This paper analyzes thermoacoustic driving - and the underlying fuel and air dynamics -during self-excited intermittent oscillations (changing amplitude and frequency) of a dual-annular partially-premixed gas turbine model combustor burning Jet A fuel at elevated temperature and pressure. Measurements were conducted using simultaneous OH* chemiluminescence, pressure transducers, stereoscopic particle image velocimetry and droplet laser scattering. The intermittent amplitude behavior was associated with a slightly positive thermoacoustic driving (in-phase coupling of pressure and heat release oscillations) at low amplitudes that transitioned into a negative energy contribution at high pressure oscillation amplitudes. Analysis of the gas-phase velocity, fuel scattering intensity, and fuel velocity oscillations indicated that the thermoacoustic coupling was through fuel oscillations at the injector, with the resultant oscillating droplet velocities rapidly accommodating to a non-oscillatory air flow. The amplitude of the total fuel scattering oscillations was linearly correlated with the pressure oscillation amplitude. The phase shift between these oscillations spanned a wide range of values at low amplitudes, but approached a value slightly over π as the amplitude increased. This phase shift therefore is hypothesized to result in the decrease in thermoacoustic driving, ultimately resulting in the intermittent amplitude behavior. Changes in the oscillation frequency between Strouhal numbers of St 0.22 and St ≈ 0.29 were associated with a cycling of the pressure/fuel phase shift by 2π. However, both the phase shift at high oscillation amplitudes and the spatial pattern of the fuel oscillations were similar at each frequency, indicating similar coupling mechanisms.
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机译：本文分析了热声驾驶 - 以及潜在的燃料和空气动力学 - 对双环形部分预混燃气涡轮机模型燃烧器燃烧喷射燃料在升高的温度和压力下的自激的间歇振荡（改变幅度和频率）。使用同时OH *化学发光，压力传感器，立体粒子图像速度和液滴激光散射进行测量。间歇幅度行为与低幅度在高压振荡幅度的低幅度下略微正热声驱动（压力和散热振荡的相位耦合）相关联。分析气相速度，燃料散射强度和燃料速度振荡，表明热声耦合是通过喷射器处的燃料振荡，所得到的振荡液滴速度快速容纳到非振荡空气流动。总燃料散射振荡的幅度与压力振荡幅度线性相关。这些振荡之间的相位偏移在低幅度下跨越了宽范围的值，但随着幅度增加，将值略微超过π。因此，该相位移位被假设以导致热声驾驶的降低，最终导致间歇性幅度行为。 ST 0.22和ST≈0.29之间的横钟数之间的振荡频率的变化与通过2π的压力/燃料相移的循环相关联。然而，在每个频率下，高振荡幅度和燃料振荡的空间图案的相移均在每个频率上相似，指示类似的耦合机构。
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