US3550721A - Silencing assembly for jet engines - Google Patents

Description

United States Patent SILENCING ASSEMBLY FOR JET ENGINES 7 Claims, 12 Drawing Figs.

U.S.Cl 181/51, 239/l27.3, 239/265.13 Int. Cl F0ln l/14, B64d 33/06 Field ofSearch ..239/265.13,

[56] References Cited UNITED STATES PATENTS 3,027,714 4/1962 Parker 181/33(.222) 3,032,974 5/1962 Meyer 239/1273 3,048,971 8/1962 Alford 239/265.4l 3,048,973 8/1962 Benedict 239/127.3 3,262,264 7/1966 Gardiner et al... 239/127.3X 3,333,772 8/1967 Bruner 181/33(.222) 3,360,074 12/1967 Ranvier et a1 181/33(.222) 3,420,442 [/1 969 Teagle 239/265.41X FOREIGN PATENTS 878,191 9/1961 Great Britain l8l/33(.221) 128,712 1960 U.S.S.R 239/265.41

Primary Examiner-Robert S. Ward, in Att0rneysRobert S. Dunham, P. E. Henninger, Lester W.

Clark, John A. Harvey, Gerald W. Griffin, Thomas F.

Moran, Howard J. Churchill and Abraham Engel ABSTRACT: A silencer assembly for a jet aeroplane comprises an annular structure immediately in front of the nozzle exit, the annular structure defining a plurality of angularly spaced channels through which air is drawn to the jet stream.

PATENTEU neczs 19m sum 1 or 5 PATENIEU 05132 91970 SHEET 2 of 5 SILENCING ASSEMBLY FOR JET ENGINES A disadvantage of jet-engined aircraft is that at takeoff they make considerable noise, something which greatly disturbs people living near airports.

Most of the silencers which are at present fitted to the output of the ejection nozzles of jet aircraft are of a nonadjustable kind which only reduce noise slightly and which reduce engine efficiency in cruising flight and thus reduce the profitability of airline operation.

The present invention provides a silencer which can be cut out during cruising flight. The silencer is based on the principle of diluting the gases by sucking in air from outside through an aspirator. During takeoff aspirated air is introduced into the jet stream in a number of channels disposed at the nozzle end. The channels are advantageously adapted to fold laterally into one another around the entire periphery of the jet stream so as to form in cruising flight a smooth annular nozzle for the jet stream.

The shapes of the channels will be such that the exhaust gas exit cross section is substantially the same, and appropriate for engine operation conditions, whether or not the silencer is in operation.

During takeoff and landing, a ring forming the aspirator may be positioned to extend completely around the nozzle exit, whereas during cruising flight such ring is retracted. The invention provides several forms of retraction.

Embodiments of the invention are shown in the accompanying drawings wherein:

FIG. 1 to 4 shows an improved silencer in accordance with the invention in position for takeoff and in position for cruising flight, the silencer including a slidable aspirator ring;

FIGS. to 7 show the silencer with the aspirator ring opening in a rearward position;

FIGS. 8 to 11 show a silencer having an extensible ring which during cruising flight folds behind the silencer; and

FIG. 12 is a perspective view of an embodiment of the invention.

As can well be seen in FIGS. 1 and 12, folding channels 1 which are open to atmosphere at the rear have air-guiding vanes 2 which also serve to stiffen the channel walls. One wall of each channel is articulated along a rib 3, folding occurring around the axis formed by the rib 3 until each channel touches the adjacent channel (see for example FIG. 4). In order that the jet stream may be confined in a nozzle having a circular cross section during cruising flight, walls 4 of each channel may be part-cylindrical.

The channels are foldable between a silencing position (see FIGS. 1 and 2) and a cruising position (see FIGS. 3 and 4).

The folding movement of the channels 1 is produced by torsion tubes 5 which are embedded in the channel structure in extension of the rib 3 which constitutes the folding axis. The end of each tube 5 is mounted in a bearing 6 forming part of a partition 7. Each tube 5 carries a lever 8 which, depending upon available space, extends either outwards, as in FIGS. 1, 3 and 12, or inwards, as in FIGS. 8 and 10. The lever ends are interconnected by a number of rods 9 visible in FIG. 12 and the system is operated through the agency of a ram 10 disposed somewhere on the periphery of this actuating facility.

The folding and unfolding movement of the channels occurs perpendicularly to the gas stream and therefore requires small actuating forces, but in the folded position for closing flight the pressure of the stream forces the channels against one another. Movement into the silencer in position occurs when the engine is either ticking over before landing or not running before takeoff.

FIGS. 1 and 2 show a unitary ring 11 whose throat 12 is positioned, when the silencer is in operation as shown in FIG. it, slightly aft of an exhaust gas exit 13. The ring 11 is carried by two or more rails 14 with the interposition of sliding shoes 15; the rails 14 form part of the stationary structure of the system, as can be seen in FIG. 4.

In cruising flight the ring 11 is advanced into the position ll shown in FIG. 3 so as to restore the outer shape of the engine fairing. Conveniently, a circular slot 16, visible in FIG. 3, can be left in front of the leading edge of the ring 11 so that the ring 17 formed by the folded channels can be supplied with external air and thus obviate possible extra baffle drag.

In a variant, shown in FIGS. 5 and 6, aspirator efficiency can be improved, more particularly as regards possible extra thrust at takeoff, if the rear part of the ring 11 forms a diffuser- -i.e., can open conically as it approaches its retracted position. To this end, the ring 11 is subdivided into a number of sections 11a, 11b, 11c, etc. as can be seen in FIG. 6, each section having two pairs of shoes 15. Also, each rail 14 bends outwards from a place 18. The ring elements can then pivot around the place 18, with a simultaneous increase in throat diameter Dc. The resulting diffuser is at an angle to the nozzle axis. Each section of the ring 11 has a member 19 which engages in the adjacent section.

FIG. 7 shows an embodiment using a pair of rails 12 and supports 15 comprising rollers 20.

FIGS. 8 and 9 show an extensible ring 11 comprising a number of main sections lie and intermediate sections 11f which are engaged in the main sections 112. Each main sec tion is connected to the stationary structure of the silencer by four rods 21 -24 forming two parallelograms. When this assembly folds to the rear, the ring takes up a position behind the zone 17 occupied by the folded channels and thus gives the nozzle exit a satisfactory shape, as can be seen in FIG. 10.

Movement is transmitted by a rod 25 connected at a place 26 to the rod 22. Through the agency of a mechanical connection between the rods 25, the movements can be synchronized and only a single actuator needs to be used.

Iclaim:

l. A silencer assembly for jet engines comprising in combination:

a. a jet ejection nozzle provided with a plurality of longitudinal air intake apertures regularly arranged around its axis in a portion adjacent its outlet end;

. a plurality of axes parallel to the axis of said nozzle and located each adjacent one longitudinal edge of one of said apertures;

c. a plurality of elongated, V-shaped channel members parallel to the axis of said nozzle located within said nozzle and one longitudinal edge of which is secured to one of said axes, said channel members being closed at their end remote to said outlet end and open at their other end; and

d. means for simultaneously rotating said axes whereby said channel members may be displaced between a position wherein they project substantially radially in front of said apertures and a position wherein they are disposed close to one another substantially tangentially with respect to said nozzle for defining an unobstructed passage for the gasjet.

2. The combination of claim I wherein said channel members are provided with spaced partitions beginning between their longitudinal edges and ending substantially in their open outlet end.

3. The combination of claim 1 wherein said channel members have arcuate longitudinal walls whereby said unobstructed passage is substantially cylindrical.

4. The combination of claim I wherein an aspirator ring is slidably mounted outside said nozzle coaxially therewith and is adapted to be displaced between a position wherein it is located in front of said apertures, an annular air intake passage being provided between said nozzle and said ring and a position wherein it is located rear the outlet end of said nozzle.

5. The combination of claim 4 wherein said ring is adapted to be radially expanded when displaced from said first mentioned position towards said second mentioned position.

6. The combination of claim 5 wherein said ring comprises a plurality of interengaging elements provided with guiding means which diverge with respect to the axis of said nozzle towards its outlet end.

zle by means of parallelogram forming rods, for the purpose specified.

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