초록 ▼

A turbofan gas turbine engine includes a fan and an intake duct upstream of the fan. The fan has a fan rotor having a plurality of fan blades. The intake duct has a liner, which includes an acoustic liner positioned upstream of the fan and a buzz-saw tone noise liner positioned upstream of the acous

A turbofan gas turbine engine includes a fan and an intake duct upstream of the fan. The fan has a fan rotor having a plurality of fan blades. The intake duct has a liner, which includes an acoustic liner positioned upstream of the fan and a buzz-saw tone noise liner positioned upstream of the acoustic liner. The buzz-saw tone noise liner is positioned substantially at, or near, an upstream end of the intake duct. The intake duct has a lip and the buzz-saw tone noise liner is positioned at, or near, the lip.

대표청구항 ▼

1. A turbofan gas turbine engine comprising: a fan,an intake duct with a liner upstream of the fan,a fan rotor having a plurality of fan blades,the intake duct liner including an acoustic liner positioned upstream of the fan and a buzz-saw tone noise liner positioned upstream of the acoustic liner,

1. A turbofan gas turbine engine comprising: a fan,an intake duct with a liner upstream of the fan,a fan rotor having a plurality of fan blades,the intake duct liner including an acoustic liner positioned upstream of the fan and a buzz-saw tone noise liner positioned upstream of the acoustic liner, the buzz-saw tone noise liner has a greater depth than the acoustic liner, wherein the buzz-saw tone noise liner is positioned substantially at, or near, an upstream end of the intake duct, the intake duct has a lip and the buzz-saw tone noise liner is positioned at, or near, the lip, which is at a position selected from the group consisting of a position of minimum cross-sectional area of the intake duct and a position close to a position of minimum cross-sectional area of the intake duct, and the buzz saw tone noise liner is positioned upstream of the position of minimum cross-sectional area of the intake duct. 2. The turbofan gas turbine engine as claimed in claim 1 wherein the acoustic liner extends substantially the whole of the axial distance from the fan to the buzz-saw tone noise liner. 3. The turbofan gas turbine engine as claimed in claim 1 wherein the acoustic liner has a radial depth between 12 mm and 76 mm. 4. The turbofan gas turbine engine as claimed in claim 1 wherein the buzz-saw tone noise liner has a radial depth of between 50 mm and 254 mm. 5. The turbofan gas turbine engine as claimed in claim 1 wherein the buzz-saw tone noise liner has a depth of 203 mm to attenuate buzz-saw tone noise at frequency around 400 Hz. 6. The turbofan gas turbine engine as claimed in claim 1 wherein the buzz-saw tone noise liner has a depth of 254 mm to attenuate buzz-saw tone noise at a frequency around 335 Hz. 7. The turbofan gas turbine engine as claimed in claim 1 wherein the buzz-saw tone noise liner has depth=speed of sound/(4× frequency of buzz-saw tone noise). 8. The turbofan gas turbine engine as claimed in claim 1 wherein the acoustic liner is selected from the group consisting of a perforate honeycomb liner, a linear liner and a bulk absorber liner. 9. The turbofan gas turbine engine as claimed in claim 1 wherein the buzz-saw tone noise liner is selected from the group consisting of a perforate honeycomb liner, a linear liner and a bulk absorber liner. 10. The turbofan gas turbine engine as claimed in claim 1 wherein the resistance of the acoustic liner is between 1 and 3 rhoc and the resistance of the buzz-saw tone noise liner is between 1 and 3 rhoc. 11. The turbofan gas turbine engine as claimed in claim 1 wherein the acoustic liner has a radial depth between 12 mm and 76 mm and the buzz-saw tone noise liner has a radial depth between 50 mm and 254 mm. 12. The turbofan gas turbine engine as claimed in claim 11 wherein the buzz-saw tone noise liner has a radial depth between 203 mm and 254 mm.