Pulsation-Amplitude-Dependent Flame Dynamics of High-Frequency Thermoacoustic Oscillations in Lean-Premixed Gas Turbine Combustors
Pulsation-Amplitude-Dependent Flame Dynamics of High-Frequency Thermoacoustic Oscillations in Lean-Premixed Gas Turbine Combustors
复制标题
稀薄预混燃气轮机燃烧室高频热声振荡的脉动幅度相关火焰动力学
DOI：
10.1115/1.4038036
复制
发表时间：
2017
影响因子：
1.5
通讯作者：
T. Sattelmayer
中科院分区：
文献类型：
--
作者：
F. Berger;T. Hummel;B. Schuermans;T. Sattelmayer
本文介绍了一种普通燃气涡轮机燃烧室中与尖叫级频率下的横向热声振荡相关的脉动振幅火焰动力学的实验研究。具体而言，在不同水平的脉动幅度的火焰行为进行评估和解释。火焰的空间动力学是通过对燃烧室面板处的动态压力同步地成像OH荧光化学发光（CL）信号来测量的。首先，线性热声稳定状态，模态动力学，火焰声学相位关系进行了评估。结果发现，不稳定的声学模式收敛到一个占主导地位的旋转字符的平均流漩涡的方向。此外，火焰调制被观察到在所有水平的振荡幅度与声压同相。其次，分布式火焰动力学的研究通过可视化的平均和振荡的放热分布在不同的脉动幅度。所观察到的火焰动力学，然后对各自的振幅相关的热声增长率，这是使用分析模型计算的非紧凑的火焰描述函数的方式进行数值评价进行比较。虽然结果显示了一个非线性的贡献，为个人的增长率，叠加的火焰变形和位移平衡了一个恒定的火焰驱动。后一种观察结果与热声气体涡轮机系统中极限环振荡的根本原因的最新认识相矛盾，对于热声气体涡轮机系统，热释放随着振幅的增加而饱和。因此，振幅相关的火焰调制的系统的观察和分析表明，替代路径的机制，可能会导致热声饱和在高频系统的解释。
This paper presents the experimental investigation of pulsation-amplitude-dependent flame dynamics associated with transverse thermoacoustic oscillations at screech level frequencies in a generic gas turbine combustor. Specifically, the flame behavior at different levels of pulsation amplitudes is assessed and interpreted. Spatial dynamics of the flame are measured by imaging the OH⋆chemiluminescence (CL) signal synchronously to the dynamic pressure at the combustor's face plate. First, linear thermoacoustic stability states, modal dynamics, and flame-acoustic phase relations are evaluated. It is found that the unstable acoustic modes converge into a predominantly rotating character in the direction of the mean flow swirl. Furthermore, the flame modulation is observed to be in phase with the acoustic pressure at all levels of the oscillation amplitude. Second, distributed flame dynamics are investigated by means of visualizing the mean and oscillating heat release distribution at different pulsation amplitudes. The observed flame dynamics are then compared against numerical evaluations of the respective amplitude-dependent thermoacoustic growth rates, which are computed using analytical models in the fashion of a noncompact flame-describing function. While results show a nonlinear contribution for the individual growth rates, the superposition of flame deformation and displacement balances out to a constant flame driving. This latter observation contradicts the state-of-the-art perception of root-causes for limit-cycle oscillations in thermoacoustic gas turbine systems, for which the heat release saturates with increasing amplitudes. Consequently, the systematic observations and analysis of amplitude-dependent flame modulation shows alternative paths to the explanation of mechanisms that might cause thermoacoustic saturation in high frequency systems.