Measurement and analysis of phased array data on haystacked tones from a source located in a free jet
Measurement and analysis of phased array data on haystacked tones from a source located in a free jet
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对来自自由喷射源的干草堆音的相控阵数据进行测量和分析
DOI：
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发表时间：
2017
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通讯作者：
P. Sijtsma
中科院分区：
文献类型：
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作者：
B. Tester;P. Sijtsma
如果音调频率和通过剪切层的路径长度足够大，则射流剪切层湍流会导致音调噪声的显著频谱展宽。光谱展宽或“音调干堆”的一个典型例子是涡轮航空发动机的音调，在发动机内部测量时很少或没有干堆，但有时远场的干堆非常强烈，以至于在测量的频谱中无法观察到原始音调。这种涡轮音调的干堆需要一种工程方法，可以预测远场干堆和相关的入射音调电平的降低。先前发表的一种方法，即所谓的“beta”相关性，与许多实验数据集显示出令人鼓舞的一致性，但与其他数据集存在重大分歧。本文对另一组实验数据进行了分析，其中包括相控阵数据。目的是借助波束形成提高我们对音调干堆机制的理解，并与弱散射理论的预测进行比较，以频率和角度散射之间的简单多普勒频移关系的形式，假设一个冻结湍流模型。本文描述的QinetiQ和CLEAN-SC波束形成器获得的实验数据开始为该预测提供验证，这可能导致解决先前观察到的β相关性与GARTEUR项目获得的数据之间的差异。
Significant spectral broadening of tone noise by jet shear-layer turbulence can occur if the tone frequency and the path length through the shear layer are sufficiently large. A typical example of spectral broadening or ‘tone haystacking’ are turbine aero-engine tones which exhibit little or no haystacking when measured inside the engine but are sometimes so strongly haystacked in the far-field that the original tone cannot be observed in the measured spectrum. This haystacking of turbine tones requires an engineering method that can predict both the far-field haystacking and the associated reduction in incident tone level. A previous published method, the so-called ‘beta’ correlation has displayed encouraging agreement with a number of experimental datasets but significant disagreement with others. In this paper another set of experimental data, which includes phased array data, is analysed. The objective is to improve our understanding of the tone haystacking mechanisms with the aid of beamforming and to compare with a prediction from weak scattering theory, in the form of a simple Doppler shift relationship between frequency and angle scattering, assuming a frozen turbulence model. The experimental data acquired by QinetiQ and CLEAN-SC beamformer results described herein begin to provide validation of that prediction, which may lead to resolution of the discrepancies previously observed between the beta correlation and the data acquired under a GARTEUR project.