In the context of combustion noise and combustion instabilities, the transport of entropy perturbations through highly simplified turbulent flows has received much recent attention. This work performs the first systematic study into the transport of entropy perturbations through a realistic gas turbine combustor flow-field, exhibiting large-scale hydrodynamic flow features in the form of swirl, separation, recirculation zones and vortex cores, these being ubiquitous in real combustor flows. The reacting flow-field is simulated using low Mach number large eddy simulations, with simulations validated by comparison to available experimental data. A generic artificial entropy source, impulsive in time and spatially localized at the flame-front location, is injected. The conservation equation describing entropy transport is simulated, superimposed on the underlying flow-field simulation. It is found that the transport of entropy perturbations is dominated by advection, with both thermal diffusion and viscous production being negligible. It is furthermore found that both the mean flow-field and the large-scale unsteady flow features contribute significantly to advective dispersion — neither can be neglected. The time-variation of entropy perturbation amplitude at combustor exit is well-modelled by a Gaussian profile, whose dispersion exceeds that corresponding to a fully-developed pipe mean flow profile roughly by a factor of three. Finally, despite the attenuation in entropy perturbation amplitude caused by advective dispersion, sufficient entropy perturbation strength is likely to remain at combustor exit for entropy noise to make a meaningful contribution at low frequencies.

中文翻译：

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通过工业燃气轮机燃烧器传输的熵扰动的色散

在燃烧噪声和燃烧不稳定性的背景下，通过高度简化的湍流传输熵扰动最近受到了很多关注。这项工作首次系统地研究了熵扰动通过真实燃气轮机燃烧器流场的传输，以涡流、分离、再循环区和涡核的形式表现出大规模的流体动力流动特征，这些特征在真实的燃烧器中无处不在。流动。反应流场使用低马赫数大涡模拟进行模拟，模拟通过与可用实验数据的比较进行验证。注入了一个通用的人工熵源，它在时间上是脉冲的，并且在空间上位于火焰前沿位置。模拟描述熵输运的守恒方程，叠加在基础流场模拟上。发现熵扰动的传输以平流为主，热扩散和粘性产生都可以忽略不计。进一步发现平均流场和大尺度非定常流动特征对平流扩散都有显着贡献——两者都不能被忽略。燃烧室出口的熵扰动幅度的时间变化由高斯剖面很好地建模，其分散超过对应于完全发展的管道平均流量剖面的大约三倍。最后，尽管由平流色散引起的熵扰动幅度衰减，但足够的熵扰动强度可能会保留在燃烧室出口处，以便熵噪声在低频下做出有意义的贡献。