Modern engine concepts are based on direct fuel injection, which may lead to partially premixed combustion, where a combination of diffusion flames and propagating partially premixed flame fronts exist. In addition exhaust gas recirculation (EGR) is applied to reduce emissions. Most existing combustion models for CFD have been originally developed for specific flame types and designed for specific conditions where EGR is not relevant. In the present study a combustion modeling strategy is outlined, implemented, and tested, which allows to include the aforementioned physical processes. A quasi-steady flamelet model which is based on the mixture fraction and a presumed PDF is used in combination with a reaction progress variable to allow for the simulation of a partially premixed flame front and subsequent diffusion flames. The source term of the transport equation of the reaction progress variable is closed with a model for the burning velocity. Special attention is given to the formulation of the burning velocity of hydrogen, which differ substantially from values and expressions for hydrocarbon fuels. The description of the thermo-chemical composition is extended such that exhaust gases can be taken into account. The improved combustion model is validated against experimental data for simple test cases and applied to an internal combustion engine in order to demonstrate that one can perform efficient CFD analyses of complex applications.
Flamelet modelling of partially premixed hydrogen combustion in a direct fuel injection engine
Flamelet-Modellierung der teilvorgemischten Wasserstoffverbrennung in einem Direkteinspritzmotor
2006
8 Seiten, 5 Bilder, 6 Quellen
Aufsatz (Konferenz)
Englisch
Verbrennungsmotor , Kraftstoffeinspritzung , Direkteinspritzung , Wasserstoff , Verbrennung (Oxidation) , Vormischung , Modellieren (Gestalten) , Diffusionsflamme , Abgasrückführung , Emissionsminderung , numerische Strömungssimulation , Reaktionsmodell , Kohlenwasserstoff , Auspuffgas , chemische Zusammensetzung , Verbrennungsgeschwindigkeit
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