10th European Conference on Turbomachinery Fluid dynamics & Thermodynamics

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M . Kohlhaas, K. Bamberger, T. Carolus - University of Siegen, Germany


A major source of fan noise results from the interaction between the turbulent rotor blade wakes and the stator vanes. To control the aerodynamic structure of the wake and thus the rotor-stator interaction (RSI) noise sources, a secondary mass flow is ejected through the trailing edge of the rotor blades (trailing edge blowing, TEB). The objective of this study is to investigate the effect of this technique on the mean wake velocity and the acoustic farfield. Special attention is given to the quality of wake filling by numerical optimization of TEB mass flow rates through seven equally spaced slits in the trailing edge. The TEB fan was built and the optimized configuration was experimentally investigated. The estimated TEB rates were scaled down linearly since the wake deficit without TEB was smaller than expected and less TEB momentum was needed. The acoustic measurements showed only a small influence of TEB to the overall sound pressure level and the tonal noise on the first harmonic. However, the second harmonic decreased by TEB since most of the RSI noise affects this tone.

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