Turbojet rear body comprising a fixed shell and a rotating movable shell, both equipped with windows for adjusting fluid flow

Abstract

The invention relates to a turbojet rear body comprising: – an exhaust casing (9) carrying a confluence plate (11) which surrounds a primary flow and is surrounded by a secondary flow; – an afterburner chamber (12) comprising a casing (13) and a sleeve (16) delimiting with this casing (13) an annular space (17) extending along an axis (AX), this sleeve (16) having a diameter greater than that of the confluence plate (11); – a fixed ferrule (22) extending from the confluence plate (11) to the inner sleeve (16), this fixed ferrule (22) having windows (27); – a movable ferrule (23) running alongside the fixed ferrule (22) and which has windows (28), this ferrule (23) being movable in rotation around the axis (AX) between an opening position in which the windows (27) of the fixed ferrule are open and a closing position in which the windows (27) of the fixed ferrule (22) are closed by the movable ferrule (23).Figure for abbreviation: Figure 2.

Description

Title of the invention: Turbojet afterbody comprising a fixed shroud and a rotating shroud which are provided with windows for adjusting a fluid flow rate Technical field

[0001] The invention applies to the field of military aeronautical propulsion, and more particularly to dual-flow turbojets equipped with an afterburner chamber. STATE OF THE PRIOR ART

[0002] In a turbojet, air is admitted into an inlet sleeve to pass through a low-pressure compressor before splitting 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 before arriving in a combustion chamber, after which it is expanded in a high-pressure turbine and then in a low-pressure turbine before being discharged to the rear. The secondary flow is propelled to the rear without being compressed.

[0004] The primary and secondary flows then pass through an exhaust casing located downstream of the low-pressure turbine, which is extended by a confluence plate extending downstream.

[0005] In the case of an afterburner turbojet, an afterburner nozzle located downstream of the exhaust casing collects the primary and secondary flows to inject fuel and generate additional combustion to temporarily increase the total thrust.

[0006] In this post-combustion chamber, the fuel is introduced by injectors, downstream of which radially extending flame-holder arms and spark plugs are provided to ignite the injected fuel.

[0007] Such an engine can thus operate in so-called dry mode in which the post-combustion is not activated, or in post-combustion mode in which the post-combustion chamber is supplied with fuel.

[0008] In such an engine, the bypass ratio, which corresponds to the ratio of the secondary flow rate to the primary flow rate, determines in particular the fuel consumption and the thrust generated. The engine can be designed to correspond to an optimal bypass ratio for a given speed, but it is then not optimal at other speeds.

[0009] The engine can also be designed to match an acceptable compromise of bypass ratio for a given speed range, which is also not common. completely satisfactory. In any case, this problem is all the more critical since the engine must be able to operate in a wide range of operating speeds (which are generally referred to as "flight envelopes").

[0010] In this context, the invention aims to provide a solution for dynamically adjusting the dilution ratio according to the operating speed of the engine. Statement of the invention

[0011] To this end, the invention relates to a turbojet afterbody comprising:

[0012] - an exhaust casing carrying a confluence sheet in the form of a wall of revolution which surrounds a primary flow passing through the turbojet engine, and which is surrounded by a secondary flow passing through the turbojet engine;

[0013] - an afterburner chamber comprising a rear casing and a jacket internal delimiting with this casing an annular space extending along a longitudinal axis of the engine, this internal sleeve having a diameter greater than that of the confluence sheet;

[0014] - a fixed shell extending from the confluence sheet to the internal jacket this shell fixed with fluid passage windows;

[0015] - a movable shell covering the fixed shell and which includes windows for the passage of fluid, this movable shell being movable in rotation around the longitudinal axis between an open position in which the windows of the movable shell coincide with the windows of the fixed shell, and a closed position in which the windows of the movable shell are offset to close the windows of the fixed shell.

[0016] Adjusting the angular position of the movable shell around the longitudinal axis makes it possible to modify the flow rate of the secondary flow entering the post-combustion chamber, which makes it possible to modify the engine's dilution ratio and adapt it to its operating speed so that this ratio is optimal at all engine speeds.

[0017] The invention also relates to a rear body thus defined, in which the movable ferrule surrounds the fixed ferrule.

[0018] The invention also relates to a rear body thus defined, in which the movable ferrule has a shape identical to the shape of the fixed ferrule.

[0019] The invention also relates to a rear body thus defined, in which the movable shell extends around the confluence sheet and around the jacket.

[0020] The invention also relates to a rear body thus defined, in which the fixed shell and / or the movable shell comprises a conical portion in which the fluid passage windows are formed.

[0021] The invention also relates to a rear body thus defined, in which the windows have the shape of portions of crowns whose long sides extend circumferentially. partially around the longitudinal axis.

[0022] The invention also relates to a rear body thus defined, in which these windows are spaced circumferentially from each other by a value corresponding to their circumferential length.

[0023] The invention also relates to a rear body thus defined, comprising actuating means for moving the movable shell in rotation while the engine is in operation.

[0024] The invention also relates to a turbojet comprising an afterbody thus defined. Brief description of the drawings

[0025] [Fig-1] is a general longitudinal sectional view of a post-turbojet combustion;

[0026] [Fig.2] is a longitudinal sectional view schematically showing a portion of combustion chamber according to the invention;

[0027] [Fig.3] is a local view in longitudinal section showing the ferrules surrounding the confluence sheet and the jacket;

[0028] [Fig.4] is a partial front view of the ferrules when the movable ferrule is in opening position;

[0029] [Fig.5] is a partial front view of the ferrules when the movable ferrule is in closed position;

[0030] [Fig.6] is a partial front view of the ferrules when the movable ferrule occupies a intermediate position;

[0031] [Fig.7] is a partial front view of a mobile shell having windows round;

[0032] [Fig.8] is a partial front view of a mobile shell having oblong windows;

[0033] [Fig.9] is a partial front view of a mobile shell having windows square.

[0034] DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

[0035] In [Fig.l], the turbojet 1 according to the invention has a general shape of revolution extending around a longitudinal axis AX, it comprises at its upstream AM an inlet sleeve through which the air is admitted to pass through a low pressure compressor 2 before being split into a central primary flow F1 and a secondary flow F2 surrounding the primary flow.

[0036] The primary flow F1 is then compressed in a high pressure compressor 3 before arriving in a combustion chamber 4, after which it is expanded through a high pressure turbine 6 and a low pressure turbine 7.

[0037] The secondary flow is propelled directly towards the rear by the low pressure compressor 2 in a vein delimited externally by a main casing 8.

[0038] The primary flow F1 and secondary flow F2 then pass through an exhaust casing 9 located downstream of the low-pressure turbine, which is extended by a confluence plate 11 extending downstream thereof.

[0039] This turbojet is equipped downstream of the turbine 7 with an afterburner chamber 12 delimited by a rear casing 13, in which the secondary flow F2 joins the primary flow F1 to form the propulsion flow Fp. The two flows join downstream of the confluence plate 11 which extends the separation between the primary flow F1 and the secondary flow F2.

[0040] After passing through the low pressure turbine 7, the primary flow F1 thus circulates between the confluence sheet 11 and an outlet cone 14 surrounded by this sheet 11 to reach the post-combustion chamber 12.

[0041] The wall of the rear casing 13 is lined at the level of the chamber 12 by an internal jacket 16 delimiting with it an annular space 17. A part of the secondary flow is directed into this annular space 17 to ventilate it in order to limit heating of the casing 13.

[0042] The afterburner chamber corresponds to the rear body of the turbojet engine which may also include a nozzle comprising a convergent portion and a divergent portion which then extend in the extension of the afterburner chamber.

[0043] Injectors (not shown) located downstream of the low-pressure turbine 7 are provided to introduce additional fuel in order to generate additional combustion in the chamber 12 when the engine is in post-combustion mode. In addition, flame-holder arms 18 located downstream of the confluence plate 11 ignite the fuel introduced by the injectors, when the engine is operating in post-combustion mode.

[0044] As visible in [Fig.2], the jacket 16 has a circular upstream edge 19 having a diameter greater than the circular downstream edge 21 of the confluence sheet 11. The passage section of the flows F1 and F2 towards the post-combustion chamber 12 is thus divided into an external section SE corresponding to a crown delimited by the annular space 17, an intermediate section SI corresponding to a crown extending between the sheet 11 and the jacket 16, and a central section SC delimited internally by the cone 14 and externally by the sheet 11.

[0045] According to the invention, the engine comprises two shells 22 and 23 masking the intermediate section SI by being provided with fluid passage windows, so as to modulate the flow rate passing through this intermediate section. These two shells, which are concentric, surround the confluence sheet 11 at their upstream ends. and they surround the jacket 16 at their downstream ends.

[0046] As can be seen in more detail in [Fig. 3], the ferrule 22, which is fixed, has an upstream edge 24 at which it surrounds the external face of the confluence sheet 11, and it widens downstream to a downstream edge 26 at which it surrounds the external face of the jacket 16. This fixed ferrule 22, which is for example rigidly secured to the sheet 11 and to the jacket 16 which it surrounds, has windows 27 allowing the passage of secondary flow F2 through the intermediate section SI towards the internal space which the jacket 16 delimits.

[0047] These windows 27 are formed in the flared portion of the ferrule 22, which is a substantially conical portion in the example of the figures, this ferrule 22 being a sheet metal element of revolution.

[0048] The movable ferrule 23 has a general shape identical or similar to that of the fixed ferrule 22, having substantially larger dimensions, and it surrounds the fixed ferrule 22 to be radially superimposed thereon. It also comprises windows, marked by 28, also extending into its flared part, which is here substantially conical.

[0049] The movable ferrule 23 is rotatable about the axis AX, between an open position and a closed position. In the open position which corresponds to the situation in [Fig. 4], the movable windows 28 coincide with the fixed windows 27 of the fixed ferrule 22, so that the flow rate through the intermediate section SI is maximum. In the closed position, as in [Fig. 5], the movable windows 28 are circumferentially offset relative to the fixed windows 27 of the ferrule 22 so that the movable ferrule 23 completely closes these fixed windows 27, so that the flow rate through the intermediate section SI is substantially zero.

[0050] The movable ferrule 23 can also occupy any intermediate position, as for example in [Fig.6], in which the movable windows 28 are partially offset relative to the fixed windows 27, so that the flow rate passing through the intermediate section SI is of the order of half the maximum possible flow rate.

[0051] In the example of figures 4 to 6, the windows 27 have the shape of crown portions, similar to rectangles, the long sides of which extend in the circumferential direction.

[0052] These windows are spaced circumferentially from each other by a value corresponding to their length in the circumferential direction in the example of figures 2 to . Thus, when the movable shell is in its maximum opening position, the passage section corresponds to half of the passage section extending between the confluence sheet 11 and the jacket 16.

[0053] Other window shapes can be considered, the windows can be round as shown in [Fig.7], they can be oblong with orientations oblique to the radial direction as in the example of [Fig.8], or square as shown in [Fig.9].

[0054] The movable ferrule 23 can occupy any position between its maximum open position and its fully closed position, so as to modulate the flow rate of secondary flow admitted into the post-combustion chamber as a function of the engine speed.

[0055] Advantageously, this movable ferrule 23 is moved by a control system of the same type as those used to adjust the angular position of an arrangement of fixed vanes with variable pitch. In this case, an actuator located at the external face of the casing comprises an actuating member connected to the movable ferrule, to be able to place it at any angular position between the maximum opening position and the maximum closing position.

[0056] Such an actuator may be a motor equipped with a pinion meshed in an external toothing of the movable shell, or a jack having a movable rod by which it is connected to the external shell.

[0057] This actuator is then controlled by a turbojet control system to adjust the angular position of the movable shroud around the axis AX, in real time depending on the engine operating speed.

Claims

Claims

1. A turbojet engine afterbody comprising: - an exhaust casing (9) carrying a confluence plate (11) in the form of a wall of revolution which surrounds a primary flow passing through the turbojet engine, and which is surrounded by a secondary flow passing through the turbojet engine; - a post-combustion chamber (12) comprising a rear casing (13) and an internal jacket (16) delimiting with this casing (13) an annular space (17) extending along a longitudinal axis (AX) of the engine, this internal jacket (16) having a diameter greater than that of the confluence plate (11); - a fixed shroud (22) extending from the confluence plate (11) to the internal jacket (16), this fixed shroud (22) comprising windows (27) for the passage of fluid;- a movable shell (23) covering the fixed shell (22) and which comprises windows (28) for the passage of fluid, this movable shell (23) being movable in rotation around the longitudinal axis (AX) between an open position in which the windows (28) of the movable shell (23) coincide with the windows (27) of the fixed shell (22), and a closed position in which the windows (28) of the movable shell (23) are offset to close the windows (27) of the fixed shell (22).;

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

3. Rear body according to one of the preceding claims, in which the movable ferrule (23) has a shape identical to the shape of the fixed ferrule (22).

4. Rear body according to one of the preceding claims, in which the movable ferrule (23) extends around the confluence sheet (11) and around the jacket (16).

5. Rear body according to one of the preceding claims, in which the fixed ferrule (22) and / or the movable ferrule (23) comprises a conical portion in which the windows (27, 28) for the passage of fluid are formed.

6. Rear body according to one of claims 1 to 3, in which the windows (27, 28) have the shape of crown portions whose long sides extend circumferentially around the longitudinal axis (AX).

7. A rear body according to any preceding claim, wherein these windows (27, 28) are spaced circumferentially from each other by a value corresponding to their circumferential length.

8. Rear body according to one of the preceding claims, comprising actuating means for moving the movable ferrule (23) in rotation while the engine is in operation.

9. Turbojet comprising an afterbody according to one of the preceding claims.

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