Abstract: A tortuous path quiet exhaust eductor system may be mounted to a gas turbine engine, such as commercial aircraft APU. The system includes an oil cooler, eductor primary nozzle, oil cooler air nozzle, and surge air dump nozzle. The primary nozzle, oil cooler air nozzle, and surge air dump nozzle direct exhaust flow to entrain APU compartment cooling air, oil cooling air and surge air in a direction having both radial and axial components with respect to the APU centerline axis. The exhaust flow is directed into an eductor mixing duct angled away from the centerline axis and then is turned to enter an exit duct angled toward the centerline axis so that direct line of sight acoustic paths from the tail pipe exit to the turbine exit are blocked, suppressing core noise. The tail pipe ducts may be acoustically treated, further enhancing noise suppression.

Abstract: Disclosed is an exhaust mixer (50) including a passage (54) extending from an inlet (56) to an outlet (58) that is coincident with a centerline axis of mixer (50). Several ridges (68) are circumferentially disposed about the axis and each flare away from the centerline axis relative to a direction along the centerline axis from inlet (56) toward outlet (58). Ridges (68) each define a corresponding one of several inner channels (74) radially disposed about passage (54) that each intersect passage (54) between inlet (56) and outlet (58). Several outer channels (84) are also radially disposed about passage(54) and are each positioned between a corresponding pair of inner channels (74). Ridges are each shaped to turn inner channels (74and outer channels (84) about the axis as ridges (68) extend along the indicated direction. Inner channels (74) diverge away from the axis and one another in this direction while outer channels (84) converge toward the axis and one another in this direction.

Abstract: This invention relates to a double layer acoustic liner for attenuating noise and consisting of a plurality of cells formed in a plate in a manner to form an array of resonators, and a fluid processing device and method incorporating same.

Abstract: A jet noise suppressor is disclosed. The jet noise suppressor includes first and second high frequency pulse injection units located exteriorly of the turbine engine exhaust nozzle. The pulse injection units are located oppositely, diametrically across the exhaust nozzle. The pulse injection units include a resonance tube in outlet fluid communication with an injector nozzle. High pressure gas is supplied to the resonance tubes. A second source of high pressure gas includes a switch for supplying an alternating flow of high pressure gas to the injector nozzles. The combination of the high frequency pulses emitted from the injection units with the alternating low frequency, high amplitude mode of injection across the exhaust nozzle, provides a dramatic reduction of noise as well as exhaust temperature.

Abstract: This invention relates to an acoustic liner for attenuating noise and consisting of a plurality of cells formed in a plate in a manner to form an array of resonators, and a fluid processing device and method incorporating same.

Abstract: A gas turbine exhaust passage is realized which may suppress the radiation of strong ultra low frequency noise to the outside without amplifying the turbulence of an high speed exhaust gas flow rate or a pressure pulsation generated in a gas turbine. At least a portion of a wall of a gas turbine exhaust passage (3, 5) is formed of an acoustically transmissive material (36, 56) for allowing a low frequency noise of several tens of Hz or less to pass therethrough sufficiently. Also, the acoustically transmissive material is made of one or more of a porous material, a porous heat insulating material, a mesh having a large flow resistance, cloth or film material. Further, the acoustically transmissive material is supported by a porous plate or a frame. In a case where an acoustically transmissive material is used only for an exhaust chimney (5), the exhaust chimney (5) is supported by a rack (11). Further, a soundproof panel (12) may be attached to the rack (11).

Abstract: A muffler of a muffler made of a titanium alloy wherein advantages of lightness and corrosion-resistance that the titanium alloy originally has are used, and heat-resistance and oxidization-resistance are heightened without damaging costs or workability so that the span of life and flexibility for design are improved. A muffler made of a titanium alloy, wherein the titanium alloy comprises 0.5-2.3% by mass of Al and optionally one or more other alloying elements. The metal texture may comprise more than 90% by volume of the &agr; phase and 20% or less of the &bgr; phase. This muffler is superior in heat-resistance, oxidization-resistance, weldability and so on.

Abstract: A resonator module for a combustion turbine power plant, where the combustion turbine power plant defines a flow path. The resonator module includes a first member, an a second member. The first member has a size substantially smaller than the diameter of said flow path and a plurality of openings therethrough. The openings are in fluid communication with the flow path. The second member has a size generally equal to said first member. The second member is in a generally spaced relation to the first member and encloses a volume of gas between the first and second members.

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 exhaust nozzle includes an outlet for discharging exhaust, and a plurality of circumferentially spaced apart stub airfoils disposed adjacent the outlet. The airfoils shed vortices for mixing exhaust flow and attenuating noise and reducing infrared signature with minimum performance loss.

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: An acoustically treated structurally reinforced sound absorbing panel having particular application for use at the inlet cowl of a jet engine to reduce engine noise leaked into the environment. The sound absorbing panel includes a sound receiving chamber having a honeycomb shaped core manufactured from corrugated metallic ribbons. The sound receiving chamber is sandwiched between a metallic backskin at one side thereof, and a metallic face sheet at the opposite side. The face sheet is perforated so that incoming sound waves which represent the engine noise enter the sound receiving chamber within which they are channeled towards and reflected between the metallic backskin and face sheet.

Abstract: A middle layer (22) having partitioned cavities (28) is sandwiched between an imperforate sheet (24) and an optional perforate sheet (26) to form a low resistance acoustic liner (22). A preferred method of manufacture of the low resistance acoustic liner (20) uses aspects of the buried septum technique including placing an uncured imperforate septum (36) between a support layer (32) and a partitioned cavity middle layer (22), pressing the middle layer into the imperforate sheet (24) and through the support layer (32), curing the imperforate septum 36 to form the imperforate sheet (24), removing the support layer (32), and attaching a perforate sheet (26) of roughly at least 15% open area to the top side of the middle layer. A preferred embodiment of inner and outer linings (47), (49) is provided. Each lining includes a combination of annuluses of absorptive and/or low resistance liners (51), (53).

Abstract: The present invention relates to a gas turbine engine exhaust nozzle for suppressing jet noise. The nozzle has an arrangement of tabs that extend in radially inward and outward directions. The tabs cause the formation of vortices which pull into mixing engagement the exhaust gas streams from the core and fan ducts and the ambient air. In addition, various construction details are developed for the tab arrangement including tabs that are directed radially inwardly and outwardly, and tabs that are continuous with the nozzle duct therebetween.

Abstract: The invention relates to an exhaust device for a turbine engine, comprising a liner made of a fiber-reinforced ceramic matrix composite. The liner is preferably fitted some distance away from the inside of the exhaust section. The liner has a thickness of 1 to 10 mm, preferably of 2 to 6 mm. There is a gap of at least 10 mm, preferably 10 to 40 mm, between the liner and the inside of the exhaust.

Abstract: An infrared suppressor system for a gas turbine engine is provided for suppressing infrared radiation associated with the hot metal parts of the engine and with the hot exhaust gases exhausted from the engine. The system features a unique arrangement of multiple baffles that are connected together as a single baffle module. The baffle arrangement permits mixing of hot and cool gas flows while eliminating line-of-sight infrared radiation in an axially compact suppressor. The baffles are additionally linked together into a single insertable baffle module that permits removal of the baffle module when infrared suppression is unnecessary.

Abstract: A microporous sheet having both acoustical and structural functionality and a process for producing the sheet. Construction of the sheet requires, first of all, providing a sheet capable of functioning as a structural element of a component. A laser device capable of producing a free electron laser beam is provided, and the free electron laser beam is directed to a surface of the sheet to penetrate the sheet at a plurality of sites and thereby form a plurality of apertures. These apertures are generally uniformly dispersed and of a size and number sufficient to enable the sheet to function as an acoustical noise suppressor while retaining capability of functioning as a structural element.

Abstract: A middle layer (22) having partitioned cavities (28) is sandwiched between an imperforate sheet (24) and an optional perforate sheet (26) to form a low resistance acoustic liner (22). A preferred method of manufacture of the low resistance acoustic liner (20) uses aspects of the buried septum technique including placing an uncured imperforate septum (36) between a support layer (32) and a partitioned cavity middle layer (22), pressing the middle layer into the imperforate sheet (24) and through the support layer (32), curing the imperforate septum 36 to form the imperforate sheet (24), removing the support layer (32), and attaching a perforate sheet (26) of roughly at least 15% open area to the top side of the middle layer. A preferred embodiment of inner and outer linings (47), (49) is provided. Each lining includes a combination of annuluses of absorptive and/or low resistance liners (51), (53).

Abstract: An acoustic panel (26) for the nacelle (20) of a high bypass jet engine. The acoustic panel (26) has a perforated composite inner sheet (54), an outer composite sheet (96, 98), and a honeycomb-core material (74) sandwiched therebetween. The acoustic panel (26) includes an integral forward ring (36) and integral wedge fairings (44).

Abstract: An extended reaction acoustic liner for use in jet engine noise mitigation has a substantially non-porous outer layer, a honeycomb core disposed in laminar juxtaposition to the outer layer, and a porous inner layer in laminar juxtaposition to the honeycomb core such that the honeycomb core is sandwiched between the outer layer and the inner layer. The honeycomb core comprises a plurality of cell walls defining a plurality of cells. Some of the cells are in fluid communication with one another via the openings formed in the cell walls. The openings in the cell walls cause viscous acoustic losses, resulting in acoustic energy dissipation and enhanced noise attenuation.

Abstract: In an aircraft turbine, an assembly consisting of an air inlet structure, a air blower housing (22) and a connecting part (36), is fitted in such a way as to reduce noise including in the junction area between the structure and the housing. The connecting part (36) is fastened onto a rear section (20'), not provided with a honeycomb core, of the internal wall (20) of the air inlet structure. A honeycomb structure (44) is fitted inside the air blower housing (22). The space inside the rear section (20') houses a forward extension (44') of the honeycomb structure (44), or a different honeycomb structure.

Abstract: An array of adaptive or fixed Herschel-Quincke tubes aligned in a circumferential or helical array about an inlet of a turbofan engine. The array of tubes effectively divide the acoustic energy generated by the engine. One of the energy components propagates within the tubes while the other propagates within the engine compartment. At some time certain, the acoustic energy in the tubes is reintroduced into the engine compartment to cancel the acoustic energy remaining in the engine as it propagates from the fan towards the inlet and outlet openings.

Abstract: Muffler with catalytic converter (1) essentially arranged in direct connection with a combustion engine's exhaust port and especially intended for portable working tools such as chain saws. At least one partition (2) is embodied in the muffler, or instance in the form of a baffle (3), and the partition (2) comprises one or several apertures (9, 10), through which the exhaust flow passes in order to flow from one side of the partition to the other side, and the partition is at least partly coated with a catalyzing layer.

Abstract: A jet engine has a noise reduction system which reduces the boundary layer located on the outer surface of the nacelle. The noise reduction system includes a plurality of openings located in the outer surface of the nacelle which are in communication with a source of low pressure. The low pressure causes a reduction in the boundary layer at the openings so that resulting ambient air flow velocity near the nacelle surface is increased. This causes a reduction in the shearing between the secondary and ambient airflows thereby reducing the noise.

Abstract: Providing encapsulated electronic components on a circuit board by providing dams on a circuit board around areas on which respective electronic components will be mounted, mounting the respective electronic components within the dams on the circuit board, and printing encapsulating material through a stencil in order to provide deposits of encapsulating material over the electronic components and within the dams.

Abstract: A flue-gas duct of a gas and steam-turbine plant is constructed in such a way that reliable sound absorption is ensured with especially simple provisions, even when using internally insulated duct pieces, in particular an internally insulated waste-heat boiler. The flue-gas duct includes a duct piece having a number of sound-absorber gates. At least one sound-absorber gate has a displacement nose disposed upstream thereof on the flue-gas side. A gas-switch module having a displaceable shut-off damper is disposed downstream of the duct piece which is constructed as a sound-absorber module, on the flue-gas side. The shut-off damper includes first and second substantially mutually perpendicularly oriented shut-off plates.

Abstract: An improved acoustic panel (26) for the nacelle (20) of a high bypass jet engine. The acoustic panel (26) has a perforated composite inner sheet (54), an outer composite sheet (96, 98), and a new reinforcement structure, or pre-cured doubler (62) therein. The pre-cured doubler (62) is arranged to receive a load applied to the acoustic panel (26), and includes a face sheet (64) connected to a structural attachment area (52) of the perforated composite inner sheet (54). A structurally-reinforced core (63) is connected the face sheet (64). Preferably, the width of the face sheet (64) in an air flow direction of the acoustic panel (26) is substantially equal to the width of the structurally reinforced core (63) in the air flow direction. The pre-cured doubler (62) provides increase acoustic area in parts of the acoustic panel adjacent to attachment fittings (46). Expanded epoxy (87a) is also used to reinforce side edges and selected areas of the acoustic core (60) for the acoustic panel (26).

Abstract: The present invention is noise attenuation system and related method for suppressing noise generated by a noise source, such as a jet engine, contained in a housing. An impedance device is positioned in the housing to attenuate the amplitude of sound waves generated by the noise source propagating in one direction and to create a reflected sound wave. The reflected sound wave is out of phase with the sound waves propagating from the noise source away from the impedance device. The reflected sound wave destructively interferes with this sound wave to attenuate the amplitude.

Abstract: An extended reaction acoustic liner for use in jet engine noise mitigation has a substantially non-porous outer layer, a honeycomb core disposed in laminar juxtaposition to the outer layer, and a porous inner layer in laminar juxtaposition to the honeycomb core such that the honeycomb core is sandwiched between the outer layer and the inner layer. The honeycomb core comprises a plurality of cell walls defining a plurality of cells. Some of the cells are in fluid communication with one another via the openings formed in the cell walls. The openings in the cell walls cause viscous acoustic losses, resulting in acoustic energy dissipation and enhanced noise attenuation.

Abstract: A middle layer (22) having partitioned cavities (28) is sandwiched between an imperforate sheet (24) and an optional perforate sheet (26) to form a low resistance acoustic liner (22). A preferred method of manufacture of the low resistance acoustic liner (20) uses aspects of the buried septum technique including placing an uncured imperforate septum (36) between a support layer (32) and a partitioned cavity middle layer (22), pressing the middle layer into the imperforate sheet (24) and through the support layer (32), curing the imperforate septum 36 to form the imperforate sheet (24), removing the support layer (32), and attaching a perforate sheet (26) of roughly at least 15% open area to the top side of the middle layer. A preferred embodiment of inner and outer linings (47), (49) is provided. Each lining includes a combination of annuluses of absorptive and/or low resistance liners (51), (53).

Abstract: An aircraft engine has a nozzle shaped to reduce the volume of Mach diamonds being formed in the exhaust plume. A notch or recess is formed in the discharge edge of the nozzle. The recess provides a forward discharge edge that causes additional Mach diamonds to occur at a regular spacing from the forward discharge edge. These additional Mach diamonds are axially staggered with other Mach diamonds, which occur at regular spacing from the rearward edge of the nozzle discharge edge. Each Mach diamond has a volume that is substantially less than one-half the volume of a Mach diamond created by a conventional nozzle. This results in less high temperature areas per axial increment in the plume than the prior art exhaust plumes. Because Mach diamonds are the primary cause of high infrared emissions, as well as acoustic noise, a reduction in the total volume of Mach diamonds in the exhaust plume thus reduces infrared emissions, as well as the noise.

Abstract: A method for suppressing noise in a turbofan engine includes segmenting coaxial inner and outer flow streams into circumferentially interleaved inner and outer segments beginning at a common location along the engine axis, diverting additional portions of the outer stream radially inwardly from an axial location downstream of the common location and combining the inner segments, the outer segments and the additional portions into a common stream so that the additional portions are introduced into discrete radial locations in the common stream. The diverted additional portions of the outer stream eliminate localized regions of hot, high velocity gases in the combined stream to achieve improved noise suppression.

Abstract: An acoustic liner jet engine inlet barrel is formed from a perforated permeable skin, a honeycomb core, and a solid facesheet, each of which is formed in a one-piece configuration such that at most only a narrow single fore-to-aft splice, or no spice at all, is present in the finished product. The acoustic modal content remains unaffected, thus preserving a high degree of liner effectiveness, increasing the total active acoustic area of the barrel while decreasing its weight, and increasing its durability.

Abstract: A noise reduction system is provided for installation on a bypass turbine having a core engine, an outer casing and a thrust reverser. The system is comprised of an acoustically treated nose cowl conventional for the engine; a respaced inlet guide vane upstream of the core engine for reducing wake disturbances striking the engine fan; a flow diverter downstream of the core engine for turning fan air inward toward the engine center line and for turning core air outward; a structure for supporting and positioning said flow diverter relative to the engine; a core flow expansion chamber device for slowing the peak velocity of the exhaust gas prior to exhausting it to the atmosphere; and an acoustic tailpipe assembly configured to define an outlet area sized and shaped to compensate for the mass flow loss created by the core flow expansion chamber device.

Abstract: The invention relates to combined catalytic converter and muffler device intended for attachment to the exhaust pipe of an engine, e.g. on a lawn mower. The device comprises a housing within which a catalytic substance (14) is arranged. According to the invention, the exhaust gas inlet (3) is provided with a restriction, preferably in the form of a cone (6). Thereby, an intake of a suitable amount of air is achieved through an air inlet (7), preferably comprising an air labyrinth (8). The catalytic substance (14) is preferably provided in pellet form and arranged in an annular chamber in the housing, having a circular shape. A muffling substance (16) made of glass fibre ceramics is preferably arranged in a chamber (15) outside of the catalytic substance (14).

Abstract: A hush kit for jet aircraft engine includes a respaced inlet guide vane to provide an increased space between the fixed guide vanes of the inlet and the rotating fan blades of the fan connected to the core engine, a mixer for mixing hot exhaust gas from the core engine with colder bypass fan air, and an acoustic barrel to reduce the noise generated by the mixed air flowing through the thrust reverser downstream of the core engine. The acoustic barrel includes an outer imperforate layer, an inner perforate layer and a multi-cellular core sandwiched therebetween. The ratio of the thickness of the multi-cellular core to the open area defined by the holes in the inner perforate skin of the acoustic barrel is designed to reduce noise of a particular frequency range generated by the aircraft engine. In combination, each of the components of the hush kit described herein reduce noise generated by the jet engine for compliance with Federal Aviation Administration noise reduction requirements.

Abstract: An acoustic structure for use as a sound insulator in a jet engine is disclosed. The structure, which is carried in a sound-absorbing compartment of the engine, includes a framework and an acoustical insulation material disposed within the framework. The material is composed of a rigid matrix of randomly oriented, fused silica fibers having fiber diameters predominantly in the range 2-8 .mu.m, a three-dimensionally continuous network of open, intercommunicating voids, a flow resistivity between about 10-200K rayls/m, and a density of between about 2 and 8 lb/ft3. Also disclosed are a clad acoustical structure for sound attenuation in a jet engine, where operational temperatures exceed current jet engine designs, and a method of attenuating jet engine noise.

Abstract: A method and device for reducing the amount of noise generated by a supersonic jet engine is provided. The method creates an envelope of air around the supersonic jet exhaust. The temperature and velocity of this envelope is controlled to eliminate or reduce the formation of noise making Mach waves.

Abstract: An acoustic liner jet engine inlet barrel is formed from a perforated permeable skin, a honeycomb core, and a solid facesheet, each of which is formed in a one-piece configuration such that at most only a narrow single fore-to-aft splice, or no splice at all, is present in the finished product. The acoustic modal content remains unaffected, thus preserving a high degree of liner effectiveness, increasing the total active acoustic area of the barrel while decreasing its weight, and increasing its durability.

Abstract: A shear layer of a fluid flow has relatively large vortical structures generated by acoustic forcing from oscillations induced in a cavity closely adjacent to the flow so that these structures enhance mixing at the layer. The forcing frequency is selected by varying the dimensions of the cavity, and several cavities of different dimensions may be provided for forcing at different frequencies, including beat frequencies. The cavity provides passive, high amplitude forcing effective with a compressible shear layer due to high speed flow, including supersonic flow. Cavities of differing configuration provide forcing for fluid flow from nozzles of different geometries. The most effective enhancement is provided by particular excitation frequencies generated by a cavity having a size selected in accordance with dimensionless relations between the flow parameters and nozzle geometry.

Abstract: Single expansion ramp to extend from the exhaust opening of a fluid nozzle. A surface of the ramp lying adjacent to fluid flow exhausting the nozzle is porous. The ramp of the present invention reduces the shock wave noise resulting from supersonic flow exhausting the nozzle by causing the formation of weak compression waves in the exhaust plume, which in turn weaken the strength of the standing shock waves in the plume.

Abstract: Apparatus for the interference and manipulation of vortex formation and control of fluid flow to reduce noise and increase flow stability is provided. A specific embodiment is directed to a flexible jet noise suppressor for aircraft, particularly supersonic transport. The jet noise suppressor comprises at least one flexible filament having a length that is about 3 to 10 nozzle diameters. The filament(s) trail behind the nozzle and may be let out for take-off and climb and reeled in while the aircraft is in flight or on the ground. Surprisingly, the use of a single flexible filament eliminates the well-known "screech noise" at about 3,000 Hz and reduces the screech noise by about 50 dB while further reducing the broad band noise up to 15 dB over the entire sound spectrum.

Abstract: The damping system comprises at least one resonant acoustic cavity disposed around the combustion chamber and having a shape and dimensions such that it functions simultaneously as a quarter-wave resonator and with tangential coupling the resonant acoustic cavity comprises:a) a main annular part whose half axial section has a very elongate shape with a width dimension "e" which is very small compared to its longitudinal dimension "L.sub.1 " which extends substantially parallel to the axis of symmetry of the combustion chamber, the mean radius "R" of the main annular part being close to the equivalent radius of modes of oscillation to be damped, and b) an annular coupling part which originates from the main annular part and which opens into the combustion chamber near to a longitudinal or radial pressure anti-node, the annular coupling part having a length "L.sub.2 " in a half axial section and a width dimension "h" very much less than the sum of the longitudinal dimension "L.sub.

Abstract: The present invention generally relates to providing an improved jet mixer noise suppressor for high speed jets that rapidly mixes high speed air flow with a lower speed air flow, and more particularly, relates to an improved jet mixer noise suppressor that uses feedback of acoustic waves produced by the interaction of sheer flow instability waves with an obstacle downstream of the jet nozzle.

Abstract: A gas turbine engine flow mixer includes at least one chute having first and second spaced apart sidewalls joined together at a leading edge, with the sidewalls having first and second trailing edges defining therebetween a chute outlet. The first trailing edge is spaced longitudinally downstream from the second trailing edge for defining a septum in the first sidewall extending downstream from the second trailing edge. The septum includes a plurality of noise attenuating apertures.

Abstract: A mixing nozzle for an aircraft turbine engine having an improved aerodynamic stiffening ring secured to the lobes of the mixer. Aircraft turbine engines having a rearwardly discharging nozzle are often provided with a mixer having a generally circular forward end adapted to be attached to an engine and axially deepening corrugations leading to a multi-lobed aft end surrounding the nozzle. This mixer mixes ambient cool air with the hot gases exiting the engine thus suppressing engine sound. The lobes are generally unsupported and subject to vibration and excessive deflections in use. A circumferential stiffening ring is secured to the aft end of the mixer to reduce or prevent the vibration while simultaneously enhancing the mixing of cool ambient air with the hot engine exhaust. The stiffening ring preferably has an airfoil cross-section for lowest drag combined with the ability to direct flow past the ring in a selected optimum direction.

Abstract: A noise suppressor for attachment to the aft end of an existing turbojet engine. The noise suppressor includes a free-running turbofan wheel which includes a turbine section mounted for reaction to the exhaust gas from the jet engine, and a concentric outer fan section extending within an air duct concentric with the turbofan wheel. The jet exhaust from normal operation of the jet engine spins the free-running turbofan wheel, and the fan section of that wheel produces a flow of compressed air through the duct to surround and mix with the jet exhaust, thereby reducing the noise emission of the jet engine. A thrust reverser and an afterburner are optional for use with the noise suppressor.

Abstract: A noise suppressor for use with a turbofan engine, the suppressor being formed of a tubular exhaust shroud affixed to the engine exhaust end, the shroud providing an internal circumferential surface, a flow mixture affixed to the engine exhaust end, an elongated centerbody supported within the exhaust shroud and having an external cross-sectional area less than the internal cross-sectional area of the shroud providing an annular area through which thrust producing exhaust gases of the engine pass, acoustic lining affixed to a substantial portion of the internal circumferential area of the exhaust shroud in the portion thereof receiving the centerbody, and acoustical lining affixed to a substantial portion of the exterior area of the centerbody in the area thereof received within the exhaust shroud so that thereby the thrust producing gases pass through an area of reduced channel height. A substantial portion of the annular area through which the gases pass is encompassed by acoustical lining.

Abstract: A noise reduction kit is provided for installation on a bypass turbine engine having a core engine, an outer casing and a thrust reverser. The kit comprises a mixer downstream of the core engine for mixing fan air of the engine with the exhaust gas from the core engine to reduce the peak velocity of the exhaust gas; a structure for supporting and positioning said mixer relative to the engine; a spacer for extending the length of the exhaust gas flow path between said mixer and the thrust reverser to permit sufficient mixing of the fan air with the exhaust gas prior to reaching the thrust reverser; and an acoustic tail pipe assembly configured to define an outlet area for the engine exhaust gas flow path. The outlet area is sized and shaped to reduce pressure loss in the exhaust gas stream in an amount necessary to compensate for the pressure increase in the exhaust gas stream created by the mixer.

Abstract: In order to reduce turbine engine exhaust noise while simultaneously reducing anti-surge airflow noise, a combination noise reduction apparatus or tube (10) is provided having a series of holes (26) in its side. The tube (10) is in communication with a source of anti-surge air through an anti-surge air outlet (22) to be delivered into the exhaust airflow in an exhaust duct (12). The tube (10) diffuses the anti-surge air, shields the noise of the anti-surge air by dissipating the acoustic energy within the tube (10), and provides for an even distribution of the anti-surge air into the exhaust airflow. As a result, a temperature discontinuity is created in the exhaust duct (12) which results in an acoustic impedance that reflects acoustic noise back to the source of the noise.