Aerodynamics and characteristics of the premixed swirl flame

We report on the aerodynamics and scalar characteristics of a premixed swirl-stabilized propane-butane/air flame at the exit of a radial vane swirler. The experimental study focuses on the combustion of a well-premixed lean fuel/air mixture f = 0.57 with varying guide vane angle and hence with varying swirl number S. Mean velocity profiles are measured using laser Doppler anemometry, and mean temperature distributions are obtained by thermocouples. Optimal operating regimes of swirl- stabilized combustion are determined from visualization data, temperature distributions, and velocity profiles for different values of the geometric swirl number S. For the reacting and isothermal cases, the precessing vortex core is identified by power spectral density analysis of fluctuations of the tangential velocity at the center point of the central recirculation zone. It is shown that the precessing vortex core is determined by well-mixed isothermal swirl flow in the mixing tube of the radial vane swirler.