Active low noise fan assembly

• US 5,478,199 A
• Filed: 11/28/1994
• Issued: 12/26/1995
• Est. Priority Date: 11/28/1994
• Status: Expired due to Term

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Gliebe, Philip R.
• Primary Examiner(s): Look, Edward K.
• Assistant Examiner(s): Lee, Michael S.
• Application Number:
  US08/345,094
• Time in Patent Office: 393 Days
• Field of Search: 415/118, 415/119, 381/71
• US Class Current: 415/119
• CPC Class Codes: B64D 2033/0206 comprising noise reduction means, e.g. acoustic liners
• CPC Class Codes: B64D 2033/0286 for turbofan engines
• CPC Class Codes: B64D 33/02 of combustion air intakes air intakes for gas-turbine plants or jet-propulsion plants per se F02C7/04; air intakes for combustion engines in general F02M35/00
• CPC Class Codes: F02C 7/045 having provisions for noise suppression
• CPC Class Codes: F05D 2220/327 to drive shrouded, high solidity propeller
• CPC Class Codes: F05D 2260/962 by means of "anti-noise"
• CPC Class Codes: G10K 11/17857 Geometric disposition, e.g. placement of microphones
• CPC Class Codes: G10K 11/17861 using additional means for damping sound, e.g. using sound absorbing panels
• CPC Class Codes: G10K 11/17875 using an error signal without a reference signal, e.g. pure feedback
• CPC Class Codes: G10K 11/17881 the reference signal being an acoustic signal, e.g. recorded with a microphone
• CPC Class Codes: G10K 2210/107 Combustion, e.g. burner noise control of jet engines internal combustion engines G10K2210/121
• CPC Class Codes: G10K 2210/112 Ducts vehicle exhausts G10K2210/12822
• CPC Class Codes: G10K 2210/121 Rotating machines, e.g. engines, turbines, motors; Periodic or quasi-periodic signals in general
• CPC Class Codes: G10K 2210/3032 Harmonics or sub-harmonics
• CPC Class Codes: G10K 2210/3045 Multiple acoustic inputs, single acoustic output
• CPC Class Codes: G10K 2210/3217 Collocated sensor and cancelling actuator, e.g. "virtual earth" designs
• CPC Class Codes: G10K 2210/509 Hybrid, i.e. combining different technologies, e.g. passive and active
• CPC Class Codes: G10K 2210/511 Narrow band, e.g. implementations for single frequency cancellation

Abstract

A gas turbine engine fan assembly includes an equal number of rotor blades and stator vanes spaced axially therefrom. An annular duct surrounds the blades and vanes and has an inlet for receiving air and an outlet for discharging at least a portion of the air upon compression by the blades. The fan duct further includes a passive acoustic liner tuned for attenuating at least one harmonic noise tone generated by the blades, with a fundamental blade passing frequency noise tone being actively attenuated by a plurality of anti-noise sound transmitters disposed in the fan duct.

Claims

1. A gas turbine engine fan assembly comprising:

a number of circumferentially spaced apart rotor blades;

a number of circumferentially spaced apart stator vanes spaced axially from said blades;

an annular duct surrounding said blades and said vanes, and having an inlet for receiving air and an outlet for discharging at least a portion of said air upon compression by said blades;

said blade number being equal to said vane number so that a fundamental blade passing frequency noise tone is generated in said fan duct with a cut-off ratio greater than 1.0 and a spinning mode number of zero, and harmonic blade passing frequency noise tones are generated in said fan duct with non-zero spinning mode numbers; and

said fan duct further includes a passive acoustic liner tuned for attenuating at least one of said harmonic noise tones, and means for actively attenuating said fundamental noise tone.

2. A fan assembly according to claim 1 wherein said active attenuating means comprises:

a plurality of circumferentially spaced apart sound transmitters disposed in sound communication with said fan duct;

a noise sensor disposed in sound communication with said fan duct for sensing magnitude and phase of said fundamental noise tone;

a controller operatively joined to said noise sensor and effective for generating an anti-noise signal opposite in phase to said fundamental noise tone;

an amplifier for amplifying power of said anti-noise signal; and

an acoustic driver for driving all said sound transmitters in phase based on said amplified anti-noise signal for attenuating said fundamental noise tone.

3. A fan assembly according to claim 2 wherein:

said sound transmitters are disposed in a single ring array;

a plurality of said noise sensors are disposed in a single ring array for providing an average value of said fundamental noise tone to said controller as a single input thereto; and

said controller is effective for providing a single output to said plurality of sound transmitters.

4. A fan assembly according to claim 2 wherein said noise sensor is disposed at an end of said fan duct, and said sound transmitters and passive acoustic liner are disposed between said noise sensor and said rotor blades.

5. A fan assembly according to claim 4 wherein:

said rotor blades are fan blades, and said stator vanes are outlet guide vanes disposed downstream from said fan blades;

said duct is a fan duct disposed inside a nacelle, and includes a radially outer duct wall surrounding said blades and vanes, and having a duct inlet at a forward, upstream flow end thereof, and a duct outlet at an aft, downstream flow end thereof; and

said noise sensor is disposed adjacent to at least one of said duct inlet and outlet.

6. A fan assembly according to claim 5 wherein:

said noise sensor is disposed adjacent to said duct inlet;

said sound transmitters are disposed downstream from said noise sensor; and

said passive acoustic liner is disposed between said sound transmitters and said fan blades.

7. A fan assembly according to claim 5 wherein:

said noise sensor is disposed adjacent to said duct outlet;

said sound transmitters are disposed upstream from said noise sensor; and

said passive acoustic liner is disposed at least in part between said sound transmitters and said outlet guide vanes.

8. A fan assembly according to claim 5 further comprising:

an inlet one of said noise sensors disposed adjacent to said duct inlet in said outer duct wall;

inlet ones of said sound transmitters disposed downstream from said inlet noise sensor in said outer duct wall;

an inlet one of said passive acoustic liners disposed between said inlet sound transmitters and said fan blades in said outer duct wall;

an outlet one of said noise sensors disposed adjacent to said duct outlet;

outlet ones of said sound transmitters disposed upstream from said outlet noise sensor;

an outlet one of said passive acoustic liners disposed between said outlet sound transmitters and said outlet guide vanes; and

separate ones of said controller, amplifier and acoustic driver for independently attenuating said fundamental noise tone from said duct inlet and outlet.

9. A fan assembly according to claim 8 wherein:

said fan duct further includes a radially inner wall extending from adjacent said blades to said duct outlet;

said inner duct wall includes a passive acoustic liner therearound;

said outlet noise sensor is disposed in said inner duct wall; and

said outlet sound transmitters are disposed in said outer duct wall.

10. A fan assembly according to claim 9 wherein said outlet sound transmitters are spaced upstream from said duct outlet, and further including an additional passive acoustic liner disposed between said outlet sound transmitters and said duct outlet.