US 5,515,444 A · Active control of aircraft engine inlet noise using compact sound sources and distributed error sensors

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.

Claims6

Dependent claims

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.

5 more elements

Dependencies are inferred from the claim text.

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

Life of this patent

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

Life of this patent

Abstract

Claims6