AIRCRAFT WITH AN EXHAUST PIPE COUPLED TO A STABILIZATION SYSTEM

Description

[0001] The present invention relates to an aircraft equipped with an exhaust duct coupled to a stabilization system which is configured to stabilize the exhaust duct.

[0002] An aircraft, and for example a rotorcraft, may include an engine that expels combustion gases through an ejection nozzle.

[0003] The engine is usually housed in a compartment of the aircraft called the "engine compartment". The engine compartment may be delimited by one or more firewalls and / or at least one cowling.

[0004] The aircraft may then include an exhaust duct that is open to the engine compartment and to an environment external to the aircraft. The exhaust duct may be fixed and housed within a compartment delimited by a movable cowling, or even a firewall, for example. This exhaust duct locally surrounds the exhaust nozzle. This exhaust duct may allow the combustion gases from the engine's exhaust nozzle to be mixed with fresh air from the engine compartment and / or the gases to be directed to preferred areas. The exhaust nozzle may be referred to as the primary or main nozzle, and the exhaust duct as the secondary nozzle.

[0005] In addition, the development of an exhaust pipe is complex due in particular to the high temperature of the ejected gases, on the order of several hundred degrees Celsius, the pressure exerted by these gases on the exhaust pipe as well as vibrational phenomena.

[0006] For example, the rotation of a helicopter's main rotor, the operation of an engine, and a structure supporting the exhaust duct are all sources of vibration that can excite an exhaust duct. Air movement near the exhaust duct is also a source of vibration for that duct.

[0007] Therefore, an exhaust duct is likely to deform in flight due to these various constraints, in particular due to thermal constraints as well as its vibratory and dynamic behavior and the tuning of its natural frequency with regard to the frequencies of the excitations undergone.

[0008] Modifying the exhaust system to limit these deformations can be quite complex, in terms of cost, time, and even weight. Furthermore, modifying an exhaust system can impact its surroundings, such as the supporting structure that bears its weight.

[0009] Document EP3575219 describes a rotorcraft having at least one engine associated with an exhaust duct. The exhaust duct is attached to a fixed structure of the rotorcraft by a mechanism to be stabilized both statically and in response to thermal expansion.

[0010] Document EP2894099 describes a method for manufacturing an exhaust duct equipped with fixing rings.

[0011] Document WO2009 / 083074A1 describes a device for cooling hot gas to be exhausted from an aircraft. The device comprises a channel designed to conduct the hot gas from a hot gas source that can be connected to the device to an outlet point, and a frame surrounding the channel designed to support it. The channel consists of one or more sections of tubing and has one or more cooling air inlets that can be connected to one or more cooling air sources to mix the hot gas with cooling air. Documents WO 99 / 54204 A1 and US 2 653 585 A are also known.

[0012] The present invention then aims to provide an aircraft according to claim 1 which is equipped with an exhaust duct cooperating with an innovative stabilization system.

[0013] The invention relates to an aircraft equipped with at least one exhaust duct for ejecting gases from an engine, the exhaust duct being partially housed in an internal housing of the aircraft, the housing being separated from an external environment located outside the aircraft by at least one cowling, this cowling being movable relative to a supporting structure of the aircraft, the exhaust duct comprising an ejection section passing through a passage of the cowling without touching the cowling, a space separating the ejection section from the cowling.

[0014] This aircraft, according to claim 1, comprises at least one stabilization system coupled to the exhaust duct, the stabilization system including a stiffening ring attached to the exhaust duct and at least one fastener connecting the exhaust duct to the cowling. Thus, the stabilization system comprises two dissimilar devices that work together to improve the exhaust duct's behavior under load during operation. Optional features of this aircraft are described in dependent claims 2-13.

[0015] A stiffening ring is positioned around and against the exhaust duct. Specifically, the stiffening ring allows the exhaust duct's natural frequency to be modified, shifting it away from an excitation frequency. The stiffening ring also provides localized constraint to the exhaust duct, preventing deformation, for example, by preventing ovalization. This stiffening ring can be arranged to have an acceptable impact on the aircraft's aerodynamics, and even on the ventilation of the housing.

[0016] The mounting bracket(s) secure the exhaust duct to the cowling to stabilize it in flight. The bracket(s) can be designed to avoid impeding the exhaust duct's thermal expansion during operation while restricting its movement relative to the aircraft's frame of reference. The bracket(s) can also be designed to allow for rapid separation of the exhaust duct from the cowling, thus permitting the cowling to be opened.

[0017] This stabilization system can have a low mass impact, does not impact the exhaust duct environment except for the cowling and can be installed on an existing aircraft during a so-called "retrofit" campaign.

[0018] The aircraft may also include one or more of the following characteristics, taken alone or in combination.

[0019] Thus, the stiffening ring can surround the exhaust duct.

[0020] The stiffening ring can surround a section of the exhaust duct, namely totally and therefore 360 ​​degrees around an internal volume of the exhaust duct.

[0021] Alternatively, the stiffening ring can extend at an angle of less than 360 degrees around a geometric axis, and therefore around the internal volume. The stiffening ring then only partially surrounds the exhaust duct.

[0022] According to a possibility compatible with the previous ones, the stiffening ring can be arranged around the ejector section.

[0023] The stiffening ring generates pressure on the exhaust pipe as it expands due to the temperature of the exhaust gases. The pressure generated by the stiffening ring on the exhaust pipe can be optimized when the ring is positioned on the ejector section, which is likely to experience less thermal expansion than, for example, an inlet section of the exhaust pipe. Furthermore, the stiffening ring tends to stiffen the ejector section, which is prone to deformation within a typical exhaust pipe.

[0024] According to a possibility compatible with the previous ones, the stiffening ring can be disposed at least partially in the external environment.

[0025] The impact on the aircraft's aerodynamics is thus limited. The stiffening ring remains positioned as close as possible to, or even on, the section of the exhaust duct that is likely to deform within a conventional exhaust duct.

[0026] Alternatively, and depending on the requirements, the stiffening ring can be positioned entirely in the external environment.

[0027] According to a possibility consistent with the previous ones, the stiffening ring may have an L, T, C, or omega profile. The omega shape may include a substantially flat arm, followed by a substantially C shape, rounded or not and tilted 90 degrees to the right, and then another substantially flat arm.

[0028] Such a profile may be sufficient to adequately modify the behavior of the exhaust duct.

[0029] According to a possibility compatible with the previous ones, the stiffening ring can be fixed to the exhaust duct by means of detachable stiffening fasteners.

[0030] The term "dissociable" refers to fasteners that can be removed without damaging the stiffening ring and / or the exhaust duct during a maintenance campaign.

[0031] For example, stiffening fasteners include rivets or other fasteners.

[0032] According to a possibility compatible with the preceding ones, said at least one fixing may include a first support attached to the exhaust duct and a second support attached to the hood, said at least one fixing including a connecting attachment fixing the first support to the second support.

[0033] The connecting fastener can be a quick-release fastener. For example, the connecting fastener might include a quarter-turn fastener or a fastener known by the brand name Dzus®. An operator can then easily separate the exhaust pipe from the hood.

[0034] According to a possibility compatible with the previous ones, said at least one fixing can be arranged at least partially in said housing.

[0035] The fastener can be entirely housed within the housing or can extend outside of it. For example, the aforementioned fastener can be located in the external environment.

[0036] According to a possibility compatible with the previous ones, said at least one fixing can be accessible via said space separating the ejector section from the hood.

[0037] The space may have dimensions larger than those of a human hand or a tool capable of opening the fastener.

[0038] For illustrative purposes, the space may have a dimension of at least 5 centimeters.

[0039] Positioning the exhaust duct within a larger opening in the hood creates a space that can be accessed by a tool and / or a hand. An operator can then insert a hand into this space to detach the exhaust duct from the hood, for example, to open the hood.

[0040] According to a possibility compatible with the previous ones, said at least one fixing may be adjacent to the stiffening ring.

[0041] The fixing(s) are as close as possible to the stiffening ring to provide fixing points and stiffness in roughly the same place.

[0042] Optionally, at least one fixing can be attached to the stiffening ring.

[0043] The fastener thus connects the exhaust pipe to the hood via the stiffening ring.

[0044] Alternatively, the bracket can be attached directly to the exhaust pipe.

[0045] According to a possibility compatible with the previous ones, said at least one fixing may include several fixings arranged around the exhaust duct.

[0046] The fixings are then distributed, in an iso-distributed or non-iso-distributed manner, around the exhaust duct to stabilize the exhaust duct in several zones and along several geometric axes.

[0047] The invention and its advantages will become apparent in more detail in the following description, with illustrative examples given by reference to the attached figures which represent: there figure 1 , a diagram illustrating an aircraft according to the invention, the figure 2 , a cross-sectional diagram illustrating an aircraft according to the invention, and the figure 3 , a view partially showing an aircraft according to the invention.

[0048] Elements present in several separate figures are assigned a single reference.

[0049] There figure 1 presents an aircraft 1 according to the invention.

[0050] Such an aircraft 1 comprises a supporting structure 3 carrying at least one engine 10. The engine 10 is in particular disposed in an engine compartment 5.

[0051] The engine compartment 5 is delimited by at least one wall 6, 7, 8, and 9. The wall(s) 6, 7, 8, and 9 may be fire-resistant, for example, flame-retardant. For example, the engine compartment 5 is delimited along a longitudinal axis by at least one longitudinal wall 6, 8. For example, the engine compartment 5 is delimited along a transverse axis by at least one transverse wall 7 and a cowling, and vertically by at least one bottom wall 9.

[0052] The engine(s) 10 may be internal combustion engines capable of burning fuel to drive each power shaft. Alternatively, the engine(s) 10 may be turboshaft engines. Or, alternatively, the engine(s) 10 may be piston engines, for example.

[0053] Regardless of the nature of the engine(s) 10 and their arrangement, each engine 10 includes an ejection nozzle 20 to eject, at least in the direction of arrow F1, gases resulting from the combustion of the fuel in the engine 10 in question. For example, the ejection nozzle 20 passes through a longitudinal wall 6.

[0054] Therefore, an exhaust duct 30 according to the invention at least partially surrounds the ejection nozzle 20, namely the entire ejection nozzle 20 or a section of the ejection nozzle 20, and for example, at least a portion of the ejection nozzle 20 through which gases are expelled. For example, the exhaust duct 30 surrounds at least a portion of the ejection nozzle 20 located outside the engine compartment 5.

[0055] The exhaust duct 30 may include a peripheral wall. The peripheral wall delimits an internal volume located inside the exhaust duct 30 and housing at least one section of the ejection nozzle 20.

[0056] Furthermore, the exhaust duct 30 extends from an inlet section 301, possibly opening into the engine compartment 5, to an outlet section 302, possibly opening into an EXT medium located outside the aircraft 1. Therefore, air present in the compartment 5 can be drawn into the exhaust duct 30, then is expelled outside the vehicle with gases from the ejection nozzle 20 through the outlet section 302.

[0057] In particular, the exhaust duct may include an inlet section 31 comprising the inlet section 301, and then an ejector section 32 comprising the outlet section 302.

[0058] Furthermore, the exhaust duct 30 is partially housed in an internal housing 25 of the aircraft 1.

[0059] As illustrated on the figure 1 , the inlet section of the duct can be fixed to a wall delimiting the dwelling, and for example wall 8.

[0060] Except in cases of deformation or vibration, the exhaust duct 30 can be stationary in the aircraft's frame of reference and in the housing 25.

[0061] This housing 25 is separated from the external environment EXT by at least one hood 35. The hood 35 is movable relative to the aircraft's load-bearing structure 3 and the exhaust duct. For this purpose, the hood 35 can be connected to the load-bearing structure 3 by at least one mobility system 38, 39, as schematically illustrated. Such a mobility system 38, 39 may include at least one rail, at least one slide, and at least one hinge, for example.

[0062] The hood 35 may include a cowling panel 36. The hood 35 may include a protective cover 37 integral with the cowling panel 36 as illustrated in the figure 2 described later.

[0063] Independently of the components of the hood 35 and the mobility systems 38, 39 making it mobile relative to the supporting structure 3, the hood 35 includes a passage 40. Such a passage 40 may include a cutout made in the hooding panel 36, and where appropriate not closed by the protective casing 37.

[0064] Therefore, the ejector section 32 of the exhaust duct 30 passes through the opening 40 of the hood 35 without touching the hood 35. The ejector section can thus extend into the external environment EXT. A space 41 therefore separates the ejector section 32 from the hood 35. This space 41 is an annular space that surrounds the exhaust duct, separating it from an edge defining the opening 40.

[0065] According to another aspect, the aircraft 1 includes at least one stabilization system 50 coupled to an exhaust duct 30. In the presence of several engines 10 and several respective exhaust ducts 30, each exhaust duct 30 is coupled to its own stabilization system 50.

[0066] Regardless of the number of stabilization systems 50, such a stabilization system 50 makes it possible to modify the dynamic and vibratory behavior of the exhaust duct 30, without stressing the load-bearing structure 3 or the engine compartment 5 for example.

[0067] Such a stabilization system 50 includes a stiffening ring 55 which is attached to the exhaust duct 30. The stiffening ring can totally surround the exhaust duct, i.e. 360 degrees around a geometric axis, or can partially surround the exhaust duct.

[0068] This stiffening ring 55 is thus made integral with the exhaust duct 30.

[0069] For example, the stiffening ring 55 is arranged against the ejector section 32.

[0070] Optionally, the stiffening ring 55 can be disposed at least partially in the external environment EXT.

[0071] In one variant, the stiffening ring 55 and the exhaust duct 30 form a single piece, the stiffening ring 55 and the exhaust duct 30 being inseparable without breakage. For example, the stiffening ring 55 is welded to the exhaust duct 30.

[0072] According to another variant, the stiffening ring 55 is attached to the exhaust duct 30 by means of detachable stiffening brackets 56. According to an illustration of this option, the stiffening brackets 56 include rivets.

[0073] According to another characteristic, the stiffening ring 55 can have an L, T, C, or omega profile. Such a stiffening ring 55 allows for relatively easy and inexpensive modification of the natural frequency of the exhaust duct 30.

[0074] Regardless of how the stiffening ring 55 is made, the stabilization system 50 also includes one or more fixings 60 connecting the exhaust duct 30 to the hood 35. At least one fixing 60 can in particular be fixed to the ejector section 32. According to the illustrated examples, the stabilization system 50 includes several fixings 60 arranged around the exhaust duct 30.

[0075] Following the example of the figure 1 , at least one fixing 60 can in particular be fixed to the cowling panel 36 of the hood 35.

[0076] In a complementary or alternative manner and with reference to the figure 2 , at least one fixing 60 can in particular be fixed to the protective casing 37 of the hood 35.

[0077] Regardless of which hood component 35 is attached to a fastener 60, at least one fastener 60 is possibly positioned to be adjacent to the stiffening ring 55.

[0078] Optionally, at least one fixing 60 can be fixed to the stiffening ring 55.

[0079] Regardless of the positioning of a fixing 60, this fixing 60 may include a first support 61 and a second support 62 assembled to each other by a connecting fastener 63.

[0080] For example, the first support 61 is integral with the exhaust duct 30, either directly or via the stiffening ring 55. The first support 61 can be fixed to the exhaust duct 30 or to the stiffening ring 55 by screwing, riveting, gluing, welding, etc.

[0081] For example, the second support 62 is integral with the cover 35. The second support 62 can be fixed to the cover 35 by screwing, riveting, gluing, welding, etc...

[0082] Furthermore, the first support 61 may include a male or female clevis comprising at least one first hole. Similarly, the second support 62 may include a male or female clevis comprising at least one second hole. The connecting fastener 63 then includes, in particular, a connection passing through the first hole(s) and the second hole(s).

[0083] According to another aspect, a fastener 60 may be at least partially located in the housing 25. For example, the first support 61 of a fastener 60 may extend partly into the external environment EXT, and the second support 62 may be located in the housing 25. According to another aerodynamically optimized alternative, the entire fastener 60 is arranged in the housing 25. Alternatively, at least one fastener 60 may be entirely in the external environment EXT.

[0084] Optionally, at least one fixing 60 is accessible to an operator via space 41.

[0085] In this context, the figure 3 illustrates an example of an embodiment comprising several fixings 60. The cover 35 is made locally transparent to allow visualization of the fixings 60.

[0086] Each fixing 60 comprises a first support 61, a second support 62 and a connecting attachment 63. In addition, each fixing 60, and in particular its connecting attachment 63, is accessible to an operator via the space 41.

[0087] Naturally, the present invention is subject to numerous variations in its implementation. Although several embodiments have been described, it is understood that it is not conceivable to exhaustively identify all possible embodiments.

Claims

1. Aircraft (1) provided with at least one exhaust duct (30) for discharging gases from an engine (10), the exhaust duct (30) being partially accommodated in an internal housing (25) of the aircraft (1), the housing (25) being separated from an external environment (EXT) located outside the aircraft (1) by at least one cowl (35), the cowl (35) being movable relative to a load-bearing structure (3) of the aircraft (1), the exhaust duct (30) comprising an ejector section (32) passing through a passage (40) of the cowl (35) without touching the cowl (35), with a space (41) separating the ejector section (32) from the cowl (35), the aircraft (1) comprising at least one stabilisation system (50) coupled to the exhaust duct (30), the stabilisation system (50) comprising a stiffening ring (55) rigidly connected to the exhaust duct (30) and at least one fixture (60) connecting the exhaust duct (30) to the cowl (35).

2. Aircraft according to claim 1, characterised in that said stiffening ring (55) surrounds the exhaust duct (30).

3. Aircraft according to claim 1, characterised in that said stiffening ring (55) extends over an angle of less than 360 degrees about a geometric axis.

4. Aircraft according to any one of claims 1 to 3, characterised in that said stiffening ring (55) is disposed around the ejector section (32).

5. Aircraft according to any one of claims 1 to 4, characterised in that said stiffening ring (55) is at least partially disposed in the external environment (EXT).

6. Aircraft according to any one of claims 1 to 5, characterised in that said stiffening ring (55) comprises an L-shaped, T-shaped, C-shaped or omega-shaped profile.

7. Aircraft according to any one of claims 1 to 6, characterised in that said stiffening ring (55) is fixed to the exhaust duct (30) by removable stiffening fasteners (56).

8. Aircraft according to any one of claims 1 to 7, characterised in that said at least one fixture (60) comprises a first support (61) rigidly connected to the exhaust duct (30) and a second support (62) rigidly connected to the cowl (35), with said at least one fixture (60) comprising a connecting fastener (63) fixing the first support (61) to the second support (62).

9. Aircraft according to any one of claims 1 to 8, characterised in that said at least one fixture (60) is at least partially arranged in said housing (25).

10. Aircraft according to any one of claims 1 to 9, characterised in that said at least one fixture (60) is accessible via said space (41) separating the ejector section from the cowl.

11. Aircraft according to any one of claims 1 to 10, characterised in that said at least one fixture (60) is adjacent to the stiffening ring (55).

12. Aircraft according to any one of claims 1 to 11, characterised in that said fixture (60) is fixed to the stiffening ring (55).

13. Aircraft according to any one of claims 1 to 12, characterised in that said at least one fixture (60) comprises a plurality of fixtures (60) disposed around the exhaust duct (30).