Regimes in turbulent non-premixed combustion

Figure: Direct Numerical Simulation of turbulent methane jet diffusion flame.

Upper part of the figure: Mixture fraction field in the cross section of the jet flame. The color red corresponds to regions of pure fuel while blue indicates regions of pure oxidizer.
Lower part of the figure: Dissipation Element analysis of the mixture fraction field in the same plain. Individual elements are encompassed by a black contour.

In this project, two highly resolved direct numerical simulations (DNS) of temporally evolving jet methane diffusion flames were conducted in order to find reliable models for the highly turbulent combustion regime. The starting conditions for the DNS were chosen to instigate both local extinction and re-ignition to provide a wide range of combustion phenomena for further investigation.

The data were analyzed by means of a Dissipation Element (DE) analysis, which is a method for measuring the local turbulent scales and allows to investigate the effect of small scale mixing. A DE analysis of the Mixture fraction field, representing the state of the chemistry, is shown in the picture.

A key characteristic of the statistics obtained by the DE analysis is its strong invariance towards changes in the Reynolds number, making it predestined for future models for the small scale mixing regime.

Prof. Heinz Pitsch