摘要
针对模型燃烧室中值班火焰的燃烧不稳定性问题,实验测量燃烧室内多点动态压力和火焰图像,利用快速傅里叶分析、本征正交分解(POD)等方法进行分析。结果表明:随着当量比增大,值班火焰的稳定性发生2次分岔现象,相应的不稳定模态分别对应系统的3阶、2阶本征纵向声学模态,均发生极限环振荡。POD结果表明:涡声频率锁定,发生在燃烧室纵向声学模态频率处,燃烧室内发生声-涡-火焰耦合的不稳定过程。而伴随着当量比提高,一方面,大尺度旋涡脱落改变火焰面积引发强烈放热振荡,声能产生增大;另一方面,两分支火焰张角不断增大,火焰位置主要波动方向与主要声学波动沿同一轴线。两方面作用下热声耦合更加容易,热释放脉动与压力脉动耦合的相位角减小,进而发生模态转换。
To address he combustion instability of pilot flame in the model combustor,the multi-point dynamic pressure and flame images are experimentally measured in the combustor,and analyzed by means of fast Fourier analysis and proper orthogonal decomposition(POD).It is observed that with the increase of the equivalence ratio,two bifurcations occur with limit cycle oscillations,and the corresponding unstable modes correspond to the third-order and second-order intrinsic longitudinal acoustic modes of the system.The POD results show that the vortex-acoustic frequency lock-in occurs at the longitudinal acoustic mode frequency of the combustor,and the acoustic-vortex-flame coupling instability process occurs in the combustor.On the one hand,large-scale vortex shedding increases sound energy output by altering the flame area and producing severe oscillations in heat release with an increase in equivalency ratio.Conversely,as the angle between two flame branches increases,the main wave direction of the flame position is along the same axis as the main acoustic wave.The modal transition takes place when two factors come into play:the thermoacoustic coupling becomes easier,and the phase angle of the pressure pulsation and heat release pulsation coupling lowers.
作者
李明婧
郭志辉
LI Mingjing;GUO Zhihui(National Key Laboratory of Science and Technology on Aero-Engine Aero-thermodynamics,School of Energy and Power Engineering,Beihang University,Beijing 100191,China)
出处
《北京航空航天大学学报》
EI
CAS
CSCD
北大核心
2024年第3期951-961,共11页
Journal of Beijing University of Aeronautics and Astronautics
基金
国家科技重大专项(2017-Ⅲ-0008-0034)。
关键词
燃烧不稳定性
值班火焰
热声耦合
涡声锁定
火焰动力学
combustion instability
pilot flame
thermoacoustic coupling
vortex-acoustic lock-in
flame dynamics
