Turbojet engine afterbody comprising fixed shroud provided with window for regulating flow of fluid and rotationally moving shroud

Abstract

The invention relates to a turbojet engine afterbody comprising:-an exhaust casing (9) carrying a manifold plate (11) surrounding a primary air flow and surrounded by a secondary air flow; -an afterburner (12) comprising a casing (13) and a bushing (16) delimiting together with the casing (13) an annular space (17) extending along the axis (AX), the diameter of the bushing (16) being greater than the diameter of the converging plate (11); -a fixed shroud (22) extending from the bus plate (11) to the inner liner (16), the fixed shroud (22) comprising a window (27); -a moving cover (23) extending along the fixed cover (22) and comprising a window (28), the cover (23) being rotatably movable about an axis (AX) between an open position, in which the window (27) in the fixed cover is open, and a closed position, in which the window (27) in the fixed cover (22) is closed by the moving cover (23).

Description

TECHNICAL FIELD

[0001] The application applies to the field of military aviation propulsion and more particularly to the field of dual-flow turbojet engines, equipped with a reheating chamber. BACKGROUND

[0002] In a turbojet engine, air enters an inlet, flows through a low-pressure compressor, then divides into a central primary flow and a secondary flow surrounding the primary flow.

[0003] The primary flow is then compressed in a high-pressure compressor, then reaches a reheating chamber, then expands in a high-pressure turbine, then in a low-pressure turbine, then is expelled rearward. The secondary flow is itself pushed rearward without being compressed.

[0004] The primary flow and the secondary flow then flow through an exhaust nozzle downstream of the low-pressure turbine, the nozzle being extended by a convergent divergent duct extending downstream of the nozzle.

[0005] In the case of a reheating chamber turbojet engine, a reheating chamber nozzle downstream of the exhaust nozzle collects the primary flow and the secondary flow and injects fuel into it to produce additional reheating combustion, temporarily increasing the total thrust.

[0006] In this reheating chamber, fuel is injected by injectors, downstream of which are provided radially extending flame stabilizer arms and a spark plug to ignite the injected fuel.

[0007] This engine can thus be operated in a so-called dry-thrust state, in which the reheating chamber is not actuated, or in a reheated state, in which fuel is supplied to the reheating chamber.

[0008] In such an engine, the dilution ratio, corresponding to the ratio of the secondary flow rate to the primary flow rate, in particular conditions the fuel consumption and the thrust produced. The engine can be designed to match an optimal dilution ratio at a given speed, but not optimally at other speeds.

[0009] The engine can also be designed to match an acceptable compromise dilution ratio over a given range of speeds, but this is not entirely satisfactory either. In any case, this problem is particularly critical since the engine must be able to operate over a wide range of operating speeds, generally called "flight envelope".

[0010] Against this background, the purpose of the application is to provide a solution for dynamically adjusting the dilution ratio as a function of the operating speed of the engine. SUMMARY

[0011] To this end, the purpose of the application is to provide a turbojet engine comprising:

[0012] - an exhaust casing carrying a collector in the form of a rotating wall, which surrounds a primary flow through the turbojet and which is surrounded by a secondary flow through the turbojet;

[0013] - a thrust chamber comprising a rear casing and an inner sleeve which, with the casing, delimits an annular space extending along the longitudinal axis of the engine, the inner sleeve having a diameter greater than that of the collector;

[0014] - a fixed cover extending from the collector to the inner sleeve, the fixed cover comprising fluid flow-through windows;

[0015] - a mobile cover covering the fixed cover and comprising fluid flow-through windows, the mobile cover being rotatably mobile about the longitudinal axis between an open position in which the windows of the mobile cover coincide with the windows of the fixed cover and a closed position in which the windows of the mobile cover are offset to close the windows of the fixed cover.

[0016] Adjusting the angular position of the mobile cover about the longitudinal axis makes it possible to modify the secondary flow rate entering the thrust chamber, thereby making it possible to modify the dilution rate of the engine and to adapt it to its operating speed so that this dilution rate is optimal at all engine speeds.

[0017] The application also relates to a rear body as defined above, in which the mobile cover surrounds the fixed cover.

[0018] The application also relates to a rear body as defined above, in which the mobile cover has the same shape as the fixed cover.

[0019] The application also relates to a rear body as defined above, in which the mobile cover extends around the collector and the sleeve.

[0020] The application also relates to a rear body as defined above, in which the fixed cover and / or the mobile cover comprise a conical portion in which the fluid flow-through windows are formed.

[0021] The application also relates to a rear body as defined above, in which the windows have a portion of conical shape, the long sides of which extend circumferentially about the longitudinal axis.

[0022] The application also relates to a rear body as defined above, in which the windows are circumferentially spaced apart from each other by a distance value corresponding to their circumferential length.

[0023] The application also relates to a rear body as defined above, comprising actuating means for moving the rotationally mobile sleeve during operation of the engine.

[0024] The application also relates to a turbojet comprising a rear body as defined above. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a longitudinal section overview of a turbojet engine with afterburner;

[0026] Figure 2 is a longitudinal section view schematically showing the afterburner part according to the application;

[0027] Figure 3 is a longitudinal section partial view showing the shroud surrounding the collector and the bushing;

[0028] Figure 4 is a partial front view of the shroud when the mobile shroud is in the open position;

[0029] Figure 5 is a partial front view of the shroud when the mobile shroud is in the closed position;

[0030] Figure 6 is a partial front view of the shroud when the mobile shroud occupies an intermediate position;

[0031] Figure 7 is a partial front view of the mobile shroud comprising a circular window;

[0032] Figure 8 is a partial front view of the mobile shroud comprising an oblong window;

[0033] Figure 9 is a partial front view of the mobile shroud comprising a square window. DETAILED DESCRIPTION

[0034] In Figure 1 the turbojet engine 1 according to the application has a general shape of a revolution around a longitudinal axis AX, which comprises at its upstream AM an air intake through which air enters, flows through a low-pressure compressor 2 and is then divided into a central primary flow Fl and a secondary flow F2 of an annular primary flow.

[0035] The primary flow Fl is then compressed in a high-pressure compressor 3, then reaches an afterburner 4, after which it expands through a high-pressure turbine 6 and a low-pressure turbine 7.

[0036] The secondary flow is in itself directly pushed by the low-pressure compressor 2 into a duct externally delimited by a main casing 8.

[0037] The primary flow Fl and the secondary flow F2 then flow through an exhaust nozzle 9 located downstream of the low-pressure turbine, this nozzle being extended by a collector 11 which extends downstream thereof.

[0038] The turbojet is equipped, downstream from the turbine 7, with a thrust chamber 12 delimited by a rear casing 13, in which the secondary flow F2 is merged with the primary flow Fl to form a propulsive flow Fp. The two flows are merged downstream from a merging panel 11 which extends the separation between the primary flow Fl and the secondary flow F2.

[0039] After passing through the low-pressure turbine 7, the primary flow Fl then flows between the merging panel 11 and an outlet cone 14 which is surrounded by the panel 11, to the thrust chamber 12.

[0040] The walls of the rear casing 13 are lined, at the chamber 12, with a lining sleeve 16, between which an annular space 17 is delimited. Part of the secondary flow is directed into the annular space 17 to ventilate it, so as to limit the heating of the casing 13.

[0041] The thrust chamber corresponds to the rear body of the turbojet, which can also comprise a nozzle comprising a convergent portion and a divergent portion which then extend in an extension of the thrust chamber.

[0042] An injector, not shown, located downstream from the low-pressure turbine 7, is provided for injecting additional fuel so as to produce additional combustion in the chamber 12 when the engine is in a thrust chamber mode. In addition, when the engine is running in a thrust state, a flame stabilizer arm 18, located downstream from the merging panel 11, ignites the fuel injected by the injector.

[0043] As Figure 2 shown, the sleeve 16 comprises a circular upstream edge 19, the diameter of which is greater than the diameter of a circular downstream edge 21 of the merging panel 11. Thus, the flow cross-section of the flows Fl and F2 into the thrust chamber 12 is divided into an outer cross-section SE corresponding to the annular area delimited by the annular space 17, an intermediate cross-section SI corresponding to the annular area extending between the merging panel 11 and the sleeve 16, and a central cross-section SC, delimited internally by the cone 14 and externally by the merging panel 11.

[0044] According to the invention, the engine comprises two shrouds 22 and 23 which mask the intermediate cross-section SI by providing fluid flow windows so as to regulate the flow through this intermediate cross-section. The two concentric shrouds surround the merging panel 11 at their upstream end and the sleeve 16 at their downstream end.

[0045] As Figure 3As can be seen in more detail, the fixed shroud 22 comprises an upstream edge 24 where it surrounds the outer surface of the collector plate 11 and it flares downstream to a downstream edge 26 where it surrounds the outer surface of the bushing 16. This fixed shroud 22 is rigidly fixed, for example, to the collector plate 11 and to the bushing 16 that it surrounds, it comprises windows 27 enabling the passage of the secondary flow F2 through the intermediate section SI into the interior space delimited by the bushing 16.

[0046] These windows 27 are formed in the flared portion of the shroud 22, which is generally a conical portion in the example illustrated, the shroud 22 being a plate-shaped metal rotating element as such.

[0047] The mobile shroud 23 has the same or similar general shape as the fixed shroud 22, with significantly greater dimensions, and it surrounds the fixed shroud 22 so as to be radially superimposed thereon. It also comprises windows, designated 28, which extend in the flared portion thereof, here generally a conical portion.

[0048] The mobile shroud 23 can be rotatably mobile about the axis AX between an open position and a closed position. In the open position, corresponding to the situation Figure 4 of maximum flow through the intermediate section SI, the mobile windows 28 coincide with the fixed windows 27 of the fixed shroud 22. In the closed position, as illustrated in Figure 5 , the mobile windows 28 are circumferentially offset with respect to the fixed windows 27 of the shroud 22 so that the mobile shroud 23 completely closes these fixed windows 27, so that the flow through the intermediate section SI is substantially zero.

[0049] The mobile shroud 23 can also occupy any intermediate position, for example Figure 6 , in which the mobile windows 28 are partially offset with respect to the fixed windows 27, so that the flow through the intermediate section SI is approximately half the maximum possible flow.

[0050] In the example Figures 4 to 6 , the windows 27 have the shape of an annular portion, similar to a rectangle, with the long sides extending in the circumferential direction.

[0051] In the example Figure 2 , the distance value at which the windows are spaced from each other in the circumferential direction corresponds to their length in the circumferential direction. Thus, when the mobile shroud is in its maximum open position, the flow section corresponds to half the flow section extending between the collector plate 11 and the bushing 16.

[0052] Other window shapes can be considered, the windows can be circular, as illustrated in Figure 7 , they can be oblong, with an oblique direction with respect to the radial direction, as illustrated in the example Figure 8 ; or they can be square, as illustrated in the example Figure 9 .

[0053] The mobile cover 23 can occupy any position between its maximum open position and its fully closed position in order to regulate the secondary flow rate into the afterburner as a function of the engine speed.

[0054] Advantageously, this mobile cover 23 is moved by a control system of the type used to adjust the angular position of a fixed vane arrangement with variable pitch. In this case, the actuator mounted on the outer surface of the casing comprises an actuating member connected to the mobile cover in order to be able to place it in any angular position between the maximum open position and the maximum closed position.

[0055] This actuator can be a motor equipped with a pinion meshing with the external gear of the mobile cover, or a pneumatic cylinder with a mobile rod by which it is connected to the mobile cover.

[0056] This actuator is then controlled by the turbojet engine control system in order to adjust in real time the angular position of the mobile cover around the AX axis as a function of the operating speed of the engine.

Claims

1. A turbojet engine rear body, comprising: - Exhaust casing (9), which carries a manifold (11) in the form of a rotating wall, which surrounds the main airflow that flows through the turbojet engine and is surrounded by the secondary airflow that flows through the turbojet engine; - Afterburner (12), which includes a rear casing (13) and an inner liner (16) that together with the casing (13) defines an annular space (17) extending along the longitudinal axis (AX) of the engine, the inner liner (16) having a diameter greater than that of the manifold (11); - A retaining cover (22) extending from the manifold (11) to the inner liner (16), the retaining cover (22) including a fluid flow window (27); - A movable cover (23) that covers a fixed cover (22) and includes a fluid flow window (28) that rotates about a longitudinal axis (AX) between an open position and a closed position, wherein in the open position the window (28) of the movable cover (23) coincides with the window (27) of the fixed cover (22), and in the closed position the window (28) of the movable cover (23) is offset to close the window (27) of the fixed cover (22).

2. The rear body according to claim 1, wherein, The movable cover (23) surrounds the fixed cover (22).

3. The rear body according to any one of the preceding claims, wherein, The shape of the movable cover (23) is the same as that of the fixed cover (22).

4. The rear body according to any one of the preceding claims, wherein, The movable cover (23) extends around the manifold (11) and around the bushing (16).

5. The rear body according to any one of the preceding claims, wherein, The fixed cover (22) and / or the movable cover (23) include a conical portion in which fluid flow windows (27, 28) are formed.

6. The rear body according to any one of claims 1 to 3, wherein, The windows (27, 28) have an annular shape, with their long sides extending circumferentially around the longitudinal axis (AX).

7. The rear body according to any one of the preceding claims, wherein, The circumferential distance between these windows (27, 28) corresponds to their circumferential length.

8. The rear body according to any of the preceding claims, including an actuation device for rotatably moving the movable cover (23) during engine operation.

9. A turbojet engine comprising a rear body as described in any of the preceding claims.

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