Dynamic Adaptation of Aerodynamic Flame Stabilization of a Premix Swirl Burner to Fuel Reactivity Using Fuel Momentum

Abstract

Due to the expected increase in available fuel gas variants in the future and the interest in independence from a specific fuel, fuel flexible combustion systems are required for future gas turbine applications. Changing the fuel used for lean premixed combustion can lead to serious reliability problems in gas turbine engines caused by the different physical and chemical properties of these gases. A new innovative approach to reach efficient, safe, and low-emission operation for fuels such as natural gas, syntheses gas, and hydrogen with the same burner is presented in this paper. The basic idea is to use the additionally available fuel momentum of highly reactive gases stemming from their lower Wobbe index (lower volumetric heating value and density) compared with lowly reactive fuels. Using fuel momentum opens the opportunity to influence the vortex dynamics of swirl burners designed for lowly reactive gases in a favorable way for proper flame stabilization of highly reactive fuels without changing the hardware geometry. The investigations presented in this paper cover the development of the optimum basic aerodynamics of the burner and the determination of the potential of the fuel momentum in water channel experiments using particle image velocimetry. The results show that proper usage of the fuel momentum has enough potential to adjust the flow field to different fuels and their corresponding flame behavior. As the main challenge is to reach flashback safe fuel flexible burner operation, the main focus of the study lies on avoiding combustion induced vortex breakdown. The mixing quality of the resulting injection strategy is determined by applying laser induced fluorescence in water channel tests. Additional OH∗ chemiluminescence and flashback measurements in an atmospheric combustion test rig confirm the water channel results for CH4, CH4/H2 mixtures, H2 with N2 dilution, and pure H2 combustion. They also indicate a large operating window between flashback and lean blow out and show expected NOx emission levels. In summary, it is shown for a conical four slot swirl generator geometry that the proposed concept of using the fuel momentum for tuning of the vortex dynamics allows aerodynamic flame stabilization for different fuels in the same burner.