AIRCRAFT PROPULSION ASSEMBLY COMPRISING AN AERODYNAMIC COWL FORMING A STRUCTURAL REINFORCEMENT

Abstract

The invention relates to an aircraft propulsion assembly (100) comprising a turbomachine (1) equipped with a first and a second structural part (22, 48), the assembly including a cowling (50) with a first axial end (60) and a second axial end (62), and including a first fastening device (64) for the first end (60) on the first structural part (22), as well as a second fastening device (66) for the second end (62) on the second structural part (48). According to the invention, each of the fastening devices includes several fastening mechanisms (70) for the first cowling (50) on its corresponding structural part, these mechanisms being circumferentially spaced from one another along the cowling (50), and each configured to retain the cowling (50) relative to its corresponding structural part (22, 40, 48), radially inward. Figure 2.

Description

Title of the invention: PROPULSION ASSEMBLY FOR AIRCRAFT INCLUDING A COWL AERODYNAMIC FORMULA FORMING A STRUCTURAL REINFORCEMENT technical field

[0001] The invention relates to the field of aircraft propulsion assemblies, and more specifically to the mechanical strength and stiffness of such assemblies.

[0002] The invention applies in particular to propulsion assemblies comprising a turbojet engine, and even more particularly a turbojet engine with one or more unfaired fan(s). STATE OF PRIOR ART

[0003] Aircraft propulsion assemblies generally include a turbomachine, such as a turbojet, as well as a nacelle forming the aerodynamic part of the propulsion assembly, and a mounting mast to which the turbomachine is attached.

[0004] The structural part of such a propulsion assembly is generally formed by the structural components of the turbomachine, such as its casings, and by the primary structure of the towing mast. As is known, fasteners connect the structural part of the turbomachine to the primary structure of the towing mast, for the transmission of forces between these two entities of the propulsion assembly.

[0005] The structural components of the turbomachine are dimensioned to provide maximum rigidity, particularly in longitudinal bending, which is generated by the thrust forces. The objective is to limit the deformations of the turbomachine as much as possible, in particular to limit the increase in wear clearances at the tips of rotating blades within the compressors and turbines.

[0006] However, such dimensioning of structural parts can significantly impact the overall mass of the propulsion assembly, with a detrimental effect on specific fuel consumption.

[0007] There is therefore a need to improve the design of current aircraft propulsion assemblies so that they can offer enhanced mechanical strength and rigidity, without too significant an impact on the overall mass. Description of the invention

[0008] To meet the need mentioned above, the invention relates to an aircraft propulsion system comprising a turbomachine equipped with a first structural part extending around a longitudinal central axis of the propulsion system, and a second structural part located downstream of the first part, also extending around the longitudinal central axis, the system comprising a first hood of which a radially external surface forms an aerodynamic surface, the first hood having a first axial end and a second axial end opposite to the first, the assembly comprising a first device for fixing the first axial end of the first hood to the first structural part, and a second device for fixing the second axial end of the first hood to the second structural part.

[0009] According to the invention, each of the first and second fastening devices comprises several fastening mechanisms for the first hood on its corresponding structural part, the fastening mechanisms being spaced circumferentially from each other along the first hood, and each configured so as to retain the first hood relative to its corresponding structural part, radially inwards.

[0010] By arranging such fastening mechanisms, it is possible to ensure the transmission of forces between the first cowling and each of the two structural turbomachine parts in a direction other than the radial direction in which these elements are normally free relative to each other. Thanks to the radial inward retention of the first cowling by each of the fastening mechanisms, as well as the multiplication of these mechanisms along the circumferential direction of each of the first and second axial ends of the cowling, actual force transfers and transmissions are observed between the first cowling and the two structural turbomachine parts. This advantageously stiffens the propulsion assembly, particularly to counteract longitudinal bending deformations resulting from the thrust forces generated by the propulsion assembly.In other words, thanks to this particular arrangement providing unique stress transfers between the structural parts of the turbomachine and the first cowling, the latter now takes on a structural character, in that it contributes to the mechanical strength and rigidity of the propulsion assembly.

[0011] Thus, by utilizing an existing element of the propulsion unit's nacelle, namely one of its cowlings, to reinforce the rigidity of this assembly, the impact on its overall mass remains very small. The invention therefore represents a result of technological research aimed at significantly improving aircraft performance and, in this respect, contributes to reducing the environmental impact of these aircraft (decarbonization).

[0012] The invention also has at least one of the following optional features, taken individually or in combination.

[0013] Preferably, each of the fastening mechanisms is also configured so as to retain the first hood relative to its corresponding structural part, radially outwards.

[0014] Preferably, each of the fastening mechanisms is also configured so as to retain the first hood relative to its corresponding structural part, axially upstream and / or downstream.

[0015] Preferably, at least one of the fastening mechanisms of each of the first and second fastening devices is arranged circumferentially at a distance from each of the two opposite circumferential ends of the first hood, being separated from each of these by an angle greater than or equal to 20°, or even greater than or equal to 30°.

[0016] Preferably, each of the first and second fastening devices comprises two fastening mechanisms spaced circumferentially from each other at an angle less than or equal to 60°, or even less than or equal to 30°.

[0017] Preferably, the first hood has a first circumferential end articulated on an element of the propulsion assembly, preferably a mast of this assembly, by means of a hood articulation device separate from the first and second fastening devices, and a second circumferential end opposite to the first, equipped with a hook and lever actuating locking device.

[0018] Preferably, the propulsion assembly comprises a turbomachine with unshod fan(s), and the first cowling radially delimits inwards a secondary flow of the turbomachine, the first cowling preferably including a ventilation channel, and preferably radially delimiting outwards a compartment housing turbomachine equipment.

[0019] Preferably, at least one of the first and second structural parts includes a part of a turbomachine attachment to a mast for attaching the assembly.

[0020] Preferably, each of the first and second structural parts is a turbomachine housing, or a ring surrounding a housing to which it is connected.

[0021] Preferably, the propulsion assembly comprises a second cowling, as well as a mechanical joining device between two circumferential ends of the first and second cowlings, the mechanical joining device comprising:

[0022] - a force transmission frame comprising a first end articulated on the circumferential end of one of the two hoods, as well as a second end opposite the first and guided in a rail of a fixed structure of the propulsion assembly; and

[0023] - a hook locking device carried by the circumferential end of the other of the two hoods, the hook cooperating with the second end of the force transmission frame.

[0024] According to a first preferred embodiment of the invention, each fastening mechanism comprises, on the one hand, a first retaining member attached to the first cover and formed by one of the elements of a hook and a loop, and on the other hand, a second retaining member carried by the corresponding structural part and formed by the other of the elements among the hook and the loop, and the fastening mechanism includes a system for moving the second retaining member relative to the structural part, so as to cause the introduction of the hook into the loop.

[0025] Preferably, the loop includes an axis for transferring radial forces, preferably oriented axially, and the hook has an opening for introducing the axis for transferring radial forces, this opening being preferably oriented circumferentially.

[0026] Preferably, the movement system of the second retaining member is common to several fastening mechanisms.

[0027] According to a second preferred embodiment of the invention, each fastening mechanism includes a locking device comprising an actuating lever and a locking member for the absorption of radial forces, the locking member being supported against the corresponding structural part so as to retain the first cover relative to its corresponding structural part, radially inwards.

[0028] Preferably, each fastening mechanism comprises, on the one hand, a first axial retaining member attached to the first cover and formed by one of the elements from a radial rib and a radial groove for receiving the rib, and on the other hand, a second axial retaining member attached to the corresponding structural part and formed by the other of the elements from the radial rib and the radial groove for receiving the rib, and the locking member is radially supported on the second axial retaining member, preferably so that the latter is radially clamped between this locking member and the first axial retaining member.

[0029] Other advantages and features of the invention will appear in the detailed, non-limiting description below. Brief description of the drawings

[0030] This description will be made with reference to the attached drawings, among which;

[0031] [Fig-1] represents a schematic view in longitudinal half-section of an assembly aircraft propulsion system, according to the invention;

[0032] [Fig.2] represents a cross-sectional view of the propulsion assembly shown on the previous figure, the connection between an axial end of a nacelle hood, and a structural part of the turbomachine of this assembly, is presented in the form of a first preferred embodiment of the invention;

[0033] [Fig.3] represents a cross-sectional view taken along line III-III of [Fig.2];

[0034] [Fig.4] represents a schematic cross-sectional view of one of the hoods of gondola of the assembly shown in figures 2 and 3;

[0035] [Fig.5] represents a front view of the assembly shown in Figures 2 and 3, with the nacelle hoods in the open position;

[0036] [Fig.6] represents a partial and enlarged view of that shown in the previous figure, with the two nacelle hoods in the closed position, and showing more particularly a mechanical joining device between the two circumferential ends opposite the two hoods;

[0037] [Fig.7] represents a perspective view of the propulsion assembly shown on the [Fig.5], with the nacelle hoods in the open position;

[0038] [Fig.8] represents a longitudinal half-sectional view of one of the nacelle hoods, incorporating a ventilation channel;

[0039] [Fig.9] represents a longitudinal cross-sectional view of part of a mechanism of fixing between an axial end of a nacelle hood, and a structural part of the turbomachine, according to a second preferred embodiment of the invention;

[0040] [Fig. 10] represents a perspective view of the fastening mechanism shown in the previous figure, in the open position;

[0041] [Fig. 11] represents a longitudinal cross-sectional view of the fastening mechanism shown in the previous figure, still in the open position;

[0042] [Fig. 12] represents a perspective view of the fastening mechanism shown in Figures 9 to 11, in the locked position;

[0043] [Fig. 13] represents a perspective view of the fastening mechanism shown in [Fig. 12], still in the locked position but from a different angle of view;

[0044] [Fig. 14] represents a longitudinal cross-sectional view of the fastening mechanism shown in Figures 9 to 13, in the locked position. DETAILED EXPLANATION OF PREFERRED METHODS OF IMPLEMENTATION

[0045] With reference first to [Fig. 1], a propulsion assembly 100 for an aircraft is shown, comprising an aircraft turbomachine 1, a nacelle 102, and a mounting mast 104 for suspending the turbomachine 1. This preferably corresponds to a twin-spool turbojet engine, comprising an unfaired fan 2. However, it could be a turbomachine of another type, for example a turboprop, without departing from the scope of the invention.

[0046] The turbojet 1 has a longitudinal axis 3 around which its various components extend. It comprises, from upstream to downstream along a main direction 5 of gas flow through this turbomachine, the fan 2, a low-pressure compressor 4, a high-pressure compressor 6, a combustion chamber 8, a high-pressure turbine 10 and a low-pressure turbine 12.

[0047] Conventionally, these elements define a primary channel 14a through which a primary flow 16a circulates, and a secondary channel 14b through which a secondary flow 16b circulates. In this dual-flow design, a casing is provided intermediate 20 arranged downstream of the blower 2. The intermediate housing includes a hub 22, as well as radial arms 24, which, like the blades of the blower 2, are not shrouded.

[0048] The high-pressure turbine 10 and the high-pressure compressor 6 are connected by a high-pressure shaft 30, while the low-pressure turbine 12 and the low-pressure compressor 4 are connected by a low-pressure shaft 32, preferably passing through the high-pressure shaft 30. A rotating blower shaft 34 is also provided, driving the blower blades in rotation around the axis 3, on which the three shafts 30, 32, 34 are centered.

[0049] In the configuration shown, the blower shaft 34 is driven by means of a reducer 36, which is itself driven by the low-pressure shaft 32. However, driving the blower directly by the low-pressure body remains possible, without departing from the scope of the invention.

[0050] The compressors and turbines are radially delimited outwards by housings, in particular a low-pressure turbine housing 40. This housing 40 includes a portion 42 of a fastener 44 for mechanically connecting the turbojet to the primary structure of the mounting mast 104. The latter is in fact equipped with a second portion 46 of this fastener, cooperating with the portion 42 which is either attached or formed as a single unit with the low-pressure turbine housing 40. According to an alternative which will be described with reference to [Fig. 2], an annular support structure 48, such as a ring, may be interposed between the low-pressure turbine housing 40 and the mounting mast 104. In this case, it is the structural ring 48 which internally supports the low-pressure turbine housing 40, for example by means of load-bearing connecting rods 47.

[0051] The propulsion unit 100 therefore also includes the nacelle 102, formed in particular by means of several aerodynamic cowlings. These consist specifically of a first cowling 50 and a second cowling 52, shown schematically in [Fig. 1]. As will be described below, each of the two cowlings 50, 52 has a general half-shell shape. In a preferred nacelle design, the cowlings 50, 52 are also hinged to the mounting mast. Each of them then has a so-called "D-duct" or "C-duct" architecture, known by the Anglo-Saxon names "D-duct" and "C-duct".

[0052] Each of the first and second cowlings 50, 52 radially delimits inwards, with its radially external surface, the secondary flow 14b. In this respect, the radially external delimitation of this flow 14b is simply materialized by the distal end of the fan blades, and by the distal end of the radial arms 24. Furthermore, between these cowlings 50, 52 and the turbine and compressor housings, a compartment 54 is radially defined, housing turbojet equipment, such as heat exchangers, pumps, etc. Thus, by dismantling or opening these cowlings, it is possible to access the equipment 56, shown schematically only in [Fig. 1]. Another feature of these cowlings is the ability to integrate a ventilation duct 58, shown in [Fig. 8], also called a tertiary duct, this duct contributing preferentially to propulsion. As is known, this duct 58 can carry cooling air intended to supply or be extracted from heat exchangers equipping the turbojet engine. This duct 58 extends essentially along the axial direction of the turbojet engine, while following the profile of the cowling 50, 52 within which it is integrated.

[0053] With further reference to [Fig. 1], it is noted that each cowl 50, 52 comprises a first axial end 60, as well as a second axial end 62 opposite the first end. The first axial end 60 of the cowl is fixed to a first structural part of the turbojet engine, here formed, for example, by the hub 22 of the intermediate casing. The connection is made by means of a first fastening device 64, which will be described below. On the other side, the second axial end 62 is fixed to a second structural part of the turbojet engine, here formed by the low-pressure turbine casing 40, or the structural ring surrounding it, arranged downstream of the hub 22. The connection is made by means of a second fastening device 66, for example, of identical or similar design to that of the first fastening device 64.Thus, subsequently, the second fastening device 66 will be described in detail, but it is understood that the first fastening device 64, between each hood 50, 52 and the hub 22, has an identical or similar design.

[0054] One of the features of the invention lies in the fact that the second fastening device 66 comprises several mechanisms 70 for fastening the second axial end 62 of each of the first and second hoods 50, 52, onto the structural ring 48, which includes the mast attachment part 42. These fastening mechanisms 70 are circumferentially spaced from one another along the relevant hood 50, 52, and each is configured to retain this hood relative to the structural ring 48, radially inwards and outwards.

[0055] In the first preferred embodiment shown in Figures 2 to 8, each of the fastening mechanisms 70 could also be configured to retain the cowl 50, 52, relative to the structural ring 48, circumferentially in one of the two directions of the circumferential direction. This direction preferably corresponds to the direction of rotation of the fan 2. The transfer of forces between the axial ends of the cowls 50, 52, and the corresponding structural parts 22, 40, makes it possible to associate a structural function with these cowls, thus improving the overall rigidity of the propulsion assembly 100, in addition to its aerodynamic function, which it retains. as a nacelle element. In particular, it is the rigidity against longitudinal bending of the turbojet that is reinforced by the presence of the structural cowlings 50, 52.

[0056] With more specific reference to Figures 2 and 4, the fastening mechanisms 70 are therefore provided in plurality along each axial end of each hood, the number of these mechanisms 70 within each fastening device 64, 66 being, for example, between two and five. Alternatively, the fastening mechanisms 70 can be arranged on only one of the two axial ends of each hood, for example at the front or the rear, depending on the constraints and requirements encountered.

[0057] In the aforementioned figures, this number is three fastening mechanisms 70, each arranged at a distance from a first circumferential end of the cover 72 and a second circumferential end of the cover 74, these corresponding respectively to the ends located in clock faces near 12 o'clock and 6 o'clock. Among these three fastening mechanisms 70, at least one of them is arranged circumferentially at a distance from the two circumferential ends, 72, 74, separated from each of them by an angle A2 preferably greater than or equal to 30°. In addition, among these fastening mechanisms 70, at least two of them are circumferentially spaced from each other by an angle A1 less than or equal to 60°, or even less than or equal to 30°.

[0058] It is noted that between these fastening mechanisms 70, the cooperation between the axial end 60, 62 of the hood 50, 52, and its corresponding structural part 22, 40, 48 can be achieved using a radial rib 114 and a radial groove 116 for receiving the rib 114. These elements, for example of V-shaped half-section, allow the transmission of all axial forces to the interfaces, in both directions of the axial direction.

[0059] As mentioned previously, the first circumferential end of the hood 72 is articulated on the primary structure of the towing mast 104, via a hinge line 76 forming a conventional articulation device, and distinct from the first and second fastening devices 64, 66.

[0060] The second circumferential end 74 of each hood 50, 52 is equipped with two hook and lever locking devices 80, one of which is present on the first axial end 60 of the hood, and the other on the second axial end 62. These locking devices 80 cooperate directly with the other of the two hoods 50, 52, or with a fixed structure 82 of the propulsion assembly, arranged in the clockwise position at 6 o'clock as shown in Figures 5 and 7. These locking devices 80 are preferably conventional, and will therefore not be described further.

[0061] In addition to the fastening devices 64, 66, the nacelle 102 includes a mechanical joining device between the first two circumferential ends 72 of the two hoods 50, 52. More specifically, two of these devices 84 are provided respectively at the two axial ends 60, 62 of the hoods 50, 52. These mechanical joining devices 84, which make it possible to create straps for retaining the hoods at the front and rear, will be described with more specific reference to Figures 5 and 6. Each of them includes a force transmission frame 86 in the form of a connecting rod, comprising a first end articulated on the first circumferential end 72 of the first hood 50, and a second end opposite the first, and guided in a rail 88 of the structural ring 48, of its attachment part to the mast 104, or of any other surrounding fixed structure.

[0062] Each mechanical joining device 84 also includes a hook locking device 90 carried by the first circumferential end 72 of the second hood 52, the hook 92 cooperating with the second end of the force transmission armature 86. In this regard, the locking of the hook 92 on the second end of the armature 86 is effected by tilting the hook, controlled automatically for example by the actuating lever of the locking device 80 located in the same transverse plane or nearby, via a cable or a similar motion transmission element.

[0063] In this first preferred embodiment of the invention, best seen in Figures 2 to 4, each fastening mechanism 70 comprises on the one hand a first retaining member 94 attached to the hood 50, 52 and formed by a loop, and on the other hand a second retaining member 96 carried by the structural ring 48 and formed by a hook. Furthermore, the fastening mechanism 70 includes a system for moving the hook 96 relative to the ring 48, so as to cause the hook 96 to be inserted into the loop 94. This movement system is here an actuating ring 98, common to several fastening mechanisms 70, or even common to all the mechanisms 70 of the second fastening device 66 associated with each of the two covers 50, 52. To do this, the actuating ring 98 extends over 360° or substantially 360° around the axis 3 and the structural ring 48, with which it cooperates via an annular rail 106 formed on the periphery of this ring 48.

[0064] The loop 94 includes a radial load-bearing axis 108, preferably axially oriented, and also includes two supports 110 for the radial load-bearing axis 108, these supports being, for example, radially oriented. Furthermore, the hook 96 has an opening for inserting the radial load-bearing axis 108, this opening being preferably circumferentially oriented. In this way, to lock each fastening mechanism 70 after the covers 50, 52 have been folded down, the actuating ring 98 is rotated relative to the structural ring 48, by a conventional means, for example manually controlled. This rotation has the effect of causing the shaft 108 to penetrate the moving hook 96, via the dedicated circumferential opening, until the hook 96 radially grips the shaft 108 on both sides. It is precisely this cooperation between these two elements 108, 96 that allows the radial retention, in both directions, of the covers 50, 52 relative to the structural ring 48.

[0065] Figures 9 to 14 show one of the fastening mechanisms 70, according to a second preferred embodiment of the invention. Here too, several of these mechanisms 70 are intended to follow one another circumferentially along each cover 50, 52, in order to form the first and second fastening devices. In the figures, only one of these fastening mechanisms 70 is shown, arranged at the interface between the second axial end 62 of one of the covers 50, 52, and the upstream end of the structural ring 48.

[0066] The fastening mechanism 70 first comprises a fitting 120, fixedly mounted on the second axial end 62 of the cover 50, 52, for example by means of bolts or rivets. It then comprises a locking device 122, including an actuating lever 124 and a locking member 126 for resisting radial forces. These two distant elements 124, 126 are pivotally mounted on the fitting 120 and connected to each other by a link 128, so as to form a three-point locking mechanism. To do this, the connecting rod 128 is mounted articulated on each of the two elements 124, 126. When the lever 124 is closed, the angle formed by the connecting rod 128, and the segment defined between the two axes of rotation of the lever, gradually flattens before reversing direction, thus providing a locking security against unwanted openings.During this rotation of the lever 124, the connecting rod 128, possibly of adjustable length, rotates the locking member 126 until it bears against a radially internal surface of the upstream end of the structural ring 48. This retains the cover 50, 52 relative to the ring 48, radially inwards. It should be noted that the connecting rod may be of adjustable length to accommodate the geometric tolerances of the assembly.

[0067] In order to also provide retention of the hood 50, 52 relative to the ring 48, radially outwards and axially upstream and downstream, the fastening mechanism 70 is supplemented by a first axial retaining member 130, attached in an adjustable manner or integrated into the fitting 120. This arrangement is preferably provided in all preferred embodiments for the transfer of axial forces. The first retaining member takes, for example, the form of a radial rib 130, extending radially inwards. It cooperates with a second axial retaining member 132 belonging to the mechanism 70, by being attached or integrated into the structural ring 48. It is preferably a radial groove 132 for receiving the rib 130, this groove 132 therefore being preferentially open radially outwards.

[0068] The cooperation between these elements 130, 132 is preferably obtained during the closing of the hood 50, 52, which leads to the introduction of the radial rib 130 into the corresponding groove 132, as for the analogous elements 114, 116 represented on the [Fig.8], present between the mechanisms 70 and which can also be implemented in this second preferred embodiment of the invention.

[0069] As can be seen in [Fig. 9], axial adjustment of the rib 130 is possible to accommodate the positional tolerances of the groove 132. To do this, the fixing screws are loosened, and the cover is closed, allowing the rib 130 to be positioned axially. These screws are then tightened, and the cover is reopened, which secures the part 130 in the axial position using the screw and nut systems located on the rear of the part 130.

[0070] One of the particularities here lies in the fact that in the locked position shown in figures 12 to 14, the locking member 126 is radially supported on the groove 132, externally to it by applying radial stress outwards, so that this groove 132 is radially clamped between this hook-shaped locking member 126, and the radial rib 130 which it receives.

[0071] The cooperation between the groove 132 and the radial rib 130 thus allows axial retention in both directions, as well as circumferential retention also in both directions, by friction, accentuated moreover by the radial support of the locking member 126 in this same groove 132, in the locked position.

[0072] Of course, various modifications can be made by a person skilled in the art to the invention just described, solely by way of non-limiting examples, and the scope of which is defined by the appended claims. In particular, the elements of the different embodiments that have been described are interchangeable.

Claims

Demands

1. A propulsion assembly (100) for an aircraft comprising a turbomachine (1) equipped with a first structural part (22) extending about a longitudinal central axis (3) of the propulsion assembly, and a second structural part (40, 48) located downstream of the first part, and also extending about the longitudinal central axis (3), the assembly comprising a first cowling (50) having a radially external surface forming an aerodynamic surface, the first cowling (50) comprising a first axial end (60) and a second axial end (62) opposite the first, the assembly comprising a first fastening device (64) for the first axial end (60) of the first cowling on the first structural part (22), and a second fastening device (66) for the second axial end (62) of the cowling on the second structural part (40, 48), characterized in that each of the first and second fastening devices (64,66) includes several fastening mechanisms (70) for the first hood (50) on its corresponding structural part (22, 40, 48), the fastening mechanisms (70) being circumferentially spaced from each other along the first hood (50), and each configured to retain the first hood (50) relative to its corresponding structural part (22, 40, 48), radially inwards.

2. Propulsion assembly according to claim 1, characterized in that each of the fastening mechanisms (70) is also configured to retain the first hood (50) relative to its corresponding structural part (22, 40, 48), radially outwards.

3. Propulsion assembly according to claim 1 or 2, characterized in that each of the fastening mechanisms (70) is also configured to retain the first hood (50) relative to its corresponding structural part (22, 40, 48), axially upstream and / or downstream.

4. Propulsion assembly according to any one of the preceding claims, characterized in that it comprises a turbomachine (1) with unshod fan(s) (2), and in that the first cowling (50) radially delimits inwardly a secondary flow (14b) of the turbomachine, the first cowling (50) preferably comprising a ventilation and propulsion channel (58), and preferably radially outwards delimiting a compartment (54) housing turbomachine equipment (56).

5. Propulsion assembly according to any one of the preceding claims, characterized in that at least one of the first and second structural parts (22, 40, 48) comprises a part (42) of a turbomachine attachment (44) to a towing mast (104) of the assembly.

6. Propulsion assembly according to any one of the preceding claims, characterized in that each of the first and second structural parts (22, 40, 48) is a turbomachine casing, or a ring surrounding a casing to which it is connected.

7. Propulsion assembly according to any one of the preceding claims, characterized in that it comprises a second hood (52), and a mechanical joining device (84) between two circumferential ends (72, 72) of the first and second hood (50, 52), the mechanical joining device (84) comprising: - a force transmission armature (86) comprising a first end articulated on the circumferential end (72) of one (50) of the two hoods, and a second end opposite to the first and guided in a rail (88) of a fixed structure (42, 48) of the propulsion assembly; and - a locking device (90) with a hook (92) carried by the circumferential end (72) of the other (52) of the two hoods, the hook (92) cooperating with the second end of the force transmission armature (86).

8. Propulsion assembly according to any one of the preceding claims, characterized in that each fastening mechanism (70) comprises, on the one hand, a first retaining member (94) integral with the first hood (50) and formed by one of the elements from a hook and a loop, and on the other hand, a second retaining member (96) carried by the corresponding structural part (22, 40, 48) and formed by the other of the elements from the hook and the loop, and in that the fastening mechanism (70) comprises a system (98) for moving the second retaining member (96) relative to the structural part (22, 40, 48), so as to cause the hook to be inserted into the loop.

9. Propulsive assembly according to any one of claims 1 to 7, characterized in that each fastening mechanism (70) includes a locking device (122) comprising an actuating lever (124) and a locking member (126) for the absorption of radial forces, the locking member (126) being supported against the corresponding structural part (22, 40, 48) so as to retain the first hood (50) relative to its corresponding structural part (22, 40, 48), radially inwards.

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