Abstract
Swirling flows are commonly used for flame stabilization in gas turbine combustors, which are equipped with suitable swirlers. The air rotation, quantified by the swirl number, is herein fixed through the geometry and represents a parameter significantly affecting flame stability and dynamics. The possibility of continuous swirl variation would be advantageous for the assessment and control of thermoacoustic instabilities. This is especially true for fuel-flexible applications, for which different swirl numbers are needed to stabilize flames arising from the combustion of different fuels. Most swirl-varying systems rely on mechanical adjustments. In this work, a novel swirl-stabilized burner is investigated experimentally, which is based exclusively on fluidic actuation. For the assessment of the resulting flow field, the axial and azimuthal velocity components are determined through Laser Doppler Anemometry measurements, which are performed in a volume downstream of the burner's mixing tube. The data is computed into swirl-numbers in order to quantify the degree of swirl as a function of the fluidic actuation. The characteristics of two different burner geometries are investigated, of which one is found to generate higher swirl over the investigated operational range. For this configuration, the technically relevant operating range is determined in which the swirl number can be continuously set from zero to around 0.9. Our experimental results show that fluidic actuation is a viable way to continuously change the swirl number, and that the achievable swirl range is quantitatively comparable to that of state-of-the-art swirl-stabilized burners.
