15th European Conference on Turbomachinery Fluid dynamics & Thermodynamics

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Felix Czwielong  - LSTM, FAU Erlangen-Nürnberg, Germany
Thomas Uffinger - LSTM, FAU Erlangen-Nürnberg, Germany
Stefan Becker - LSTM, FAU Erlangen-Nürnberg, Germany


Radial fans are a frequently used machine, which are installed in ventilation and air-conditioning systems. The radial turbomachine not only conveys air and generates a pressure rise, but also emits sound, which is often perceived as disturbing by people in the vicinity. The sound generation mechanisms within the radial fan are complex and often overlap each other. This leads to the fact that the individual mechanisms can be isolated only with difficulty from each other and effective measures against the noise generation cannot be taken. Many of the sound generation mechanisms are dependent on the inflow of the radial fan, which is usually highly inhomogeneous and hard to control, which further complicates the separation of the sound mechanisms. In order to better understand the acoustic and flow mechanics interactions in the radial fan, a special aeroacoustic radial fan test rig has been developed. With the help of the test rig, the inflow to the radial fan can be made quiet and the inflow to the fan can be changed. This allows to better understand the aeroacoustic sound sources of radial fans. Using a telemetry system it is also possible to determine the pressure fluctuations in the rotating system. With the aeroacoustic radial fan test rig it was possible to investigate different inflow conditions into the impeller. Different gradients were imposed on the flow field and the influence of inhomogeneities was considered. It was shown that, on the basis of transient pressure fluctuations in the rotating system on the blade surface, new insights into the sound radiation into the far field of the machine could be obtained. Thus, it was possible to generate a direct correlation between the flow phenomena on the fan blades and the sound pressure spectra in the far field.


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