Swirler Flow Field Characteristics in a Sudden Expansion Combustor Geometry

The present study investigates the flow field characteristics of a gas turbine swirler in a model combustion chamber, using particle image velocimetry. Detailed mean and RMS velocities, vorticity, Reynolds shear stress, and pseudoturbulent kinetic energy were obtained at various cross sections downstream of the swirler and in a plane along the inlet flow direction. The experiments were performed in a sudden expansion square geometry. A central toroidal recirculation zone and corner recirculation zone was observed and characterized. Another instability caused by swirl, called precessing vortex core, has been observed far downstream of the swirler, in the plane located at Z/D = 2.5 and 1.25 (D, diameter of the swirler) depending on the pressure drop across the swirler. High RMS velocity magnitudes are observed in several cross-sectional planes indicating high levels of turbulence generated by the swirling effect which promotes rapid mixing. The structure of the complex swirling flow field has been investigated both qualitatively and qualitatively.