Turbomachine including means for attachment to a pylon, and associated aircraft

Abstract

The application relates to an aircraft propulsion system comprising: a gas generator including at least one low-pressure compressor, one high-pressure body, and one low-pressure turbine; an exhaust casing (31b) extending around the low-pressure turbine; a structural cowling (35) extending around the gas generator and at least a portion of the exhaust casing (31b); the propulsion system comprising a first portion including means for attachment to a pylon and a second portion intended to be cantilevered from the pylon; the propulsion system further comprising a centering device (50) for the gas generator relative to the structural cowling including at least one connecting rod (51); the connecting rod(s) (51) extending between the structural cowling (35) and the second portion of the propulsion system. Figure for the abstract: Fig. 8

Description

Title of the invention: Turbomachine comprising means for attachment to a pylon, and associated aircraft. Technical field

[0001] The present invention relates generally to the field of aircraft propulsion systems and more particularly to aeronautical turbomachinery comprising a shrouded or unshrouded fan with a high bypass ratio. It relates more particularly to the field of attaching a turbomachine to an aircraft pylon. STATE OF THE ART

[0002] An aircraft turbomachine comprises, for example, from upstream to downstream in the direction of gas flow, a gas generator including a fan section, a compressor section which may include a low-pressure compressor and a high-pressure compressor, a combustion chamber, and a turbine section which may include a high-pressure turbine and a low-pressure turbine. The high-pressure compressor is driven in rotation by the high-pressure turbine via a high-pressure shaft. The fan and, where applicable, the low-pressure compressor are driven in rotation by the low-pressure turbine via a low-pressure shaft. The high-pressure compressor, the combustion chamber, and the high-pressure turbine form a high-pressure unit. Environmental aspects

[0003] Climate change is a major concern for many legislative and regulatory bodies worldwide. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies to both new types of aircraft and those already in service, requiring the implementation of technological solutions to bring them into compliance with current regulations. Civil aviation has been actively working for several years now to contribute to the fight against climate change.

[0004] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. The Applicant takes these factors into consideration in all phases of design and development in order to obtain less energy-intensive and more environmentally friendly aeronautical components and products, the integration and use of which in civil aviation have moderate environmental consequences, with the aim of improving the energy efficiency of aircraft.

[0005] Consequently, the Applicant is constantly working to reduce its negative climate impact by using methods and operating virtuous development and manufacturing processes that minimize greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0006] This sustained research and development work focuses on new generations of aircraft engines, the weight reduction of aircraft, in particular through the materials used and lighter on-board equipment, the development of the use of electrical technologies to provide propulsion, and, as essential complements to technological progress, aviation biofuels.

[0007] Thus, in order to improve the propulsive efficiency of the propulsion system and reduce its specific fuel consumption, it has been found that, to obtain the same thrust, it is more advantageous to accelerate a large quantity of air less than to accelerate a smaller quantity of air more strongly. With this in mind, a new generation of propulsion systems, known as Open Fan, has been proposed, in which the fan blades are unshod and have variable pitch, as do the fan stator blades, generally called outlet guide vanes (OGVs).Open-fan propulsion systems, designed to improve propulsion efficiency, offer a high bypass ratio (BPR, the ratio between the secondary airflow and primary airflow) by increasing the fan diameter and, consequently, the external dimensions of the propulsion system (and therefore its mass and drag). This makes integration of the propulsion system more difficult, in addition to increasing its mass. Furthermore, the flow rate in the high-pressure section and the size of the high-pressure section are reduced, and the high-pressure section must support the low-pressure turbine. Structural aspects

[0008] The attachment of a turbomachine to an aircraft, for example to a wing of the aircraft, is done by means of a pylon, also called a mast, connected to the rest of the aircraft.

[0009] In the current technique, the pylon includes upstream and downstream turbomachine attachment elements located upstream of the turbomachine, respectively on a compressor casing around the low-pressure compressor and on an intermediate casing surrounding an inter-compressor section.

[0010] Thus, the entire part of the gas generator downstream of the downstream fixing member, including in particular the majority of the high-pressure body and the low-pressure turbine, is cantilevered, which induces several important problems, which are aggravated by the fact that this part of the gas generator supports substantial additional masses (accessory relay box, oil tank, pipes, electrical harnesses, supports, sheet metal, ...).

[0011] Indeed, in operation, this configuration ensures a transmission of forces via the gas generator between the upstream and downstream fixing members which result in deformations of the gas generator, for example by a sagging of the high-pressure body under acceleration, and by modifications of the relative clearances between the turbomachine in its downstream part and the pylon.

[0012] More specifically, the gas generator is subject to:

[0013] - to maneuvering loads induced by acceleration variations when the aircraft performs maneuvers such as turns in flight,

[0014] - to gravitational loads induced during the aircraft's cruise phase, and,

[0015] - to aerodynamic forces of different types, in particular, when the fan If the engine is not enclosed in a fairing, there are moments, known as "IP moments," related to the angle of incidence between the aircraft's movement and the rotation of the fan blades. Or, in the case of an engine enclosed by a large-diameter casing, there are loads induced by a tilting force related to the angle of incidence between the aircraft's movement and the air intake.

[0016] These different loads suffered by the gas generator, its cantilevered position, and the additional loads it supports lead to its sagging under acceleration, to its deformation and that of its casings.

[0017] The deformation of the gas generator degrades the clearances at the top of the high-pressure compressor blades, which creates wear and degrades its performance.

[0018] In addition to the risk of bending of the gas generator, the cantilevered position of the gas generator results in significant displacements of the turbomachine, specifically of its portion downstream of the downstream mounting element, which tilts as it moves away from and towards the pylon. In particular, for limiting cases corresponding to maneuvering loads and considering the moments related to aerodynamic forces, the values ​​of these displacements can be much greater than known displacement values ​​for other turbomachines. Such displacements can lead to damage to the aircraft, the mountings, the parts interfacing the turbomachine with the pylon, and the turbomachine itself.

[0019] The gas generator must therefore be protected against the aerodynamic forces generated by the blower. It must also be securely supported to limit its deformation under operating and gravitational loads to prevent such displacements. EXPOSED

[0020] One aim of the present application is therefore to overcome the aforementioned disadvantages by proposing an improved gas generator support system which protects it from such deformations and which limits and controls the displacements of the turbomachine in its downstream part.

[0021] To this end, according to a first aspect, an aircraft propulsion system is proposed, the propulsion system comprising: - a gas generator comprising at least one low-pressure compressor, one high-pressure body and one low-pressure turbine; - an exhaust casing extending around the low-pressure turbine; and - a structural hood extending around the gas generator and at least one part of the exhaust casing,

[0022] the propulsion system comprising a first part intended to be fixed to a pylon and a second part intended to be cantilevered from the pylon, the propulsion system further comprising a device for centering the gas generator with respect to the structural hood, the centering device comprising at least one connecting rod, the connecting rod or each connecting rod extending between the structural hood and the gas generator in the second part of the propulsion system.

[0023] The propulsion system may also have at least one of the following characteristics: - where each connecting rod extends between the structural cover and the gas generator, in particular between the structural cover and the exhaust housing; - the or each connecting rod forms with a plane perpendicular to a longitudinal axis of the propulsion system a non-zero positive angle of less than 10°, in particular less than 5°, for example equal to 1.9°, when the propulsion system is stopped cold; - in view of the end of the propulsion system, the connecting rod or each connecting rod forms with a vertical direction an angle between 10° and 45°, in particular between 20° and 30°, possibly between 24° and 28°, for example 26°; - where each connecting rod extends tangentially to the exhaust housing; - each connecting rod includes a first end fixed to the hood structural and which is an upstream end with reference to a direction of airflow from the propulsion system and a second end fixed to the exhaust casing and which is a downstream end; - where each connecting rod includes a ball joint at at least one of its ends; - there are at least two connecting rods, the second ends of the connecting rods being uniformly distributed on the exhaust casing; - the exhaust casing comprises an upper portion, a lower portion opposite and symmetrical to the upper portion, and two lateral portions, the second end of each of the connecting rods being fixed to one of the lateral portions; - the centering device comprises 2, 4, 6 or 8 connecting rods, the number of connecting rods fixed to one of the lateral portions being equal to the number of connecting rods fixed to the other of the lateral portions; and - there are at least two connecting rods and they form a symmetrical arrangement with respect to a median vertical plane of the propulsion system.

[0024] The present application also relates in a second aspect to an aircraft comprising a propulsion system as defined above. DESCRIPTION OF THE FIGURES

[0025] We will now present examples of implementation by way of non-limiting example and in support of the drawings on which:

[0026] Fig. 1 is a schematic axial cross-sectional view of a first type of propulsion system;

[0027] Figure 2 is a schematic axial cross-sectional view of a second type of system propulsive;

[0028] The [Fig.3] is an example of an aircraft comprising at least one propulsion system;

[0029] Fig. 4 illustrates a schematic axial cross-sectional view of a propulsion system;

[0030] Figure 5 illustrates a schematic profile view of part of the propulsion system of the [Fig.4];

[0031] Figure 6 illustrates a perspective view of part of the propulsion system of the [Fig.5];

[0032] Figure 7 is a side view of the propulsion system centering device of the [Fig. 6]; and

[0033] The [Fig.8] is an axial end view of the centering device of the propulsion system of the [Fig.6].

[0034] Throughout the figures, similar elements bear identical references. DETAILED DESCRIPTION Propulsion system

[0035] Figure 1 illustrates a first type of engine forming a propulsion system 1 compatible with the invention. The propulsion system 1 is, for example, an aircraft turbomachine. The propulsion system 1 has a principal direction extending along a longitudinal axis X and comprises, from upstream to downstream in the direction of gas flow in the propulsion system 1 when it is in operation, a fan section 2 and a primary body 3, often called a "gas generator," comprising a compressor section 4, 5, a combustion chamber 6, and a turbine section 7, 8. As will be seen, the gas generator 3 forms the high-pressure part of the gas generator. The propulsion system 1 is here an aircraft propulsion system configured to be mounted on an aircraft 100 by means of a pylon (or mast) 101.

[0036] The compressor section 4, 5 comprises a series of stages, each including a rotating blade wheel (rotor) 4a, 5a in front of a fixed blade wheel (stator) 4b, 5b. The turbine section 7, 8 also comprises a series of stages, each including a fixed blade wheel (stator) 7a, 8a behind which a rotating blade wheel (rotor) 7b, 8b rotates.

[0037] In the present application, the axial direction corresponds to the direction of the longitudinal axis X, corresponding to the rotation of the shafts of the gas generator 3, and a radial direction is a direction perpendicular to and passing through this axis X. Furthermore, the circumferential direction corresponds to a direction perpendicular to and not passing through the longitudinal axis X. Unless otherwise specified, internal (respectively, inside) and external (respectively, outside) are used with reference to a radial direction such that the inner part or face of an element is closer to the axis X than the outer part or face of the same element.

[0038] In operation, an airflow F entering the propulsion system 1 is divided between a primary airflow Fl and a secondary airflow F2, which flow from upstream to downstream in the propulsion system 1.

[0039] The secondary airflow F2 flows around the gas generator 3. The secondary airflow F2 is used to generate most of the thrust provided by the propulsion system 1.

[0040] The primary airflow Fl flows in a primary channel inside the gas generator 3, passing successively through the compressor section 4, 5, the combustion chamber 6 where it is mixed with fuel to serve as an oxidizer, and the turbine section 7, 8. The passage of the primary airflow Fl through the turbine section 7, 8 receiving energy from the combustion chamber 6 causes a rotation of the rotor of the turbine section 7, 8, which in turn drives the rotation of the rotor of the compressor section 4, 5 as well as a rotor part 9 of the blower section 2.

[0041] In a twin-spool propulsion system 1, the compressor section 4, 5 may include a low-pressure compressor 4 and a high-pressure compressor 5. The turbine section 7, 8 may include a high-pressure turbine 7 and a low-pressure turbine 8. The rotor of the high-pressure compressor 5 is driven in rotation by the rotor of the high-pressure turbine 7 via a high-pressure shaft 10. The rotor of the low-pressure compressor 4 and the rotor portion 9 of the blower section 2 are driven in rotation by the rotor of the low-pressure turbine 8 via a low-pressure shaft 11. Thus, the gas generator 3 comprises a high-pressure body including the high-pressure compressor 5, the combustion chamber 6, the high-pressure turbine 7, and the high-pressure shaft 10, and a low-pressure body including the blower section 2, the low-pressure compressor 4, the The low-pressure turbine 8 and the low-pressure shaft 11. The rotational speed of the high-pressure body is greater than the rotational speed of the low-pressure body. In a three-body propulsion system 1, the turbine section 7, 8 further includes an intermediate turbine, positioned between the high-pressure turbine 7 and the low-pressure turbine 8 and configured to drive the rotor of the low-pressure compressor 4 via an intermediate shaft. The blower rotor 9 and the rotor of the high-pressure compressor 5 remain driven by the low-pressure shaft 11 and the high-pressure shaft 10, respectively.

[0042] The low-pressure shaft 11 is generally housed, along a portion of its length, within the high-pressure shaft 10 and is coaxial with the latter. The low-pressure shaft 11 and the high-pressure shaft 10 may be co-rotating, that is, driven in the same direction around the longitudinal axis X. Alternatively, they may be counter-rotating, that is, driven in opposite directions around the longitudinal axis X. If applicable, the intermediate shaft is housed between the high-pressure shaft 10 and the low-pressure shaft 11. The intermediate shaft and the low-pressure shaft 11 may be co-rotating or counter-rotating.

[0043] The fan section 2 comprises at least the fan rotor 9, which is driven in rotation relative to a fan housing 12 by the turbine section 7, 8. Each fan rotor 9 comprises a hub 13 and blades 14 extending radially from the hub 13. The blades 14 of each rotor 9 may be fixed relative to the hub 13 or have variable pitch. In this case, the root of the blades 14 of each rotor 9 is pivotally mounted about a pitch axis and is connected to a pitch-changing mechanism 15 mounted in the propulsion system 1, the pitch being adjusted according to the flight phases by the pitch-changing mechanism 15. This mechanism 15 is optional.

[0044] The fan section 2 may further include a fan stator 16, or rectifier, which comprises blades 17 mounted on a hub 18 of the fan stator 16 and whose function is to rectify the secondary airflow F2 exiting the fan rotor 9. The fan stator blades 17 may be fixed relative to the hub 18 or have variable pitch. Similar to the rotor blades 14, the base of the stator blades 17 is pivotally mounted about a pitch axis X and is connected to a pitch-changing mechanism 15a, which is generally separate from that of the fan rotor 9, the pitch being adjusted according to the flight phases by the pitch-changing mechanism. This mechanism 15a is optional.

[0045] In order to improve the propulsive efficiency of the propulsion system 1 and to reduce its specific consumption as well as the noise emitted by the fan section 2, the propulsion system 1 has a high bypass ratio. By A high dilution ratio is defined here as a dilution ratio greater than or equal to 10, for example, between 10 and 80 inclusive. To calculate the dilution ratio, the mass flow rate of the secondary airflow F2 and the mass flow rate of the primary airflow Fl are measured when the propulsion system 1 is stationary, uninstalled, in takeoff mode in a standard atmosphere (as defined by the International Civil Aviation Organization (ICAO) manual, Doc 7488 / 3, 3rd edition) and at sea level. It should be noted that, in this application, the parameters (pressure, flow rate, thrust, speed, etc.) are systematically determined under these conditions. "Uninstalled" here means that the measurements are taken when the propulsion system 1 is on a test bench (and not installed on an aircraft 100), as the measurements are then simpler to perform.

[0046] The fan rotor 9 can be decoupled from the low-pressure shaft 11 by means of a reduction mechanism 19, located between an upstream end of the low-pressure shaft 11 and the fan rotor 9, in order to independently optimize their respective rotational speeds. In this case, the propulsion system 1 further includes an additional shaft, referred to as the fan shaft 20. The low-pressure shaft 11 connects the low-pressure turbine 8 to an inlet of the reduction mechanism 19, while the fan shaft 20 connects the outlet of the reduction mechanism 19 to the fan rotor 9. The fan rotor 9 is therefore driven by the low-pressure shaft 11 via the reduction mechanism 19 and the fan shaft 20 at a rotational speed lower than the rotational speed of the low-pressure turbine 8.

[0047] This decoupling makes it possible to reduce the rotational speed and pressure ratio of the blower rotor 9 and to increase the power extracted by the low pressure turbine 8.

[0048] The blower section 2 may be shrouded or unshrouded. In the case of a shrouded blower section 2 as illustrated in [Fig. 1], the blower section 2 comprises a blower housing 12 and the blower rotor 9 is housed in the blower housing 12.

[0049] A shrouded fan section 2 comprises a fan rotor 9 extending upstream of a fan stator. The fan stator blades are then generally called outlet guide vanes (OGVs) and have a fixed or variable pitch relative to the fan stator hub. Furthermore, the bypass ratio of the propulsion system 1 is preferably greater than or equal to 10, for example, between 10 and 35 inclusive, preferably between 10 and 18 inclusive.

[0050] In an unshrouded fan section 2, which corresponds to the second type of engine illustrated in [Fig. 2], the fan section 2 is not surrounded by a fan housing. Since the fan section 2 is unshrouded, the rotor blades 14 of The fan 9 has variable pitch. Propulsion systems comprising at least one unshod fan 9 rotor are known as "open rotor" or "unducted fan." The propulsion system 1 may comprise two unshod, counter-rotating fan 9 rotors. Such a propulsion system 1 is known by the acronym CROR for "Contra-Rotating Open Rotor" or UDF for "Unducted Double Fan." The fan 9 rotor(s) may be positioned at the rear of the gas generator 3 to be of the pusher type or at the front of the gas generator 3 to be of the tractor type. Alternatively, the propulsion system 1 may comprise a single unshod fan 9 rotor and an unshod fan stator 16 (rectifier). Such a propulsion system 1 is known by the English acronym USF for "Unducted Single Fan".In the case of a USF-type propulsion system 1, the blades 17 of the stator 16 are fixed in rotation relative to the X-axis of rotation of the upstream fan rotor 9 and consequently do not experience centrifugal force. The blades 17 of the stator 16 also have variable pitch.

[0051] Removing the fairing around the fan section 2 allows the dilution ratio to be increased very significantly without the propulsion system 1 being penalized by the mass of the housings or the nacelle intended to surround the fan section 2. The dilution ratio is thus greater than or equal to 40, for example between 40 and 80 inclusive.

[0052] Attaching the propulsion system to an aircraft

[0053] We will present an example of implementation applied to a propulsion system illustrated in [Fig.4] and which may be of the type of that of Figures 1 and 2. [Fig.4] is a schematic cross-sectional view of the internal structure of the propulsion system 1.

[0054] This propulsion system 1 is here of the type of that of [Fig.2]. It has a main longitudinal axis X and includes in particular a blower 2 and a gas generator 3, which comprises, from upstream to downstream in the direction of the gas flow in the propulsion system 1 when it is in operation, a low-pressure compressor 4, a high-pressure compressor 5, a combustion chamber 6, a high-pressure turbine 7 and a low-pressure turbine 8. The high-pressure compressor 5, the combustion chamber 6 and the high-pressure turbine 7 together form a high-pressure body.

[0055] In an alternative not shown, the blower 2 can be shrouded.

[0056] Fig. 5 illustrates a partial schematic profile view of the gas generator 3 of the propulsion system 1 on which structural housings around the gas generator 3 can be observed.

[0057] The propulsion system 1 thus comprises a compressor housing 30 extending around the low-pressure compressor 4. The compressor housing 30 comprises a section upstream 30a, an intermediate section 30b and a downstream section 30c adjacent to each other along the longitudinal axis X.

[0058] Extending axially along the X-axis of the compressor housing 30, the propulsion system 1 comprises a structural cover 35, which will be described in detail below. The structural cover 35 may comprise, successively from upstream to downstream, an upstream ring 36, a cover body 37, and a downstream ring 38. The upstream ring 36 is axially adjacent to the compressor housing 30. For example, it is fixed downstream of the compressor housing 30.

[0059] Furthermore, the propulsion system 1 comprises, within the structural cowling 35, a turbine blade center frame extending around the low-pressure turbine blades 8, and an exhaust casing 31b attached directly to the turbine blade center frame, the exhaust casing 31b being located axially downstream of the turbine blade center frame. The structural cowling 35 extends around the turbine blade center frame, which is therefore not visible in the figures because it is covered by the structural cowling 35. Similarly, the structural cowling 35 extends around and thus at least partially covers the exhaust casing 31b.

[0060] The propulsion system 1 is here an aircraft turbomachine configured to be fixed on an aircraft by means of a pylon (or mast) 101 schematically illustrated in [Fig.5].

[0061] The pylon 101 has a generally elongated shape along a direction parallel to the longitudinal axis X. It is designed to extend above the propulsion system 1 in a vertical direction. The vertical direction is understood to be an upward direction, perpendicular to the longitudinal axis X, and the horizontal direction is understood to be a direction perpendicular to the vertical direction. A vertical plane is therefore a plane comprising a vertical axis, and a horizontal plane is a plane perpendicular to a vertical plane. In particular, a median horizontal plane H comprising the longitudinal axis X and a median vertical plane V comprising the longitudinal axis X are thus defined and coincide at the longitudinal axis X. Finally, the lateral direction is understood to be a direction from left to right, that is to say, a direction perpendicular to the vertical direction and parallel to the horizontal direction.

[0062] The pylon 101 includes fastening elements 33 for attaching the propulsion system 1 to the aircraft 100. In this case, the pylon 101 includes an upstream fastening element 33a and a downstream fastening element 33b.

[0063] To fix the propulsion system 1 to the pylon 101, the propulsion system 1 includes fastening elements 34 to which the fastening members 33 of the pylon can be attached. In particular, the propulsion system 1 includes an upstream fastening element 34a and a downstream fastening element 34b.

[0064] The fixing of the upstream fixing member 33a to the upstream fixing element 34a is done in an upstream fixing plane which is perpendicular to the longitudinal axis X. Similarly, the fixing of the downstream fixing member 33b to the downstream fixing element 34b is done in a downstream fixing plane which is perpendicular to the longitudinal axis X.

[0065] The upstream fastening member 33a is, for example, configured to absorb forces along the longitudinal axis X and in a lateral direction within the upstream fastening plane. The upstream fastening member 33a is further, for example, configured to allow displacement of the propulsion system 1 in the vertical direction within the upstream fastening plane.

[0066] The downstream fixing member 33b is, for example, configured to take up forces in the vertical and lateral directions in the downstream fixing plane, and to allow displacements of the propulsion system 1 along the longitudinal axis X. This makes it possible to avoid hyperstaticity of the assembly formed by the propulsion system 1 and the pylon 101.

[0067] It can be foreseen that the propulsion system 1 is devoid of any other attachment element to the pylon 101, and in particular of an intermediate attachment element located axially between the upstream attachment element 34a and the downstream attachment element 34b. In other words, the upstream attachment element 34a and the downstream attachment element 34b are, for example, the only attachment points of the propulsion system 1 to the pylon 101. The propulsion system 1 therefore comprises a first part fixed to the pylon 101 which extends axially along the longitudinal axis X between the upstream attachment elements 34a and downstream attachment elements 34b, and a second part cantilevered from the pylon 101 and which extends entirely downstream along the longitudinal axis X of the downstream attachment element 34b.

[0068] It can be foreseen that the upstream fastening element 34a is located on the compressor housing 30, for example on the upstream section 30a or the intermediate section 30b, and / or that the downstream fastening element 34b is located on the structural hood 35, in particular on the downstream ring 38, for example at the level of a portion of the structural hood 35 surrounding the turbine blade frame or the exhaust housing 31b. Structural cover around the gas generator 3

[0069] The structural hood 35 extends along the longitudinal axis X between the upstream mounting element 34a and the downstream mounting element 34b, more precisely between the compressor housing 30 and the downstream mounting element 34b. The structural hood 35 surrounds a portion of the gas generator 3 defined between the upstream mounting element 34a and the downstream mounting element 34b, which in this example comprises a portion of the low-pressure compressor 4, the high-pressure body, and all or part of the low-pressure turbine 8. Figure 6 illustrates a perspective view of a portion of the propulsion system 1 and the structural hood 35.

[0070] The downstream ring 38 extends for example around the turbine blade frame and / or the exhaust housing 31b.

[0071] The hood body 37 may include a first beam 37a and a second beam 37b. Each of the beams 37a, 37b extends axially so as to connect the upstream ring 36 to the downstream ring 38. The first beam 37a and the second beam 37b are opposite each other with respect to the longitudinal axis X. For example, the first beam 37a extends above the longitudinal axis X and the second beam 37b extends below the longitudinal axis X, in the vertical direction.

[0072] The hood body 37 may include at least one lateral structural panel 37c axially connecting the upstream ring 36 to the downstream ring 38, and circumferentially connecting the first beam 37a to the second beam 37b. Thus, it can be foreseen that the hood body 37 comprises a first lateral structural panel 37c and a second lateral structural panel 37d connecting the first beam 37a to the second beam 37b in a circumferential direction around the gas generator 3. The structural panels 37c, 37d are opposite each other on either side of the longitudinal axis X.

[0073] It can be foreseen that the first beam 37a, the second beam 37b, and the lateral structural panels 37c and 37d are all concave with respect to the longitudinal axis X, in order to improve the transfer of forces.

[0074] Thus, in any plane perpendicular to the longitudinal axis X, the structural cover 35 has a substantially circular or rounded cross-section. It can be foreseen that, in any plane perpendicular to the longitudinal axis X, the first beam 37a is located at the highest point of the cover 35, for example at 12 o'clock when this cross-section is circular, and the second beam 37b is located at the lowest point of the cover 35, for example at 6 o'clock when this cross-section is circular. In this way, the first beam 37a forms the shortest path on the structural cover 35 to connect the upstream fastener 33a to the downstream fastener 33b, and therefore a preferred path through which the forces pass.

[0075] It can be foreseen that, in any plane perpendicular to the longitudinal axis X between the upstream fastening element 34a and the downstream fastening element 34b, the structural cover 35 has a cross-sectional area between 1200 and 1700 millimeters. For example, in this plane, the upstream ring 36 has a cross-sectional area between 1600 and 1700 millimeters, and the downstream ring 38 has a cross-sectional area between 1200 and 1300 millimeters.

[0076] Such dimensions of the structural hood 35 contribute to its significant stiffness. It is thus configured to form a predominant load path C between the upstream fastening element 34a and the downstream fastening element 34b. This load path C is shown in dashed lines in Figures 4 and 5. It does not pass through the Gas generator 3. It bypasses it by passing mainly through beam 37a, and secondarily through the lateral structural panels 37c, 37d and beam 37b. The high-pressure body is therefore no longer in the path of the predominant force C and is thus protected.

[0077] With this configuration, the gas generator 3, and more particularly the high-pressure body and especially the low-pressure turbine 8, are protected, the impact of IP and gravitational loads being greatly reduced. The addition of the large-radius, high-stiffness structural cowling 35, forming a predominant load path bypassing the gas generator 3, notably allows for better management of 1P loads and minimizes problems related to the cantilevered position of the second part of the propulsion system 1. Gas generator centering device

[0078] The propulsion system 1 further comprises a centering device 50 for the gas generator 3 relative to the structural cowling 35. The centering device 50 is illustrated in detail in a partial profile view in [Fig. 7] and in a front or end view in [Fig. 8]. It is also visible in [Fig. 6]. The centering device 50 is, however, suitable for any type of propulsion system, particularly turbomachinery and engine mountings, characterized by large turbomachine displacements. The centering device 50 is configured to maintain the gas generator 3, more precisely a portion of the gas generator 3 located in the second cantilevered part of the propulsion system 1, in a position centered about the longitudinal axis X, and thus to compensate for the tilting and bending forces experienced by the gas generator 3 during the operation of the aircraft equipped with the propulsion system 1.

[0079] For this purpose, the centering device 50 comprises one or more connecting rods 51, each extending between the structural cover 35 and the gas generator 3. In what follows, the centering device 50 will be considered to comprise several connecting rods 51. This is not, however, a limitation, and the characteristics described may apply to the case of a single connecting rod when this is mechanically feasible. The connecting rods 51 may all be identical.

[0080] It can be foreseen that the connecting rods 51 extend into the second cantilevered part of the propulsion system 1, i.e. downstream of the downstream attachment element 34b. For example, the connecting rods 51 extend between the structural cover 35 and the exhaust housing 31b.

[0081] In this case, each of the connecting rods 51 comprises a first end 51a fixed, for example directly, to the structural cover 35 and a second end 51b connected to the gas generator 3, for example by direct attachment to the exhaust casing 31b (or to the turbine blade frame where applicable when the downstream attachment plane is located at the level of the latter). On [Fig.7], the structural hood 35 is not shown in order to make the connecting rods 51 visible. In addition, in the example illustrated on this [Fig.7], the second ends 51b of the connecting rods 51 are connected to the exhaust housing 31b.

[0082] The structural cover 35 includes an inner wall 52 opposite an outer wall 53 of the exhaust housing 31b. The first ends 51a of the connecting rods 51 can be fixed to the inner wall 52 of the structural cover 35, and the second ends 51b of the connecting rods 51 can be fixed to the outer wall 53 of the exhaust housing 31b.

[0083] As illustrated in [Fig. 8], the outer wall 53 of the exhaust housing 31b is an annular circumferential wall, which comprises an upper portion 53a and a lower portion 53b opposite and symmetrical to the upper portion 53a with respect to the median horizontal plane H comprising the longitudinal axis X. The upper circumferential portion 53a and the lower circumferential portion 53b each comprise one of the two outermost points radially along the vertical direction of the outer wall 53 of the exhaust housing 31b. In other words, these points correspond respectively to the points located at 12 o'clock and 6 o'clock in a section of the exhaust housing along a plane perpendicular to the longitudinal axis X or in a front view as illustrated in [Fig. 8].

[0084] Furthermore, the outer wall 53 comprises two lateral portions 53c and 53d connecting each of the opposite ends of the upper portion 53a and lower portion 53b. The first lateral portion 53c connects, for example, the upper portion 53a to the lower portion 53b on the left side of the vertical plane V comprising the longitudinal axis X, and the second lateral portion 53d connects, for example, the upper portion 53a to the lower portion 53b on the right side of the vertical plane V, as shown in [Fig. 8]. The two lateral portions 53c and 53d are thus opposite each other and symmetrical with respect to this vertical plane V.

[0085] Each of the second ends 51b of the connecting rods 51 is fixed, for example directly, to one of the lateral portions 53c and 53d. It can be provided that as many second ends 51b of connecting rods 51 are fixed to the first lateral portion 53c as to the second lateral portion 53d. It can be provided that the second ends 51b fixed to the first lateral portion 53c are uniformly distributed circumferentially on this first lateral portion 53c, and are located symmetrically to a second end 51b fixed to the second lateral portion 53d with respect to the vertical plane V. The second ends 51b fixed to the second lateral portion 53d are therefore also uniformly distributed circumferentially on this second lateral portion 53d.

[0086] In this case, each of the connecting rods 51 extending from one side of the vertical plane V is symmetrical to one of the connecting rods 51 extending from the other side of the vertical plane V. From this In this way, the connecting rods 51 are distributed so as to effectively take up the tilting of the propulsion system 1 at any time of its operation in order to maintain the gas generator 3, and more specifically its portion located in the second cantilevered part, in a position centered around the longitudinal axis X by compression forces of some of the connecting rods 51 and tensile forces of the rest of the connecting rods 51 according to their positioning and the direction of tilting and bending of the second cantilevered part of the propulsion system 1.

[0087] In one embodiment, as many second ends 51b of connecting rods 51 are fixed above the horizontal plane H comprising the longitudinal axis X as below, and each second end 51b of a connecting rod 51 fixed above the horizontal plane H is located symmetrically to a second end 51b of another connecting rod 51 fixed to the same lateral portion 53c, 53d with respect to the horizontal plane H. To summarize and more generally, in this embodiment, each of the connecting rods 51 that extends from one side of the vertical plane V and from one side of the horizontal plane H is symmetrical to one of the connecting rods 51 extending from the other side of the vertical plane V and to one of the connecting rods 51 extending from the other side of the horizontal plane H.

[0088] Thus, in this embodiment, for any situation of operation or shutdown of the propulsion system 1, half of the number of connecting rods 51 are in compression, and the other half are in tension, so that the centering device 50 maintains the gas generator 3, and more precisely its portion extending in the second cantilevered part of the propulsion system 1, in a position centered around the longitudinal axis X.

[0089] In all embodiments, the centering device 50 is therefore configured to maintain the gas generator 3, and more specifically its portion extending into the second cantilevered part of the propulsion system 1, in the position centered around the longitudinal axis X or at least in a position located at a distance greater than a predetermined threshold from the inner wall 52 of the structural hood 35. This threshold may, for example, be at least 10 centimeters.

[0090] The connecting rods 51 extend further tangentially to the exhaust housing 31b, or where applicable to the turbine blade frame when the downstream attachment element 34b is located at its axial level along the longitudinal axis X, so as to exert forces on the gas generator 3 less abruptly than by a radial extension. This also allows for better adaptation to displacements or thermal expansions of the propulsion system 1.

[0091] In this sense in particular, it can be provided that each connecting rod 51 includes a ball joint at each of its ends 51a and 51b, so as to allow relative movements of the connecting rods 51 with respect to the gas generator 3 and / or the structural hood 35 around axes that are not parallel to each other.

[0092] It can be foreseen that the first end 5la is an upstream end and the second end 51b is a downstream end, that is to say, each of the connecting rods 51 extends between the structural cowling 35 and the gas generator 3 from upstream to downstream and not in a plane perpendicular to the longitudinal axis X. It can be foreseen that, when the propulsion system 1 is in a cold standstill, each of the connecting rods 51 forms with a plane P perpendicular to the longitudinal axis X a non-zero positive angle α of less than 10°, in particular less than 5°, for example 1.9°. This angle is visible in [Fig. 7]. In this way, the connecting rods 51 are configured so as not to constrain the gas generator 3 during thermal displacement or thermal expansion of the gas generator 3 along the longitudinal axis X. To illustrate this aspect, [Fig.[7] further illustrates in dashed lines, by way of example, a situation in which the gas generator 3 of the propulsion system 1 has undergone an axial thermal displacement of 10 millimeters downstream, for example, as represented by a line L. The connecting rods 51 have accompanied this thermal expansion, now occupy a position illustrated in dashed lines, and now form a larger angle a', with a value of 2° to 15° with this plane P. Thus, the connecting rods 51 have not constrained the exhaust casing 31b during the thermal displacement of the gas generator 3.

[0093] In another possible embodiment, the first end 51a is a downstream end and the second end 51b is an upstream end, i.e., each of the connecting rods 51 extends between the structural cover 35 and the gas generator 3, forming a non-zero negative angle with the plane P, greater than -5°. In this configuration, the connecting rods 51 exert slightly more constraint on the gas generator 3 during thermal displacement or thermal expansion along the longitudinal axis X, but still allow these phenomena to be accommodated without critically constraining the exhaust housing 31b.

[0094] Furthermore, when the propulsion system 1 is at rest, the connecting rods 51 are inclined with respect to a vertical direction V at an angle [3] of 10° to 45°, in particular from 20° to 30°, possibly from 24° to 28°, for example 26°. Thus, the projection of each connecting rod 51 into a plane perpendicular to the longitudinal axis X, for example into the plane including the upstream end 51a of the connecting rod 51, forms with the vertical direction an angle of 10° to 45°, possibly from 20° to 30°, in particular from 24° to 28°, for example 26°. This angle [3] is visible in [Fig. 8].

[0095] In this way, the connecting rods 51 are configured so as not to constrain the gas generator 3 during a thermal displacement or thermal expansion of the gas generator 3 radially with respect to the longitudinal axis X. Indeed, when the propulsion system 1, and more specifically the exhaust housing 31b, undergoes a radial thermal displacement outwards, the connecting rods 51 accommodate this thermal expansion by pivoting around an axis that passes through their first end 51a and which is parallel to the longitudinal axis X, so as to increase the angle they form with the vertical direction. Conversely, when the propulsion system 1, and more specifically the exhaust housing 31b, cools and undergoes radial thermal contraction towards the inside, the connecting rods 51 accommodate this contraction by pivoting around the same axis so as to reduce the angle they form with the vertical direction. For example, when the exhaust housing undergoes radial thermal expansion outwards by 3 millimeters, the connecting rods 51 accommodate this thermal expansion by pivoting around an axis that passes through their first end 5la and is parallel to the longitudinal axis X, so as to form a larger angle of up to 2 degrees with the vertical direction. Thus, the connecting rods 51 have adapted without stress to the deformations of the exhaust housing 31b during the thermal displacement of the gas generator 3.

[0096] The centering device 50 can include an even number of connecting rods 51, for example two, four, six, eight or ten connecting rods 51, in particular four or six connecting rods 51.

[0097] The centering device 50, and in particular its connecting rods 51, are not located on the predominant force path C and therefore do not participate substantially in the force transfer between the gas generator 3 and the pylon 101. The centering device 50 therefore only performs a positioning of the gas generator 3 taking into account the deflections of the gas generator 3 due to its cantilevered position.

[0098] The connecting rods 51 are dimensioned at least under limit loads, and for example under ultimate loads.

[0099] The centering device 50 therefore ensures centering of the gas generator 3 relative to the structural hood 35, whether under gravity, inertial loads and / or maneuvering loads, at rest or in operation of the propulsion system 1.

Claims

Demands

1. Aircraft propulsion system (1), the propulsion system (1) comprising: - a gas generator (3) comprising at least a low-pressure compressor (4), a high-pressure body and a low-pressure turbine (8); - an exhaust casing (31b) extending around the low-pressure turbine (8); - a structural hood (35) extending around the gas generator (3) and at least part of the exhaust casing (31b), the propulsion system (1) comprising a first part having means for attachment to a pylon (101) and a second part intended to be cantilevered from the pylon (101), the propulsion system (1) further comprising a centering device (50) of the gas generator with respect to the structural hood, the centering device (50) comprising at least one connecting rod (51), the connecting rod or each connecting rod (51) extending between the structural hood (35) and the second part of the propulsion system (1).

2. Propulsion system (1) according to claim 1, wherein the connecting rod or each connecting rod (51) extends between the structural hood (35) and the exhaust housing (31b).

3. Propulsion system (1) according to any one of claims 1 or 2, wherein, when the propulsion system (1) is at a cold standstill, the connecting rod or each connecting rod (51) forms with a plane (P) perpendicular to a longitudinal axis (X) of the propulsion system (1) a non-zero positive angle (a) less than 10°, in particular less than 5°, for example equal to 1.9°.

4. Propulsion system (1) according to any one of claims 1 to 3, wherein, in view of the end of the propulsion system (1), the or each connecting rod (51) forms with a vertical direction an angle between 10° and 45°, in particular between 20° and 30°, possibly between 24° and 28°, for example 26°.

5. Propulsion system (1) according to any one of claims 1 to 4, wherein the connecting rod or each connecting rod (51) comprises a first end (51a) fixed to the structural cowling (35) and which is an upstream end with reference to a direction of airflow from the propulsion system (1) and a second end (51b) fixed to the exhaust housing (31b) and which is a downstream end.

6. Propulsion system (1) according to claim 5, wherein the connecting rods (51) are at least two in number, the second ends (51b) of the connecting rods being uniformly distributed on the exhaust housing (31b).

7. Propulsion system (1) according to any one of claims 5 or 6, wherein the exhaust casing (31b) comprises: - an upper portion (53a); - a lower portion (53b) opposite the upper portion (53a); and - two lateral portions (53c; 53d), the second end (51b) of each of the connecting rods (1) being fixed to one of the lateral portions (53c; 53d).

8. Propulsion system (1) according to claim 7, wherein the centering device (50) comprises 2, 4, 6 or 8 connecting rods (51), a number of connecting rods (51) fixed to one of the lateral portions (53c;53d) being equal to a number of connecting rods fixed to the other lateral portion.

9. Propulsion system (1) according to any one of claims 1 to 8, wherein there are at least two connecting rods and the connecting rods (51) form a symmetrical arrangement with respect to a median vertical plane (H) of the propulsion system (1).

10. Aircraft (100) comprising a propulsion system (1) according to any one of the preceding claims.

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