Aircraft propulsion system comprising a structural platform between an annular support attached to the pylon and an upstream casing of the propulsion system

Abstract

The aircraft propulsion unit (100) comprises a gas generator (104), at least one fan (102) driven in rotation by a shaft of the gas generator (104), and at least one annular separation nozzle adapted to separate the airflow entering the propulsion unit (100) under the effect of the rotation of the fan (102) into a primary flow and a secondary flow. Upstream suspension members (114) are attached to the pylon (101) and to an upstream housing (103, 108) of the gas generator (104). Downstream suspension members (115) are attached to the pylon (101) and to an annular support (116) surrounding the downstream housing (106). Connecting means link the annular support (116) to the downstream housing (106). A structural deck (110) positioned between the gas generator (114) and the pylon (101) has an upstream end (110a) fixed to the upstream casing (103, 108) and a downstream end (110b) fixed to the annular support (116). Figure 4

Description

Title of the invention: Aircraft propulsion assembly comprising a structural platform between an annular support attached to the pylon and an upstream casing of the propulsion assembly. Technical field of the invention

[0001] The present invention relates to a propulsion assembly for an aircraft intended to be supported by a pylon of the aircraft.

[0002] The invention also relates to a system comprising such a propulsion assembly and an aircraft pylon for attaching the propulsion assembly to the aircraft.

[0003] For example, the invention can find application in cases where the propulsion assembly is part of a dual-flow or triple-flow turbojet engine. State of the art

[0004] The prior art includes, for example, document WO2023 / 198962A1.

[0005] Conventionally, an aircraft is propelled by several propulsion systems. A propulsion system refers to a turbomachine that produces motive power, dedicated to the propulsion of the aircraft and equipped or not with a nacelle. Among these turbomachines, we distinguish in particular: - turbojet engines providing the thrust necessary for propulsion by reaction to the high-speed ejection of hot gases, - and turboshaft engines in which motive power is supplied by the rotation of a drive shaft.

[0006] For example, turboshaft engines are used as engines for helicopters, ships, trains, or even as industrial engines. Turbopropellers, which are turboshaft engines driving a propeller, are turboshaft engines used as aircraft engines.

[0007] A turbojet is frequently a turbofan or triple-flow turbojet.

[0008] A turbojet conventionally comprises a gas generator comprising successively (viewed in the direction of fluid flow through the turbojet) at least one compressor housed in a compressor casing, a combustion chamber and at least one turbine housed in a downstream casing.

[0009] A turbojet engine further comprises at least one propulsion propeller which is driven by a shaft (or rotor) of the turbine. The propulsion propeller can generally be located upstream of the gas generator along the axial direction of the turbojet engine, and in this case the propulsion propeller is called a "fan". However, there are arrangements where the propulsion propeller is positioned downstream of the gas generator. The blower generates a flow of hot gases via its blades.

[0010] A turbojet also includes a first annular separation nozzle adapted to separate the airflow entering the propulsion assembly (under the effect of the rotation of the fan) into a first flow which is guided towards the gas generator and into a second flow which circulates around the gas generator.

[0011] Furthermore, a propulsion assembly may frequently include a nacelle, in which the gas generator, the fan, and the first annular separation nozzle are housed. The nacelle also contains a set of auxiliary actuation devices related to its operation and performing various functions when the turbojet is running or stopped. The nacelle defines a generally annular passage, also called a flow, formed between two concentric walls of the nacelle. The first and second flows are ejected from the turbojet through the rear of the nacelle.

[0012] The blower is designed to accelerate the intake air. A portion of the airflow exiting the blower, referred to as the "primary flow" in the remainder of this document, is intended to circulate successively through at least one compressor where it is compressed, then through the combustion chamber where the gases are burned after mixing with the fuel, and then through at least one turbine where the combustion gases are subsequently expanded to rotate the turbine shaft and, consequently, the blower. The remaining portion of the airflow exiting the blower, referred to as the "secondary flow" in the remainder of this document, is intended to generate the majority of the thrust produced by the propulsion system.

[0013] The fan includes blades which generally have an angular position, called pitch, which is fixed around a radial direction. Even in low engine speed phases, such as idle, this pitch is configured so that the flow rate of the generated second stream is sufficient to supply fluid / air heat exchangers installed in the second stream's flow path, in order to cool turbofan equipment.

[0014] In some variants, the fan is housed in a fan casing, which acts as a peripheral shroud. In other variants, particularly for large-diameter fans, such a fan casing is absent.

[0015] A turbojet nacelle generally has a tubular structure comprising: - a front section, or air intake, located downstream of the turbojet engine, - a mid-section, designed to surround the turbojet engine's fan, - a rear section, designed to surround the combustion chamber of the gas generator, - an ejection nozzle, the outlet of which is located downstream of the turbojet engine.

[0016] The rear section of the nacelle generally has an external structure which, together with a concentric internal structure (called "Inner Fixed Structure" or "IFS"), defines the annular vein used to channel the secondary flow.

[0017] If a fan housing is present, the central section of the nacelle is mounted around the fan housing. Furthermore, the upstream end of the rear section of the nacelle can also cooperate with the fan housing to hold it along the axial direction and in the plane perpendicular to the axial direction.

[0018] Frequently, a nacelle can also incorporate thrust reverser means which, during aircraft landing, improve the aircraft's braking capacity by redirecting a majority of the thrust generated by the turbojet engine downstream. In this phase, the thrust reverser generally obstructs the secondary flow path and directs the latter towards the front of the nacelle along the axial direction, thereby generating a counter-thrust which adds to the braking force of the aircraft's wheels.

[0019] Three main types of structural configuration are known for the rear section of a nacelle, namely the so-called “C-duct” structures, the so-called “D-duct” structures and the so-called “O-duct” structures.

[0020] In a D-shaped structure, the nacelle's rear section consists of two independent parts, each with a D-shaped configuration and each defining a flow path for a portion of the secondary flow along the axial direction. Each of these two parts of the nacelle's rear section is directly hinged to the aircraft's pylon. For each of the D-shaped parts, the internal and external structures of the nacelle's rear section are joined together by two connecting islands called bifurcations. The bifurcations are arranged respectively at the "twelve o'clock" (upper bifurcation) and "six o'clock" (lower bifurcation) positions. It should be noted that the "twelve o'clock" and "six o'clock" positions are conventionally defined by analogy with a clock face, with the nacelle in its operating position, i.e., under the wing.The "twelve o'clock" position is thus located at the level of the planned attachment pylon under the wing of the aircraft, while the "six o'clock" position corresponds to the diametrically opposite position with respect to the axial direction.

[0021] In an O-shaped or C-shaped nacelle, the rear section of the nacelle is configured in such a way that a lower bifurcation is not necessary, which allows for gains in efficiency and mass, but at the expense of ease of maintenance and overall rigidity.

[0022] Figures 1 and 2 schematically and in a simplified manner illustrate certain parts of a known example of a propulsion assembly 1 and a possible and known configuration for suspending and attaching this propulsion assembly 1 to a part of the aircraft, such as a wing, by means of a mounting pylon 2 (or mast). In other words, the pylon 2 is rigidly attached to the rest of the wing frame, while the propulsion assembly 1 is attached and suspended from this pylon 2. The pylon 2 has a generally elongated shape along the axial direction X of the propulsion assembly 1. In [Fig. 1], it can be seen that the gas generator comprises at least one compressor and one combustion chamber housed in a central casing 3, as well as at least one turbine housed in a downstream casing 4.The propulsion assembly 1 also includes a blower-type propulsion propeller, positioned upstream of the gas generator, set in rotation by a rotating shaft itself set in rotation by the turbine, and housed in a blower casing 9.

[0023] In figures 1 and 2, only the rear section 5 of the nacelle is partially represented, but the front section, the middle section and the ejection nozzle of the nacelle are not represented.

[0024] In the particular case represented, the rear section 5 of the nacelle consists of two parts 5a, 5b independent of each other, each having a D-shaped configuration called D-duct and each delimiting a circulation vein 6a, 6b, to guide a part of the secondary flow along the axial direction X.

[0025] Each of the two parts 5a, 5b of the rear section 5 of the nacelle is articulated directly on the pylon 2. More specifically, the pylon 2 includes a pair of hinges 7a, 7b having respective pivot axes offset from each other by a spacing 8 considered in an azimuthal direction: the hinge 7a allows a pivot mounting of the part 5a of the rear section 5 of the nacelle relative to the pylon 2 around its pivot axis and the other hinge 7b allows a pivot mounting of the other part 5b of the rear section 5 of the nacelle relative to the pylon 2 around its pivot axis.

[0026] In [Fig. 2], a fire-sealing element 10a is shown positioned between pylon 2 and the upper bifurcation of part 5a of the rear section 5 of the nacelle, and a fire-sealing element 10b is shown positioned between pylon 2 and the upper bifurcation of part 5b of the rear section 5 of the nacelle. For each of the parts 5a, 5b of the rear section 5 of the nacelle, each adopting a D-duct configuration, the external structure 12a, 12b, which defines the circulation channel 6a, 6b used to channel the secondary flow in combination with the concentric internal structure 13a, 13b (“Inner Fixed Structure” or “IFS”), is delimited by two internal and external walls between which a honeycomb structure is arranged. The inner face of the internal structure 13a, 13b is, as for it is covered with a thermal protection panel, respectively 1 la, 11b, in order to protect the nacelle from the heat emitted by the gas generator.

[0027] It can be seen in [Fig. 2] that the aerodynamic flow is disturbed in the twelve o'clock zone, due to the presence of pylon 2 in the gap between the upper bifurcations of the two parts 5a, 5b of the rear section 5 of the nacelle. This obviously reduces the efficiency of the propulsion system accordingly.

[0028] Furthermore, the upstream end of the rear section 5 of the nacelle also includes male engagement means 14 capable of cooperating by interlocking or simple radial insertion with female engagement means 15 arranged in the outer face of the blower housing 9, which makes it possible to maintain the rear section 5 of the nacelle in this area along the axial direction X and in the plane perpendicular to the axial direction X.

[0029] The propulsion assembly 1 further includes upstream suspension members 16 directly attached to the pylon 2 and the fan casing 9. The propulsion assembly 1 also includes downstream suspension members 17 directly attached to the pylon 2 and the downstream casing 4. Thrust linkages 18 directly connect the gas generator (for example in the area between the fan casing 9 and the central casing 3) and the pylon 2.

[0030] Thus, the rear section 5 of the nacelle is a floating assembly around the central casing 3 and the downstream casing 4 of the gas generator, and it does not contribute to suspending or stiffening the downstream part of the engine. In other words, there is no direct mechanical link in the downstream area between the nacelle and the gas generator. This reduces the rigidity of the propulsion assembly.

[0031] Furthermore, to improve turbofan performance (higher thrust and lower fuel consumption), some engine architectures aim to increase the bypass ratio, also known as BPR (Bypass Ratio), by increasing the fan diameter. To reduce the turbofan's mass, the cowling with the fan casing 9 located around the fan can be eliminated. In addition, the fan blades can be made adjustable, and therefore have variable pitch, to control the thrust level of the propulsion system.

[0032] However, it sometimes happens that during certain phases, such as idle on the ground, hovering, or thrust reversal phases, the secondary flow rate is insufficient for the thermal management of the propulsion system, which requires heat exchange between fluids and air to ensure the cooling of its equipment and its optimal operation. To address this problem, a triple-flow turbofan engine has already been proposed, which incorporates an additional bypass flow dedicated to the thermal management of the propulsion system.

[0033] Thus, and with reference to [Fig. 3], it is known, for example, from document WO2023 / 198962A1 that the propulsion assembly 1 is to include a secondary propeller 20 driven in rotation by a shaft of the gas generator. This secondary propeller 20, independent of the fan 9, is then located downstream of the first annular separation nozzle 21 but upstream of a second annular separation nozzle 22.If, as previously indicated, the first annular separation nozzle 21a has the effect of separating the outgoing flow from the blower 9 into a first flow Fl which is guided towards the gas generator 23 through a flow channel VI and into a second flow F2 which circulates around the gas generator 23, the second annular separation nozzle 22 has the function of separating said first flow Fl into, on the one hand, an internal flow Fil which circulates first in a flow channel V11 and then successively in at least one compressor 24, the combustion chamber 25 and at least one turbine 26 of the gas generator 23, and on the other hand, an external flow F12 circulating in a flow channel V12 (where surface or non-surface fluid / air exchangers 29 are located, in order to cool equipment) delimited between two annular compartments Cl, C2 of the gas generator 23 which extend around the axial direction X, with: . - a hot compartment Cl relatively close to the annular flow vein VI1 where the flow Fl 1 circulates and exposed to the heat generated by compression, by the combustion chamber 25 and by the combustion gases: this hot compartment Cl extends axially between the second annular separation nozzle 22 and a first ejection nozzle 27 of the flow Fil, - a cold compartment C2 which is less exposed to heat, in particular because it is separated from the hot compartment Cl by the annular flow vein V12 where the external flow F12 circulates: this cold compartment C2 extends axially between the first annular separation nozzle 21 and a second ejection nozzle 28 of the external flow F12.

[0034] In architectures without a second annular separation nozzle, which are therefore of the dual-flow type, the primary flow consists of the first flow obtained at the outlet of the first annular separation nozzle, and the secondary flow consists of the second flow obtained at the outlet of the first annular separation nozzle. Conversely, in architectures equipped with a second annular separation nozzle, which are therefore of the triple-flow type, the primary flow consists of the internal flow obtained at the outlet of the second annular separation nozzle, while the secondary flow consists of the combination of, on the one hand, the second flow obtained at the outlet of the first annular separation nozzle and, on the other hand, the external flow obtained at the outlet of the second annular separation nozzle.

[0035] In engine architectures which aim to increase the dilution rate by increasing the diameter of the fan or even eliminating the fan shroud and casing, the propulsion propellers generate such high thrust forces and a mechanical moment on the suspension components that the management of force regeneration and transmission of mechanical forces is very complex both within the components of the gas generator and in the means of suspending and fixing the gas generator to the aircraft pylon.

[0036] These problems are all the more difficult to manage as the twelve-hour environment is very constrained, in particular due to the larger size of engines aiming for a high dilution rate.

[0037] It is necessary to find solutions that improve the existing one, while taking care to achieve a solution that meets the needs of maintenance, lightness, ease of access and aerodynamic efficiency. Object of the invention

[0038] The present invention aims to provide a propulsion system for an aircraft intended to be supported by an aircraft pylon that addresses the aforementioned problems.

[0039] In particular, the propulsion system proposed in this document is intended to meet at least one of the following objectives: - limit bulk and be usable in a very constrained twelve-hour environment between the gas generator and the aircraft attachment pylon; - to meet maintenance and ease of access needs; - meet the requirements, in particular for the intended applications of high bypass ratio engines, with regard to the recovery and transmission of mechanical forces both within the gas generator and with respect to the means ensuring suspension and attachment to the pylon; - exhibit good aerodynamic performance, by optimizing the secondary airflow in the twelve o'clock zone; - to have a reduced mass, for improved performance.

[0040] This can be achieved by implementing a propulsion system for an aircraft intended to be supported by an aircraft pylon, the propulsion system having an axial direction and comprising: - a gas generator comprising at least one compressor, one combustion chamber and at least one turbine, - at least one blower driven in rotation by a shaft of the gas generator and located upstream of the gas generator along the axial direction, - at least one annular separation nozzle adapted to separate the airflow entering the propulsion assembly under the effect of the fan's rotation into a primary flow circulating successively in at least one compressor, the combustion chamber and at least one turbine, and into a secondary flow, - upstream suspension components intended to be fixed to the pylon, and fixed to an upstream casing of the gas generator, the upstream casing being positioned axially upstream of the combustion chamber along the axial direction, - downstream suspension components intended to be fixed to the pylon, and axially provided at the level of a downstream casing of the gas generator, the downstream casing being positioned axially downstream of the combustion chamber along the axial direction,

[0041] the propulsion assembly further comprising:

[0042] - an annular support located in a principal plane transverse to the axial direction, surrounding the downstream casing, and fixed to the downstream suspension components,

[0043] - connecting means for indirectly linking the annular support to downstream crankcase,

[0044] - a structural deck intended to be positioned between the gas generator and the pylon, the structural deck having an upstream end fixed to the upstream casing and a downstream end fixed to the annular support.

[0045] In a preferred configuration, the upstream casing may consist of a fan casing surrounding the fan in the case of a shrouded fan for a dual-flow engine, or alternatively, it may consist of a gas generator casing axially positioned at a compression stage in the case of a triple-flow engine as previously described, such as, for example, an intermediate casing axially positioned between the fan and the combustion chamber. The downstream casing is preferably a gas generator casing arranged at a turbine stage or an exhaust casing.

[0046] Advantageously, the structural deck plays both a structural role in the twelve o'clock zone (i.e., in the highly constrained environment between the tower and the gas generator) and an aerodynamic role. Indeed, at twelve o'clock, the structural deck helps to transfer the mechanical forces from the annular support to the upstream casing, and vice versa. In particular, the structural deck allows for the indirect suspension (via the annular support) of the turbine section of the gas generator. It forms part of the suspension path of the gas generator and the fan relative to the tower.

[0047] The structural deck is therefore particularly efficient, despite its very small size, which is also a significant additional advantage. important because the environment where it is positioned (at twelve o'clock) is particularly constrained, even more so in the non-limiting applications of engines with high bypass ratios.

[0048] In addition to its structural function, the single-piece structural deck plays a crucial aerodynamic role by acting as a guide channel, ensuring aerodynamic guidance of the secondary flow at the twelve o'clock position. The structural deck allows for the efficient flow, without significant pressure loss, of the entire fraction of the secondary flow destined to circulate in the twelve o'clock position. All this air flows naturally along and within the structural deck before exiting into the circulation channels defined by the two sections of the nacelle's rear face. The resulting structure improves secondary flow circulation by preventing air blockages and pressure losses present in the configurations shown in Figures 1 and 2.

[0049] Moreover, all these advantages are obtained despite an advantageously very low overall mass, due to the small number of parts and their dimensions.

[0050] The solution proposed here finally makes it possible to advantageously meet the requirements for dismantling for maintenance purposes and ease of access in general.

[0051] Some preferred but not limiting aspects are the following. These following features may be used individually or in combination with each other.

[0052] The structural deck internally delimits a conduit allowing a fraction of the secondary flow to circulate through the structural deck along the axial direction. This results in very high aerodynamic efficiency of the propulsion system.

[0053] The propulsion assembly includes a nacelle in which the gas generator, the blower and at least one annular separation nozzle are housed, the nacelle comprising a rear section surrounding the combustion chamber of the gas generator, the rear section of the nacelle being made up of two parts independent of each other, each having a D-shaped configuration and each delimiting a circulation channel for the circulation of a part of the secondary flow along the axial direction, each of these two parts of the rear section of the nacelle being hinged on the structural deck.

[0054] Advantageously, the structural deck allows the components of the nacelle's rear section to be mounted on the structural deck, rather than directly or indirectly on the pylon, as was the case in the prior art presented previously. On the one hand, this eliminates the need to provide components other than the structural deck for mounting the nacelle's rear section. It also advantageously results in the possibility of varying the two parts of the nacelle's rear section between a closed operational configuration and an open configuration. The opening is temporary, for maintenance and ease of access. Furthermore, this contributes to the rigidity of the propulsion system.

[0055] The structural apron includes a pair of first hinges having respective pivot axes offset from each other by a spacing in an azimuthal direction, one of the first hinges allowing a pivot mounting of one of the two parts of the rear section of the nacelle relative to the structural apron around its pivot axis and the other of the first hinges allowing a pivot mounting of the other of the two parts of the rear section of the nacelle relative to the structural apron around its pivot axis.

[0056] The conduit delimited by the structural deck has a downstream opening allowing fluidic communication between said conduit and, jointly, the circulation channels delimited by the two parts of the nacelle's rear section. This results in very high aerodynamic efficiency of the propulsion system, by avoiding blockages and pressure losses with respect to the aerodynamic flow of the twelve o'clock fraction of the secondary flow.

[0057] The propulsion assembly comprises a tubular casing arranged to surround the gas generator, being radially interposed between the nacelle and the gas generator. The tubular casing has an upstream end bearing axially against the upstream casing and a downstream end bearing axially against the annular support. This results in high rigidity of the propulsion assembly, over 360° around the axial direction, in addition to the effect already conferred by the presence of the structural tabler.

[0058] The tubular casing consists of two parts arranged like independent half-shells, each of these two parts of the tubular casing being hinged to the structural deck. On the one hand, this eliminates the need for components other than the structural deck. It also advantageously allows the two parts of the tubular casing to be changed between a closed operational configuration and a temporary open configuration, for maintenance and ease of access.

[0059] The structural deck includes a pair of second hinges having respective pivot axes offset from each other by a non-zero distance along the azimuthal direction, one of the second hinges allowing a pivot mounting of one of the two parts of the tubular envelope relative to the structural deck around its pivot axis and the other of the second hinges allowing a pivot mounting of the other of the two parts of the tubular envelope relative to the structural deck around its pivot axis.

[0060] The means of connection between the annular support and the downstream housing are configured to provide a possibility of radial movement between the annular support and the downstream housing in the main plane, the connecting means including prestressing elements stressing the downstream casing towards a predetermined natural rest position relative to the annular support.

[0061] This allows in practice a mounting of the propulsion assembly on the cantilevered pylon from the downstream suspension elements, with in parallel a degree of freedom at the rear part of the gas generator: this is a very important advantage to avoid oversizing or deterioration in the increasingly sought-after cases where the use of engines with a high dilution ratio (large diameter fan) and without a fan casing is planned.

[0062] The invention also relates to a system comprising such a propulsion assembly and an aircraft pylon for attaching the propulsion assembly to the aircraft, the pylon having a generally elongated shape parallel to the axial direction and being fixed respectively to the upstream suspension members and the downstream suspension members of the propulsion assembly.

[0063] The technical advantages provided by this system derive from all the aforementioned advantages conferred by the propulsion assembly previously described.

[0064] According to one embodiment, the structural deck positioned between the gas generator and the pylon is configured to provide a fire-sealing function between the pylon and the rest of the propulsion assembly. These arrangements make it possible to fulfill this safety function without the need for additional parts for this purpose, guaranteeing an economical, lightweight, and easy-to-assemble solution. Brief description of the drawings

[0065] Other aspects, objectives, advantages and features of the invention will become more apparent upon reading the following detailed description of preferred embodiments thereof, given by way of non-limiting example, and made with reference to the accompanying drawings in which:

[0066] [Fig-1] is a schematic side view of an example of a known propulsion assembly according to the state of the art, fixed to a pylon for the purpose of its suspension.

[0067] [Fig.2] is a cross-sectional view of the propulsion assembly of [Fig.1] in a cutting plane substantially perpendicular to the axial direction X, in the area located at twelve o'clock relative to the gas generator.

[0068] [Fig.3] is a schematic side section view, in a cutting plane passing through the axial direction X, of another example of a propulsion assembly known according to the prior art, of the triple flow type.

[0069] [Fig.4] is a schematic side view of a first example of a propulsion assembly according to the invention, fixed and suspended from an aircraft pylon, the propulsion assembly being dual flow.

[0070] [Fig.5] is a cross-sectional view of the propulsion assembly of the [Fig.4] in a plane of cut substantially perpendicular to the axial direction X, in the area located at twelve o'clock relative to the gas generator.

[0071] [Fig. 6] is a cross-sectional view of the propulsion assembly of Figures 4 and 5 in a plane of a cut substantially vertical parallel to the axial direction X, in the area located at twelve o'clock relative to the gas generator.

[0072] [Fig.7] is a cross-sectional view of the propulsion assembly of figures 4 to 6 in a substantially horizontal cross-sectional plane parallel to the axial direction X, in the area located at twelve o'clock relative to the gas generator.

[0073] [Fig.8] is a schematic side view of a second example assembly propulsion system according to the invention, fixed and suspended from an aircraft pylon, the propulsion system assembly being triple flow. Detailed description

[0074] In the figures and throughout the description, the same reference numerals represent identical or similar elements. Furthermore, the various elements are not drawn to scale in order to enhance the clarity of the figures. Moreover, the different embodiments and variants are not mutually exclusive and may be combined.

[0075] Unless otherwise stipulated, the term "substantially" means, in this document, "exactly or to within 10% or to within 10°".

[0076] In this description, the term "propulsion system" refers to all turbomachinery or gas turbine devices producing motive power, dedicated to the propulsion of an aircraft and equipped with or without a nacelle. Among these devices, a distinction is made between turbojets, which provide the thrust necessary for propulsion by reaction to the high-speed ejection of gas, and turboshaft engines, in which motive power is supplied by the rotation of a drive shaft. For example, turboshaft engines are used as helicopter engines. Turboprop engines (turboshafts driving a propeller) are turboshaft engines used as aircraft engines.

[0077] Generally, the axial direction X corresponds to the direction of the axis of rotation of the gas generator. A radial direction Z is a direction perpendicular to the axial direction X. The azimuthal or circumferential direction Y corresponds to the direction describing a ring around the axial direction X. The three axial, radial, and azimuthal (or circumferential) directions correspond respectively to the directions defined by the elevation, radius, and angle in a cylindrical coordinate system. Furthermore, upstream and downstream are defined with respect to the normal flow direction of the fluid (from upstream to downstream) through the propulsion assembly 100. Finally, except To be precise, the adjectives interior / internal and exterior / external are used in reference to the radial direction Z so that the internal (i.e. radially internal) part of an element is closer to the axis defining the axial direction X than the external (i.e. radially external) part of the same element.

[0078] With reference to Figures 4 to 8, two examples of propulsion assemblies according to the invention will now be described. More specifically, Figures 4 to 7 show a first example of a propulsion assembly 100 according to the invention, in which the propulsion assembly 100 is, by way of non-limiting agreement, a turbofan engine where the fan is shrouded and is, for this purpose, arranged in a fan shroud or casing. In [Fig.4], the fan (not visible) is housed in a fan casing 103. On the other hand, [Fig.8] shows a second example of a propulsion assembly 100 according to the invention, in which the propulsion assembly 100 is, again in a non-limiting manner, a triple-flow turbojet where the fan 102 is not arranged in a shroud, intended to constitute a high bypass ratio engine (the diameter of the fan used in [Fig.8] is larger than the diameter of the fan used in [Fig.4]).

[0079] The propulsion assembly 100 according to the first example and according to the second example includes a gas generator 104. Each gas generator 104 comprises successively (viewed in the direction of fluid flow through the propulsion assembly 100) at least one compressor housed in a compressor housing 105, a combustion chamber housed in a central housing 107 and at least one turbine housed in a downstream housing 106.

[0080] The propulsion assembly of figures 4 or 8 further includes the blower 102 which is driven by a shaft (or rotor) of the turbine, located upstream of the gas generator 104 along the axial direction X. It is emphasized that the term "blower" used in this document corresponds to a shrouded propeller or a potentially unshrouded propeller.

[0081] Each of the propulsion assembly 100 of Figures 4 and 8 includes a first annular separation nozzle as previously mentioned, adapted to separate the airflow entering the propulsion assembly 100 (under the effect of the rotation of the blower 102) into a first flow which is guided towards the gas generator 104 and into a second flow which circulates around the gas generator 104.

[0082] The second example of a propulsion assembly 100 in [Fig.8] includes, downstream of the blower 102 and the first annular separation nozzle (not visible), stator blades 109 which extend radially outwards through the flow channel in which the secondary flow circulates.

[0083] Unlike the first example in [Fig. 4], the propulsion assembly 100 according to [Fig. 8] is such that the gas generator 104 includes an intermediate casing 108 axially arranged between the blower 102 and the combustion chamber, in particular between the stator blades 109 and the compressor housing 105.

[0084] Again, unlike the first example in [Fig. 4], the propulsion assembly 100 according to [Fig. 8] is such that the gas generator 104 includes a second annular separation nozzle (not visible) located downstream of the first annular separation nozzle. The first annular separation nozzle 21a has the effect of separating the outgoing flow from the blower 102 into: - a first flow which is guided towards the gas generator 104 through a flow channel, - and in a second flow which circulates around the gas generator 104.

[0085] The second annular separation nozzle is precisely provided at a given point in this flow stream and thus has the function of separating this first flow (itself resulting from the fluidic separation carried out by the first annular separation nozzle) into, on the one hand: - an internal flow which then circulates successively in at least one compressor, the combustion chamber and at least one turbine of the gas generator 104, - an external flow circulating in a delimited flow channel between two annular hot and cold compartments of the gas generator 104 and where surface or non-surface fluid / air exchangers are located in order to cool equipment.

[0086] In the example of [Fig. 4], which is an example of a dual-flow propulsion assembly, the primary flow consists of the first flow obtained at the outlet of the first annular separating nozzle, while the secondary flow consists of the second flow obtained at the outlet of the first annular separating nozzle. In the example of [Fig. 8], which is an example of a triple-flow propulsion assembly, the primary flow consists of the internal flow obtained at the outlet of the second annular separating nozzle, while the secondary flow consists of the combination of, on the one hand, the second flow obtained at the outlet of the first annular separating nozzle and, on the other hand, the external flow obtained at the outlet of the second annular separating nozzle.

[0087] The propulsion unit 100 of [Fig. 4] is intended to be supported by a pylon 101 of the aircraft. The pylon 101 is rigidly fixed to the rest of the wing frame of the aircraft, while the propulsion unit 100 is fixed and suspended from this pylon 101. The pylon 101 has a generally elongated shape along the axial direction X of the propulsion unit 100. Due to the presence of the structural deck 110, which will be described later, the dimension of the pylon 101 along the radial direction Z may be smaller in Figures 4 and 8 than in the prior art shown in Figures 1 and 2.

[0088] Each of the propulsion assemblies 100 in Figures 4 and 8 comprises a nacelle in which the gas generator 104, the blower 102, and the first annular separation nozzle are housed. The nacelle comprises:

[0089] - a forward section, or air inlet, located downstream of the propulsion assembly 100 concerned,

[0090] - a median section surrounding the blower 102,

[0091] - a rear section surrounding the combustion chamber of the gas generator 104,

[0092] - an ejection nozzle, the outlet of which is located downstream of the propulsion assembly 100 concerned.

[0093] In figures 4 to 8, only the rear section of the nacelle is partially shown.

[0094] According to a particular embodiment, the rear section of the nacelle consists of two parts 111a, 111b independent of each other, each having a D-shaped configuration (a configuration known as "D-duct" in the relevant field) and each delimiting a circulation channel 112a, 112b adapted to the circulation of a part of the secondary flow along the axial direction X. Each of these two parts 111a, 111b of the rear section of the nacelle is directly articulated on the structural deck 110.

[0095] This also advantageously results in the possibility of varying the two parts 111a, 111b of the rear section of the nacelle between a closed operational configuration and a temporary open configuration, for maintenance and ease of access needs.

[0096] Furthermore, the upstream end of the rear section of the nacelle also includes male engagement means (not shown) capable of cooperating by interlocking or simple radial insertion with female engagement means 113 arranged in the outer face of the compressor housing 105 for the first example of [Fig.4] and for the second example of [Fig.8], which makes it possible to maintain the rear section of the nacelle in this area along the axial direction X and in the plane perpendicular to the axial direction X.

[0097] Each of the propulsion assemblies 100 in Figures 4 and 8 comprises upstream suspension members 114 attached to the pylon 101 and fixed to an upstream casing. In the case of [Fig. 4], the upstream casing is the blower casing 103 surrounding the blower 102. In other words, in the first example of [Fig. 4], the propulsion assembly 100 comprises upstream suspension members 114 attached to the pylon 101 and fixed to the blower casing 103. In the case of [Fig. 8], the upstream casing is a gas generator casing 104 axially positioned at a compression stage, such as, for example, the intermediate casing 108 axially positioned between the blower 102 and the combustion chamber. In other words, in the second example of [Fig.8], the propulsion assembly 100 includes upstream suspension components 114 fixed to the pylon 101 and fixed to the intermediate casing 108.

[0098] In addition, each of the propulsion assemblies 100 of figures 4 and 8 includes downstream suspension members 115 fixed to the pylon 101 and axially provided at the level of the downstream casing 106. The downstream casing 106 is preferably a casing of the gas generator 104 arranged at the level of a turbine stage or an exhaust casing.

[0099] More specifically, each of the propulsion assemblies 100 in Figures 4 and 8 comprises an annular support 116 situated in a principal plane transverse to the axial direction X and surrounding the downstream casing 106, the downstream suspension members 115 being fixed to the annular support 116 in the twelve o'clock position. The propulsion assembly also includes connecting means for linking the annular support 116 to the downstream casing 106, detailed later.

[0100] Each of the propulsion assemblies 100 of Figures 4 and 8 comprises a structural apron 110 positioned between the gas generator 104 and the pylon 101, the structural apron having an upstream end 110a fixed to the upstream casing mentioned above (i.e. the blower casing 103 in the first example of [Fig.4] and the intermediate casing 108 in the case of the second example of [Fig.8]) and a downstream end 110b fixed to the annular support 116.

[0101] The term "structural" associated with the term apron means that the apron has a rigidity and mechanical resistance which enables it to ensure a transmission of forces between the annular support 116 and the upstream casing in the twelve o'clock part.

[0102] Advantageously, the structural deck 110 plays both a structural role in the twelve o'clock zone (i.e., in the highly constrained environment between the pylon 101 and the gas generator 104) and an aerodynamic role. Indeed, at twelve o'clock, the structural deck 110 contributes to the transfer of mechanical forces from the annular support 116 to the upstream casing (i.e., the fan casing 103 in the first example of [Fig. 4] and the intermediate casing 108 in the second example of [Fig. 8]), and vice versa. In particular, the structural deck 110 allows for the indirect suspension (via the annular support 116) of the turbine section of the gas generator 104. It forms part of the suspension path of the gas generator 114 and the fan 102 relative to the pylon 101.

[0103] In a single piece, the structural deck 110 also plays a very important aerodynamic role in addition to its structural function, by providing aerodynamic guidance of the secondary flow at the twelve o'clock position. The structural deck 110 constitutes part of an annular channel and a vertical part, known as the twelve o'clock bifurcation, of this channel. The structural deck 110 allows the efficient flow, without high pressure loss, of the entire fraction of the secondary flow intended to circulate in the area located at twelve o'clock. All this air flows naturally along the structural deck 110 and within it, before flowing into the circulation veins 112a, 112b delimited by the two parts 111a, 111b of the rear section of the nacelle.

[0104] The structural deck 110 internally delimits a conduit 117 allowing a fraction of the secondary flow to circulate through the structural deck 110 along the axial direction X. This results in a very high aerodynamic efficiency of the propulsion assembly 100.

[0105] With reference to figures 6 and 7, the conduit 117 delimited by the structural deck 110 has a downstream opening 118 allowing fluidic communication between the conduit 117 and each of the two circulation veins 112a, 112b delimited by the two parts 111a, 111b of the rear section of the nacelle.

[0106] Preferably, the structural deck 100 positioned between the gas generator 114 and the pylon 101 is configured to provide a fire-sealing function between the pylon 101 and the rest of the propulsion assembly 100, whereas in known techniques it was common for the pylon itself to perform this function for the purpose of protection against the aircraft.

[0107] With reference to [Fig.5], the structural deck 110 includes a pair of first hinges 119a, 119b having respective pivot axes offset from each other by a spacing 120 along the azimuthal direction Y. The hinge 119a allows a pivot mounting of the part 11a of the rear section of the nacelle relative to the structural deck 110 about its pivot axis and the other hinge 119b allows a pivot mounting of the other part 111b of the rear section of the nacelle relative to the structural deck 110 about its pivot axis.

[0108] Each of the propulsion assemblies 100 of figures 4 and 8 includes a passage 121 oriented substantially along the radial direction Z and which passes through the entire thickness of the structural deck 110. This passage 121 opens at its upper end into the pylon 101 and at its lower end into one of the casings of the gas generator 101. This passage 121 is intended to allow services (for example electrical cables or hydraulic pipes, for a power or control function) from the propulsion assembly 100 to the pylon 101 and vice versa.

[0109] Each of the propulsion assemblies 100 of Figures 4 and 8 comprises a tubular casing 122 arranged to surround the gas generator 104 by being radially interposed between the nacelle and the gas generator 104. The tubular casing 122 has an upstream end 123a bearing along the axial direction X against the upstream casing (i.e. the blower casing 103 in the first example of [Fig.4] and the intermediate casing 108 in the case of the second example of [Fig.8]) and a downstream end 123b bearing along the axial direction X against the annular support 116.

[0110] According to one embodiment, the tubular envelope 122 consists of two parts 122a, 122b arranged in the manner of independent half-shells, each of these two parts 122a, 122b of the tubular envelope 122 being articulated on the structural deck 110.

[0111] This also advantageously results in the possibility of varying the two parts 122a, 122b of the tubular casing 122 between a closed operational configuration and a temporarily open configuration, for maintenance and ease of access purposes. By placing parts 122a, 122b of the tubular casing 122 in the open configuration, it is possible to access, in particular, the gas generator 104.

[0112] The structural deck 110 includes a pair of second hinges 124a, 124b having respective pivot axes offset from each other by a distance 125 along the azimuthal direction Y. The second hinge 124a allows pivot mounting of the portion 122a of the tubular casing 122 relative to the structural deck 110 about its pivot axis, and the second hinge 124b allows pivot mounting of the portion 122b of the tubular casing 122 relative to the structural deck 110 about its pivot axis. In [Fig. 5], it can be seen that the two pivot axes are separated, along the azimuthal direction Y, by a distance 125.

[0113] Not shown, the means of connection between the annular support 116 and the downstream casing 106 are configured to offer a possibility of radial movement between the annular support 116 and the downstream casing 106 in the main plane, the means of connection comprising prestressing elements stressing the downstream casing 106 towards a predetermined natural rest position relative to the annular support 116.

[0114] In the particular case shown in figures 4 to 8, the structural deck 110 consists of three stacked (and fixed to each other) caissons in the radial direction Z in the twelve o'clock zone: - an upper box facing pylon 101 and comprising the first hinges 119a, 119b for the pivoting assembly of parts 111a, 111b of the rear section of the nacelle, - a lower box opposite the gas generator 104 and comprising the second hinges 124a, 124b for the tilting mounting of the parts 122a, 122b of the tubular casing 122, - an intermediate box placed between the lower box and the upper box, and fixed to the latter, the intermediate box delimiting the conduit 117 and the downstream opening 118.

[0115] These three boxes are fixed together by any known means suitable for the function sought.

[0116] The upper casing is fixed at its upstream end to the aforementioned upstream housing (i.e., the blower housing 103 in the first example of [Fig. 4] and the intermediate housing 108 in the second example of [Fig. 8]) and its downstream end is free. The lower casing is fixed at its downstream end to the annular support 116 and its upstream end is also fixed to the upstream housing.

[0117] Each of the lower, intermediate and upper boxes is arranged in the manner of a hollow body, which is a unitary construction element which delimits voids, hollows or cavities by means of partitions arranged for this purpose, the organization of these partitions giving rigidity to the whole of the box concerned.

[0118] These provisions allow the simple and economical obtaining of a structural deck 110 meeting all requirements in terms of rigidity in operation and mechanical resistance, while being light and efficient in terms of aerodynamics.

[0119] Figures 4 to 8 show the general principle of a system as a whole, this system comprising such a propulsion unit 100 and an aircraft pylon 101 for attaching the propulsion unit 100 to the aircraft, the pylon 101 having a general elongated shape parallel to the axial direction X and being fixed respectively to the upstream suspension members 114 and the downstream suspension members 115 of the propulsion unit 100.

Claims

1. Demands Propulsion assembly (100) for an aircraft intended to be supported by a pylon (101) of the aircraft, the propulsion assembly (100) having an axial direction (X) and comprising: - a gas generator (104) comprising at least one compressor, one combustion chamber and at least one turbine, - at least one blower (102) driven in rotation by a shaft of the gas generator (104) and located upstream of the gas generator (104) along the axial direction (X), - at least one annular separation nozzle adapted to separate the airflow entering the propulsion assembly (100) under the effect of the rotation of the blower (102) into a primary flow circulating successively in at least one compressor, the combustion chamber and at least one turbine, and into a secondary flow, - upstream suspension components (114) intended to be fixed to the pylon (101), and fixed to an upstream casing (103, 108) of the gas generator (104), the upstream casing (103, 108) being positioned axially upstream of the combustion chamber along the axial direction (X), - downstream suspension elements (115) intended to be fixed to the pylon (101), and axially provided at the level of a downstream casing (106) of the gas generator (104), the downstream casing (106) being positioned axially downstream of the combustion chamber along the axial direction (X), the propulsion assembly (100) further comprising: - an annular support (116) located in a principal plane transverse to the axial direction (X), surrounding the downstream casing (106) and fixed to the downstream suspension members (115), - connecting means for linking the annular support (116) to the downstream casing (106), - a structural deck (110) intended to be positioned between the gas generator (114) and the pylon (101), the structural deck (110) having an upstream end (110a) fixed to the upstream casing (103, 108) and a downstream end (110b) fixed to the annular support (116).

2. Propulsive assembly (100) according to claim 1, in which the structural deck (110) internally delimits a conduit (117) allowing circulation of a fraction of the secondary flow through the structural deck (110) along the axial direction (X).

3. Propulsion assembly (100) according to any one of claims 1 or 2, which includes a nacelle in which the gas generator (104), the blower (102) and at least one annular separation nozzle are housed, the nacelle comprising a rear section surrounding the combustion chamber of the gas generator (104), the rear section of the nacelle being made up of two parts (111a, 111b) independent of each other, each having a D-shaped configuration and each delimiting a circulation channel (112a, 112b) for the circulation of a portion of the secondary flow along the axial direction (X), each of these two parts (111a, 111b) of the rear section of the nacelle being articulated on the structural deck (110).

4. Propulsion assembly (100) according to claim 3, wherein the structural apron (110) comprises a pair of first hinges (119a, 119b) having respective pivot axes offset from each other along a spacing (120) along an azimuthal direction (Y), one (119a) of the first hinges (119a, 119b) allowing a pivot mounting of one (111a) of the two parts (111a, 111b) of the rear section of the nacelle relative to the structural apron (110) about its pivot axis and the other (119b) of the first hinges (119a, 119b) allowing a pivot mounting of the other (111b) of the two parts (111a, 111b) of the rear section of the nacelle relative to the structural apron (110) about its pivot axis.

5. Propulsion assembly (100) according to claim 2 and according to any one of claims 3 or 4, wherein the conduit (117) delimited by the structural deck (110) has a downstream opening (118) allowing fluidic communication between said conduit (117) and jointly the circulation veins (112a, 112b) delimited by the two parts (111a, 111b) of the rear section of the nacelle.

6. Propulsion assembly (100) according to any one of claims 3 to 5, comprising a tubular casing (122) arranged to surround the gas generator (104) by being radially interposed between the nacelle and the gas generator (104), the tubular casing (122) having an upstream end (123a) supported along the axial direction (X) against the upstream casing (103, 108) and a downstream end (123b) supported along the axial direction (X) against the annular support (116).

7. Propulsion assembly (100) according to claim 6, in which the tubular casing (122) is made up of two parts (122a, 122b) arranged in the manner of independent half-shells, each of these two parts (122a, 122b) of the tubular casing (122) being articulated on the structural deck (110).

8. Propulsion assembly (100) according to any one of claims 1 to 7, wherein the connecting means between the annular support (116) and the downstream casing (106) are configured to provide a possibility of radial travel between the annular support (116) and the downstream casing (106) in the principal plane, the connecting means comprising prestressing elements stressing the downstream casing (106) towards a predetermined natural rest position relative to the annular support (116).

9. System comprising a propulsion unit (100) according to any one of the preceding claims and an aircraft pylon (101) for attaching the propulsion unit (100) to the aircraft, the pylon (101) having a generally elongated shape parallel to the axial direction (X) and being attached respectively to the upstream suspension members (114) and the downstream suspension members (115) of the propulsion unit (100).

10. System according to claim 9, wherein the structural deck (100) positioned between the gas generator (114) and the pylon (101) is configured to provide a fire-sealing function between the pylon (101) and the rest of the propulsion assembly (100).

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