Modeling of the transition mechanism from combustion noise to tangential-mode combustion instability via velocity perturbations

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K15217
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 24010:Aerospace engineering-related
• Research Institution: Japan Aerospace EXploration Agency
• Principal Investigator: Shoji Takeshi 国立研究開発法人宇宙航空研究開発機構, 航空技術部門, 研究開発員 (20833172)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 環状燃焼器 / 弱旋回流 / 水素火炎 / 燃焼振動 / 希薄予混合 / モード解析 / 光学計測 / 遷移現象

Outline of Final Research Achievements

The present study explores flame-flow interaction during combustion instability based on a series of atmospheric, lab-scale lean-premixed hydrogen combustion experiments using single and annular low swirl combustors. For the single combustor, a relatively flat flame involving large-scale vortical structures is first observed in the present study. This flame structure is caused by the interaction between large-scale vortices and flame with strong pressure and velocity fluctuations, which is a unique phenomenon of a hydrogen premixed flame.
For the annular combustor, single-tone, azimuthal pressure oscillations are observed at a frequency of approximately 1300 Hz. Also, axial velocity acceleration in between two adjacent flames is confirmed caused by the flame-flame interaction. The phenomenon is possibly associated with the onset of azimuthal-mode combustion instability in an annular combustor.

Free Research Field

燃焼工学

Academic Significance and Societal Importance of the Research Achievements

ガスタービン・航空機エンジン等の燃焼器で発生する燃焼振動は、強い発熱率・圧力・流速変動を伴うため、燃焼器の構造破壊に直結する。実機燃焼器においては、軸方向モードの振動に加えて、より抑制されにくい周方向モードの振動が発生する可能性があり、燃焼器運用の安全性に多大な影響を与える。また近年、水素航空機開発の機運が急速に高まっており、航空エンジン用低NOx燃焼器の水素燃料対応に向けた技術開発が世界的に加速している。そのため、本研究成果である水素燃焼器特有の燃焼振動中における火炎や流れ場の干渉理解は、学術的意義及び燃焼振動が発生しにくい燃焼器の最適設計に繋がる技術的試験の獲得に寄与する。