Experimental Study on Stabilization of Lifted Swirl Flames in a Model GT Combustor

This study reports on experimental investigations on isothermal and reacting swirled non-premixed flows under varying pressure conditions. In this configuration, a central high speed fuel jet was surrounded by a heated swirling air flow. For the reacting case natural gas served as fuel whereas for isothermal conditions fuel was replaced by a mixture of helium and air to achieve Reynolds-similarity. The optically accessible combustor allowed for application of laser diagnostics. Here we report on Laser Doppler Anemometry and planar laser-induced fluorescence (PLIF) experiments used to characterize the flow field and visualize selected scalars, respectively. Acetone served as a fluorescence marker for mixture fraction investigations. The hydroxyl radical was used to provide general features of the reaction zone such as flame shape and mean stabilization. To expose the influence of pressure on the flame structure three different operating points were investigated varying the combustor pressure between 2 and 6 bar while the inflow bulk velocities remained the same. Striking features of the present configuration are a detached flame, multiple recirculation zones, and complex coherent flow structures.