Duct linings

Details Duct linings Duct linings

1977-04-04

1978-10-31

Garrett, Robert E.

Power plants

Reaction motor

Interrelated reaction motors

181222, F02K 306, F02K 126

Patent

active

041226720

ABSTRACT:
When fan-blade tips in a turbofan aero engine reach a velocity of greater than about mach 1.1, the regular shock-wave pattern near the blade tips degenerates into an irregular pattern as it moves upstream, thus causing "buzz-saw" noise. An anit-buzz acoustic liner of the spaced-cell type forms part of the fan duct wall near the blade tips and combats the degeneration by reinforcing the regular shock-wave pattern at the expense of the irregular one. This is achieved by making the depth of the cells equal to half the wavelength of the blade passing frequency at the supersonic condition of interest.

REFERENCES:
patent: 3439774 (1969-04-01), Callaway et al.
patent: 3508838 (1970-04-01), Martenson
patent: 3542152 (1968-04-01), Adamson et al.
patent: 3821999 (1974-07-01), Guess et al.
patent: 3948346 (1976-04-01), Schindler
Benzakein et al., "Multiple Pure Tone Noise. .", AIAA Aero-Acoustics Conf., Oct., 1973.

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