Structure and thermoacoustic instability of turbulent swirling lean premixed methane/hydrogen/air flames in a model combustor
(2024) In International Journal of Hydrogen Energy 60. p.890-901- Abstract
The structure and thermoacoustic instability (TI) of premixed CH4/H2/air swirling flames were experimentally investigated for a range of hydrogen fraction (ηH2) up to 80% under different equivalence ratio (Φ) and swirl number (S) conditions. It is shown that the onset of TI is enhanced when increasing either ηH2, S, or Φ. The dominant frequency of TI increases dramatically with ηH2. The higher dominant frequency in the hydrogen-enriched flames can be attributed to a shorter flame length which results in a reduced flame convection time. It is observed that the unstable flames are always accompanied by the appearance of outer recirculation zone (ORZ) flame. Therefore, the flame kernel... (More)
The structure and thermoacoustic instability (TI) of premixed CH4/H2/air swirling flames were experimentally investigated for a range of hydrogen fraction (ηH2) up to 80% under different equivalence ratio (Φ) and swirl number (S) conditions. It is shown that the onset of TI is enhanced when increasing either ηH2, S, or Φ. The dominant frequency of TI increases dramatically with ηH2. The higher dominant frequency in the hydrogen-enriched flames can be attributed to a shorter flame length which results in a reduced flame convection time. It is observed that the unstable flames are always accompanied by the appearance of outer recirculation zone (ORZ) flame. Therefore, the flame kernel residing in the ORZ can be an indicator of the occurrence of TI. The flame front of thermoacoustic unstable flames was observed to be more wrinkled, e.g., with larger mean absolute curvature (κ abs) and local flame surface area ratio (δΣmax). Importantly, the phase-locked analysis shows that κ abs and δΣmax can be modified at different oscillation phases, and their maximum and minimum values are simultaneously achieved at phase angles θ of about 0° and 180°, respectively. Variations of κ abs and δΣmax are in phase with the heat release rate, indicating a strong correlation between the TI and flame structure modification; however, they show a phase lag of about 72° behind the pressure in this work. These results are vital when understanding and predicting the TI based on the flame structure, especially when adopting a visual detection method of the instability.
(Less)
- author
- Ji, Longjuan LU ; Wang, Jinhua ; Zhang, Weijie ; Wang, Yuncheng ; Huang, Zuohua and Bai, Xue Song LU
- organization
- publishing date
- 2024-03-22
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Flame structure, Hydrogen enrichment, Lean premixed combustion, Swirl number, Thermoacoustic instability
- in
- International Journal of Hydrogen Energy
- volume
- 60
- pages
- 12 pages
- publisher
- Elsevier
- external identifiers
-
- scopus:85185784576
- ISSN
- 0360-3199
- DOI
- 10.1016/j.ijhydene.2024.02.162
- language
- English
- LU publication?
- yes
- id
- ab8f2a52-7bfe-4734-b109-71aba7e28f77
- date added to LUP
- 2024-03-14 10:24:31
- date last changed
- 2024-03-14 10:24:56
@article{ab8f2a52-7bfe-4734-b109-71aba7e28f77,
abstract = {{<p>The structure and thermoacoustic instability (TI) of premixed CH<sub>4</sub>/H<sub>2</sub>/air swirling flames were experimentally investigated for a range of hydrogen fraction (η<sub>H2</sub>) up to 80% under different equivalence ratio (Φ) and swirl number (S) conditions. It is shown that the onset of TI is enhanced when increasing either η<sub>H2</sub>, S, or Φ. The dominant frequency of TI increases dramatically with η<sub>H2</sub>. The higher dominant frequency in the hydrogen-enriched flames can be attributed to a shorter flame length which results in a reduced flame convection time. It is observed that the unstable flames are always accompanied by the appearance of outer recirculation zone (ORZ) flame. Therefore, the flame kernel residing in the ORZ can be an indicator of the occurrence of TI. The flame front of thermoacoustic unstable flames was observed to be more wrinkled, e.g., with larger mean absolute curvature (κ <sub>abs</sub>) and local flame surface area ratio (δΣ<sub>max</sub>). Importantly, the phase-locked analysis shows that κ <sub>abs</sub> and δΣ<sub>max</sub> can be modified at different oscillation phases, and their maximum and minimum values are simultaneously achieved at phase angles θ of about 0° and 180°, respectively. Variations of κ <sub>abs</sub> and δΣ<sub>max</sub> are in phase with the heat release rate, indicating a strong correlation between the TI and flame structure modification; however, they show a phase lag of about 72° behind the pressure in this work. These results are vital when understanding and predicting the TI based on the flame structure, especially when adopting a visual detection method of the instability.</p>}},
author = {{Ji, Longjuan and Wang, Jinhua and Zhang, Weijie and Wang, Yuncheng and Huang, Zuohua and Bai, Xue Song}},
issn = {{0360-3199}},
keywords = {{Flame structure; Hydrogen enrichment; Lean premixed combustion; Swirl number; Thermoacoustic instability}},
language = {{eng}},
month = {{03}},
pages = {{890--901}},
publisher = {{Elsevier}},
series = {{International Journal of Hydrogen Energy}},
title = {{Structure and thermoacoustic instability of turbulent swirling lean premixed methane/hydrogen/air flames in a model combustor}},
url = {{http://dx.doi.org/10.1016/j.ijhydene.2024.02.162}},
doi = {{10.1016/j.ijhydene.2024.02.162}},
volume = {{60}},
year = {{2024}},
}