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978-3-8439-4540-0, Reihe Ingenieurwissenschaften
Large Eddy Simulation of Turbulent Multi-Regime Combustion: Potentials and Limitations of Flamelet-Based Chemistry Modeling
258 Seiten, Dissertation Technische Universität Darmstadt (2020), Softcover, A5
In theory and modeling, combustion processes are often classified as premixed or non-premixed. However, in technical applications, turbulent combustion processes are more complex and partially premixing leads to inhomogeneous mixture formation. Thus, the associated local reaction zones can exhibit premixed and non-premixed flame characteristics in close proximity, which simultaneously contribute to the overall flame structure and heat release. Such conditions are termed as multi-regime combustion.
In turbulent combustion modeling, flamelet-based tabulated chemistry approaches represent a very efficient concept to reduce the overall computational cost, while preserving a detailed chemistry description. Both aspects are highly relevant for modeling of technical combustion applications. However, within flamelet-based approaches the asymptotic limits of premixed and non-premixed combustion represent an inherent model assumption.
Based on these scientific problems, the thesis deals with the analysis of multi-regime combustion and the associated potentials and limitations of flamelet-based chemistry modeling. Therefore, a piloted turbulent partially-premixed dimethyl ether (DME) flame and a novel multi-regime burner (MRB) configuration for methane flames, specifically designed to study multi-regime combustion effects, are investigated. In this context, the assessment of multi-regime combustion is twofold. On the one hand, sophisticated experimental data is used in conjunction with tabulated chemistry, by means of a prior analysis, to evaluate the underlying flame structure assumptions and identify deviations from the asymptotic limits of combustion. On the other hand, large eddy simulations (LES) are applied to assess the specific combustion phenomena of the two turbulent benchmark flames, which differ in fuel and flow complexity, using premixed and non-premixed LES combustion models based on tabulated chemistry.