Designing a Radial Swirler Vortex Breakdown Burner

Abstract

Most gas turbine premix burners without centrebody employ the breakdown of a swirling flow at the transition between the mixing section and the combustor for aerodynamic flame stabilization [1]. As the formation of the desired vortex breakdown pattern depends very sensibly on the distribution of axial and azimuthal velocity in the mixing section, the design of suitable swirlers is usually a cumbersome iterative process. The presented burner design was found through the implementation of design guidelines derived from CFD-calculations and on the basis of analytical considerations [5]. The swirling flow is generated by a radial swirler with tangential inlets. In order to stabilize the flow pattern, the swirling flow confines a slow non-swirling flow on the centreline. The centre flow being set into azimuthal motion creates increasing azimuthal velocity in streamwise direction in the vortex core. This process is reinforced by a conical nozzle and leads to the production of positive azimuthal vorticity inside the nozzle which stabilizes the flow field. First atmospheric test runs and Large Eddy Simulations of the isothermal as well as reactive flow field prove that the design goals have been reached: The burner creates stable vortex breakdown in the primary zone of the combustion chamber without flame flashback or backflow on the centreline over the entire operating range and even for difficult fuels like hydrogen containing gases. This finding indicates that reliable vortex breakdown burners with remarkable fuel flexibility can be designed using the guidelines presented in [5].