Acoustic attenuation vanes for fan ducts in an aircraft
An engine of an aircraft comprising an engine core that produces thrust to propel the aircraft. A fan duct extends along a length of the engine core and is positioned between an engine core nacelle and a fan nacelle with the fan duct. A thrust reverser is positioned along the fan duct and has blocker doors and drag links. The thrust reverser is positionable between an open position and a closed position. The open position locates the blocker doors for the air to move along the fan duct and exit at the nozzle exit. The closed position locates the blocker doors across the fan duct to direct the air out of the fan duct through an opening in the fan nacelle. An acoustic attenuation system is mounted in the fan duct and positioned between the thrust reverser and the nozzle exit with the acoustic attenuation system configured to reduce noise caused by fan blade-pass frequency moving through the fan duct.
1. An engine of an aircraft comprising:
a fan;
an engine core that produces thrust to propel the aircraft;
a fan duct positioned downstream from the fan and that extends along a length of the engine core and is positioned between an engine core nacelle inner wall and a fan nacelle, the fan duct comprising an inlet and a nozzle exit;
a thrust reverser positioned along the fan duct and comprising a plurality of blocker doors and drag links, the thrust reverser positionable between an open position and a closed position, the open position locates the blocker doors for the air to move along the fan duct and exit at the nozzle exit, the closed position locates the blocker doors across the fan duct to direct the air out of the fan duct through an opening in the fan nacelle;
an acoustic attenuation system comprising acoustic vanes mounted in the fan duct and positioned between the thrust reverser and the nozzle exit and aft of the drag links with each one of the acoustic vanes aligned behind a respective one of the drag links, the acoustic attenuation system configured to reduce fan blade-pass frequency noise caused by the fan; and
wherein the acoustic vanes comprise:
a first section mounted to and extending outward into the fan duct from a first side wall of the fan duct;
a second section mounted to and extending outward from a second side wall of the fan duct; and
the first section and the second section aligned on opposing sides of the fan duct and comprising inner lateral sides that face together.
2. The engine of claim 1 , wherein the acoustic vanes are aligned in the fan duct around the engine core nacelle inner wall and connected to a wall of the fan duct.
3. The engine of claim 1 , wherein the acoustic vanes comprise a forward end that is tapered, an opposing aft end, an inner lateral side, and an outer lateral side with the outer lateral side mounted to a wall of the fan duct.
4. The engine of claim 3 , wherein the forward end of each of the acoustic vanes is aligned with one of the drag links for the acoustic vanes to be positioned in the fan duct in disturbed air flow.
5. The engine of claim 3 , wherein the inner lateral sides of the acoustic vanes are exposed within the fan duct.
6. The engine of claim 1 , wherein the acoustic vanes comprise a forward end and an aft end with the aft ends aligned with a plane aligned at the nozzle exit.
7. The engine of claim 1 , wherein the fan nacelle comprises a forward section that is fixed and an aft section that translates along the fan duct with the second section of the acoustic vanes mounted to the aft section.
8. The engine of claim 1 , wherein the acoustic vanes comprise a forward end, an opposing aft end, an inner lateral side, and an outer lateral side, the acoustic vanes comprising a shape that is curved between the inner lateral side and the outer lateral side.
9. The engine of claim 1 , wherein the fan nacelle comprises chevrons at the nozzle exit and the acoustic vanes are aligned with the chevrons along the fan nacelle.
10. The engine of claim 1 , wherein the acoustic vanes comprise different thicknesses.
11. An engine of an aircraft comprising:
a fan;
an engine core configured to produce thrust to propel the aircraft;
a fan duct that extends along the engine core downstream from the fan;
blocker doors mounted in the fan duct;
drag links mounted in the fan duct, each one of the drag links connected to one of the blocker doors, the drag links configured to move the blocker doors between an open position to direct airflow along the fan duct and a closed position to direct air out of the fan duct;
acoustic vanes mounted in the fan duct aft of the drag links, each of the acoustic vanes aligned with one of the drag links to be positioned in disturbed air caused by the respective one of the drag links; and
wherein the acoustic vanes comprise:
a first section mounted to and extending outward into the fan duct from a first side wall of the fan duct;
a second section mounted to and extending outward from a second side wall of the fan duct; and
the first section and the second section aligned on opposing sides of the fan duct and comprising inner lateral sides that face together.
12. The engine of claim 11 , wherein the acoustic vanes comprise a forward end and a trailing end, the acoustic vanes positioned in the fan duct with the forward ends aligned with the drag links.
13. The engine of claim 11 , wherein the acoustic vanes comprise a flat shape with an inner lateral side that is straight, the inner lateral sides aligned with the drag links.
14. The engine of claim 11 , further comprising a fan nacelle with a forward section that is fixed relative to the fan duct and an aft section that translates relative to the fan duct with the second section of the acoustic vanes mounted on the aft section of the fan nacelle.
15. The engine of claim 14 , wherein the fan nacelle comprises chevrons at the aft section.
16. The engine of claim 11 , wherein the inner lateral sides of the first section and the second section abut together.
17. The engine of claim 11 , wherein the acoustic vanes comprise different thicknesses.
18. A method of reducing noise of an engine of an aircraft, the method comprising:
mounting acoustic vanes in a fan duct of the engine with the acoustic vanes positioned aft of and aligned behind drag links of a reverse thruster and positioned in disturbed air caused by the drag links;
positioning the drag links in a first position and positioning blocker doors in an open position to enable airflow through the fan duct from an inlet to a nozzle exit;
positioning the drag links in a second position and positioning the blocker doors in a closed position to direct the airflow in the fan duct away from the nozzle exit; and
wherein each of the acoustic vanes comprises an inner section and an outer section and further comprising translating the outer section relative to the inner section when moving the drag links from the first position to the second position.
19. The method of claim 18 , further comprising translating the acoustic vanes along the fan duct while moving the drag links from the first position to the second position.
20. The method of claim 18 , further comprising maintaining the inner sections of the acoustic vanes in fixed positions while translating the outer sections.