Research Topic

Towards a Multi-dimensional Simulation of Combustion with focus on Filtered Density Function Approach

Mixing of methane and air in a pipe as a preparation step for the combustion
Partially premixed flame over a inhomogeneous jet burner

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 lower emissions and improved performance can be achieved. However, the gain related to decreasing of the harmful pollutant formation might be invalidated by increasing the combustion in stabilities, as the reliability of such systems can be a challenging issue.

This project aims at developing and validating an advanced CFD tool based on the Transported Filtered Density Function Approach which is able to compute well all kind of combustion regimes including wall effects along with flame - wall interaction occur ring in combustion engines, especially in lean-burn devices.

Large Eddy Simulation (LES) technique is used for capturing the unsteady processes which feature practical turbulent combustion. This approach represents the best compromise between practicality and physical accuracy, since the turbulent motion associated with the large, energy-containing eddies is computed directly, whereas the effects of the smallest ones are modeled.

Implementing the combustion chemistry into LES involves finding suitable reaction mechanism and solving filtered equation for each individual species in the reaction mechanism. The latter may involve hundreds of species and thousands of reactions leading to an enormous requirement on computer resources for a three-dimensional numerical simulation with LES.

Within this work a reduction strategy according to the Flamelet-Generated Manifold (FGM) technique will beapplied. This aims at describing detailed chemistry by only a few controlling variables using tabulation. However, the need to capture the flame front which is still unresolvable on the LES computational mesh will necessitate the formulation of suitable combustion models. One such model is the well-established Artificially Thickened Flame (ATF), where the flame front is thickened and therewith resolvable on coarser grids. Unfortunately this model copes essentially with turbulent premixed combustion properties.

One of the tasks in this work will be to extend this modeling to stratified combustion along with partially premixed, and to non-premixed combustion regimes. This will be achieved in the framework of the Monte Carlo Stochastic Field Method which enables to describe all combustion regimes while being coupled to the FGM tabulated chemistry.

Key Research Area

Combustion; Fluid- and Thermodynamics; Numerical simulations

Contact

Alija Bevrnja
M.Sc.

Address:

Dolivostraße 15

D-64293 Darmstadt

Germany

Phone:

+49 6151 16 - 24388

Fax:

+49 6151 16 - 24404

Email:

bevrnja (at) gsc.tu...

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