Abstract The combustion noise in modern engines is mainly originating from two types of mechanisms. First, chemical reactions in the combustion chamber leads to an unsteady heat release which is responsible of the direct combustion noise. Second, hot and cold blobs of air coming from the combustion chamber are advected and accelerated through turbine stages, giving rise to entropy noise (or indirect combustion noise). In the present work, numerical characterization of indirect combustion noise of a Nozzle Guide Vane passage was assessed using three-dimensional Large Eddy Simulations. The present work offers an overview to the analytical, computational and experimental studies of the topic. Numerical simulations are conducted to reproduce the effects of incoming planar entropy waves from the combustion chamber and to characterize the generated acoustic power. The dynamic features of the flow are addressed by the means of frequency domain and modal analyses techniques such as Fourier Decomposition and Proper Orthogonal Decomposition. Finally, the predicted entropy noise from numerical calculations is compared with the analytical results of an actuator disk model for a stator stage. The present paper proves that the generated indirect combustion noise can be significant for transonic operating conditions. The blade acoustic response is characterized by the excitation of a latent dynamics at the forcing frequency of the planar entropy waves, and it increases as the amplitude of the incoming disturbances increases.

中文翻译：

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跨音速工况下喷嘴导向叶片间接燃烧噪声产生机制的计算分析

摘要 现代发动机的燃烧噪声主要来源于两种机制。首先，燃烧室中的化学反应导致不稳定的热释放，这是直接燃烧噪音的原因。其次，来自燃烧室的热空气和冷空气团通过涡轮级对流并加速，从而产生熵噪声（或间接燃烧噪声）。在目前的工作中，使用三维大涡模拟评估了喷嘴导向叶片通道的间接燃烧噪声的数值特征。目前的工作概述了该主题的分析、计算和实验研究。进行数值模拟以再现来自燃烧室的入射平面熵波的影响并表征产生的声功率。流动的动态特征通过频域和模态分析技术（例如傅立叶分解和适当正交分解）来解决。最后，将数值计算的预测熵噪声与定子级致动器盘模型的分析结果进行比较。本论文证明，产生的间接燃烧噪声对于跨音速运行条件可能很重要。叶片声学响应的特征在于在平面熵波的强迫频率下激发潜在动力学，并且随着传入扰动幅度的增加而增加。流动的动态特征通过频域和模态分析技术（例如傅立叶分解和适当正交分解）来解决。最后，将数值计算的预测熵噪声与定子级致动器盘模型的分析结果进行比较。本论文证明，产生的间接燃烧噪声对于跨音速运行条件可能很重要。叶片声学响应的特征在于在平面熵波的强迫频率下激发潜在动力学，并且随着传入扰动幅度的增加而增加。流动的动态特征通过频域和模态分析技术（例如傅立叶分解和适当正交分解）来解决。最后，将数值计算的预测熵噪声与定子级致动器盘模型的分析结果进行比较。本论文证明，产生的间接燃烧噪声对于跨音速运行条件可能很重要。叶片声学响应的特征在于在平面熵波的强迫频率下激发潜在动力学，并且随着传入扰动幅度的增加而增加。将数值计算的预测熵噪声与定子级致动器盘模型的分析结果进行比较。本论文证明，产生的间接燃烧噪声对于跨音速运行条件可能很重要。叶片声学响应的特征在于在平面熵波的强迫频率下激发潜在动力学，并且随着传入扰动幅度的增加而增加。将数值计算的预测熵噪声与定子级致动器盘模型的分析结果进行比较。本论文证明，产生的间接燃烧噪声对于跨音速运行条件可能很重要。叶片声学响应的特征在于在平面熵波的强迫频率下激发潜在动力学，并且随着传入扰动幅度的增加而增加。