模型燃烧室中值班火焰稳定器的燃烧不稳定性研究

Combustion Instability of Pilot Flame Holder in Model Combustor

关键词:  燃烧室  值班火焰  火焰稳定器  燃烧不稳定性  模态转换  漩涡脱落

Key words:  Combustor  Pilot flame  Flame holder  Combustion instability  Modal transition  Vortex shedding

摘要:

针对值班火焰的燃烧不稳定性，通过试验得到了不同当量比工况下的火焰结构、压力脉动信号和热释放脉动信号。对脉动信号进行傅立叶分析，获得了脉动信号的频率和振幅。结果表明，随着当量比增加，火焰形态发生变化，燃烧室内发生了164Hz三阶模态向109Hz二阶模态的转换。对火焰平均结构、火焰瞬态结构和火焰正交分解结果进行分析后发现，漩涡脱落频率和燃烧室某一阶声学模态耦合是维持燃烧不稳定性的机理，耦合的强弱和漩涡脱落的尺度大小决定了热声振荡的振幅大小，火焰形态的变化导致热释放中心位置的变化是引起模态转换的机理。

Abstract:

The experimental method was used to study combustion instability of the pilot flame. The flame structure， pressure pulsation signal and heat release pulsation signal under different equivalence ratios were obtained. Through Fourier analysis of the pulsation signals， the frequency and amplitude of pulsation signals were obtained. The results show that the flame morphology changed and a transition from three order mode（164Hz） to two order mode（109Hz） occurred as the equivalence ratio increased in the combustion chamber. After analysing the flame average structure， the periodic change of flame transient structure and the result of proper orthogonal decomposition（POD）， it was found that the coupling between the vortex shedding frequency and a certain order acoustic mode of the combustion chamber is the mechanism maintaining combustion instability. The strength of the coupling and the scale of the vortex shedding determine the amplitude of the thermoacoustic oscillation. Changing of the heat release center location caused by the changing of flame morphology is the mechanism causing modal transition.