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 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. The multi channel control system is used to control fan tones and a high pressure compressor BPF tone simultaneously, and any spinning mode. A compact sound source is employed to generate the control field. This compact sound source consists of an array of identical thin, cylindrically curved panels (125) with an inner radius of curvature corresponding to that of the engine inlet. These panels are flush mounted inside the inlet duct (Inlet Wall) and sealed on all edges to prevent leakage around the panel.
Abstract:
A ducted axial fan for large diameter ducts (11) which includes equidistantly spaced sensors (22, 23) upstream and downstream of an axial fan and spaced actuators (24, 26) located around the periphery of said duct to cancel tonal noise caused by the air turbulence generated by the rotation of the fan.
Abstract:
A noise attenuator for a wind turbine blade includes a first attenuator portion having a plurality of first attenuator elements, each first attenuator element being separated from an adjacent first attenuator element by an interface; and a second attenuator portion having a plurality of second attenuator elements, each second attenuator element being separated from an adjacent second attenuator element by an interface. The first and second attenuator portions are configured to be juxtapositioned in an overlapping relation relative to each other to collectively form the noise attenuator. Adjacent attenuator elements on the noise attenuator may effectively intersect each other at a substantially sharp corner. A method of reducing wind turbine noise includes juxtapositioning the first and second attenuator portions relative to each other so that the attenuator elements effectively intersect each other at a substantially sharp corner.
Abstract:
Sistema de supresión y anulación de ruido en aerogeneradores formado por micrófonos dispuestos por toda la envergadura de las palas y de las torres que captan el ruido y transmiten la señal generada a un módulo de análisis que controla fuentes de alimentación eléctrica que generan señales eléctricas de sonido de la misma frecuencia y amplitud pero de fase opuesta, ambos dispuestos en la nacelle. Las fuentes de alimentación eléctrica transmiten dichas señales a unos altavoces también situados en las palas y en las torres, de forma que se produce la cancelación del ruido generado por el rotor y su interacción con la torre.
Abstract:
A ducted axial fan for large diameter ducts (11) which includes equidistantly spaced sensors (22, 23) upstream and downstream of an axial fan and spaced actuators (24, 26) located around the periphery of said duct to cancel tonal noise caused by the air turbulence generated by the rotation of the fan.
Abstract:
A jet engine fan noise reduction system. The noise reduction system includes active noise control to suppress fan (15) tone noise of an airplane flyover noise signature. The active noise control includes microphones (1, 11) with acoustic transducers upstream and downstream of the engine fan (15) and fan exit guide vane (16) stage to sense control system errors. Control signals are derived from the fan angular speed or blade passing frequency and the error signal sensed by the acoustic transducers. The control output signals actuate (modulate) air control valves (45) on each side of the fan stage to direct conditioned (pressure and temperature regulated) high pressure primary air flow, thereby producing acoustic cancelling of fan tone noise.
Abstract:
The present invention relates to airfoils having surface treatments to reduce trailing edge noise. The surface treatment is designed to reduce trailing edge noise by modifying the boundary layer turbulence as it approaches the trailing edge. The surface treatment accomplishes its function by breaking up spanwise-oriented turbulence approaching the trailing edge, thereby reducing the spanwise correlation lengthscales; deflecting the boundary layer turbulence away from the edge; and/or creating spanwise vortices or instability waves to reduce the turbulence-edge interaction.
Abstract:
The present invention is embodied in an aircraft engine noise absorption system having a resonator cavity for absorbing incident noise except for a residue noise signal having a predominant frequency, the system comprising an actuator providing an actuator acoustic signal, a noise sensor for sensing the predominant frequency, and a control means for setting the actuator acoustic signal to the predominant frequency and varying one of a phase and an amplitude of the actuator acoustic signal to decrease the residue noise signal.
Abstract:
A method and system for reducing the acoustic levels of internal and external sound fields (23 and 24) generated by gas turbine engines (2) has several actuators to generate sound (50, 84, and 115), several sensors to measure the acoustic levels (49 and 69), and one or more controllers (113). The controllers are adaptive self-learning neural networks (112) that control the actuators to generate sound in order to effect the reduction of the internal and external sound field as measured by the sensors.