Combustion with fractal grid generated turbulence

Gas turbines play an important role in the generation of power and heat. Examples of applications are in airplane engines and large-scale electricity production. One of the main drivers in gas turbine design is the reduction of pollutants, like NOx. A reduction of NOx can be achieved by lean combustion. Stabilizing the flame is however difficult. A promising new technique, low-swirl stabilization, stabilizes the flame by a diverging flow field.
A downside to the low-swirl burner is the limited flame surface in the center of the flame, which in turn limits the conversion rate in this area.
Experimental evidence suggests that an increase in flame surface can be realized by using fractal grids to generate turbulence instead of standard regular grids. In this master assignment the effect of fractal-grid-generated turbulence on the flame characteristics is studied in more detail. The effect on the turbulence and the flame response, when varying different parameters that define the fractal grid, is experimentally investigated. The results show a clear dependence of the turbulent flame speed on the level of turbulence generated. The turbulent flow properties can be predicted solely by information of the grid parameters. With the obtained results developers can now design fractal grids with tailor-made turbulence and flame characteristics.