Case 1 Small Scale Gas Turbine Burner

The first example presents typical cold flow fields with swirl ( 9.2), as well as reacting flow fields ( 9.2), and compare them with experimental data. 

The burner of Case 1 uses a swirled injector (Fig. 9.1) where swirl is produced by tangential injection downstream of a plenum. A central hub contributes to flame stabilization. In the experiment methane is injected through holes located in the swirler but mixing is fast so that perfect premixing is assumed for computations. Experiments include LDV (Laser Doppler Velocimetry) measurements for the cold flow as well as a study of various combustion regimes. The dimensions of the combustion chamber are 86 mm X 86 mm x 110 mm. 

For LES, the critical question of boundary conditions is avoided in Case 1 by extending the computational domain upstream and downstream of the chamber the swirlers and the plenum are fully meshed and computed and even a part of the outside atmosphere (not shown on Fig. 9.1 for clarity) is meshed to avoid having to specify a boundary condition at the chamber outlet. This procedure is applicable only for certain configurations a real gas turbine combustion chamber is surrounded by more complex passages for air or by moving parts (the blades of the turbine for example) for which specifying boundary conditions remains much more difficult. 

The RMS fluctuations in both LES and experimental results (Fig. 9.3 and 9.5) are very intense around the axis, close to the injector nozzle (of the order of 20 m/s at x = 1.5 mm). These oscillations are t3rpical of most swirled burners. They may be due to  

Mode no. Mode name Cold flow (Hz) Reacting flow (Hz) 

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