A weak-scattering model for turbine-tone haystacking

作者：McAlpine A^*; Powles C J; Tester B J

来源：Journal of Sound and Vibration, 2013, 332(16): 3806-3831.

DOI：10.1016/j.jsv.2013.02.023

Noise and emissions are critical technical issues in the development of aircraft engines. This necessitates the development of accurate models to predict the noise radiated from aero-engines. Turbine tones radiated from the exhaust nozzle of a turbofan engine propagate through turbulent jet shear layers which causes scattering of sound. In the far-field, measurements of the tones may exhibit spectral broadening, where owing to scattering, the tones are no longer narrow band peaks in the spectrum. This effect is known colloquially as %26apos;haystacking%26apos;. In this article a comprehensive analytical model to predict spectral broadening for a tone radiated through a circular jet, for an observer in the far field, is presented. This model extends previous work by the authors which considered the prediction of spectral broadening at far-field observer locations outside the cone of silence. The modelling uses high-frequency asymptotic methods and a weak-scattering assumption. A realistic shear layer velocity profile and turbulence characteristics are included in the model. The mathematical formulation which details the spectral broadening, or haystacking, of a single-frequency, single azimuthal order turbine tone is outlined. In order to validate the model, predictions are compared with experimental results, albeit only at polar angle equal to 90 degrees. A range of source frequencies from 4 to 20 kHz, and jet velocities from 20 to 60 ms(-1), are examined for validation purposes. The model correctly predicts how the spectral broadening is affected when the source frequency and jet velocity are varied.

• 出版日期2013-8-5