Active control of tone noise in engine ducts

• US 5,692,702 A
• Filed: 04/30/1996
• Issued: 12/02/1997
• Est. Priority Date: 07/28/1994
• Status: Expired due to Fees

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Andersson, Anders O.
• Primary Examiner(s): BAREFOOT, GALEN L
• Application Number:
  US08/641,293
• Time in Patent Office: 581 Days
• Field of Search: 381/165, 381/64, 381/71, 244/1 N, 415/118, 415/119, 181/206
• US Class Current: 244/1.00N
• CPC Class Codes: F02C 7/042 having variable geometry
• CPC Class Codes: F02C 7/045 having provisions for noise suppression
• CPC Class Codes: F04D 29/663 Sound attenuation
• CPC Class Codes: F04D 29/681 especially adapted for elastic fluid pumps
• CPC Class Codes: F05D 2220/36 specially adapted for the fan of turbofan engines
• CPC Class Codes: F05D 2260/96 Preventing, counteracting or reducing vibration or noise
• CPC Class Codes: F05D 2260/962 by means of "anti-noise"
• CPC Class Codes: F05D 2270/803 Sampling thereof
• CPC Class Codes: F05D 2270/81 Microphones

Abstract

The application of active noise control to influence the fan-noise components in engine ducts. The fan is used as a source of counter noise by introducing flow distortions upstream or downstream of the fan. Microphone arrays sense the noise and produce a control output signal for controlling a distortion producer. The control output signal for the distortion producer comes from a control algorithm utilizing the output of the microphone signals sampled at a defined rate based on the fan blade passing frequency.

Claims

1. A method for control of the fan-generated component of noise emanating from ducts of jet engines, comprising the steps of:

a) providing devices for introducing flow distortions in the form of wakes;

b) collecting sensor signals harmonically related to rotor blade-passing frequency for controlling the wake-producing devices; and

,

c) providing means for absorbing the broad-band sound generated by said wake-producing devices.

2. The method according to claim 1 wherein collecting said sensor signals comprises collecting through sampling at a multiple of the rotor blade passing frequency.

3. The method according to claim 1 wherein collecting said sensor signals comprises collecting inputs from at least one circumferential array of sensors.

4. The method according to claim 3 in which modal amplitudes of each circumferential mode at each blade-passing-frequency harmonic is utilized for control of the circumferential distortion of harmonics of said wake-producing devices.

5. A system for control of the fan generated component of noise emanating from ducts of jet engines, comprising in combination:

a) a plurality of devices for introducing wakes to the fan;

b) said control means responsive to a plurality of signals sampled at a predetermined rate related to the fan blade passing frequency; and

,

c) means for absorbing the broad-band sound generated by said wake-producing devices.

6. The system of claim 5 wherein said plurality of devices provide steady flow distortions in the inlet upstream of the fan.

7. The system of claim 5 wherein said plurality of devices provide steady flow distortions in the fan duct downstream of the fan.

8. The system of claim 5 wherein said plurality of devices comprise a number of nozzles around the inlet.

9. The system of claim 5 wherein said plurality of devices comprise a plurality of rods capable of variable immersion into the flow.

10. The system of claim 5 where said sound-absorbing means is the same device that provides the spatial flow distortions.

11. The system of claim 5 wherein the flow distortions are produced by suction.

12. The system of claim 11 wherein the average suction of all devices is determined by the broadband-noise component of the sensors.