US3263931A

US3263931A - Silencers for jet engines

Info

Publication number: US3263931A
Application number: US386194A
Authority: US
Inventors: Bartek Joseph; Anton F Nagelschmidt; Ranvier Gaston Jean-Louis; Richter Gerhard
Original assignee: SNECMA SAS
Current assignee: Safran Aircraft Engines SAS
Priority date: 1963-08-02
Filing date: 1964-07-30
Publication date: 1966-08-02
Anticipated expiration: 1983-08-02
Also published as: GB1078421A; SE313462B; DE1294394B; FR86258E; US3360074A; US3344882A; FR1376576A

Description

Aug. 2, 1966 J. BARTEK ETAL SILENCERS FOR JET ENGINES Filed July 30, 1964 4 Sheets-Sheet 1 Fig; 1a

Aug. 2, 1966 J. BARTEK ETAL SILENCERS FOR JET ENGINES 4 Sheets-Sheet 2 Filed July 30, 1964 6 VHL vHIL.

2, 1966 J. BARTEK ETAL 3,263,931

SILENCERS FOR JET ENGINES Filed July 30, 1964 4 Sheets-Sheet 3 Fig,10

Aug. 2, 1966 J. BARTEK ETAL SILENGERS FOR JET ENGINES Filed July 30. 1 964 4 Sheets-Sheet 4 United States Patent 3,6 9 Claims. (Cl. 239-26511) The invention relates to the devices known as silencers which enables the noise of aircraft jet engines, and more particularly that of supersonic jet aircraft, to be reduced.

The operation of heavy civil aircraft equipped with jet engines having a powerful thrust is accompanied by considerable noise, due to the dissipation of a great part of the energy of the ejection jet in the air.

This drawback is all the more serious as the engines must operate at full speed at the moment of take-off, that is to say, at low altitude. The maximum noise is therefore produced close to the inhabitated areas bordering airports, which thus suffer the disastrous physiological effects thereof.

It has already been proposed to introduce into a jet, at the rear of the nozzle, a fluid which serves to reduce the noise.

To this end it is known to locate in the nozzle an inlet conduit for ambient air which is picked up externally, this conduit opening into the jet at the rear of the nozzle. In known devices the air inlet conduit is fixed in the nozzle, so that it creates permanent obstructions in the jet, both inside the nozzle and outside it. The presence of these obstructions, although acceptable on take-off for reducing the noise, is undesirable in cruising flight, where efficiency is of prime importance.

According to the present invention, the silencer effect is obtained, at least on take-off, by means of tubes of circular or profiled cross-section, the upstream end of each of which is subjected to the ambient pressure at the external periphery of the nozzle, or in the vicinity of this periphery,

and the downstream end of each of which opens into the jet outside the nozzle, means being provided for retracting the said tubes at will in order to reduce or clear the space occupied by them in the nozzle and/or in the jet.

Research aimed at better operation of aircraft of the above-mentioned kind has resulted in them being provided with a nozzle of variable cross-section on which the mounting of this device is possible by reason of its advantageous design. The downstream ends of the tubes therefore open into the jet, at least in the closed position of the nozzle, that is to say in that condition of the latter which offers the minimum outlet orifice, and control of the spreading of the tubes can be combined with control of the opening of the nozzle.

In one form of embodiment, the silencer device is fast with the nozzle and preferably with the movable elements which adjust its outlet cross-section. This device, and in particularthe operation thereof, may also be independent of the outlet cross-section of the nozzle.

The description which follows with reference to the accompanying drawings, which is given by way of nonlimitative example only, will enable the various features of the invention and the manner of carrying them into effect to be clearly understood, any arrangement appearing both from the text and from the drawings falling within the scope of the present invention.

FIGURES 1 and 2 show a first embodiment of the invention in longitudinal section through the nozzle, the respective figures showing two different arrangements of the nozzle;

FIGURES 3 and 4 are end views in the direction of the arrows F and F in FIGURES 1 and 2 respectively;

FIGURES 1a and 3a are half views, corresponding to the views of FIGURES 1 and 3, respectively, but showing a modified form of the first embodiment employing tubes of non-circular cross-section;

FIGURES 5 and 6 are views corresponding to FIG-

URES

1 and 2 showing a second embodiment;

FIGURES 7 and 8 are transverse sectional views on the lines VIIVII and VIIIVIII, respectively, of FIG- URE 5;

FIGURES 9 and 10 are views corresponding to FIG-

URES

5 and 6 but showing a modified form of the second embodiment;

FIGURES 11 and 12 are sectional views on the lines XIXI and XII-XII, respectively, of FIGURE 9;

FIGURES 13 and 14 are views corresponding to FIG-

URES

5 and 6 showing another modification;

FIGURES 15, 16 and 17 are sectional views on the lines XV-XV, XVIXVI and XVII-XVII, respectively, of FIGURE 13.

Referring to the drawings, FIGURES 1 to 4 show a device of simple construction in which the tubes are fixed to the adjustable nozzle of an aircraft.

The nozzle comprises in known manner a duct 1 to which there are articulated outlet flaps 2 producing an outlet orifice 2a of variable cross-section. In FIGURE 1, the nozzle is open and emits a jet of large diameter; this arrangement is employed at the cruising speed of the aircraft. In FIGURE 2, the nozzle has been closed by pivoting of the flaps 2 and the cross-section of the orifice 2a determined by the latter has thus been reduced so that the jet emitted j, is restricted, this arrangement being employed at take-off.

The silencer arrangement comprises a plurality of elbowed tubes 3 distributed regularly over the cross-section of the nozzle. To this end, certain of the flaps 2 have apertures 3a formed in them in which the elbowed tubes 3 are welded. The latter arc open upstream at 3b, at the outer periphery of the nozzle, and their downstream ends 3c open into the jet j to the rear of the outlet orifice 2a in a zone where the jet is sufficiently expanded for the static pressure to be little different from the ambient pressure. Air is drawn in by induction at the upstream end of the tubes and is discharged at 30 into the jet.

Under the conditions of operation which prevail at take-off (FIGURE 2), the tubes 3 penetrate deeply into the jet and the air discharged at 30 in the vicinity of the central zone of the jet reduces the kinetic energy thereof sufiiciently to decrease its sound energy very considerably. When the nozzle fiaps 2 are operated in order to change to cruising speed conditions (FIGURE 1), the flaps carry the tubes 3 with them and the latter move away from, or spread open radially relatively to, the axis X-X 0f the nozzle, thus reducing the bulk of the material obstruction which they form in the nozzle and in the jet. In the arrangement of FIGURE 1, the tubes still open into the jet at 36, although they are arranged less deeply therein, and they still produce a silencer effect, but the loss of thrust due to the presence of the tubes 3 is substantially lower with the nozzle open (as in FIGURES 1 and 3) than with the nozzle closed (as in FIGURES 2 and 4).

FIGURES 1a and 3a illustrate the application of the device, the principle of which has just been described, to the ejection nozzle of a civil aircraft. In this application, the tubes 3 are suitably profiled so as to reduce the obstruction in the nozzle and in the jet. Twelve tubes 3 are provided which are spaced angularly from one another at 30 intervals FIGURE 3a). The outlet flaps, which are articulated to the duct 1 of the nozzle in known manner at 1a, comprise twelve flaps 2b having aperatures 3a Patented August 2, 1966 in which the tubes 3 are welded, as has been stated above, and twelve flaps 20 which are connected in known manner to the flaps 2b so as to overlap them and form a deformable surface with them, the flaps 20 causing the flaps 2b to pivot above their respective articulations.

To control the pivoting of the flaps 20, a ring 4 is provided sliding axially around the duct 1 of the nozzle and connected to these flaps 20 by connecting rods 6a. The sliding of the ring 4 is controlled by jacks distributed at regular intervals around the duct 1, the rods 6 of which jacks are articulated to the said ring 4. By actuating the jacks 5 opening or closing of the nozzle is produced. The jacks drive the ring 4 in translation and the latter causes pivoting of the flaps by means of the connecting rods 6a, the flaps 20 carrying with them the flaps 2b to which the tubes 3 are fixed. In FIGURES 1a and 3a the nozzle closed position of the tubes 3 is shown by dash lines.

The inlet 3b of each tube 3 is provided with vanes forming a grille 3d which guides the flow of incident air as it enters the tube 3 in the direction of the arrows f.

In the embodiment shown in FIGURES 5 to 8, the tubes are movable with respect to the adjustable nozzle. They are located outside the nozzle and, when they are placed in the positions in which they perform their silencing function, their downstream ends penetrate into a zone of the propulsive jet where the pressure is not substantially higher than the atmospheric pressure.

As in the preceding figures, the duct 1 supports the movable flaps 2 of the adjustable nozzle, but the shifting of these flaps is independent of that of the silencer tubes.

The ring 4 surrounding the duct 1 can be driven in axial translation by means of the jacks 5, the rods 6 of which are connected to lugs 7 welded to the ring 4. The tubes 3 are provided at the front with studs 9 by means of which they are articulated in yokes 8 Welded to the ring 4. The tubes 3 are also provided with studs 10 which slide in inclined slots 11 constituting slideways, which are formed in yokes 12 welded to the duct 1. The tubes 3 are open at their upstream ends at 311 and, as will be seen in the drawing, the Open ends thereof are located in the vicinity of the external periphery of the duct 1 of the nozzle. They are bent inwardly in such manner that the open downstream end of each tube penetrates into the interior of the jet 1' or 1' downstream of the outlet orifice 2a of the nozzle, when the ring 4 and the tubes 3 whose displacement it controls are in the extreme rearward position shown in FIGURE 5.

To retract the silencer, the jacks 5 are actuated so that they bring the ring 4 back towards the front, the ring carrying the tubes 3 with it, so that they pivot at 9 in the yokes 8 while the studs 10 slide in the slideways 11, the latter being suitably inclined so that the tubes 3 pivot outwardly as they slide towards the front, in such manner that the downstream end 3c of each tube is brought into a position outside the jet (FIGURE 6).

This form of silencer device can operate both with the nozzle closed and with the nozzle open, that is to say both on take-off and in cruising flight, and it has the advantage that in the retracted position there is no loss of thrust of the jet engine, the tubes being outside the jet.

It will be observed that the tubes are completely outside the nozzle and that, consequently, even in the operative position (FIGURE 5), they do not alter the profile of the nozzle.

The arrangement shown in FIGURES 9 to 12 enables the amplitude of pivoting of the tubes 3 to be increased owing to the provision of a supplementary slideway. In this arrangement likewise, the duct 1 supports the movable flaps 2 of the adjustable nozzle and their operation is independent of that of the silencer.

As in the case of the construction shown in FIGURES 5 to 8, the ring 4 moves axially under the action of the jacks 5, the rods of which are connected to the lugs 7 fixed to the ring 4, and the tubes 3 are articulated in the yokes 8 of the ring 4 by means of the studs 9. In FIG- URES 9 to 12, however, the yokes 12 on the nozzle duct 1 also have slots 13 forming slideways parallel to the axis X-X', which serve to guide the ring 4 during its translational movement. To this end, the sides 8a and 8b of the yokes 8 of the ring have holes through which the studs 9 of the tubes extend and these studs enter the slots 13, the studs being slidable in the slots 13 while being free to pivot in the said holes.

The movement of introducing the tubes into the jet is obtained by sliding the studs 10 of the tubes in the slideways 11a of the yokes 12, which slideways are similar to the slideways 11 of FIGURES 5 to 8 but are arched and more inclined with respect to the axis X--X.

To operate the silencer, the ring 4 is made to slide towards the rear to introduce the tubes into the jet (as in FIGURE 10) or towards the front to withdraw them therefrom (as in FIGURE 9). During this movement, the studs 10 slide in the slideways 11a, while the studs 9 pivot in the yokes 8 and slide in the slideways 13.

As will be seen from the drawings, this form of construction is particularly advantageous in cases in which, from the point of view of installation, the space occupied downstream to the outlet plane of the nozzle must be small.

FIGURES 13 to 17 show a modified form of the arrangement shown in FIGURES 10 to 12, in which one and the same group of jacks controls both the tubes of the silencer and the flaps of the nozzle. In the arrangement of FIGURES 13 to 17, a third series of slideways 14 carried by lugs 15 fixed to the outside of the flaps 2 permits the latter to be controlled by means of the tubes 3 which are themselves controlled by the jacks 5, the control of the flaps 2 being effected by pins 16 which are carried by the tubes 3 and slide in the said slideways 14.

It will be understood that during the movement of translation and rotation of the tubes 3, which has been described hereinbefore with reference to FIGURES 10 to 12, the pins 16 carried by the tubes, while sliding in the slideways 14, carry the latter with them, and with them also the flaps 2 to which the slideways 14 are fixed, the flaps pivoting about the pivots 2b of the flaps, either towards the inside when the tubes 3 are advanced into the jet (as in FIGURE 14), or towards the outside when the tubes are withdrawn from the jet (as in FIGURE 13).

We claim:

1. A device for reducing noise arising from a supersonic jet emitted by a nozzle, comprising a plurality of tubes the each having an inlet end which is subjected to the ambient pressure adjacent to the external periphery of the nozzle, and an outlet end which opens into the jet at a point substantially spaced downstream of the nozzle, and retracting means for moving said tubes away from the axis of the jet at will, at least at their outlet end portions.

2. A device according to claim 1, for reducing noises arising from a supersonic jet emitted by a nozzle having an outlet orifice adjustable between an open position and a closed position, wherein the outlet ends of the tubes open into the jet, at least in said closed position of the nozzle, and means are provided for simultaneously effecting the opening of the nozzle and the moving apart of the tubes.

3. A device according to claim 2, wherein flaps are provided for adjusting the outlet orifice of the nozzle and the tubes are fast with said flaps.

4. A device according to claim 3, wherein the tubes are fixed to the flaps in the vicinity of the inlet ends of the respective tubes, each of which opens outside the flaps.

5. A device according to claim 1, wherein the tubes are arranged around the nozzle outside the latter and the retracting means are provided for shifting the tubes between a position in which their outlet ends penetrate into the jet and a position in which said outlet ends are retracted beyond the jet.

6. A device according to claim 5, wherein the tubes are mounted in such manner as to be able to slide axially with respect to the nozzle while pivoting, so that during pivoting their outlet ends move nearer to or away from the axis of the nozzle.

7. A device according to claim 6, wherein the tubes are pivotally mounted on pivoting supports which slide axially along the nozzle, elements being provided on the tubes to co-operate with elements mounted on the nozzle in such manner as to cause the tubes to pivot when said pivoting supports are displaced in translation and means being provided for simultaneously controlling the sliding of all the pivoting supports along the nozzle.

8. A device according to claim 6 for reducing noise arising from a supersonic jet emitted by a nozzle having an adjustable outlet orifice comprising a single control 9. A device according to claim 8, wherein flaps are provided for adjusting the outlet orifice of the nozzle and means are provided for connecting the flaps to the tubes in such manner that the displacement of the tubes 5 controls the orientation of the flaps.

References Cited by the Examiner UNITED STATES PATENTS 1,382,690 6/1921 Stokes 181-43 2,697,907 12/ 1954 Gaubatz 60-35.6 2,982,092 5/1961 Keen 6035.6

MARK NEWMAN, Primary Examiner.

device for simultaneously effecting the shifting of the tubes 15 RALPH D. BLAKESLEE, Assistant Examiner.

and adjusting of said outlet orifice.

Claims

1. A DEVICE FOR REDUCING NOISE ARISING FROM A SUPERSONIC JET EMITTED BY A NOZZLE, COMPRISING A PLURALITY OF TUBES THE EACH HAVING AN INLET END WHICH IS SUBJECTED TO THE AMBIENT PRESSURE ADJACENT TO THE EXTERNAL PERIPHERY OF THE NOZZLE, AND AN OUTLET END WHICH OPENS INTO THE JET AT A POINT SUBSTANTIALLY SPACED DOWNWSTREAM OF THE NOZZLE, AND RETRACTING MEANS FOR MOVING SAID TUBES AWAY FROM THE AXIS OF THE JET AT WILL, AT LEAST AT THEIR OUTLET END PORTIONS.