Matthias Ihme

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The flamelet/progress variable approach (FPVA) has been proposed by Pierce and Moin as a model for turbulent non-premixed combustion in large-eddy simulation. The filtered chemical source term in thismodel appears in unclosed form, and is modeled by a presumed probability density function (PDF) for the joint PDF of the mixture fraction Z and a flamelet(More)
Detailed simulations of the bifurcation and ignition of an Argon-diluted Hydrogen/Oxygen mixture in the two-stage weak ignition regime are performed. An adaptive meshrefinement (AMR) technique is employed to resolve all relevant physical scales that are associated with the viscous boundary-layer, the reaction front, and the shock-wave. A high-order hybrid(More)
Combustion instabilities in gas turbine engines often give rise to acoustic resonances. These resonances occur as manifestations of different acoustic modes, of which a single or multiple modes may be present. In this work, the acoustic behavior of a model gas turbine combustor, developed at DLR Stuttgart by Meier, was investigated using both syn(thetic)(More)
A unified treatment of general fluid thermodynamics is developed to handle fluid flows over their entire thermodynamic states. In particular, attention has been focused on the correct evaluation of the p − v − T relationship in the transand super-critical regime, using a modified version of the Peng Robinson cubic equation of state and deriving from it(More)
Numerical simulations of combustion in aircraft engines is quite complex, as it requires an adequate description of liquid fuel injection, liquid fuel atomization, drop breakup, drop dynamics, and evaporation, large-scale turbulent fuel air mixing, small scale molecular fuel air mixing, chemical reactions, and turbulence/chemistry interactions. In the(More)
A new engine model has been developed for applications requiring run times shorter than a few seconds, such as design optimization or control evaluation. A reduced-order model for mixing and combustion has been developed that is based on nondimensional scaling of turbulent jets in crossflow and tabulated presumed probability distribution function flamelet(More)
A pattern search optimization method is applied to the generation of optimal artificial neural networks (ANNs). Optimization is performed using a mixed variable extension to the generalized pattern search method. This method offers the advantage that categorical variables, such as neural transfer functions and nodal connectivities, can be used as parameters(More)
An unsteady flamelet/progress variable model has been developed and formulated as an extension of the steady flamelet/progress variable model. For this model, a large number of unsteady laminar flamelet simulations is performed for various conditions, and solutions are recorded as function of time. From this, a flamelet library is generated, which provides(More)