1986 Volume 29 Issue 255 Pages 2909-2916
Clarification of fan noise source variation due to a flight effect is important for a turbofan noise reduction and a noise estimation. A fan noise spectral extent and a range of fan operation influenced by the flight effect were studied experimentally using a large turbofan engine and a geodesic 4m diameter semi-sphere inflow control device that can simulate the flight effect on fan noise in static engine tests. The fan noise reduction by the flight effect in a fan approach condition was higher than that in a fan take-off condition, because the fan rotor generates BPF tones by itself near the take-off condition. The highest reduced component in fan noise spectra was a fundamental fan blade passing frequency (BPF) tone, whose reduced level was 20 dB at maximum. Higher harmonic BPF tones and a buzz saw noise were also reduced by the flight effect, but a reduction of broadband noise was not evaluated in the whole range of fan operation.
JSME International Journal Series C Mechanical Systems, Machine Elements and Manufacturing
JSME International Journal Series B Fluids and Thermal Engineering
JSME International Journal Series A Solid Mechanics and Material Engineering
JSME international journal. Ser. C, Dynamics, control, robotics, design and manufacturing
JSME international journal. Ser. 3, Vibration, control engineering, engineering for industry
JSME international journal. Ser. A, Mechanics and material engineering
JSME international journal. Ser. 1, Solid mechanics, strength of materials