Cooling system for a convergent divergent nozzle

The invention relates to a ventilation system of a convergent-divergent nozzle equipping a turbojet engine for military use.

It relates more specifically to a turbofan engine having an axis afterburner chamber X delimited by an annular wall situated radially inside an annular casing, said annular wall and said casing defining an annular passage through which circulates a cooling air stream, a convergent divergent axisymmetric nozzle arranged downstream of said afterburn chamber and comprising a ring of converging flaps articulated at the downstream end of said housing and a ring of diverging flaps articulated at the downstream end said convergent flaps, each ring of flaps comprising alternately a plurality of controlled flaps and a plurality of follower flaps, a cold flaps ring disposed radially outside said nozzle and hinged at their upstream end to a conical shell connected to the downstream portion of said casing, means for creating a cooling air film on the internal faces of said convergent flaps and means of cooling said divergent flaps.

<patcit id="pcit0001" dnum="US5435127A"><text>US 5435127</text></patcit> A turbojet engine of the type mentioned above wherein the cooling of the divergent flaps is achieved by a mixture of nacelle air flow with an air sample in the downstream portion of the annular channel in which circulates the cooling flow of the annular wall.

<patcit id="pcit0002" dnum="EP1333172A"><text>EP 1333172</text></patcit> and <patcit id="pcit0003" dnum="EP0541346A"><text>EP 0541346</text></patcit> are an example of the state of the art concerning the ventilation system for convergent-divergent nozzle.

The air bleed is operated directly by tapping on the channel with a control valve in stitching output. Downstream of the tapping bend is arranged a jet nozzle which directs the mixture between air motor at high pressure and unpressurized air nacelle. The exact shape of the levy is not indicated in this document. However, direct removal from the channel may not be effective for removing significant amounts of flow of the cooling flow, because it disturbs the operation of the ventilation. It may be hot gases reintroductions in the annular wall and poor cooling film supply convergent flaps. Moreover, it is difficult to accommodate such a device within the footprint of the nozzle, as this environment is very occupied by the control flap actuators and levers.

The object of the invention is to effectively and consistently supply the divergent flaps of a convergent-divergent nozzle cooled with a device that has a high rate of integration with existing parts.

The invention achieves its object by the fact that the means for cooling said divergent flaps comprise:<ul><li>an annular plenum chamber delimited downstream by said conical shell and fed with cooling air through holes formed in a boundary wall between said plenum chamber and the downstream end of said annular passage,</li><li>a plurality of distribution cells surrounding the plenum chamber and connected to the latter, said cells being delimited downstream by said conical shell and being arranged around the X axis in the follower flaps planes of symmetry, and</li><li>telescopic pipes each connecting a cell to follower divergent flap located in the same plane of symmetry of the said cell.</li></ul>

Thus the structure of the plenum chamber and the cells is constituted by the conical shell and complementary walls that strengthen the conical shell. On the other hand, the divergent follower flaps are powered by a pressurized cooling air from the annular channel bounded by the annular wall and the casing.

The plenum chamber will slow the velocity of the air received and increase the pressure of the cooling air of the divergent flaps.

The following provisions are also advantageously suited:<ul><li>the divergent flaps are boxed and cooled by the air delivered by the telescopic pipelines while the controlled divergent flaps are single skin;</li><li>the convergent flaps are simple skin types;</li><li>the conical wall comprises openings between the cells to allow the circulation of a nacelle air in the space surrounding the convergent divergent nozzle; </li><li>the cooling air flow circulating in the annular channel is divided into two streams by means of a stationary ring integral with the boundary wall, the radially inner stream being injected upstream of the convergent flaps via a slot and the radially outer flow being injected into the plenum chamber through the bores in the boundary wall.</li></ul>

This provision avoids the creation of depressions to the connections of the prior art and the hot gas reintroductions. This ensures, in addition, a homogeneous cooling of the converging flaps.

Advantageously, the divergent flaps cooling means further comprise means for adjusting the cooling air flow of said flaps.

The flow control means preferably comprise a ring mounted movably in a slide integral with the boundary wall, said ring and said slide each comprising a plurality of flow rate adjustment holes capable of being matched with the holes in the wall border movement of said ring.

According to a first embodiment, the ring is rotatably mounted about the axis X and is rotated by a rack and pinion system by means of an actuator driving said pinion.

According to a second embodiment, the ring is mounted movably in translation parallel to the X axis and is displaced by a plurality of synchronized jacks.

Other advantages and characteristics of the invention appear on reading the following description given by way of example and with reference to the accompanying drawings in which:<ul><li>the <figref idrefs="f0001">figure 1</figref> is a sectional view of a nozzle for turbofan engine according to the invention, the upper part of this figure being a section in the plane of the controlled flaps, the nozzle being open, and the lower part of this figure being a section in the plane follower flaps, the nozzle being closed;</li><li>the <figref idrefs="f0001">2</figref> is a half-section, according to the median plane of the follower flaps, the air manifold in place at the back of the support casing of the nozzle and backed the conical shell; </li><li>the <figref idrefs="f0002">3</figref> is a half-section, according to the median plane of the controlled flaps of the plenum shown <figref idrefs="f0002">3</figref> ;</li><li>the <figref idrefs="f0002">4</figref> is a perspective view of the conical shell, this view being taken from upstream;</li><li>the <figref idrefs="f0003">5</figref> is similar to the <figref idrefs="f0002">3</figref> and shows a first embodiment of the adjusting ring the flow of cooling air of the divergent flaps;</li><li>the <figref idrefs="f0004">6</figref> similar to <figref idrefs="f0003">5</figref> shows a second embodiment of the air flow of the adjusting ring;</li><li>the <figref idrefs="f0005">7</figref> developed shows the closure system of the plenum chamber by the rotary control ring of the <figref idrefs="f0003">5</figref>and</li><li>the <figref idrefs="f0005">8</figref> developed shows the closure system of the plenum chamber by the slide control ring of the <figref idrefs="f0004">6</figref>.</li></ul>

The <figref idrefs="f0001">figure 1</figref> 1 shows the rear body of a turbofan aircraft turbojet that comprises a post-combustion chamber 2 of axis X in which circulates the hot primary flow F1.

This post-combustion chamber 2 is delimited by an annular wall 3 of axis X disposed radially inside a casing 4. The annulaire3 wall and the casing 4 define between them an annular channel 6 through which a secondary stream cold F2, for cooling the annular wall 3 and a convergent-divergent nozzle 10 disposed downstream from the post-combustion chamber 2.

This convergent-divergent nozzle 10 comprises a first ring of converging flaps has controlled converging flaps 11, articulated on the downstream end of the casing 4 and circumferentially alternating with convergent flaps followers 12 also hinged to the downstream end of the casing 4, and a second ring of divergent flaps having alternately controlled divergent flaps 13 hinged at the downstream end of the convergent flaps 11 controlled, and divergent flaps 14 hinged at the downstream end of the convergent flaps followers 12, the number of convergent flaps being even and equal to the number of divergent flaps.

Around the nozzle 10 are provided cold flaps 15 articulated at their downstream end a conical shell 16 integral with the downstream portion of the casing 4.

At the downstream end of the annular channel 6 there is provided a ring 20 which divides the cold secondary flow F2 in a radially inner flow F3 which opens via a slot tangentially to the inner wall of the convergent flaps, so as to form an air film cold driven by the hot flows F1 and licking the convergent flaps, the latter may well be the single skin type and a radially outer flow F4 for cooling the divergent flaps.

As is seen in <figref idrefs="f0001">figures 2</figref> and <figref idrefs="f0002">3</figref>The F4 flow enters openings 21 formed in the end wall 22 of the casing 4 located downstream of the conical shell 16, an annular plenum chamber 23 having an axis X, defined upstream by the radially inner portion 17 of the conical shell 16, and downstream by the structure 24 for hooking the convergent-divergent nozzle 10, secured to the casing 4. the end wall 22 having the openings 21 forms the boundary between the annular channel 6 and the plenum chamber 23.

All around the plenum chamber 23 are provided a plurality of cells 30, each arranged in the plane of symmetry of a Convergent Stream follower 12 and follower divergent flap 14 hinged to said convergent flap follower 12. Each cell 30 is bounded upstream by a middle portion 18 of the conical shell 16, and circumferentially by two substantially parallel walls 19 coming from the forming of the conical shell 16, as is shown in <figref idrefs="f0002">4</figref>. It is bounded downstream by a sealing wall 31 which connects the gripping structure 24 to upper portion 32 of the conical shell 16, the closure wall 31 having an orifice 33 whose use will be explained further in herein.

Between two consecutive chambers 30, the plenum chamber 23 is closed by a substantially axial wall 34, visible in <figref idrefs="f0002">4</figref>Which connects the radially inner ends of two adjacent walls 19.

We also see the <figref idrefs="f0002">Figures 3 and 4</figref> that the conical shell 16 further has a wall 35, steeply inclined that extends between the downstream edge of the axial wall 34, the downstream edges of said two adjacent walls 19 and the upstream edge of the upper part 32, two cavities 30 adjacent. This wall 35 has several holes 36 for circulating air unpressurized F5 nacelle in order to cool the various control devices of the flaps of the convergent-divergent nozzle 10.

The orifice 33 of each cell comprises a coupling 40 for fixing the upstream end of a pipe or tube 41 telescopically connected to the follower divergent flap 14 located in the same axial plane passing through the axis X.

The divergent flaps 14 are of box-type and within these flaps 14 receives part of the F4 flow of air that is pressurized. Suitable openings are provided to evacuate the air in the flux F1 and to the inner wall of the controlled divergent flaps 13 which may advantageously simple skin types.

The radially outer stream F4 is injected into the plenum chamber 23 through the partition 22 border breakthrough. The F4 flow then splits out of the chamber 23 between the different cells 30 for supplying the telescopic tubes 41 and the divergent flaps 14. The plenum chamber 23 allows for a regular sampling at the end of the annular channel 6 and to supply the cavities 30 with a uniform pressure and flow. In this way, the film cooling of the inner walls of convergent flaps 11 and 12 is not disturbed even in strong sampling F4 flow.

In addition, the shape given to the conical shell 16 as is shown in <figref idrefs="f0002">4</figref>, Allows for the cooling circuit of the divergent flaps 13, 14 without excessive clutter and stiffens this conical shell 16, through the walls 19 defining the cells 30 and walls 35.

Advantageously, there is further provided a device 50 for controlling gradually the F4 flow injected at the level of the follower divergent flaps 14. This device 50 includes a driven ring 51 for closing the entrance of the plenum chamber 23 according to the flight conditions. The shutter does not need to be highly sealing, because the goal is to appreciably reduce the cooling flow F4, which is costly for performance under certain conditions of engine operation. Conversely, in some cases, we wish to cool the nozzle with a high flow rate to achieve the lowest possible temperature on shutters, to reduce infrared signature example, even lose some performance engine.

The <figref idrefs="f0003">5</figref> shows a first embodiment of the device 50. The ring 51 is rotatably mounted about the axis X and its position is adjusted by an actuator 52. The ring 51 is located radially inside of the boundary wall 22 in opposite the openings 21. on its underside the ring 51 is held in place by another fixed wall 53 in which are formed openings 54 facing the openings 21. a pinion 55 mounted on the actuator rod 52 causes the ring 51 in rotation by means of a rack integral with the ring 51. the sealing rings 56 limit leakage between the ring 51 and the plenum chamber 23 when the latter is closed.

The ring 51 also has apertures 57 which, in the maximum flow position, are aligned with the apertures 21 and 54. Upon rotation of ring 51 about the axis X, the apertures 57 are shifted circumferentially relative to the openings 21 and 54, as is shown in <figref idrefs="f0005">7</figref>, Between the maximum open position and a fully closed position, in which there is almost no flow, except leakage. It is thus possible to determine the rate continuously.

The <figref idrefs="f0004">6</figref> shows a second embodiment of the device 50 which also comprises a ring 51 having openings 57 may be disposed in front of openings 21 of the boundary wall 22 and apertures 54 of a fixed partition 53 integral with the downstream end of the housing 4. instead of being mounted rotatably about the axis X, the ring is capable of being moved parallel to the axis X by means of a plurality of synchronized jacks 60, for example three cylinders, of which the pins 61 slide in guides 62. the connection between the pins 61 and the ring takes place by rods 63 passing through the casing 4 by sealed passages 64.

In the maximum flow position, the openings 57 are arranged opposite the openings 21 and 54 and the system is retailer. In another position of the ring 51, shown in<figref idrefs="f0004">6</figref>21 and 54 apertures are closed by the ring 51 and there is practically no flow, apart from the leakage rates. To an intermediate position shown in<figref idrefs="f0005">8</figref>, It is possible to meter the air flow continuously.

In both embodiments of the device 50, the seals between the ring 51 and the stationary parts can be provided by the segments, to delay rapid wear of the joints.

The device 50 provides the possibility of regulating the flow taken in a certain range to suit the engine operating conditions and operational circumstances.