This paper examines the effects of steady state and transient hydrogen-enrichment on thermoacoustic instability in a model gas turbine combustor. Combustion instability, a feedback loop between flame heat release rate oscillations and combustor acoustics, is characterized in a swirl-stabilized flame operated at a range of hydrogen-natural gas fuel blends and a range of equivalence ratios. Measurements of combustor chamber pressure fluctuations and chemiluminescence imaging are used to characterize the instability at a range of operating conditions. Steady-state tests show that both mixture equivalence ratio and hydrogen content effect system stability. At a given equivalence ratio, higher levels of hydrogen result in unstable combustion. As equivalence ratio increases, instability occurs at lower concentrations of hydrogen in the fuel. Transient operation was tested in two directions – instability onset and instability decay – and two hydrogen-addition timescales – a short timescale of 1 milliseconds and a long timescale of 4 seconds. Results show that instability onset processes, through the transient addition of hydrogen, are highly repeatable regardless of timescale. However, certain instability decay processes are less repeatable, resulting in certain cases that do not fully transition from unstable to stable combustion despite the same change in hydrogen fuel rate. Flame behavior during the transient is characterized using high-speed chemiluminescence imaging, showing changes in flame stabilization and dynamics during the onset and decay processes. The results of this study could have implications for systems that experience variations in fuel composition, particularly in light of growing interest in hydrogen as a renewable fuel.


Effect of Hydrogen on Steady-State and Transient Combustion Instability Characteristics

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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