Turbojet engine rear body comprising a stationary shroud and a rotatably movable shroud that are provided with windows for adjusting a fluid flow rate
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- SAFRAN AIRCRAFT ENGINES SAS
- Filing Date
- 2024-06-19
- Publication Date
- 2026-04-29
AI Technical Summary
Turbofan engines face challenges in maintaining optimal dilution rate across a wide range of operating speeds, as existing designs are either optimized for specific speeds or compromise on bypass ratio, leading to suboptimal fuel consumption and thrust generation.
A turbojet rear body design featuring a fixed and rotating shell with fluid passage windows, allowing the rotating shell to adjust its position to modify the secondary flow rate into the post-combustion chamber, thereby dynamically adjusting the dilution rate based on engine speed.
Enables optimal dilution rate adjustment across varying engine speeds, improving fuel efficiency and thrust generation by modulating the secondary flow rate through the post-combustion chamber.
Smart Images
Figure FR2024050803_26122024_PF_FP_ABST
Abstract
Description
[0001] DESCRIPTION
[0002] TITLE: TURBOJET ENGINE AFTERBODY COMPRISING A FIXED SHELL AND A ROTATING SHELL WHICH ARE PROVIDED WITH WINDOWS FOR ADJUSTING A FLUID FLOW
[0003] TECHNICAL FIELD
[0004] The invention applies to the field of military aeronautical propulsion, and more particularly to dual-flow turbojets equipped with an afterburner chamber.
[0005] STATE OF THE PRIOR ART
[0006] 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.
[0007] The primary flow is then compressed in a high-pressure compressor before entering 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.
[0008] 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.
[0009] In the case of an afterburning 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.
[0010] Into this afterburner 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. Such an engine can thus operate in so-called dry mode in which the afterburner is not activated, or in afterburner mode in which the afterburner chamber is supplied with fuel.
[0011] 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.
[0012] The engine can also be designed to match an acceptable compromise of bypass ratio for a given rpm range, which is also not completely satisfactory. In any case, this problem is all the more critical since the engine must be able to operate over a wide range of operating rpms (which are generally referred to as "flight envelopes").
[0013] In this context, the invention aims to provide a solution for dynamically adjusting the dilution ratio according to the engine operating speed.
[0014] STATEMENT OF THE INVENTION
[0015] To this end, the invention relates to a turbojet afterbody comprising:
[0016] - an exhaust casing carrying a confluence plate in the form of a revolution wall which surrounds a primary flow passing through the turbojet engine, and which is surrounded by a secondary flow passing through the turbojet engine;
[0017] - a post-combustion chamber comprising a rear casing and an internal sleeve 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;
[0018] - a fixed shell extending from the confluence sheet to the internal jacket, this fixed shell comprising fluid passage windows; - a movable shell covering the fixed shell and which comprises fluid passage windows, 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.
[0019] Adjusting the angular position of the movable shroud around the longitudinal axis allows the secondary flow rate entering the post-combustion chamber to be modified, which allows the engine's bypass ratio to be modified and adapted to its operating speed so that this ratio is optimal at all engine speeds.
[0020] The invention also relates to a rear body thus defined, in which the movable ferrule surrounds the fixed ferrule.
[0021] 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.
[0022] The invention also relates to a rear body thus defined, in which the movable shell extends around the confluence sheet and around the jacket.
[0023] 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.
[0024] The invention also relates to a rear body thus defined, in which the windows have crown portion shapes whose long sides extend circumferentially around the longitudinal axis.
[0025] The invention also relates to a rear body thus defined, in which these windows are circumferentially spaced from each other by an amount corresponding to their circumferential length.
[0026] 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.
[0027] The invention also relates to a turbojet engine comprising an afterbody thus defined. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] [Fig. 1] is a general longitudinal sectional view of an afterburning turbojet engine;
[0029] [Fig. 2] is a longitudinal sectional view schematically showing a portion of a combustion chamber according to the invention;
[0030] [Fig. 3] is a local view in longitudinal section showing the shells surrounding the confluence plate and the jacket;
[0031] [Fig. 4] is a partial front view of the ferrules when the movable ferrule is in the open position;
[0032] [Fig. 5] is a partial front view of the ferrules when the movable ferrule is in the closed position;
[0033] [Fig. 6] is a partial front view of the ferrules when the movable ferrule occupies an intermediate position;
[0034] [Fig. 7] is a partial front view of a mobile shell having round windows;
[0035] [Fig. 8] is a partial front view of a mobile shell having oblong windows;
[0036] [Fig. 9] is a partial front view of a mobile shell having square windows.
[0037] DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
[0038] In Figure 1, 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.
[0039] The primary flow Fl 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. 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.
[0040] 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.
[0041] This turbojet is equipped downstream of the turbine 7 with a post-combustion chamber 12 delimited by a rear casing 13, in which the secondary flow F2 joins the primary flow Fl to form the propulsion flow Fp. The two flows join downstream of the confluence plate 11 which extends the separation between the primary flow Fl and the secondary flow F2.
[0042] After passing through the low pressure turbine 7, the primary flow Fl thus circulates between the confluence plate 11 and an outlet cone 14 surrounded by this plate 11 to reach the post-combustion chamber 12.
[0043] 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.
[0044] 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.
[0045] 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. 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 plate 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.
[0046] 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.
[0047] As can be seen in more detail in Figure 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 that it surrounds, has windows T1 allowing the passage of secondary flow F2 through the intermediate section SI towards the internal space that the jacket 16 delimits.
[0048] These windows T1 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 revolution element.
[0049] 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.
[0050] The movable shell 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 T1 of the fixed shell 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 T1 of the shell 22 so that the movable shell 23 completely closes these fixed windows T1, so that the flow rate through the intermediate section SI is substantially zero.
[0051] The movable shell 23 can also occupy any intermediate position, as for example in Figure 6, in which the movable windows 28 are partially offset relative to the fixed windows T1, so that the flow rate passing through the intermediate section SI is of the order of half the maximum possible flow rate.
[0052] In the example of figures 4 to 6, the windows T1 have the shape of crown portions, similar to rectangles, the long sides of which extend in the circumferential direction.
[0053] 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.
[0054] Other window shapes can be considered, the windows can be round as shown in Figure 7, they can be oblong with oblique orientations relative to the radial direction as in the example of Figure 8, or even square as shown in Figure 9.
[0055] The movable shell 23 can occupy any position between its maximum open position and its fully closed position, so as to modulate the secondary flow rate admitted into the post-combustion chamber as a function of the engine speed.
[0056] 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.
[0057] Such an actuator may be a motor equipped with a pinion meshed with an external toothing of the movable shell, or a cylinder having a movable rod by which it is connected to the external shell.
[0058] This actuator is then controlled by a turbojet control system to adjust the angular position of the movable shroud around the AX axis, in real time depending on the engine operating speed.
Claims
CLAIMS 1. Turbojet 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 sleeve (16) delimiting with this casing (13) an annular space (17) extending along a longitudinal axis (AX) of the engine, this internal sleeve (16) having a diameter greater than that of the confluence sheet (11); - a fixed shell (22) extending from the confluence sheet (11) to the internal jacket (16), this fixed shell (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. Rear body according to claim 1, in which 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 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. Rear body according to one of the preceding claims, in which 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 engine comprising an afterbody according to one of the preceding claims.