# US 10,502,134 B2 · Reduction of turbofan noise

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- Number: US 10,502,134 B2
- Document ID: US10502134B2
- Status: Granted
- Kind: B2
- Application number: 14/948,623
- Filed: 2015-11-23
- Published: 2016-05-26
- Granted: 2019-12-10
- Earliest claimed: 2014-11-24
- Assignees: Safran Aircraft Engines
- Applicants: Snecma
- Inventors: Laurent Louis Robert Baudoin; Georges Jean Xavier Riou
- Web page: https://patentgrep.com/patent/US10502134B2

## CPC

- F02C 7/045: having provisions for noise suppression
- F04D 19/002: {Axial flow fans}
- F04D 29/522: {especially adapted for elastic fluid pumps}
- F04D 29/663: {Sound attenuation}
- G10K 11/172: using resonance effects
- B64D 2033/0206: {comprising noise reduction means, e.g. acoustic liners}
- F05D 2220/36: specially adapted for the fan of turbofan engines
- F05D 2240/91: on a stationary structure
- F05D 2250/182: crenellated, notched
- F05D 2250/283: honeycomb
- F05D 2260/96: Preventing, counteracting or reducing vibration or noise
- F05D 2260/963: by Helmholtz resonators
- Y02T 50/60: Efficient propulsion technologies, e.g. for aircraft
- F02C: GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS (construction of turbines F01D; jet-propulsion plants F02K; construction of compressors or fans F04; generating combustion products of high pressure or high velocity F23R; using gas turbines in compression refrigeration plants F25B11/00)
- F04D: NON-POSITIVE-DISPLACEMENT PUMPS (engine fuel-injection pumps F02M; ion pumps H01J41/12; electrodynamic pumps H02K44/02)
- G10K: SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- B64D: EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
- F05D: INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## Abstract

The invention relates to an aircraft turbofan type engine (1) comprising an air intake duct (2) having an inner face provided with an acoustic attenuation shroud (11) located upstream from a fan (3) of this engine (1). This acoustic attenuation shroud (11) comprises a regular alternation of first portions and second portions with different first and second thicknesses along the radial direction, the number of alternations being greater than twice the number of passing azimuth acoustic vibration modes occurring in the engine (1) without the acoustic attenuation shroud (11) operating under conditions corresponding to a landing phase and a take-off phase.

## Claims

### Claim 1

Turbofan type aircraft engine comprising a fan case provided with an acoustic attenuation shroud having regular alternation of first portions and second portions provided with different first and second thicknesses along a radial direction, the number of alternations being greater than twice the number of passing azimuth acoustic vibration modes occurring in an engine without the acoustic attenuation shroud and operating under conditions corresponding to a landing phase and a take-off phase, the acoustic attenuation shroud located in the engine, upstream from a fan of the engine.

### Claim 2 (depends on 1)

Engine according to claim 1, in which the acoustic attenuation shroud is fixed to an engine case surrounding an air intake duct immediately upstream from the fan.

### Claim 3 (depends on 2)

Engine according to claim 2, in which the first portions form grooves on an outer face of the acoustic attenuation shroud, the grooves being oriented parallel to an axis of revolution of the acoustic attenuation shroud.

### Claim 4 (depends on 2)

Engine according to claim 2, wherein at least one of the first portion of the attenuation shroud is fixed to the engine case.

### Claim 5 (depends on 1)

Engine according to claim 1, wherein the acoustic attenuation shroud is made from a composite material with a honeycomb structure in which cells of the honeycomb structure extend in the radial direction and are partially open to form resonators.