Aircraft exhaust system with rear ventilation

Abstract

Aircraft exhaust system comprising a nozzle (1) and a ventilation member (10) at the rear of the nozzle (1), the ventilation member (10) being configured to introduce air into the nozzle (1) by venturi effect. Aircraft equipped with such an exhaust system.

Description

Description Title of the invention: Rear-ventilated aircraft exhaust system technical field

[0001] The invention relates to the aeronautical field and more specifically to an exhaust system for combustion gases generated by an aircraft engine.

[0002] The invention can be implemented on different types of aircraft, in particular helicopters or airplanes. State of the art

[0003] Aircraft exhaust systems typically include a nozzle mounted at the rear of an engine to ensure the exhaust of combustion gases generated by that engine.

[0004] Some exhaust systems allow the combustion gases to be cooled by introducing a fluid such as ambient air into the nozzle inlet.

[0005] There is a need to optimize ventilation and, more generally, the performance of exhaust systems known in the prior art. Description of the invention

[0006] The invention relates to an aircraft exhaust system, comprising a nozzle that extends around a so-called flow axis to form a main cavity, the nozzle comprising: - a front part forming an inlet of the nozzle, the inlet of the nozzle being intended to introduce combustion gases into the main cavity, - a rear part forming an outlet of the nozzle, the outlet of the nozzle being intended to evacuate from the main cavity a fluidic mixture comprising the combustion gases conveyed by the main cavity to the outlet of the nozzle.

[0007] According to the invention, the rear part of the nozzle comprises one or more ventilation elements configured to allow the introduction into the main cavity of a so-called cooling fluid, so that said fluidic mixture exiting the main cavity comprises cooling fluid thus introduced.

[0008] The said cooling fluid can typically be a fluid whose temperature is lower than that of the combustion gases.

[0009] In one embodiment, the cooling fluid comprises a fluid present in the environment of the exhaust system, in particular present outside the nozzle, this fluid being possible to be ambient air.

[0010] The invention makes it possible to introduce into the nozzle a fluid which mixes with the combustion gases, thus lowering its temperature, without affecting the disturbances of the flow passing through the nozzle.

[0011] In other words, the system of the invention makes it possible to ensure a ventilation function at the rear of the nozzle.

[0012] It is preferred that the nozzle, particularly its rear part, include one or more openings, also called "side openings".

[0013] In the present description, such an opening is said to be lateral in the sense that it crosses the nozzle along an axis perpendicular or oblique to the flow axis.

[0014] In one embodiment, this or these openings each form one of said ventilation components.

[0015] In other words, each of the ventilation components may include an opening formed in the rear part of the nozzle.

[0016] In one embodiment, for each of the ventilation elements, the ventilation element includes a deflector.

[0017] In one embodiment, for each of the ventilation element(s), the ventilation element comprises both a lateral opening as defined above and a deflector.

[0018] Preferably, for each of the ventilation components, the deflector is configured to guide the cooling fluid towards the opening of that ventilation component.

[0019] In one embodiment, for each of the ventilation organ(s), the deflector extends radially outwards relative to the nozzle.

[0020] In one embodiment, for each of the ventilation components, the deflector forms a duct and includes a front end delimiting an inlet of this duct.

[0021] Preferably, for each of the ventilation organ(s), the duct formed by the deflector has an outlet formed by the opening of that ventilation organ.

[0022] In one embodiment, for each of the ventilation organ(s), the deflector extends towards the outlet of the nozzle so that the duct it forms has a cross-section which decreases from its front end towards, and preferably to, a rear end of this deflector.

[0023] In an embodiment in which the system includes several ventilation elements, these can be angularly spaced from each other relative to the flow axis and aligned with each other along the flow axis.

[0024] In other words, several of these ventilation devices can be arranged in a row, or alternatively in several rows which can be spaced apart from each other along the flow axis.

[0025] In one embodiment, the ventilation device(s) are configured to allow the introduction of said cooling fluid into the main cavity by venturi effect.

[0026] In one embodiment, the system includes a nozzle that extends around the flow axis so as to form a primary cavity in fluidic communication with the main cavity of the nozzle in order to convey the combustion gases to the main cavity.

[0027] In one embodiment, the nozzle and the nozzle form, radially between them, a secondary cavity in fluidic communication with the main cavity of the nozzle in order to allow an introduction into the main cavity, by venturi effect, of a part of said cooling fluid.

[0028] In other words, the exhaust system can be two-stage.

[0029] Such a two-stage exhaust system allows coolant to be introduced both at the front and rear of the nozzle, forming a double venturi effect system producing a synergistic effect that multiplies performance.

[0030] In one embodiment, the nozzle and / or the deflector(s) comprise titanium.

[0031] The invention also relates to an aircraft comprising an engine and an exhaust system as defined above, the exhaust system being configured to evacuate combustion gases generated by the engine.

[0032] In one embodiment, the aircraft is an airplane.

[0033] In another embodiment, the aircraft is a helicopter.

[0034] In an embodiment in which the aircraft is a helicopter, the exhaust system is arranged so that one or more of said ventilation components are opposite the helicopter blades.

[0035] Such an arrangement allows the introduction of cooling fluid into the nozzle, via the ventilation device(s), while hovering.

[0036] Other advantages and features of the invention will become apparent from the detailed, non-limiting description that follows. Brief description of the figures

[0037] The detailed description that follows refers to the attached drawings on which: - [Fig.1] is a schematic perspective view of an aircraft exhaust nozzle; - [Fig.2] is a schematic longitudinal section view of part of a two-stage aircraft exhaust system, comprising a nozzle and a pipe; - [Fig.3] is a schematic side view of part of an aircraft exhaust system, comprising a nozzle with a side opening and a deflector, the side opening and the deflector forming a scoop-type ventilation device allowing ambient air to be introduced into the nozzle; - [Fig.4] is a schematic perspective view of part of an exhaust system similar to that of [Fig.3]; - [Fig.5] is a schematic longitudinal cross-sectional view of a two-stage aircraft exhaust system, comprising a nozzle, a pipe and a ventilation device according to the invention; - [Fig.6] is a schematic top view of an aircraft exhaust system comprising a nozzle and three ventilation components according to the invention; - [Fig.7] is a schematic view of a helicopter equipped with an exhaust system according to the invention.

[0038] In the different figures, identical reference symbols are used to designate identical or similar elements. Detailed description of implementation methods

[0039] Figure [1] schematically shows a nozzle 1 of an aircraft exhaust system.

[0040] In general, an aircraft exhaust system is arranged at the rear of an aircraft engine in order to evacuate combustion gases generated by that engine.

[0041] In this description, the terms "front" and "rear" are defined relative to a direction of flow of combustion gases generated by such an engine.

[0042] The figures include a reference frame defining orthogonal DI, D2 and D3 directions.

[0043] In the following description, DI corresponds to a flow direction, in particular the flow of combustion gases.

[0044] With reference to the simplified drawing in [Fig.1], the nozzle 1 extends around an axis Al so as to form a cavity Cl, here called the "main cavity".

[0045] The Al axis, also called the flow axis, is here parallel to the DI direction.

[0046] The nozzle 1 comprises a front part 2 forming an inlet of the nozzle 1 and a rear part 3 forming an outlet of the nozzle 1.

[0047] The front section 2 and the rear section 3 correspond to respective segments of the nozzle 1, which can be formed as a single piece or joined directly or via one or more intermediate segments. In this non-limiting example, the front section 2 and the rear section 3 are formed as a single piece, thus making the nozzle 1 a single unit.

[0048] More specifically, the inlet of nozzle 1 is thus formed by a front end of said front part 2, while the outlet of nozzle 1 is formed by a rear end of said rear part 3.

[0049] In the simplified example of [Fig.1], the inlet and outlet of nozzle 1 each have a circular cross-section and the cross-section of nozzle 1 increases from its inlet to its outlet.

[0050] In other words, nozzle 1 of [Fig.l] is frustoconical and divergent.

[0051] In operation and in a manner known per se, a flow Fl containing combustion gases from an engine is introduced into the cavity Cl of the nozzle 1 through its inlet and is evacuated through its outlet.

[0052] Figure 2 schematically shows part of an aircraft exhaust system 5. This system 5 comprises a nozzle 1 and a nozzle 6. Figure 2 is described only in terms of its differences from the embodiment of Figure 1, the preceding description applying by analogy.

[0053] The nozzle 1 of [Eig.2] differs essentially from that of [Eig.2] in that its section is globally constant along the axis Al, with the exception of its front end 7 which has a flared geometry.

[0054] The nozzle 6 extends around the Al axis so as to form a cavity C2, here called the "primary cavity".

[0055] In this example, a rear part of the nozzle 6 extends inside the nozzle 1 so that the nozzle 6 and the nozzle 1 form, radially between them, a cavity C3, here called the "secondary cavity".

[0056] The cavity C2 formed by the nozzle 6 is fluidically connected to the cavity Cl of the nozzle 1. In other words, the cavity C2 of the nozzle 6 opens into the cavity Cl of the nozzle 1.

[0057] Given the arrangement of the nozzle 6 and the nozzle 1, the secondary cavity C3 allows a fluidic communication to be established between a space outside the system 5 and the main cavity Cl.

[0058] The system 5 of [Eig.2] thus forms a two-stage exhaust known as such, the nozzle 6 and the nozzle 1 also being designated by their Anglo-Saxon names "nozzle" and "eductor", respectively, or by the expressions "primary nozzle" and "secondary nozzle", respectively.

[0059] In operation and in a manner known per se, a flow El of combustion gas from an engine is conveyed to the cavity Cl of the nozzle 1 via the cavity C2 of the nozzle 6. A flow E2 of a fluid present in said space outside the system 5, typically ambient air, is introduced into the cavity Cl of the nozzle 1 by venturi effect, i.e. by being drawn in under the action of a depression created by the flow Fl passing through the exhaust system 5. The flows Fl and F2 thus form a fluidic mixture which exits the cavity Cl in the form of a flow designated by the reference F3 on the [Fig.2].

[0060] Such an exhaust system 5 allows the combustion gas flow Fl to be cooled using the ambient air flow F2, which thus constitutes a cooling fluid.

[0061] The invention relates more specifically to a technique for mixing a fluid, in particular a cooling fluid, with combustion gases at the rear part of the cavity Cl of a nozzle 1 as illustrated in [Fig. 1] or 2. Of course, the invention can be implemented on a nozzle or more generally on an exhaust system which differs from the embodiments described above, figures 1 and 2 illustrating embodiment principles which are not limiting.

[0062] Figures 3 and 4 show an organ 10 intended to fulfill such a ventilation function.

[0063] In the non-limiting embodiment of Figures 3 and 4, the ventilation element 10 comprises on the one hand an opening 11 (see [Fig.4]) made in a nozzle 1 of an exhaust system according to the invention and, on the other hand, a deflector 12, forming in this example a scoop.

[0064] With reference to [Fig.4], the opening 11 here results from a cut in the nozzle 1 made so that the opening 11 has four edges 1 IA, 1 IB, 1 IC and 11D.

[0065] In this example, edges 1 IA and 1 IC are spaced apart along the direction D1, defining a length XI of the opening 11. Edges 1 IB and 11D are spaced apart along the direction D3, defining a width X2 of the opening 11.

[0066] Without limitation, edges IA and IC are parallel to each other, so that the length XI of the aperture 11 is constant along D3, that is, circumferentially around the axis Al of the nozzle 1. Edges IB and D are also parallel to each other, so that the width X2 of the aperture 11 is constant along DL

[0067] With reference to figures 3 and 4, the deflector 12 is presented in this non-limiting example as a wall element attached to the nozzle 1, so as to extend radially outwards relative to the nozzle 1.

[0068] In this embodiment, the deflector 12 includes a front edge 12A, side edges 12B and 12D, a rear edge 12C, as well as fold lines 12E and 12F.

[0069] In this example, the edges 12B, 12C and 12D of the deflector 12 coincide, respectively, with the edges 11B, 11C and 11D of the opening 11.

[0070] With reference to [Fig.4], the edges 1 IA and 1 IB of the opening 11 and the edges 12A and 12B of the deflector 12 meet at a point PI, while the edges 1 IA and 11D of the opening 11 and the edges 12A and 12D of the deflector 12 meet at a point P2.

[0071] In addition, edge 12A and line 12E of deflector 12 meet at a point P3, while edge 12A and line 12F of deflector 12 meet at a point P4.

[0072] In this example, the edge 12A of the deflector 12 moves away radially from the edge 1 IA of the opening 11, on the one hand from point PI to point P3, on the other hand and symmetrically from point P2 to point P4.

[0073] Circumferentially from point P3 to point P4, the edge 12A of the deflector 12 is in this example far from the edge 1 IA of the opening 11 by a distance X3.

[0074] Following the direction Dl, that is, from the front to the rear of the nozzle 1, the distance along D2 between the deflector 12 and the aperture 11 decreases. More precisely, this distance decreases from the front edge 12A of the deflector 12, where the distance X3 is at its maximum, until it becomes zero at the rear edge 12C of the deflector 12, since in this example the latter coincides with the rear edge 1IC of the aperture 11.

[0075] The deflector 12 thus forms a conduit C4 which corresponds to the space located radially between the deflector 12 and the opening 11 of the nozzle 1.

[0076] A front end of the deflector 12 thus delimits, in this example with the edge 1 IA of the opening 11, an inlet of the conduit C4, while the opening 11 forms an outlet of the conduit C4.

[0077] Therefore, in this example, the C4 duct has a cross-section that decreases from the front end of the deflector 12 to its rear end.

[0078] According to the invention, such a ventilation organ 10 can be positioned on the rear part of a nozzle 1, for example as described below, so as to allow an introduction, into the main cavity of the nozzle 1, of a flow F4 of a fluid present outside the nozzle 1, typically ambient air, by venturi effect, that is to say by being drawn in under the action of a depression created by a flow passing through the main cavity of the nozzle 1.

[0079] The flow F4 is thus introduced into the main cavity of the nozzle 1 through the opening 11, being guided in this example by the deflector 12.

[0080] Of course, the ventilation device of the invention may have a structure and geometry different from those illustrated in figures 3 and 4. In particular, a person skilled in the art will be able, using known sizing and simulation techniques, to size the opening 11 and the deflector 12 according to the intended application, for example according to the dimensions and geometry of the nozzle and its arrangement on the aircraft.

[0081] In unrepresented embodiment variants, the opening 11 may include three edges forming a triangular section, or four edges forming a non-rectangular quadrilateral section, or more generally several edges forming a polygonal section, or one or more edges defining a circular or oval section or any other geometry.

[0082] In an alternative embodiment, not shown, the ventilation unit lacks a deflector attached to the nozzle.

[0083] In another embodiment, not shown, the ventilation element includes a deflector formed by the nozzle itself, for example by deformation and / or machining of the latter, or taking into account its geometry defining for example one or more surfaces suitable for guiding the ventilation flow towards the opening of the ventilation element.

[0084] When the ventilation element includes a deflector, the deflector may cover all or part of the opening 11. The deflector may also be arranged opposite a part of the nozzle 1, so that the duct it forms is also delimited by a part such as an external surface of the nozzle 1 (not shown).

[0085] The invention generally relates to an exhaust system comprising one or more ventilation elements such as that illustrated in figures 3 and 4, or according to any variants not limited to those mentioned above.

[0086] The exhaust system equipped with this or these ventilation organs can be single stage, as illustrated in [Fig.1], or double stage, as illustrated in [Fig.2].

[0087] Furthermore, the nozzle of the exhaust system equipped with this or these ventilation components can be divergent or straight or have any other geometry.

[0088] Generally, it is proposed to arrange one or more ventilation elements according to the invention towards the rear of the exhaust nozzle. Such an arrangement prevents disruption to the flow of combustion gases passing through the nozzle.

[0089] Figure 5 schematically illustrates an example of an exhaust system 5 according to the invention. The system 5 comprises a nozzle 1 and a nozzle 6 of the type shown in Figure 2, as well as a ventilation element 10 similar to that shown in Figures 3 and 4. The preceding description applies by analogy to this embodiment.

[0090] Thus, in the embodiment of [Fig.5], the exhaust system 5 allows the introduction into the cavity Cl of the nozzle 1 of a first part of ambient air forming the flow F2, under the action of a first venturi effect resulting from the arrangement of the nozzle 6 and the nozzle 1, and a second part of ambient air forming the flow F4, under the action of a second venturi effect resulting from the structure of the ventilation organ 10.

[0091] Figure 6 shows another example of an exhaust system 5 according to the invention, which differs essentially from that of Figure 5 in that it includes three ventilation elements 10. The preceding description applies, of course, by analogy, to this embodiment.

[0092] Figure 6 shows a single-stage system 5, lacking a nozzle at the inlet of the nozzle 1. Naturally, the embodiment of Figure 6, in which the system 5 comprises several ventilation elements, can be implemented on a two-stage exhaust system. More generally, the invention covers an exhaust system having at least one nozzle equipped with one or more ventilation elements on the rear part of the nozzle.

[0093] As mentioned above, the sizing of the ventilation unit(s) depends on parameters specific to the intended application.

[0094] Some indications are given below, as non-exhaustive examples.

[0095] Regarding the opening 11 of a ventilation device 10, the leading edge 1 IA of the opening 11 is preferably closer to the outlet of the nozzle 1 than to its inlet. For example, the edge 1 IA can be positioned along DI between the outlet of the nozzle 1 and a coordinate corresponding to the midpoint of the nozzle 1, that is, a coordinate midway between the inlet and outlet of the nozzle 1.

[0096] The rear edge 1 IC of the opening 11 of a ventilation element 10 is preferably located as close as possible to the outlet of the nozzle 1. For example, in an embodiment not shown, the edge 1 IC of the opening 11 may coincide with a front edge of a stiffening element delimiting the outlet of the nozzle 1, or be positioned near such a stiffening element. In a variant not shown, the edge 1 IC of the opening 11 may be formed by a material element constituting both the edge 12C of a corresponding deflector 12 and the rear end of the nozzle 1.

[0097] The length XI of the opening 11 of a ventilation device 10 is preferably less than half the length of the nozzle 1 and preferably greater than one tenth of the length of the nozzle 1. For example, the ratio between the length XI of the opening 11 and the length of the nozzle 1 may be between 0.1 and 0.5, or between 0.2 and 0.4, or be equal to or close to 0.3.

[0098] The curvilinear dimension corresponding to the width X2 of the opening 11 of a ventilation device 10 may be less than its length XL

[0099] As an indication, the width X2 of the opening 11 of a ventilation device 10 can be chosen in a range from cn / 24 rad to m / 2 rad, for example from en / 12 rad to 5m / 12 rad, for example m / 3 rad or cn / 4 rad or cn / 6 rad.

[0100] The dimension X3 of the inlet of the duct C4 of a ventilation unit 10 is preferably less than XI and / or X2.

[0101] When the exhaust system includes several ventilation components, the openings they form can be angularly spaced from each other relative to the Al axis and aligned with each other along the Al axis, as illustrated for example in [Fig.6].

[0102] Figure 7 shows a helicopter 20 which is typically intended to provide passenger and / or cargo transport, medical service, search and rescue, law enforcement, surveillance or firefighting missions.

[0103] In a manner known per se, the helicopter 20 comprises a fuselage 21, a main rotor carrying blades 22, rotating about a substantially vertical axis A22 when the helicopter is on the ground, a tail boom 23 extending rearward and carrying an anti-torque rotor 24, and an engine 25 (not shown) of the gas turbine type configured to drive the main rotor.

[0104] The helicopter 20 of [Fig.7] includes an exhaust system 5 as described above, for example as illustrated in [Fig.6], configured to evacuate combustion gases generated by the engine 25.

[0105] The ventilation element(s) of the exhaust system 5 of the invention can advantageously be arranged opposite the blades 22, i.e., vertically upwards. Such an arrangement allows ambient air displaced by the blades 22 to be introduced into the nozzle 1 of the system 5 when the helicopter is hovering. The invention thus makes it possible to further optimize the cooling of the combustion gases in hover and, more generally, to optimize the fluid mixture in different flight regimes.

[0106] Among other advantages of the invention, the exhaust system of the invention makes it possible to obtain at the outlet of the nozzle 1 a fluidic mixture whose temperature is such that the tail boom 23 can be devoid of metallic heat shield.

[0107] Of course, the invention can be implemented on a helicopter different from that described above, for example on a helicopter with two engines by equipping it with two exhaust systems according to the invention, or on another type of aircraft, for example on an airplane.

Claims

Demands

1. Aircraft exhaust system (5) (20), comprising a nozzle (1) extending around a flow axis (Al) so as to form a main cavity (Cl), the nozzle (1) comprising: - a front part (2) forming an inlet of the nozzle (1), the inlet of the nozzle (1) being designed to introduce combustion gases (Fl) into the main cavity (Cl), - a rear part (3) forming an outlet of the nozzle (1), the outlet of the nozzle (1) being intended to evacuate from the main cavity (Cl) a fluidic mixture (F3) comprising the combustion gases conveyed by the main cavity (Cl) to the outlet of the nozzle (1), characterized in that the rear part (3) of the nozzle (1) includes one or more ventilation members (10) configured to allow the introduction into the main cavity (Cl) of a fluid (F4) said to be a cooling fluid such as ambient air, so that said fluidic mixture (F3) exiting the main cavity (Cl) includes cooling fluid thus introduced.

2. System (5) according to claim 1, wherein the nozzle (1) includes one or more openings (11) each forming one of said ventilation organs (10).

3. System (5) according to claim 2, wherein, for each of the ventilation element(s) (10), the ventilation element (10) includes a deflector (12) configured to guide the cooling fluid (F4) towards the opening (11) of that ventilation element (10).

4. System (5) according to claim 3, wherein, for each of the ventilation element(s) (10), the deflector (12) extends radially outwards relative to the nozzle (1).

5. System (5) according to claim 3 or 4, wherein, for each of the ventilation element(s) (10), the deflector (12) forms a duct (C4) and comprises a front end (12A) defining an inlet of this duct (C4), the duct (C4) having an outlet formed by the opening (11) of this ventilation element (10).

6. System (5) according to claim 5, wherein, for each of the ventilation element(s) (10), the deflector (12) extends towards the outlet of the nozzle (1) such that the duct (C4) which it forms has a cross-section which decreases from its front end (12A) to a rear end (12C) of this deflector (12).

7. System (5) according to any one of claims 1 to 6, comprising several of said ventilation organs (10) which are angularly spaced from each other relative to the flow axis (Al) and aligned with each other along the flow axis (Al).

8. System (5) according to any one of claims 1 to 7, wherein the ventilation member(s) (10) are configured to permit the introduction of the cooling fluid (F4) into the main cavity (Cl) by venturi effect.

9. System (5) according to any one of claims 1 at 8, comprising a nozzle (6) which extends around the flow axis (Al) so as to form a primary cavity (C2) in fluidic communication with the main cavity (Cl) of the nozzle (1) in order to be able to convey the combustion gases to the main cavity (Cl), the nozzle (6) and the nozzle (1) preferably forming, radially between them, a secondary cavity (C3) in fluidic communication with the main cavity (Cl) of the nozzle (1) in order to allow an introduction into the main cavity (Cl), by venturi effect, of a part (F2) of the cooling fluid.

10. Aircraft, for example helicopter (20) or airplane, comprising an engine (25) and an exhaust system (5) according to any one of claims 1 to 8, the exhaust system (5) being configured to discharge combustion gases generated by the engine

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