Dynamics and mechanisms of pressure, heat release rate, and fuel spray coupling during intermittent thermoacoustic oscillations in a model aeronautical combustor at elevated pressure
Dynamics and mechanisms of pressure, heat release rate, and fuel spray coupling during intermittent thermoacoustic oscillations in a model aeronautical combustor at elevated pressure
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DOI：
10.1016/j.combustflame.2017.07.017
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发表时间：
2017-11
影响因子：
4.4
通讯作者：
S. Kheirkhah;J. D. Cirtwill;P. Saini;Krishna Venkatesan;Adam M. Steinberg
中科院分区：
文献类型：
--
作者：
S. Kheirkhah;J. D. Cirtwill;P. Saini;Krishna Venkatesan;Adam M. Steinberg
在10 bar左右的压力下，对一台燃用Jet A燃料的液体燃料航空燃气涡轮机模型燃烧室中发生的热声振荡动力学进行了实验研究。数据采集使用5 kHz重复率立体粒子图像测速仪（S-PIV）的气相和燃料液滴速度，10 kHz重复率OH* 化学发光（CL），和各种压力传感器。在这些条件下的PIV应用解决的挑战的方法。压力和CL数据的分析表明，两个共存的热声模式在Strouhal数的St = 0.3和0.8，这两个都表现出间歇性的变化的振荡幅度。瞬态压力-热释放率耦合的空间分布，即，瑞利指数，表现出在间歇性振荡的重复动力学。具体地，不同的燃烧器区域在不同的时间从振荡中增加和/或去除能量。对于测试的实验条件，气相速度没有任何可检测到的相干振荡。然而，燃烧室排放平面附近的燃料液滴速度显示出与压力和CL类似的间歇性频谱特征的振荡，表明通过燃料中的振荡的耦合。为了进一步研究燃料耦合，评估了来自燃料液滴的激光散射信号。相干振荡的燃料液滴散射持续在整个长度的燃料喷雾，这是一致的振荡的燃料供应被对流的非振荡的空气供应的条件下，在这里研究。总的燃料液滴散射振荡的振幅与压力振荡的振幅线性相关。随着压力振幅的增加，液滴和压力振荡周期变得更加一致地异相，这被假设为导致所观察到的间歇性行为。
Dynamics of thermoacoustics oscillations occurring in a liquid fueled aeronautical gas turbine model combustor burning Jet A fuel were investigated experimentally at a pressure of approximately 10 bar. Data was acquired using 5 kHz repetition-rate stereoscopic particle image velocimetry (S-PIV) for both gas phase and fuel droplet velocities, 10 kHz repetition-rate OH* chemiluminescence (CL), and a variety of pressure transducers. Methods for addressing challenges in the application of PIV at these conditions are presented. Analysis of the pressure and CL data showed two coexisting thermoacoustic modes at Strouhal numbers ofSt≈ 0.3 and 0.8, both of which exhibited intermittent changes in the oscillation amplitudes. The spatial distribution of the transient pressure-heat release rate coupling, i.e., Rayleigh index, demonstrated repeated dynamics during intermittent oscillations. Specifically, different combustor regions added and/or removed energy from the oscillations at different times. For the tested experimental conditions, the gas phase velocity did not feature any detectable coherent oscillations. However, the fuel droplet velocities in the immediate vicinity of the combustor dump plane exhibited oscillations with a similar intermittent spectral signature as the pressure and CL, indicating coupling through oscillations in the fuel. To further investigate the fuel coupling, the laser scattering signal from the fuel droplets was evaluated. Coherent oscillations in the fuel droplet scattering persisted over the entire length of the fuel spray, which is consistent with an oscillating fuel supply being convected by a non-oscillating air supply for the conditions studied here. The amplitude of the total fuel droplet scattering oscillations was linearly correlated with that of the pressure oscillations. As the pressure amplitude increased, the droplet and pressure oscillation cycles became more coherently out-of-phase, which is hypothesized to lead to the observed intermittent behavior.