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Proposing Institution

Institut für numerische Methoden in der Luft- und Raumfahrttechnik, Universität der Bundeswehr München
Project Manager

Prof. Dr.-Ing. Markus Klein
Werner-Heisenberg-Weg 39a
85577 Neubiberg
Primary energy is often supplied by combustion processes. In many technical applications, such as gas turbine combustion chambers or supercharged piston engines, combustion takes place at elevated pressure. Due to the high energy density of fossil fuels, they are indispen-sable for commercial aircrafts in the foreseeable future and at least medium-term, despite increasing electrification, piston engines will still be used in conventional or hybrid drives. In order to optimize the flow and combustion process as well as to reduce development times and to save costs, numerical flow simulation is becoming increasingly important. Specifical-ly, the large eddy simulation (LES) approach has become an important tool for flow simula-tion in recent years and is already used for first industrial configurations. Instead of model-ling all turbulent scales, as often done in the past in the so called RANS approach, many physical processes can be resolved with LES. However, in existing LES subgrid combustion models the effect of pressure has rarely been taken into account. The models are often insufficiently validated regarding high-pressure combustion. The occurrence of hydrodynamic instabilities, which can lead to a stronger flame wrinkling, is also ignored. Finally, it is becoming more and more apparent that differ-ent closure terms interact strongly with each other as well as with the numerical scheme. These individual parts should not be considered independent of each other and care should be taken when selecting appropriate model combinations. The overall goal of this project is the development and validation of an integral LES model for high pressure turbulent premixed combustion. The project is divided into two closely interlinked parts. First, a DNS data base is created for turbulent, statistically planar and Bun-sen flames at different pressure levels. Subsequently, the data is spatially filtered to produce pseudo-LES fields (a-priori analysis). In this way modeling approaches can be compared with unclosed terms and promising models can be identified. However, the final assessment of a model has ultimately to take place in a real LES, the so-called a-posteriori analysis. This is the scope of the second part of the project. The previously selected closure approaches are implemented in an LES flow solver and validated using DNS data and experimental data from literature. The LES will also show the interaction of different submodels. In a second step, the analyses and the model development will be extended to situations with spatially varying air-fuel ratio. This will be done by building a DNS data base of stratified turbulent flames using detailed chemical mechanisms.Computing resources within this grant will be mainly needed for establishing the DNS data-base.

Impressum, Conny Wendler