US3635308A - Sound suppression system - Google Patents
Sound suppression system Download PDFInfo
- Publication number
- US3635308A US3635308A US838947A US3635308DA US3635308A US 3635308 A US3635308 A US 3635308A US 838947 A US838947 A US 838947A US 3635308D A US3635308D A US 3635308DA US 3635308 A US3635308 A US 3635308A
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- Prior art keywords
- lobes
- shroud
- nozzle
- gaseous mixture
- flow
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- Expired - Lifetime
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- 230000001629 suppression Effects 0.000 title claims description 8
- 239000003570 air Substances 0.000 claims abstract description 25
- 239000008246 gaseous mixture Substances 0.000 claims abstract description 18
- 239000012080 ambient air Substances 0.000 claims abstract description 15
- 239000000203 mixture Substances 0.000 claims abstract description 4
- 238000007599 discharging Methods 0.000 claims description 6
- 230000002093 peripheral effect Effects 0.000 claims description 4
- 238000000034 method Methods 0.000 claims 1
- 230000008901 benefit Effects 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 240000001829 Catharanthus roseus Species 0.000 description 1
- 244000089486 Phragmites australis subsp australis Species 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000008439 repair process Effects 0.000 description 1
Images
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02K—JET-PROPULSION PLANTS
- F02K1/00—Plants characterised by the form or arrangement of the jet pipe or nozzle; Jet pipes or nozzles peculiar thereto
- F02K1/40—Nozzles having means for dividing the jet into a plurality of partial jets or having an elongated cross-section outlet
Definitions
- ABSTRACT System includes a shroud immediately downstream of turbine exhaust nozzle to form confined zone to receive turbine discharge.
- Conduit which preferably surrounds nozzle, supplies fan air to mix with exhaust gas in zone, cool it, and increase mass flow.
- Shroud is corrugated to form peripherally spaced, radially extending lobes to discharge gaseous mixture. Spaces between lobes define flow paths for ambient air to flow between lobes and mix with gaseous mixture at fluted exit margin to further attenuate noise.
- This invention lies in the field of sound suppression of gas turbine or jet engines, which produce reaction thrust by ejecting a high-velocity stream of gas from the exhaust nozzle or tailpipe of the gas turbine.
- One of the problems of airplanes equipped with jet engines on which a great deal of efforthas been expended is that the exhaust stream creates a very high level of sound energy or noise" in a wide range of frequencies, and a portion of this noise reaches the ground from lowflying airplanes, as during takeoff and climb, at an energy level which is not acceptable to the public.
- the invention is directed to a system in which air is mixed with the exhaust gas to cool it and add mass and to raise the sound frequencies to levels which are more readily attenuated. It is directed particularly to a system of this type applied to a fan-jet engine in which maximum use is made of the fan air in reducing the noise level. While various schemes have been proposed for applying sound suppression systems to fan-jet engines, so far as known none of them has made use of both fan air and ambient air in a manner which will produce the most effective results.
- the present invention provides a very satisfactory solution to the problem with a minimum amount of equipment and with no moving parts requiring repair' and maintenance.
- the system includes a shroud which is positioned immediately downstream of the engine exhaust nozzle to form a confined discharge zone for the turbineexhaust.
- the fan air is fed into this zone and mixes thoroughly with the exhaust gas, cooling it, and increasing the mass flow.
- the turbulence of mixing also raises the frequencies.
- the fan air conduit completely surrounds the exhaust nozzle, providing maximum area of mixing contact.
- the forward end of the shroud is preferably circular or cylindrical to form a virtual continuation of the fan air conduit and the balance is formed with gradually deepening. corrugations defining a plurality of peripherally spaced radiallyextending lobes which constitute rearwardly directed discharge passages for the gaseous mixture of exhaust gas and .fan air.
- the spaced lobes define between them rearwardly converging flow paths for ambient air and the streams come into contact at the fluted exit margin of the shroud.
- the peripheral extent of the exit margin is about twice as great as the circumference of the forward end of the shroud, thus doubling the junction line and doubling the mixing effectiveness.
- FIG. 1 is a schematic side elevational view of a fan-jet engine incorporating the invention.
- FIG. 2 is a schematic rear elevational view of the engine.
- FIG. 1 The general arrangement of the invention is illustrated in FIG. 1, in which a typicalv jet engine'10 having an exhaust'nozzle 12 is circumscribed by a double-walled fan air duct or'conduit means 14 enclosed in a housing 16 which-maybe a
- the shroud serves as a confined discharge zone 22 to contain and direct the flow of the gaseous mixture.
- the fan air flowing from duct 14 completely surrounds the gas stream issuing from the engine nozzle to provide the maximum area of mixing contact.
- the exhaust gas is cooled and. the mass of the air is added to it before the gaseous mixture is discharged, and the sound energy level is already greatly reduced.
- the balance of the shroud is formed with gradually deepening corrugations defining a plurality of peripherally spaced and radially extending lobes 24. These lobes are open at their aft ends to constitute reanvardly directed discharge passages for the gaseous mixtureof exhaust gas and fan air. They also define between them an equal number of flow passages 26 for ambient air, which passages are of maximum depth at the fluted exit margin 28 of theshroud.
- the total peripheral extent of the exit margin is approximately twice as great as the circumference of the forward end 20 or a reference circle circumscribing the lobes.
- the junction line of mixing contact between the gaseous mixture and the ambient air is twice as great as if the shroud were formed as a cylinder.
- a streamlined plug 30, coaxial with the engine centerline, may be located with its maximum diameter in the plane of exit margin 28.
- the plug is about one-third of the diameter of the shroud and the radial extent of each lobe is about two-thirds of the radius of the shroud.
- the location of theplug tends to force the exhaust gas outwardly and the convergence of the ambient airflow passages 26 tends to force some of the fan air inwardly in discrete portions.
- peripheral length of said exit margin being approximately twice the circumference of a reference circle circumscribing said lobes.
- conduit means being generally cylindrical and surrounding the, turbine exhaust nozcomprising: discharging the turbine exhaust gas stream into a confined zone; discharging the fan air into the same zone and dividing the fan air into a plurality of separate streams therein to mix with the exhaust gas and cool it; and discharging the gaseous mixture into further mixing relation with a flow of ambient air efiectively enhanced by said division of the fan air to further cool the mixture and raise the frequency level.
Abstract
System includes a shroud immediately downstream of turbine exhaust nozzle to form confined zone to receive turbine discharge. Conduit, which preferably surrounds nozzle, supplies fan air to mix with exhaust gas in zone, cool it, and increase mass flow. Shroud is corrugated to form peripherally spaced, radially extending lobes to discharge gaseous mixture. Spaces between lobes define flow paths for ambient air to flow between lobes and mix with gaseous mixture at fluted exit margin to further attenuate noise.
Description
United States Patent Millman 451 Jan. 18,1972
[54] SOUND SUPPRESSION SYSTEM [72] inventor: Victor Millman, San Diego, Calif.
[73] Assignee: Rohr Corporation, Chula Vista, Calif.
[22] Filed: July 3, 1969 [21] Appl. No.2 838,947
[52] U.S.Cl ..l8l/33 HC,239/127.3,239/265.l7,
v 181/51 [51] lnt.C1 ..B64d 33/06, F01n 1/14 [58] Field of Search ..181/33, 43, 51, 33.21, 33.22, 18l/33.221, 33.222; 239/1273, 265.11, 265.13,
[56] References Cited UNlTED STATES PATENTS 2,934,889 5/1960 Poulds..... ..18l/33 HC 3,027,? 10 4/1962 Maytner. ....239/127.3 3,053,340 9/1962 Kutney ...18l/33 HC 3,262,264 7/1966 Gardiner et al. ..181/33 HC 3,390,837 7/1968 Freeman ..239/265.l7 3,409,228 ll/l968 Mehr ..239/l65.l7 X 3,463,402 8/1969 Langston.... v ..l 81/33 HC FORElGN PATENTS OR APPLICATIONS 1,032,274 6/1966 Great Britain ..l8i/33 HC Primary Examiner-Robert S. Ward, Jr. Attorney-George E. Pearson [57] ABSTRACT System includes a shroud immediately downstream of turbine exhaust nozzle to form confined zone to receive turbine discharge. Conduit, which preferably surrounds nozzle, supplies fan air to mix with exhaust gas in zone, cool it, and increase mass flow. Shroud is corrugated to form peripherally spaced, radially extending lobes to discharge gaseous mixture. Spaces between lobes define flow paths for ambient air to flow between lobes and mix with gaseous mixture at fluted exit margin to further attenuate noise.
7 Claims, 2 Drawing Figures PATENIEnJmm 3,535,308
ENTOR. VICTOR LMAN BY Quad AT TORNEY SOUND SUPPRESSION SYSTEM BACKGROUND OF THE INVENTION This invention lies in the field of sound suppression of gas turbine or jet engines, which produce reaction thrust by ejecting a high-velocity stream of gas from the exhaust nozzle or tailpipe of the gas turbine. One of the problems of airplanes equipped with jet engines on which a great deal of efforthas been expended is that the exhaust stream creates a very high level of sound energy or noise" in a wide range of frequencies, and a portion of this noise reaches the ground from lowflying airplanes, as during takeoff and climb, at an energy level which is not acceptable to the public.
The invention is directed to a system in which air is mixed with the exhaust gas to cool it and add mass and to raise the sound frequencies to levels which are more readily attenuated. It is directed particularly to a system of this type applied to a fan-jet engine in which maximum use is made of the fan air in reducing the noise level. While various schemes have been proposed for applying sound suppression systems to fan-jet engines, so far as known none of them has made use of both fan air and ambient air in a manner which will produce the most effective results.
SUMMARY OF THE INVENTION The present invention provides a very satisfactory solution to the problem with a minimum amount of equipment and with no moving parts requiring repair' and maintenance. Generally stated, the system includes a shroud which is positioned immediately downstream of the engine exhaust nozzle to form a confined discharge zone for the turbineexhaust. The fan air is fed into this zone and mixes thoroughly with the exhaust gas, cooling it, and increasing the mass flow. The turbulence of mixing also raises the frequencies. Preferably the fan air conduit completely surrounds the exhaust nozzle, providing maximum area of mixing contact.
The forward end of the shroud is preferably circular or cylindrical to form a virtual continuation of the fan air conduit and the balance is formed with gradually deepening. corrugations defining a plurality of peripherally spaced radiallyextending lobes which constitute rearwardly directed discharge passages for the gaseous mixture of exhaust gas and .fan air. The spaced lobes define between them rearwardly converging flow paths for ambient air and the streams come into contact at the fluted exit margin of the shroud. The peripheral extent of the exit margin is about twice as great as the circumference of the forward end of the shroud, thus doubling the junction line and doubling the mixing effectiveness.
Thus, there is a first thorough mixing of the exhaustigas and the fan air in a confined discharge zone followed by contact of the gaseous mixture along a practically maximum line with the ambient air to achieve the greatest possible mixing and cooling of the jet stream and maximum sound suppression.
BRIEF DESCRIPTION OF THE DRAWINGS Various other advantages and features of novelty will become apparent as the description proceeds in conjunction with the accompanying drawing, in which:
FIG. 1 is a schematic side elevational view of a fan-jet engine incorporating the invention; and
FIG. 2 is a schematic rear elevational view of the engine.
DESCRIPTION OF THE PREFERRED EMBODIMENT The general arrangement of the invention is illustrated in FIG. 1, in which a typicalv jet engine'10 having an exhaust'nozzle 12 is circumscribed by a double-walled fan air duct or'conduit means 14 enclosed in a housing 16 which-maybe a The shroud serves as a confined discharge zone 22 to contain and direct the flow of the gaseous mixture.
The fan air flowing from duct 14 completely surrounds the gas stream issuing from the engine nozzle to provide the maximum area of mixing contact. Thus the exhaust gas is cooled and. the mass of the air is added to it before the gaseous mixture is discharged, and the sound energy level is already greatly reduced.
Starting adjacent to the forward end 20, the balance of the shroud is formed with gradually deepening corrugations defining a plurality of peripherally spaced and radially extending lobes 24. These lobes are open at their aft ends to constitute reanvardly directed discharge passages for the gaseous mixtureof exhaust gas and fan air. They also define between them an equal number of flow passages 26 for ambient air, which passages are of maximum depth at the fluted exit margin 28 of theshroud.
With this construction and arrangement, the total peripheral extent of the exit margin is approximately twice as great as the circumference of the forward end 20 or a reference circle circumscribing the lobes. Thus the junction line of mixing contact between the gaseous mixture and the ambient air is twice as great as if the shroud were formed as a cylinder.
In addition, a streamlined plug 30, coaxial with the engine centerline, may be located with its maximum diameter in the plane of exit margin 28. The plug is about one-third of the diameter of the shroud and the radial extent of each lobe is about two-thirds of the radius of the shroud. The location of theplug tends to force the exhaust gas outwardly and the convergence of the ambient airflow passages 26 tends to force some of the fan air inwardly in discrete portions. These two factors ensure a thorough mixing of the exhaust gas and the fanair.
Thus'it will be apparent that a system has been devised to take advantage of the availability of fan air in a fan-jet engine by first mixing it directly and thoroughly with the turbine exhaust gas in a confined zone to appreciably lower the sound level, and then mixing the resultant gaseous mixture with ambient air with the maximum practical area of contact for further noise reduction. The improvement has been accom plished with a minimum amount of material and weight and the system functions with complete reliability.
What is claimed as new and useful and desired to be secured by US. Letters Patent is:
l. A sound suppression system for a fan-jet engine having a turbine exhaust nozzle of circular configuration in the region of its exit plane, said nozzle having a discharge zone extending immediately downstream of its exit plane, comprising: conduit means surrounding said nozzle to supply fan air to said discharge zone of said nozzle for mixing with the turbine exhaust gas stream to cool the stream and increase the mass flowyand a shroud extension of said conduit means surrounding the discharge zone to contain and direct the flow of the gaseous mixture; said shroud being corrugated to define a plurality of peripherally spaced, radially extending lobes; each lobe'constituting arearwardly directed discharge passage for a portion of the gaseous mixture; each pair of adjacent lobes defining between them a flow passage for ambient air; the fluted exit margin of said shroud providing an elongated junction line for mixing of the ambient air with the gaseous mixture.
2. A system as claimed in claim 1; the peripheral length of said exit margin being approximately twice the circumference of a reference circle circumscribing said lobes.
3. A system as claimed in claim 1; said lobes each having a radial extent equal to approximately two-thirds of the radius of theircircumscribing circle.
4. A system as claimed in claim 3; including a streamlined plug coaxial with the engine and occupying the space between the innerends of said lobes.
5. A system as claimed in claim 1; said conduit means being generally cylindrical and surrounding the, turbine exhaust nozcomprising: discharging the turbine exhaust gas stream into a confined zone; discharging the fan air into the same zone and dividing the fan air into a plurality of separate streams therein to mix with the exhaust gas and cool it; and discharging the gaseous mixture into further mixing relation with a flow of ambient air efiectively enhanced by said division of the fan air to further cool the mixture and raise the frequency level.
i l 1 l 9
Claims (7)
1. A sound suppression system for a fan-jet engine having a turbine exhaust nozzle of circular configuration in the region of its exit plane, said nozzle having a discharge zone extending immediately downstream of its exit plane, comprising: conduit means surrounding said nozzle to supply fan air to said discharge zone of said nozzle for mixing with the turbine exhaust gas stream to cool the stream and increase the mass flow; and a shroud eXtension of said conduit means surrounding the discharge zone to contain and direct the flow of the gaseous mixture; said shroud being corrugated to define a plurality of peripherally spaced, radially extending lobes; each lobe constituting a rearwardly directed discharge passage for a portion of the gaseous mixture; each pair of adjacent lobes defining between them a flow passage for ambient air; the fluted exit margin of said shroud providing an elongated junction line for mixing of the ambient air with the gaseous mixture.
2. A system as claimed in claim 1; the peripheral length of said exit margin being approximately twice the circumference of a reference circle circumscribing said lobes.
3. A system as claimed in claim 1; said lobes each having a radial extent equal to approximately two-thirds of the radius of their circumscribing circle.
4. A system as claimed in claim 3; including a streamlined plug coaxial with the engine and occupying the space between the inner ends of said lobes.
5. A system as claimed in claim 1; said conduit means being generally cylindrical and surrounding the turbine exhaust nozzle to supply fan air to the entire periphery of the turbine discharge.
6. A system as claimed in claim 5; the forward end of said shroud being substantially cylindrical to form a virtual continuation of said conduit; and the flow passages for ambient air converging rearwardly to achieve full depth at the exit margin of the shroud.
7. A method of reducing the noise level of a fan-jet engine, comprising: discharging the turbine exhaust gas stream into a confined zone; discharging the fan air into the same zone and dividing the fan air into a plurality of separate streams therein to mix with the exhaust gas and cool it; and discharging the gaseous mixture into further mixing relation with a flow of ambient air effectively enhanced by said division of the fan air to further cool the mixture and raise the frequency level.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US83894769A | 1969-07-03 | 1969-07-03 |
Publications (1)
Publication Number | Publication Date |
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US3635308A true US3635308A (en) | 1972-01-18 |
Family
ID=25278462
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US838947A Expired - Lifetime US3635308A (en) | 1969-07-03 | 1969-07-03 | Sound suppression system |
Country Status (1)
Country | Link |
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US (1) | US3635308A (en) |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4813635A (en) * | 1986-12-29 | 1989-03-21 | United Technologies Corporation | Projectile with reduced base drag |
US4835961A (en) * | 1986-04-30 | 1989-06-06 | United Technologies Corporation | Fluid dynamic pump |
US5058703A (en) * | 1987-11-23 | 1991-10-22 | United Technologies Corporation | Automotive exhaust noise attenuator |
US20090013675A1 (en) * | 2007-07-13 | 2009-01-15 | Paccar Inc | Flow diffuser for exhaust pipe |
US20090014235A1 (en) * | 2007-07-13 | 2009-01-15 | Paccar Inc | Flow diffuser for exhaust pipe |
US20090120066A1 (en) * | 2007-11-14 | 2009-05-14 | Paccar Inc. | Cooling device for high temperature exhaust |
Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2934889A (en) * | 1956-02-14 | 1960-05-03 | United Aircraft Corp | Noise abatement means |
US3027710A (en) * | 1960-10-10 | 1962-04-03 | Stephen P Maytner | Methods and apparatus for suppressing jet noise |
US3053340A (en) * | 1958-07-21 | 1962-09-11 | Gen Electric | Noise suppression nozzle |
GB1032274A (en) * | 1962-03-03 | 1966-06-08 | Messerschmitt Ag | Mounting of ducted fan turbine engines in the tail of an aircraft |
US3262264A (en) * | 1962-09-03 | 1966-07-26 | Bristol Siddeley Engines Ltd | Jet propulsion power plant |
US3390837A (en) * | 1965-12-08 | 1968-07-02 | Gen Electric | Convergent-divergent plug nozzle having a plurality of freely-floating tandem flaps |
US3409228A (en) * | 1966-02-10 | 1968-11-05 | Gen Electric | Ejector nozzle |
US3463402A (en) * | 1966-12-28 | 1969-08-26 | United Aircraft Corp | Jet sound suppressing means |
-
1969
- 1969-07-03 US US838947A patent/US3635308A/en not_active Expired - Lifetime
Patent Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2934889A (en) * | 1956-02-14 | 1960-05-03 | United Aircraft Corp | Noise abatement means |
US3053340A (en) * | 1958-07-21 | 1962-09-11 | Gen Electric | Noise suppression nozzle |
US3027710A (en) * | 1960-10-10 | 1962-04-03 | Stephen P Maytner | Methods and apparatus for suppressing jet noise |
GB1032274A (en) * | 1962-03-03 | 1966-06-08 | Messerschmitt Ag | Mounting of ducted fan turbine engines in the tail of an aircraft |
US3262264A (en) * | 1962-09-03 | 1966-07-26 | Bristol Siddeley Engines Ltd | Jet propulsion power plant |
US3390837A (en) * | 1965-12-08 | 1968-07-02 | Gen Electric | Convergent-divergent plug nozzle having a plurality of freely-floating tandem flaps |
US3409228A (en) * | 1966-02-10 | 1968-11-05 | Gen Electric | Ejector nozzle |
US3463402A (en) * | 1966-12-28 | 1969-08-26 | United Aircraft Corp | Jet sound suppressing means |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4835961A (en) * | 1986-04-30 | 1989-06-06 | United Technologies Corporation | Fluid dynamic pump |
US4813635A (en) * | 1986-12-29 | 1989-03-21 | United Technologies Corporation | Projectile with reduced base drag |
US5058703A (en) * | 1987-11-23 | 1991-10-22 | United Technologies Corporation | Automotive exhaust noise attenuator |
US20090013675A1 (en) * | 2007-07-13 | 2009-01-15 | Paccar Inc | Flow diffuser for exhaust pipe |
US20090014235A1 (en) * | 2007-07-13 | 2009-01-15 | Paccar Inc | Flow diffuser for exhaust pipe |
US7971432B2 (en) | 2007-07-13 | 2011-07-05 | Paccar Inc | Flow diffuser for exhaust pipe |
US20090120066A1 (en) * | 2007-11-14 | 2009-05-14 | Paccar Inc. | Cooling device for high temperature exhaust |
US8046989B2 (en) | 2007-11-14 | 2011-11-01 | Paccar Inc | Cooling device for high temperature exhaust |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: ROHR INDUSTRIES, INC.,CALIFORNIA Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:CITIBANK, N. A.;REEL/FRAME:004201/0686 Effective date: 19830819 Owner name: ROHR INDUSTRIES, INC. Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:CITIBANK, N. A.;REEL/FRAME:004201/0686 Effective date: 19830819 |