Active control of aircraft engine inlet noise using compact sound sources and distributed error sensors

• US 5,515,444 A
• Filed: 10/07/1994
• Issued: 05/07/1996
• Est. Priority Date: 10/21/1992
• Status: Expired due to Term

• Current Assignee: Verity Group PLC, Virginia Tech Intellectual Properties, Inc.
• Original Assignee: The Center For Innovative Technology, Virginia Polytechnic Institute and State University, Virginia Tech Intellectual Properties, Inc.
• Inventors: Burdisso, Ricardo, Thomas, Russell H., Fuller, Chris R., Dungan, Mary E., O'Brien, Walter F.
• Primary Examiner(s): Isen, Forester W.
• Application Number:
  US08/320,153
• Time in Patent Office: 578 Days
• Field of Search: 381/71, 381/190
• US Class Current: 381/71.5
• CPC Class Codes: F05B 2260/962 by means creating "anti-noise"
• CPC Class Codes: G10K 11/1785 Methods, e.g. algorithms; Devices G10K11/1781, G10K11/1783 take precedence
• CPC Class Codes: G10K 11/17854 the filter being an adaptive filter
• CPC Class Codes: G10K 11/17857 Geometric disposition, e.g. placement of microphones
• CPC Class Codes: G10K 11/17883 the reference signal being derived from a machine operating condition, e.g. engine RPM or vehicle speed
• 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 2210/1281 Aircraft, e.g. spacecraft, airplane or helicopter
• CPC Class Codes: G10K 2210/1291 Anti-Vibration-Control, e.g. reducing vibrations in panels or beams
• CPC Class Codes: G10K 2210/3032 Harmonics or sub-harmonics
• CPC Class Codes: G10K 2210/3042 Parallel processing
• CPC Class Codes: G10K 2210/3045 Multiple acoustic inputs, single acoustic output
• CPC Class Codes: G10K 2210/3046 Multiple acoustic inputs, multiple acoustic outputs
• CPC Class Codes: G10K 2210/3226 Sensor details, e.g. for producing a reference or error signal
• CPC Class Codes: G10K 2210/32271 Active resonators
• CPC Class Codes: G10K 2210/3229 Transducers
• CPC Class Codes: G10K 2210/32291 Plates or thin films, e.g. PVDF foil-type piezoelectric elements B06B1/0688
• CPC Class Codes: G10K 2210/511 Narrow band, e.g. implementations for single frequency cancellation

Abstract

An active noise control system using a compact sound source is effective to reduce aircraft engine duct noise. The fan noise from a turbofan engine is controlled using an adaptive filtered-x LMS algorithm. Single multi channel control systems are used to control the fan blade passage frequency (BPF) tone and the BPF tone and the first harmonic of the BPF tone for a plane wave excitation. A multi channel control system is used to control any spinning mode. The multi channel control system to control both fan tones and a high pressure compressor BPF tone simultaneously. In order to make active control of turbofan inlet noise a viable technology, a compact sound source is employed to generate the control field. This control field sound source consists of an array of identical thin, cylindrically curved panels with an inner radius of curvature corresponding to that of the engine inlet. These panels are flush mounted inside the inlet duct and sealed on all edges to prevent leakage around the panel and to minimize the aerodynamic losses created by the addition of the panels. Each panel is driven by one or more piezoelectric force transducers mounted on the surface of the panel. The response of the panel to excitation is maximized when it is driven at its resonance; therefore, the panel is designed such that its fundamental frequency is near the tone to be canceled, typically 2000-4000 Hz.

Claims

1. An active noise control system for reducing aircraft engine noise which emanates from an aircraft engine inlet of a gas turbine engine, said gas turbine engine having a fan and compressor the revolution of which generates a primary sound field, said active noise control system comprising:

a blade passage sensor mounted within said turbine engine adjacent to said fan for generating a reference acoustic signal, said blade passage sensor sensing a blade passage frequency and harmonics which are correlated with radiated sound;

a distributed error sensor positioned to be responsive to said primary sound field for generating an error acoustic signal;

acoustic driver means comprised of an array of piezoelectric driven panels mounted circumferentially flush about an interior surface of said inlet preceding said fan, said acoustic driver means comprising

(i) a plurality of said piezoelectric driven panels curved about and conforming to said interior surface, each of said curved panels having an interior radius of curvature and an exterior radius of curvature and an exterior surface defined by said exterior radius of curvature, and

(ii) one or more surface strain piezoelectric actuator means mounted on said exterior surface of each of said curved panels;

controller means responsive to said reference acoustic signal and said error acoustic signal for driving said acoustic driver means by driving said surface strain piezoelectric actuator means to generate a secondary sound field having an approximately equal amplitude but opposite phase as said primary sound field to thereby effectively reduce said engine noise; and

a mechanical dynamically tuning means for tuning resonance frequencies of said piezoelectric driven panels.

2. The active noise control system recited in claim 1 wherein said mechanical tuning means comprises a means for selectively changing the stiffness of said piezoelectric driven panels.

3. The active noise control system of claim 2 wherein said means for selectively changing the stiffness of said piezoelectric driven panels comprises a means for applying gas pressure against said piezoelectric driven panels.

4. A compact acoustic driver for generating a controlled sound field for canceling noise, comprising:

a curved panel having an interior radius of curvature and an exterior radius of curvature, said curved panel having an exterior surface defined by said exterior radius of curvature;

a mechanical means for dynamically tuning said curved panel to have a fundamental frequency near a tone in said noise to be canceled;

surface strain actuator means mounted only on said exterior surface of said curved panel, said surface strain actuator means being mechanically coupled to said curved panel to impart mechanical motion thereto; and

electrical generator means connected to said surface strain actuator means for driving said surface strain actuator means and imparting mechanical motion to said curved panel at said fundamental frequency to general said controlled sound field for canceling said tone in said noise.

5. The compact acoustic driver recited in claim 4 wherein said mechanical tuning means comprises a means for selectively changing the stiffness of said curved panel.

6. The active noise control system of claim 5 wherein said means for selectively changing the stiffness of said curved panel comprises a means for applying gas pressure against said curved panel.