Abstract: The gas turbine has a plurality of inlet guide vanes each having a blade having a leading edge, a trailing edge, a span extending along the leading edge, and pivot members at opposite ends of the leading edge, and being pivotally mounted across the radial-to-axial intake via the pivot members, the pivot axis extending axially across a radial portion of the radial-to-axial intake. The plurality of inlet guide vanes include a plurality of first inlet guide vanes, and a plurality of second inlet guide vanes, the second inlet guide vanes having a trailing edge recess differing from the corresponding portion of the first inlet guide vanes. During operation, when the inlet guide vanes are pivoted past a given angle toward the tangential orientation, a radial flow of gas is allowed through the trailing edge recesses to avoid or impede vortex whistle.

Abstract: The gas turbine has a plurality of inlet guide vanes each having a blade having a leading edge, a trailing edge, a span extending along the leading edge, and pivot members at opposite ends of the leading edge, and being pivotally mounted across the radial-to-axial intake via the pivot members, the pivot axis extending axially across a radial portion of the radial-to-axial intake. The plurality of inlet guide vanes include a plurality of first inlet guide vanes, and a plurality of second inlet guide vanes, the second inlet guide vanes having a trailing edge recess differing from the corresponding portion of the first inlet guide vanes. During operation, when the inlet guide vanes are pivoted past a given angle toward the tangential orientation, a radial flow of gas is allowed through the trailing edge recesses to avoid or impede vortex whistle.

Abstract: An exciting sound wave generator is positioned within a nacelle of a jet engine at its inlet to generate an exciting sound wave having a primary frequency generally different from a frequency of the primary tone of the noise. The exciting sound wave is used to modulate the primary tone of the noise and, therefore, distribute sound energy of the noise from the primary tone to a broad range of side bands so that the amplitude of the primary tone of the noise is reduced.

Abstract: A gas turbine engine of a fan bypass type includes an exhaust shroud having a perforated tubular wall extending between a forward end and an aft end. The exhaust shroud is adapted to be affixed to a gas turbine engine exhaust for discharging engine exhaust gases without substantial blockage thereto. The perforations formed in the shroud wall communicate the regions at both sides of the shroud wall to pass fluid flow across the perforated shroud wall so that the mixing of the engine exhaust gases with a surrounding fluid flow is enhanced. The mixing of the engine exhaust gases with the surrounding fluid flow is further enhanced by a trailing edge of the exhaust shroud. The trailing edge is deviated from a straight line in a circumferential direction of the tubular wall to effectively increase the peripheral length of the mixing boundary. Thus, the jet noise contribution volume of the engine exhaust gases is effectively reduced, thereby significantly reducing the aero-engine jet noise.

Abstract: A gas turbine engine includes an exhaust flow guide attached to the engine exhaust end. The exhaust flow guide is made of a piece of sheet metal curved about the central longitudinal axis of the engine to form a partial portion of a nozzle having curved leading and trailing edges, and side edges. The exhaust flow guide asymmetrically affects the downstream jet noise contribution volume of the exhaust gases discharged from the engine exhaust end to change the jet noise directivity and reduce its power level. The exhaust flow guide can further include additional features such as perforations, corrugated surfaces, reinforcing strips and irregularly shaped trailing edges to further improve the mixing of exhaust gas flow with surrounding fluid flow to further reduce the downstream jet noise contribution volume, thereby resulting in jet noise reduction. The exhaust flow guide according to the present invention also improves attenuation of engine noise generated in the engine and emitted from the engine exhaust end.

Abstract: A gas turbine engine includes an exhaust flow guide attached to the engine exhaust end. The exhaust flow guide is made of a piece of sheet metal curved about the central longitudinal axis of the engine to form a partial portion of a nozzle having curved leading and trailing edges, and side edges. The exhaust flow guide asymmetrically affects the downstream jet noise contribution volume of the exhaust gases discharged from the engine exhaust end to change the jet noise directivity and reduce its power level. The exhaust flow guide can further include additional features such as perforations, corrugated surfaces, reinforcing strips and irregularly shaped trailing edges to further improve the mixing of exhaust gas flow with surrounding fluid flow to further reduce the downstream jet noise contribution volume, thereby resulting in jet noise reduction. The exhaust flow guide according to the present invention also improves attenuation of engine noise generated in the engine and emitted from the engine exhaust end.

Abstract: A butterfly valve noise suppressor is provided for reducing the noise generated by a gas flow passing through an open butterfly valve having a disc pivotally mounted in a valve housing for rotation about a transverse axis between an open and a closed position thereof. The noise suppressor includes a plurality of flat and perforated baffle plates arranged in a cruciform configuration, mounted in a flow path immediately downstream of the pivotal disc, axially extending and thereby dividing the downstream flow path into four axial and quadrant cross-sectional segments. The gas flow passing the edge of the pivotal disc in the valve generates a flow turbulence to form an unsteady large wake downstream of the valve. This unsteady wake is the source of noise. The cruciform baffle plates permit the gas flow to pass therethrough without obstruction thereto, while allowing the turbulence to communicate laterally through the perforation, thereby dissipating the wake unsteadiness to reduce noise.

Abstract: A gas turbine engine fan assembly includes fan blades spaced axially from stator vanes inside an annular bypass duct. A plurality of perforated baffle plates are installed in the annular bypass duct downstream of the stator vanes. The perforated baffle plates extend in a generally axial direction and are unevenly, circumferentially spaced apart from one another to divide a major section of the annular bypass duct into a plurality of axial flow-path segments in an asymmetrical pattern to disrupt continuity, destroy a symmetrical pattern and absorb sound energy of a spinning mode of sound pressures imbedded in the air flow downstream of the stator vanes, without substantially affecting a thrust provided by the air flow when discharged from the bypass duct.

Abstract: A gas turbine engine rotor assembly such as a fan or compressor includes fan blades spaced axially from stator vanes inside an annular duct. A controlled air blowing system is secured to the annular duct and adapted to blow a hot air flow in a direction opposite to the rotation of the fan blades into the annular duct between the fan blades and the stator vanes, to impart an opposite rotational momentum with respect to the air compressed by the rotor blades, in a asymmetrical pattern to interfere with or destroy a symmetrical pattern of the blade rotation-wake of the compressed air, thereby reducing the strength or preventing the generation of the spinning mode so that the fan-stator interaction tones are significantly reduced.

Abstract: A gas turbine engine of a fan bypass type includes an exhaust shroud having a perforated tubular wall extending between a forward end and an aft end. The exhaust shroud is adapted to be affixed to a gas turbine engine exhaust for discharging engine exhaust gases without substantial blockage thereto. The perforations formed in the shroud wall communicate the regions at both sides of the shroud wall to pass fluid flow across the perforated shroud wall so that the mixing of the engine exhaust gases with a surrounding fluid flow is enhanced. The mixing of the engine exhaust gases with the surrounding fluid flow is further enhanced by a trailing edge of the exhaust shroud. The trailing edge is deviated from a straight line in a circumferential direction of the tubular wall to effectively increase the peripheral length of the mixing boundary. Thus, the jet noise contribution volume of the engine exhaust gases is effectively reduced, thereby significantly reducing the aero-engine jet noise.

Abstract: A gas turbine engine fan assembly includes fan blades spaced axially from stator vanes inside an annular bypass duct. A plurality of perforated baffle plates are installed in the annular bypass duct downstream of the stator vanes. The perforated baffle plates extend in a generally axial direction and are unevenly, circumferentially spaced apart from one another to divide a major section of the annular bypass duct into a plurality of axial flow-path segments in an asymmetrical pattern to disrupt continuity, destroy a symmetrical pattern and absorb sound energy of a spinning mode of sound pressures imbedded in the air flow downstream of the stator vanes, without substantially affecting a thrust provided by the air flow when discharged from the bypass duct.

Abstract: A noise attenuating device for reducing the noise generated by a gas flow passing through an open butterfly valve having a disc pivotally mounted in a valve housing for rotation about a transversal axis between an open and a closed position thereof. The noise attenuating device comprises a first series of elongated members extending from the upstream side of the disc above the transversal axis and a second series of generally diametrically opposed elongated members extending from the downstream side of the disc below the horizontal axis. Typically, the elongated members extend at 45 degree from the disc of the butterfly valve.