D. Lohmann

A comprehensive theoretical and experimental investigation of radiator fan aerodynamics and acoustics is reported here for both, first the case of fans with their housing and second the case of isolated fans with axisymmetric onset flow 1). Parameters include airfoil geometry and advance ratio. Furthermore, in one test case the fan is run as a rotor without a duct. Ground and shielding effects caused by the housing are discussed. Some experiments are conducted with now visualization to indicate separated now. Two methods are presented. Code 1 is a lifting surface method that is based on the Ffowcs Williams/Hawkings equation calculating both aerodynamics and acoustics. Code 2 is a semiempirical method for random acoustics predicting far-field broadband noise of fans using turbulence models. Computed results of Code 1 show excellent agreement with the experimental data for the acoustic near-field. Because Code 1 calculates the periodic part of the noise, only good agreement in the far-field is obtained, if the measured acoustic far-field signature is averaged to present the statistic mean. For the prediction of broadband noise originated in random noise sources, Code 2 was used. The calculated results of the far-field acoustics compare well with the experiment. Possibilities to adapt the prediction technique of Code 2 for random noise within Code 1 are discussed. In a first step laminar airfoils for fan noise reduction have been designed, using an inverse method that consists of a 2-D Euler-Code coupled with a Boundary Layer Code [50]. The experiment shows a noise reduction of 2.2 dB(A) without any significant change in efficiency.

DGLR/AIAA 14th Aeroacoustics Conference, 1992

Conference Paper

englisch

21,0 x 29,7 cm, 11 Seiten

DGLR-Bericht, 1992, 1992-03, DGLR/AIAA 14th Aeroacoustics Conference - Proceedings; S.576-586; 1992; Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn

NA

aeroacoustics

Bibliothek

1992