Session: 04-13 Combustor Design I

Paper Number: 152856

Characterization of a Fluidically-Variable Swirl Burner: Effects of the Imprinted Swirl on Flame Shapes and Emissions for Hydrogen-Methane Blends 

Modern gas turbine combustors widely rely on swirling flows for the stabilization of flames. The flow's swirl number is characterized by the geometry of the swirler in the burner used to stabilize the flame. In addition to aid flame stability, the swirl induced within a combustor represents an important parameter affecting emissions, flame shapes, and flame dynamics. In consequence, understanding the effect of swirl is important for the assessment and control of thermoacoustic instabilities. Furthermore, with the progression of carbon-free and carbon-reduced fuels, as e.g. hydrogen or hydrogen-enriched gas mixtures, novel technological solutions are gaining importance. Due to hydrogen's high flammability, pure hydrogen flames are found to be well stabilized by axial jets comprising a high axial flow momentum. A stable combustion of pure methane, on the other hand, is optimally maintained by highly swirled flows. For the investigation of the aforementioned parameters, as well as for the transition towards carbon-free combustion, the active and continuous variation of the degree of swirl is found to play a significant role, especially with focus on fuel flexible solutions ranging between pure hydrogen and pure methane.

In this work, the experimental characterization of a novel swirl-stabilized burner is presented, which allows for the variation of the imprinted swirl number solely relying on fluidic actuation. Instead of employing geometry variations, the swirl variation is achieved through the controlled injection of a secondary air mass flow, resulting in a linearly controllable flow regime ranging from a non-swirled axial jet, ideal for stabilizing hydrogen flames, to a fully swirled flow, suitable for stabilizing natural gas flames. The working principle has been demonstrated, and the operating range has been assessed qualitatively and quantitatively, both numerically and through experiments in cold, non-reacting conditions. The fluidic burner is now characterized under reacting conditions in a suitable combustion test rig. For a broad range of hydrogen-methane gas mixtures, ranging from pure hydrogen to pure methane, the characteristics of the burner and the stabilized flames are experimentally investigated. For each fuel blend, several swirl regimes are tested, creating a wide span of operating points. In this respect, the emissions within the exhaust gas are analyzed through a gas analyzing system for each operating point. Additionally, the respective flame shapes are acquired through OH*-imaging.

The experimental characterization of the novel fluidically-variable swirl burner demonstrates its operational capability over a broad range of utilized fuel blends. For each investigated fuel composition, an optimal degree of swirl could be identified, allowing for a stable and safe combustion, and minimizing the produced emissions. Additionally, all stable operating points could be mapped into a stability map, showing the operational limits of the investigated burner. In consequence, the experimental findings of this work demonstrate that the proposed concept prospects to facilitate the development and further investigation of robust combustion systems processing carbon-free fuels.

Presenting Author: Mattias E. G. Eck Technische Universität Berlin

Presenting Author Biography: Mattias is a Ph.D. candidate and junior researcher at the Chair of Fluid Dynamics since March 2022. As part of the HYPOTHESis project, his work focuses on the experimental assessment of flame dynamics, stability, and emissions in gas turbine combustors, with special emphasis on hydrogen combustion and thermoacoustics.

Authors:

Mattias E. G. Eck Technische Universität Berlin
Philipp Zur Nedden Technische Universität Berlin
Jakob G. R. Von Saldern Technische Universität Berlin
Alessandro Orchini Technische Universität Berlin
C. Oliver Paschereit Technische Universität Berlin