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-emissions operation for fuels like 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 to 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 the 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 (PIV). The results show that a proper usage of the fuel momentum has enough potential to adjust the flow field to the 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 (CIVB). The mixing quality of the resulting injection strategy is determined applying laser induced fluorescence (LIF) 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.

Impact of the heat release distribution on high-frequency transverse thermoacoustic driving in premixed swirl flames

“…The air excess ratio can be adjusted to any value between ¼ 2 and 1. More information on the test rig can be found in Schwing 3 and Mayer 9 ; design and concept of the flow field are discussed in Sangl et al 10,11 In this test rig, self-excited thermoacoustic instability occurs. During testing a set of parameters (b, a D , T pre , _ m L , Fuel) is kept constant, while the air excess ratio is varied.…”

“…More information on the test rig can be found in Schwing 3 and Mayer 9 ; design and concept of the flow field are discussed in Sangl et al. 10,11…”

Impact of Cooling Air Injection on the Combustion Stability of a Premixed Swirl Burner Near Lean Blowout

“…[8], whose high reliability in terms of flashback and combustion stability was demonstrated by Mayer et al [9]. The applied burner design is based on a generic swirl burner for basic combustion research, described in Ref.…”

“…[10] and [8]. To provide similarity of the isothermal experiments with combustion tests, the mass flow is scaled with injection-to-main flow momentum flux ratio according to Refs.…”

“…To provide similarity of the isothermal experiments with combustion tests, the mass flow is scaled with injection-to-main flow momentum flux ratio according to Refs. [8]). The injected cooling air, which is injected without swirl, has no impact on the main flow field but is driven by the swirling burner flow (see Ref.…”