W. Dobrzynski, B. Gehlhar, J. Böttcher

Worldwide efforts are undertaken to develop counter rotating propf an aeroengines due to their fuel frugality and thus their environmental sociability compared to conventional fan-engines. Among the different design concepts the German manufacturer MTU has developed the CRISP (Counter Rotating Integrated Shrouded Propfan) model-scale engine which- has been- recently tested in the German Dutch Wind Tunnel. Acoustic experiments - conducted by DLR in cooperation with MTU - provided information on the radiated sound field characteristics. The test matrix entailed variations of relevant operational parameters, such as rotational speed, fan-blade stagger angle, wind tunnel speed and inflow angle. As a consequence of the particular model-engine design (two counter-rotating 10-bladed fan stages and 7 downstream shroud-supporting struts) the azimuthal noise level patterns were observed to be either dominated by rotor 1/rotor 2 - or rotor 2/strut - interaction noise. Rotor/rotor-interaction noise is radiated into the rear arc with maximum levels at the 3rd rotational harmonic ([estimates] 3 times blade passing frequency). This harmonic level largely determines the maximum overall A-weighted noise level at high rotational speeds. At low rotational speeds, broadband noise contributes significantly to the total noise signature with a pronounced level maximum in the rear arc. The test results indicate further promising measures for additional noise reduction.

DGLR/AIAA 14th Aeroacoustics Conference, 1992

Conference Paper

englisch

21,0 x 29,7 cm, 10 Seiten

DGLR-Bericht, 1992, 1992-03, DGLR/AIAA 14th Aeroacoustics Conference - Proceedings; S.816-825; 1992; Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn

NA

aeroacoustics

Bibliothek

1992