresses the numerical simulation and the modeling strategies of technical combustion systems, in particular the large eddy simulation of lean premixed and stratified flames. One of the important aspects of this work represents the development and the application of suited combustion modeling approaches. More precisely, the chosen strategy combines the detailed chemistry tabulation and the Eulerian Monte Carlo stochastic field method. The developed combustion models are further used to improve the understanding of the essential combustion physics and the processes that can be reproduced by the simulations. Herein an important aspect considered in this work is the interaction of the flame with the mixing layer in lean stratified flames. Hence, a detailed investigation accompanied by different shear layer intensities superimposed onto the mixing and the reaction layer is performed. Furthermore, the physical phenomena covering the fuel stratification, the heat losses in the near wall region, and the flame lift-off are studied as they are of practical relevance.