Effect of fuel line acoustics on the flame dynamics of H2/CH4 syngas in a partially premixed gas turbine combustor

• Published in: Fuel (Guildford) Vol. 285; p. 119231
• Main Authors: Joo, Seongpil, Kwak, Sanghyeok, Lee, Min Chul
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.02.2021
• Subjects: Combustion dynamics; Dynamic response; Fuel modulation; Hydrogen flame; Synthetic natural gas; Dynamic response; Fuel modulation; Hydrogen flame; Synthetic natural gas; Combustion dynamics
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2020.119231

•Low-pass behaviors are observed in gain of FTF for various H2/CH4 compositions.•The flame length and flow momentum influence the dynamic response of the flame.•Resonance in FTF and CTF is observed when fuel is modulated at natural frequency.•High H2 in fuel reduces dependency of CTF and FTF to modulation frequency.•Strouhal number is confirmed to be a key indicator to determine the phase of FTF. This paper investigates the dynamic response of flames, considering H2-enriched CH4 fuels that are submitted to upstream mechanical perturbations in a model gas turbine combustor, resulting in fuel velocity oscillations. Flame transfer function (FTF) and cold-flow transfer function (CTF), which represent, respectively, the dynamic responses in the flow of the flame and fuel induced by a velocity modulation in the fuel feed line (FFL), are derived. The gain of FTF shows a low-pass behavior and gradually increases until a specific modulation frequency is reached, which is identical to the frequencies of the corresponding peak gains of the CTF. The periodic variation of OH* intensity is observed from the images collected with a high-speed OH-PLIF. The high oscillation near the injector indicates that the fuel velocity perturbation leads to the amplification of the heat release fluctuation at specific modulation frequencies. The singularity frequencies corresponding to the peaks of the gain of both transfer functions coincide with the resonance frequencies in the FFL. The phase of FTF and CTF decreases as the H2 ratio increases and the phase of FTF is well fitted into a single line by nondimensionalization through Strouhal number. Most of these findings on the characteristics of combustion instability and acoustical characteristics of FFL can be used as a crucial methodology of H2 combustor design, such as an anti-resonance fuel/air feed line, which can ensure the stable operation of combustion system by avoiding H2 induced combustion instability failure.