Abstract
It is shown in a numerical simulation that the rotor-stator interaction tones radiated by an ultra-high-bypass ratio turbofan in the upstream direction can be modified substantially by disturbing the flow near the trailing edge of the rotor blades with the aid of jets emanating from nozzles in the fan casing. The interaction between the rotor blades and these jets causes an additional sound field. The number of nozzles is identical to the number of vanes in the stator in order to generate the same azimuthal modes as the stator. By varying the azimuthal location of the nozzles the phase relationship between the primary sound field of rotor-stator and the secondary field of rotor-jet interaction is changed. The optimum position yields a noise reduction of up 13 dB for the first radial mode but higher order modes are increased. This result is expected to improve after the axial location, diameter and flow rate of the jets are included in the optimization process. The unsteady turbomachinery flow solver TRACE was enhanced to cope with the extreme requirements of the unsteady flow field near the trailing edge of the rotor of an ultra-high-bypass-ratio turbofan. The quality of the numerical results is compared with experimental data from the baseline case with no flow control and shows excellent agreement.
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Steger, M., Michel, U., Ashcroft, G., Thiele, F. (2010). Turbofan Tone Noise Reduction by Flow-Induced Unsteady Blade Forces. In: King, R. (eds) Active Flow Control II. Notes on Numerical Fluid Mechanics and Multidisciplinary Design, vol 108. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-11735-0_11
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DOI: https://doi.org/10.1007/978-3-642-11735-0_11
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