Liu Weijie, Xue Ranran, Jiang Jingjing, Su He, Wang Xionghui
State Key Lab of Clean Energy Utilization, State Environmental Protection Engineering Center for Coal-Fired Air Pollution Control, Zhejiang University, Hangzhou 310027, P. R. China.
Zhejiang Laboratory of Energy and Carbon Neutralization, Hangzhou 310027, P. R. China.
ACS Omega. 2024 May 11;9(20):21983-21993. doi: 10.1021/acsomega.3c10234. eCollection 2024 May 21.
Self-excited combustion instability in an annular combustor with low-swirl flames is studied with a combination of large eddy simulation (LES) and acoustic solvers. Acoustic analysis with a Helmholtz solver provides an estimate of frequencies and modal structures in the annular combustor. LES gives detailed modal dynamics for specific instability modes. Combustion instabilities in the annular combustor including longitudinal, spinning, and standing modes are successfully captured in a single LES. Numerical results show that the instability modes are not constant; they switch among these modes randomly and rapidly. The flow oscillates back and forth in phase with the largest pressure amplitude located near the outlet of the injectors for the longitudinal mode. The azimuthal instability oscillates in the 1A2L mode of the annular system. In the spinning mode, the pressure antinodes move forward while the modal structure keeps constant. For the standing mode, the locations of pressure antinodes are fixed in the annular combustor and the fluctuations at the pressure antinodes keep out of phase. The near-zero value of the mean spin ratio indicates that the dominant azimuthal mode is the standing mode. The azimuthal modes captured by LES are in good agreement with that predicted by Helmholtz solver in terms of frequency and modal structure. The maximum deviation of the predicted frequency is less than 5%. This adds values before the low-swirl injector is placed into the actual annular combustor.
采用大涡模拟（LES）与声学求解器相结合的方法，研究了具有低旋流火焰的环形燃烧室中的自激燃烧不稳定性。使用亥姆霍兹求解器进行声学分析，可估算环形燃烧室中的频率和模态结构。LES可给出特定不稳定模态的详细模态动力学。在单个LES中成功捕捉到了环形燃烧室中的燃烧不稳定性，包括纵向、旋转和驻波模式。数值结果表明，不稳定模式并非恒定不变；它们会在这些模式之间随机且快速地切换。对于纵向模式，流动在喷油器出口附近压力振幅最大处同相地来回振荡。方位不稳定性在环形系统的1A2L模式下振荡。在旋转模式中，压力波腹向前移动，而模态结构保持不变。对于驻波模式，压力波腹的位置在环形燃烧室中固定，且压力波腹处的波动保持异相。平均自旋比的近零值表明主导方位模式为驻波模式。LES捕捉到的方位模式在频率和模态结构方面与亥姆霍兹求解器预测的结果高度吻合。预测频率的最大偏差小于5%。这在将低旋流喷油器放入实际环形燃烧室之前就增加了价值。
