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Active control of aircraft engine inlet noise using compact sound sources and distributed error sensors
| Details |
Inventors: Burdisso, Ricardo; Fuller, Chris R.; O'Brien, Walter F.; Thomas, Russell H.; Dungan, Mary E.;
Assignee: Virginia Polytechnic Institute and State University (Blacksburg, VA); Virginia Tech Intellectual Properties (Blacksburg, VA); The Center for Innovative Technology (Herndon, VA)
Primary Examiner: Isen; Forester W.
Assistant Examiner:
Attorney, Agent or Firm: Whitham, Curtis, Whitham, & McGinn
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. |
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DETAILED DESCRIPTION It is therefore an object of the present invention to provide an active noise control system for the effective control of aircraft engine inlet noise.
It is another object of the invention to provide a compact sound source suitable for use in an active noise control mechanism which is applicable for an operational aircraft engine.
According to the present invention, an effective active noise control system is applied to reduce the noise emanating from the inlet of an operational turbofan engine.
In a specific application, the fan noise from a turbofan engine is controlled using an adaptive filtered-x LMS algorithm.
Single and 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 or combination of spinning modes.
The preferred embodiment of the invention uses a 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, it is necessary to provide a suitable sound source to generate the control field.
In a specific implementation of the invention, the control field sound source consists of an array of thin, cylindrically curved panels with inner radii of curvature corresponding to that of the engine inlet so as to conform to the inlet shape.
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 induced strain actuators, such as piezoelectric force transducers, mounted on the external surface of the panel.
The response of the panel, driven by an oscillatory voltage, is maximized when it is driven at its resonance frequency.
The panel response is adaptively tuned such that its fundamental frequency is near the tone to be canceled
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Audio Signal Processing 
