US3463402A - Jet sound suppressing means - Google Patents

Description

c. E. LANGsToN, JR 3,463,402

JET SOUND sUPPREssING MEANS 4 Sheets-Sheet l Aug. 26, 1969 Filed Dec. 28, 1966 Aug 26,` 1969 c. E. LANGsToN, JR 3,463,402

JET SOUND SUPPRESSING MEANS Filed Deo. 28, 1966 4 Sheets-Sheet 2 U8 26 1969 c. E. LANGsroN, JR 3,463,402

JET SOUND SUPPRBSSING MEANS Filed Dec. 28, 1966 4 Sheets-Sheet 3 Aug. 26, 1969 c. e. LANGs'roN. JR

.JETSOUND sUPPRr-:ssmo MEANS Filed Dec. 28, 1966 4 Sheets-Sheet United States Patent O i 3,463,402 JET SOUND SUPPRESSING MEANS Chandos E. Langston, Jr., North Palm Beach, Fla., as-

signor to United Aircraft Corporation, East Hartford,

Conn., a corporation of Delaware Filed Dec. 28, 1966, Ser. No. 605,454 Int. Cl. B64d 33/06; B64c 15/10 U.S. Cl. Z39-265.13 13 Claims ABSTRACT OF THE DISCLOSURE A gas turbine engine having an exhaust iiow means which will reduce the perceived noise level associated with the discharge of a high velocity gas jet or jets. An exhaust duct having flaps at the rear end thereof having a pod thereon onto which blow-in doors are pivotally mounted to open inwardly toward said duct. An annular body being positioned rearwardly of said pod with its inner surface forming an inlet passageway with each blow-in door when it is in its inward position. Nozzles means are located in the annular body for a balance between engine performance and noise suppression. Means are provided for inducing turbulence where the blow-in doors end in an inward position. Said turbulence inducing means can comprise means for directing a gas flow into said passageways or involve some other devices which project into said passageways.

This invention relates to means for reducing the perceived noise level associated with the discharge, usually through an ejector shroud, of a high velocity gas jet or jets primarily from a gas turbine engine.

It is an object of this invention to provide a blunt base region at the place where two streams of gas, which are flowing at high but dissimilar velocities, are permitted contact therebetween.

It is another object of this invention to provide means for generating a thick region of vorticity around an expanding gas jet.

It is a further object of this invention to provide a gas outlet on a gas turbine engine with a configuration having a large blunt area separating the terminal part of the inner surface of an annular gas passage surrounding a nozzle and the rear edge of the convergent nozzle.

It is another object of this invention to provide a duct having a primary gas fiow with a converging nozzle with turbulence inducing means located in an annular passageway surrounding said rear end of said duct and said nozzle admitting tertiary air.

It is a further object of this invention to provide means for injecting gas into the tertiary flow admitted through blow-in doors at a point where turbulence is desired.

It is another object of this invention to provide blow-in doors or a fixed ramp of an annular passage around a converging nozzle with a roughened surface in order to initiate turbulence or flow separation.

It is a further object of this invention to provide a surface around the converging nozzle which can be used for the ow, separating from a point forward of said surface to attach to, so that it can separate a second time. It is another object of this invention to provide an engine having a central primary flow and an annular primary flow therearonnd with a blunt surface between the two primary flows where they are permitted to come together with blow-in doors arranged to provide an effective blunt surface between the annular primary flow and the tertiary air being admitted.

It is a further object of this invention to provide clamshells within a fixed annular body mounted rearwardly Patented Aug. 26, 1969 ICC of a pod enclosing an engine having a primary central flow and a primary annular flow therearound, said clamshells being adjustable to achieve an optimum balance between noise attenuation and nozzle performance.

It is another object of this invention to provide an ejector nozzle through which one or more central primary ows and a tertiary fiow pass. The exit area of said ejector being Set in or adjusted to an optimum position to obtain the most favorable balance between noise attenuation and nozzle performance.

It is a further object of this invention to provide actuating means for varying the position of clamshells mounted within a fixed annular body, or shroud, so that they can be placed at some predetermined position when desired.

It is another object of this invention to provide actuating means for varying the position of flaps mounted around the exit of a fixed annular body or shroud to place the Cflaps in a predetermined operating position when desire Other objects and advantages will be apparent from the specification and claims and from the accompanying drawings which illustrate an embodiment of the invention.

FIGURE l is a longitudinal schematic view of the exhaust section of a jet engine showing the invention.

FIGURE 2 is a view showing a modification of FIG URE l which provides an annular liange to permit airow around a nozzle at the end of a ramp.

FIGURE 3 is an enlarged view showing a mechanism for varying the direction of an air jet around a nozzle.

FIGURE 4 is a view taken along the line 4-4 of FIG- URE 3 while also showing the slots.

FIGURE 5 is a view showing a modification of FIG- URE 2 which provides an annular flange to permit airflow around the nozzle and provides an annular trip extending into the outer airfioW.

FIGURE 6 is a view showing a modification of FIG- URE l with the ramp leading into the nozzle having a roughened surface.

FIGURE 7 is a view showing a modification of FIG- URE l wherein a second attaching surface is fixed to the converging nozzle portion.

FIGURE 8 is a view showing the invention applied to an engine having two primary gas liows, one through an inner duct and one through an annular duct around said inner duct.

As stated hereinbefore, FIGURE l shows the rear end of a conventional high speed aircraft jet engine 12. Engine 12 is of a conventional design and may be of the type described more fully in vU.S. Patent No. 2,747,367. The primary duct 26 has at its downstream end an eX- haust nozzle 48 forming an outlet. While the exhaust nozzle 48 is shown consisting of a number of sectioned pieces 10 positioned at a fixed angle, this exhaust nozzle 48 may be made up of movable aps so sectioned and adapted to move to other positions (note U.S. Patent Nos. 3,062,003; 2,815,643 and 2,836,034). The exhaust nozzle 48 is shown fixed in this position since it is in this position during takeoff, and other times demanding high power, and it is at this time that noise attenuation is most desirable.

An annular manifold 32 extends around the rear end of the primary duct 26 adjacent the location where the aps 10 of the nozzle 48 are connected to the primary duct; said manifold 32 includes a plurality of openings 3=8 through which a fluid can be injected to make sure that ow separation occurs at that point. The manifold is consrtucted having a raised center so that a step is formed where the blow-in doors 44 end, and the flaps 10 for nozzle 48 begin, to start the flow separation.

The engine 12 has a nacelle or pod 34 around it with a fixed member 40 positioned axially downstream of the nacelle or pod 34. This xed member 40 can be supported from means associated with the engine such as by a plurality of axially extending struts, or the fixed member 40 can be attached to parts of the aircraft structure. A plurality of sealably, overlapping, and circumfcrentially positioned pivotal blow-in doors 44 are positioned between the end of pod 34 and the forward part of fixed member 40. In their outermost position, the blow-in doors extend between the end of the pod 34 and the forward part of fixed member 40 to provide a continuation of the pod 34 to the outer surface 84 of the fixed member 4). The blow-in doors 44 move inwardly until their rear ends touch or nearly touch the rear portion of the engine at the top of the raised manifold 32 adjacent the attachment -point of the flaps 48 forminga step. While the blow-in doors 44 and the flaps 46 extending from the rearward end of the fixed member 40 are shown as free floating, they may be power actuated.

The nozzle 48 is the primary nozzle and the nozzle .formed by the fixed member 40 and aps 46 is the secondary nozzle. As seen in FIGURE l, the primary nozzle 48 has its flaps 10 positioned inwardly and the blow-in doors are located inwardly with the rear ends thereof positioned against the manifold 32 thereby forming an annular inwardly extending ramp while the flaps 46 are angled inwardly.

For takeoff, an engine having the elements as shown in FIGURE 1 should have them in the position as shown. That is, the flaps 10 forming the primary nozzle 48 are located essentially as shown, i.e., to form a blunt base region surrounding the nozzle throat (radius r1), and blow-in doors 44 are located in an inward position forming the annular ramp as shown with the inner ends of the doors resting or held on or above the raised portion of the manifold to create a step where the flaps 10 extend inwardly from the end of the duct 26. With the flow of tertiary air through the annular passageway formed between the blow-in doors 44 and the forward inner surface f the fixed member 40, a turbulent sheer layer is started at the step formed at the end of the duct 26 which grows into the turbulent sheer layer extending from the annular end of the nozzle 48. The rapid growth of the turbulent sheer layer provides sound suppression by reducing the area of the surface over which the sound is being emitted. To aid in the growth of the turbulent sheer layer extending from the rear end of the nozzle 48, a gas can be injected through the openings 38. The gas is brought from an inlet pipe 14 through a control 16 and outlet pipe 18 which is connected to the manifold 32. The control 16 can be automatically controlled by an engine parameter such as a power setting, or it can be manually operated if desired. Inlet pipe 14 can be connected to an engine compressor stage or some other source of high pressure gas.

FIGURE 2 is a modification of FIGURE 1 wherein the manifold 32 is replaced by a solid annular flange 50 having spaced projections 52 extending therefrom. It can be seen that when the end of blow-in doors 44 engage the tops of the spaced projections S2, space is provided for the injection of a gas which could be directed between the inside of blow-in doors 44 and around the primary duct 26. It can be seen that a more pronounced step is formed by this arrangement.

As a modification to FIGURE l wherein the gas jets are located at a fixed angle with respect to the primary duct 26, FIGURES 3 and 4 show means for varying the angle at which a gas jet is injected.

In this modification, the exit end of the primary duct 26 is shaped as a polygon with each side having a mounting sleeve 60 with a movable manifold section 62 therein. Adjacent ends of mounting sleeves 60 are connected by Wedge-shaped nieces of conduit 6l which are xed in place and sealed so that iiuid ow can pass between manifold sections `62. A plurality of the pieces of conduit 61 have an opening 63 therein which would be connected to a source of gas such as pipe 18. Each mounting sleeve 60 has a large slot 64 extending from a line parallel to the surface of the blow-in door 44 upwardly for a range of about 50 about the centerline of said sleeve. Each movable manifold section has a long narrow slot 66 or a line of holes for directing gas flow from the interior of the section through slot 64. An arm 70 extends from the center of each manifold section 62 forwardly through an opening 72 in each sleeve member 60.

An elongated slot 74 is located along the free end of each arm 70. A bell crank 76 mounted for pivotal movement to the top of a bracket 78 fixed to duct 26 has one arm 80 with a pin 82 which rides in the slot 74. The other arm 86 of the bell crank lever is pivotally connected to a tab on a synchronizing ring 88. The ring 88 is moved backwards and forward in accordance with movements of a plurality of links 90.

It can be seen that as the links 90 of this system are moved rearwardly, the lower ends of all of the arms 86 go rearwardly Vand the arms 80 move upwardly with the pins 82 moving the arms 70 upwardly to lower the flow from 66. As the links 90 of this system `are moved forwardly, the lower ends of all of the arms 86 go forwardly and the arms 80 move downwardly with the pins 82 moving the arms 70 downwardly to raise the flow from 66.

FIGURE 5 is a modification of FIGURE 2 where the rearward part of the tops of projections 52 have an annular projection 53 extending outwardly therea-round to form a trip at that location to further aid in starting flow separation and increasing turbulence. An annular fla-nge 101 extends around the outer end of duct 26 having a sealing material 103 around the outer edge. As the blowin doors come inwardly, they cont-act the sealing material 103 along their length and the ends rest against the projections 52. Gas can be injected into the chamber formed by the duct 26, blow-in doors 44, fiange 50, and flange 101 through openings in the flange 101. As in FIGURE 1, the pipes 18 can be connected thereto.

FIGURE 6 differs from FIGURE 1 in that the downstream portion of the outer surface of each blow-in door is roughened as at 45. The roughening need not be too severe. This roughening provides an additional means for creating turbulence.

FIGURE 7 adds a second attaching surface to each flap 10 of the nozzle 48 so that when the fiaps are in their innermost position, a surface is formed around the nozzle so that the flow which separates at the rear end the ramp formed by blow-in doors 44 will attached thereto and then separate again. This action increases the level of turbulence as desired to promote rapid growth of the sheer layer surrounding the expanding jet.

FIGURE 8 shows the incorporation of applicants device on an engine such as shown in U.S. Patent No. 3,338,051. This engine is of a type wherein an annular duct extending rearwardly from the fan of a fan engine includes a duct burner wherein heat is added to the bypass air for increasing augmentation of the stream. An engine of this type has two primary gas iows, one from the conventional jet engine and one from the surrounding annular duct burner. The engine shown has an annular duct 6 formed by an outer wall 8 and an inner wall 12. The inner wall 12 extends around a jet engine or gas generator having an outer wall 20 with a center cone 22 positioned therein by struts 24. The end of the outer wall 20 forms a converging-diverging section and the rear part of the inner wall 12 of duct 6 ends in a plug surface along which the gas fiowing through duct 6 expands as in a conventional plug nozzle. The rear end of each of these walls, 12 and 20, are connected by an annu; lar blunt base 28,

A track mechanism 30 is located in a fixed position around the end of the outer wall 8 which has a plurality of flaps 33 slidably mounted thereon to provide a nozzle capable of having its converging angle varied. An actuator (not shown) provides movement of rods 31. A pod or nacelle 35 encircles the engine and has a plurality of blow-in doors 37. The blow-in doors 37 are constructed of two parts, a forward section 37a and a rearward section 37b. The front part of each forward section 37a is pivoted at the rear of the pod or nacelle 3S.

An annular fixed member, or shroud, 39 is spaced downstream from the pod 35 so that the forward edge thereof is adjacent the trailing edges of the blow-in doors when they are in their outermost position completing the outer pod surface (dotted position in FIG. 8). Flaps 41 are pivotally attached to the rearward end of the annular member 39 to change the exit opening. Asshown, the rear part of a section 37a and the forward part of a section 37b are pivotally connected at 54. The hinge point of each blow-in door has a roller 56 at each side which travels in a cam opening which is part of the connecting linkage between all of the blow-in doors and the two clamshells 43 of a clamshell nozzle which is mounted Within the annular member, or shroud, 39. A linkage (not shown) between the two clamshells 43 and the blow-in doors could be used which permits the :movement of the blow-in doors between the solid position shown in FIGURE 8 and the dotted position to move the clamshells between their solid position and their dotted position. The solid position of the blow-in doors 37, clamshells 43, and flaps 41 represents their location when the engine is in subsonic Hight and the position of the members is dotted outline shows their respective locations during supersonic flight.

A turbulence inducing means is provided in each of walls 12 and 20 upstream of the blunt base 28 to increase the rate of growth of the turbulent sheer layer which lies between the gas generator discharge stream Iand the fan stream over and above that which would result from the blunt base 28 alone. The turbulence inducing means shown consists of slots or holes 45 and 47 to which a gas can be directed by a plurality of pipes 49 and 51, respectively. Pipes 49 and 51 are connected to an annular manifold 58 which is fed from a source of gas under pressure by conduit 55.

A turbulence inducing means is provided to induce a turbulent region leaving the blowin doors 37. The turbulence inducing means shown is an annular manifold 57 xed to the rear of the track mechanism 30 with openings 59. This manifold 57 is fed a gas under pressure in the same manner as manifold 53.

Further attenuation of jet noise is provided by adjustment of the positions of clamshells 43 and iiaps 41 relative to the blow-in doors and to each other. The linkage between the clamshells and blow-in doors can be adjusted so that the position of the blow-in doors as shown in solid line can position the clamshells to a specific position within a range of positions. The position of these parts being adjusted to provide the optimum balance between performance (thrust) and noise.

If there were no linkage between the clamshells and blow-in doors, the clamshells 43 could be power actuated so that they could be placed in a predetermined position to achieve the optimum balance referred to above. Further, the aps 41 could be power actuated so that they could be placed in a predetermined position to achieve the optimum balance referred to above. The precise positioning of the blow-in doors, clamshells and flaps 41 can only be given for a specific engine. The positioning of these elements will vary from engine to engine. It would be necessary to actually have tests made of a particular engine to determine precise positioning of the blow-in doors, clamshells and flaps to achieve desired positions for maintaining a proper balance between performance and noise.

A specific linkage between clamshells and blow-in doors is shown in copending application Ser. No. 605,453, filed herewith, to Richard E. Teagle, for Engine Exhaust Controller.

I claim.

1. In combination:

(a) an engine having a duct for a first exhaust gas (b) an annular duct surrounding said first-named duct for a second exhaust gas flow.

(c) flaps positioned to form a convergent section adjacent the end of said annular duct,

(d) a casing surrounding said annular duct having blow-in doors pivotally mounted to move inwardly to a point adjacent said flaps,

(e) the ends of said blow-in doors being located rearwardly outward of the ends of said flaps when said blow-in doors are at an inward position,

(f) said rst duct having a blunt end separating the ow from the first duct and annular duct,

(g) an annular body position rearwardly of said blowin doors with the outer surface thereof arranged to be an extension of the blow-in doors when they are in their closed position,

(h) nozzle means mounted within said annular member and being movable to a position forming a coverging nozzle when the blow-in doors are in their inward position,

(i) trailing edge flaps being connected to the downstream end of the annular member, and

(j) means for inducing turbulence where the blow-in doors end in an inward position.

2. In combination, an engine as set forth in claim 1 wherein:

(k) said turbulence inducing means includes means for directing a ow of fluid rearwardly adjacent the ends of the blow-in doors to mix with uid ow passing throuhg the openings made by said blow-in doors.

3. In combination, an engine as set forth in claim 1 wherein:

(k) said turbulence inducing means comprises an annular manifold fixedly positioned adjacent the end of said annular duct having openings directed rearwardly along the underside of the blow-in doors.

4. In combination, an engine as set forth in claim 1 wherein:

(k) means are provided for directing a flow of fluid rearwardly over the outer edge of the blunt end of the lirst duct.

5. In combination, an engine as set forth in claim 1 wherein:

(k) means are provided for directing a ow of uid along the inner edge of the blunt end of the first duct.

6. In combination, an engine having:

(a) a duct for exhaust gas flow,

(b) aps positioned to form a converging section adjacent the end of said duct,

(c) a pod around said duct,

(d) blow-in doors pivotally mounted at the end of said pod and extending rearwardly, said doors being movable inwardly to a point adjacent said flaps,

(e) an annular body positioned rearwardly of said pod with the inner surface of said body forming an inlet passageway with each door,

(f) means for inducing turbulance where the doors end in an inward position, and

(g) said annular body having nozzle sections mounted therein which are movable to vary their position in forward tiight to provide an optimum balance between engine performance and noise suppression.

7. In combination, an engine having:

(a) a duct for exhaust gas flow,

(b) flaps positioned to form a converging section adjacent the end of said duct,

(c) a pod around said duc-t,

(d) blow-in doors pivotally mounted at the end of said pod and extending rearwardly, said doors being movable inwardly to a point adjacent said flaps,

(e) an annular body positioned rearwardly of said pod with the inner surface of said body forming an inlet passageway with each door,

(f) means for inducing turbulence where the doors end in an inward position, and

(g) said turbulence inducing means including a preroughenend surface on the downstream surface of the blow-in doors facing the annular body.

8. In combination, an engine having:

(a) a duct for exhaust gas ow,

(b) flaps positioned to form a converging section adjacent the end of said duct,

(c) a pod around said duct,

(d) blow-in doors pivotally mounted at the end of said pod and extending rearwardly, said doors being inwardly to a point adjacent said llaps,

(e) an annular body positioned rearwardly of said pod with the inner surface of said body forming an inlet passageway with each door,

(f) means for inducing turbulence where the doors end in an inward position, and

(g) said turbulence inducing means including a radially extending flange adjacent the end of the blow-in doors which extend outwardly into the inlet passageways.

9. In combination, an engine having:

(a) a duct for exhaust gas flow,

(b) flaps positioned to form a converging section adjacent 4the end of said duct,

(c) a pod around said duct,

(d) blow-in doors pivotally mounted at the end of said pod and extending rearwardly, said doors being movable inwardly to a point adjacent said flaps,

(e) an annular body positioned rearwardly of said pod with the inner surface of said body forming an inlet passageway with each door,

(f) means for inducing turbulence where the doors end in an inward position, and

(g) said turbulence inducing means including a builtup surface located midway on the outside of each flap downstream from the ends of said blow-in doors to provide a second attaching surface area for holding the flow from the lower portion of the ow passing through the inlet passageways.

10. In combination, an engine having:

(a) a duct for exhaust gas ow,

(b) aps positioned to form a converging section adjacent the end of said duct,

(c) a pod around said duct,

(d) blow-in doors pivotally mounted at the end of said pod and extending rearwardly, said doors being movable inwardly to a point adjacent said aps.

(e) an annular body positioned rearwardly of said pod with the inner surface of said body forming an inlet passageway with each door,

(f) means for inducing turbulence where the doors end in an inward position, and

(g) a second duct being located within said duct for exhaust gas flow,

(h) said second duct having an elfective blunt end to separate flow passing through said duct for exhaust gas liow and said second duct.

11. In combination, an engine having:

(a) a duct for exhaust gas iiow,

(b) aps positioned to form a converging section adjacent the end of said duct,

(c) a pod around said duct,

(d) blow-in doors pivotally mounted at the end of said pod and extending rearwardly, positioned inwardly to a point adjacent said flaps,

(e) an annular body positioned rearwardly of said pod with the inner surfaces of said body forming an inlet passageway with each door,

(f) means for inducing turbulence where the doors end in .an inward position, and

(g) a raised abutment having channel cuts in the `top thereof extends radially outwardly from the end of the duct so that the free end of the blow-in doors will contact it in an inward position.

12. In combination, an engine having:

(a) a duct for a first exhaust gas How,

(b) aps positioned to form a converging section adjacent the end of said duct,

(c) a pod around said duct forming an annular space therewith,

(d) blow-in doors pivotally mounted at the end of said pod and extending rearwardly, said doors being movable inwardly -to a point adjacent said aps,

(e) an annular body positioned rearwardly of said pod with the inner surface of said body forming an inlet passageway with each door for a second gas flow, and

(f) means for inducing turbulence where the doors end in an inward position, including,

(l) means for directing a third gas flow to mix with fluid flow passing tthrough said inlet passageways adjacent the ends of the blow-in doors,

(2) said directing means having opening means through which the lthird gas flow passes.

(g) said means for directing a third flow of gas being movable so that the angle of iiow can be changed relative to the position of the end of the blow-in doors.

13. In combination, an engine as set forth in claim 11 wherein:

(h) the downstream end of the raised abutment has a solid flange extending upwardly so that when the blow-in doors are resting on the abutment, the flange enters into each inlet passageway formed by the blow-in doors.

EVERETT W. KIRBY, Primary Examiner U.S. Cl. X.R.

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