T. Carolus

The acoustic and aerodynamic performance of low pressure axial fan rotors with a hub/tip ratio of 0.45 is examined. Six rotors are designed for the same working point by means of the wellknown airfoil theory. Two rotors have a free vortex swirl (i.e. constant load) distribution. Keeping the mean solidity constant the blade chord length and thus the number of blades is varied. The blades of the two further rotors are designed with a reduced root and root as well as tip load, resp. The condition of an equilibrium between the static pressure gradient and the centrifugal forces is maintained. Finally two rotors have blades with increased load on the outer blade section, neglecting, however, the radial equilibrium condition. All rotors have unequally spaced blades to diminish tonal noise. The rotors are tested in a short cylindrical housing without guide vanes. All rotors show very similar volume flux - pressure difference charateristics. The peak efficiency and the noise performance, however, is considerably influenced by the chosen blade design. The aerodynamically and acoustically optimal rotor is the one with the reduced load at the hub and increased load in the tip region under satisfied equilibrium condition. It runs at the highest aerodynamic efficiency. Its noise spectrum is fairly smooth. The overall sound pressure level of this rotor is up to 8 dB (A) lower compared to the other examined rotors.

DGLR/AIAA 14th Aeroacoustics Conference, 1992

Conference Paper

englisch

21,0 x 29,7 cm, 6 Seiten

DGLR-Bericht, 1992, 1992-03, DGLR/AIAA 14th Aeroacoustics Conference - Proceedings; S.809-814; 1992; Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn

NA

aeroacoustics

Bibliothek

1992