Turbine engine comprising means for fastening to a pylon, and associated aircraft

Abstract

The application relates to an aircraft propulsion system comprising: - a gas generator comprising at least a low-pressure compressor, a high-pressure body and a low-pressure turbine; - an exhaust casing (31b) extending around the low-pressure turbine; - a structural cover (35) extending around the gas generator and at least part of the exhaust casing (31b), the propulsion system comprising a first part comprising means for fastening to a pylon and a second part intended to be cantilevered in relation to the pylon, the propulsion system further comprising a device (50) for centring the gas generator in relation to the structural cover comprising at least one connecting rod (51), the or each connecting rod (51) extending between the structural cover (35) and the second part of the propulsion system.

Description

[0001] DESCRIPTION

[0002] TITLE: Turbomachine including means for attachment to a pylon, and associated aircraft

[0003] TECHNICAL FIELD

[0004] 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 specifically to the attachment of a turbomachine to an aircraft pylon.

[0005] STATE OF THE ART

[0006] An aircraft turbomachine, for example, comprises, 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 optionally 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 together form a high-pressure unit.

[0007] Environmental aspects

[0008] 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 different countries. 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.

[0009] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. The Applicant takes these factors into account in all phases of design and development to obtain less energy-intensive and more environmentally friendly aeronautical components and products whose integration and use in civil aviation have moderate environmental consequences, with the aim of improving aircraft energy efficiency.

[0010] 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.

[0011] This sustained research and development work focuses on new generations of aircraft engines, the weight reduction of aircraft, particularly 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.

[0012] 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 casing and the size of the high-pressure casing are reduced, and the high-pressure casing must support the low-pressure turbine.

[0013] Structural aspects

[0014] Attaching a turbomachine to an aircraft, for example to a wing of the aircraft, is done via a pylon, also called a mast, connected to the rest of the aircraft.

[0015] 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.

[0016] Thus, the entire part of the gas generator downstream of the downstream fixing element, 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, ...).

[0017] Indeed, in operation, this configuration ensures a transmission of forces via the gas generator between the upstream and downstream fixing elements 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.

[0018] More specifically, the gas generator is subject to:

[0019] - to maneuvering loads induced by acceleration variations when the aircraft performs maneuvers such as turns in flight,

[0020] - to gravitational loads induced during the aircraft's cruise phase, and,

[0021] - to aerodynamic forces of various types, notably, when the fan is unfaired, moments, known as "1P moments", related to the angle of attack 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, loads induced by a tilting force related to the angle of attack between the aircraft's movement and the air intake.

[0022] These different loads experienced by the gas generator, its cantilevered position, and the additional loads it supports lead to its sagging under acceleration, its deformation and that of its casings.

[0023] 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.

[0024] In addition to the risk of gas generator bending, the cantilevered position of the gas generator results in significant displacements of the turbomachine, specifically of the section downstream of the downstream mounting bracket, which tilts as it moves away from and towards the pylon. In particular, for extreme cases corresponding to maneuvering loads and considering the moments related to aerodynamic forces, the values ​​of these displacements can be much greater than those observed in other turbomachines. Such displacements can lead to damage to the aircraft, the mountings, the components interfacing the turbomachine with the pylon, and the turbomachine itself.

[0025] 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.

[0026] STATEMENT One aim of this application is therefore to overcome the aforementioned disadvantages by proposing an improved gas generator support system that protects it from such deformations and that limits and controls the displacements of the turbomachine in its downstream part.

[0027] According to a first aspect, an aircraft propulsion system is proposed, the propulsion system comprising: a gas generator including at least one low-pressure compressor, a high-pressure body and a low-pressure turbine; an exhaust casing extending around the low-pressure turbine; and a structural cowling extending around the gas generator and at least part of the exhaust casing, 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 cowling, the centering device comprising at least one connecting rod, the connecting rod or each connecting rod extending between the structural cowling and the gas generator in the second part of the propulsion system.

[0028] The propulsion system may also have at least one of the following characteristics: the connecting rod(s) extend between the structural cowling and the gas generator, in particular between the structural cowling and the exhaust housing; the connecting rod(s) form a non-zero positive angle of less than 10°, in particular less than 5°, for example equal to 1.9°, with a plane perpendicular to a longitudinal axis of the propulsion system; in the end view of the propulsion system, the connecting rod(s) form an angle between 10° and 45°, in particular between 20° and 30°, possibly between 24° and 28°, for example 26°, with a vertical direction; the connecting rod(s) extend tangentially to the exhaust housing;each connecting rod(s) comprises a first end fixed to the structural cowling 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 housing and which is a downstream end; each connecting rod(s) comprises 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 over the exhaust housing; the exhaust housing 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 the connecting rods are at least two in number and form a symmetrical arrangement with respect to a median vertical plane of the propulsion system.

[0029] This application also relates, in a second aspect, to an aircraft comprising a propulsion system as defined above.

[0030] DESCRIPTION OF THE FIGURES

[0031] We will now present examples of implementation, by way of example only, supported by drawings on which:

[0032] Figure 1 is a schematic axial cross-sectional view of a first type of propulsion system;

[0033] Figure 2 is a schematic axial cross-sectional view of a second type of propulsion system;

[0034] Figure 3 is an example of an aircraft comprising at least one propulsion system;

[0035] Figure 4 illustrates a schematic axial cross-sectional view of a propulsion system;

[0036] Figure 5 illustrates a schematic profile view of part of the propulsion system of Figure 4;

[0037] Figure 6 illustrates a perspective view of part of the propulsion system of Figure 5;

[0038] Figure 7 is a side view of the propulsion system centering device shown in Figure 6; and

[0039] Figure 8 is an axial end view of the propulsion system centering device of Figure 6.

[0040] Across all figures, similar elements bear identical references.

[0041] DETAILED DESCRIPTION

[0042] Propulsion System 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 aeronautical propulsion system configured to be mounted on an aircraft 100, as illustrated, for example, in Figure 3, by means of a pylon (or mast) 101.

[0043] The compressor section 4, 5 comprises a series of stages, each including a rotating blade wheel (rotor) 4a, 5a in front of a stationary blade wheel (stator) 4b, 5b. The turbine section 7, 8 also comprises a series of stages, each including a stationary blade wheel (stator) 7a, 8a behind which a rotating blade wheel (rotor) 7b, 8b rotates.

[0044] In this 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 X axis than the outer part or face of the same element.

[0045] In operation, an airflow F entering the propulsion system 1 is divided between a primary airflow F1 and a secondary airflow F2, which flow from upstream to downstream in the propulsion system 1.

[0046] 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.

[0047] The primary airflow F1 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 F1 through the turbine section 7, 8, receiving energy from the combustion chamber 6, causes the rotor of the turbine section 7, 8 to rotate, which in turn drives the rotor of the compressor section 4, 5 as well as a rotor portion 9 of the blower section 2. 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 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-spool 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.

[0048] The low-pressure shaft 11 is generally housed, along a portion of its length, within the high-pressure shaft 10 and is coaxial with it. 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.

[0049] The fan section 2 includes 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.

[0050] 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.

[0051] To improve the propulsive efficiency of propulsion system 1 and reduce its specific fuel consumption and the noise emitted by fan section 2, propulsion system 1 has a high bypass ratio. A high bypass ratio is defined here as a ratio greater than or equal to 10, for example, between 10 and 80 inclusive. To calculate the bypass ratio, the mass flow rate of the secondary airflow F2 and the mass flow rate of the primary airflow F1 are measured when propulsion system 1 is stationary, uninstalled, in takeoff mode under standard atmospheric conditions (as defined by the International Civil Aviation Organization (ICAO) Manual, Doc 7488 / 3, 3). eedition) 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. The term "not installed" here means that the measurements are taken when the propulsion system 1 is in a test bench (and not installed on an aircraft 100), as the measurements are then simpler to perform.

[0052] It can be foreseen that the fan rotor 9 is decoupled from the low-pressure shaft 11 by means of a reduction mechanism 19, positioned 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.

[0053] 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.

[0054] The blower section 2 may be shrouded or unshrouded. In the case of a shrouded blower section 2 as illustrated in Figure 1, the blower section 2 comprises a blower housing 12 and the blower rotor 9 is housed in the blower housing 12.

[0055] 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.

[0056] In an unshod fan section 2, which corresponds to the second type of engine illustrated in Figure 2, the fan section 2 is not enclosed by a fan casing. Because the fan section 2 is unshod, the blades 14 of the fan rotor 9 have variable pitch. Propulsion systems comprising at least one unshod fan rotor 9 are known as "open rotor" or "unducted fan." The propulsion system 1 may comprise two unshod, counter-rotating fan rotors 9. Such a propulsion system 1 is known by the acronym CROR for "Contra-Rotating Open Rotor" or UDF for "Unducted Double Fan." The blower rotor(s) 9 can be placed at the rear of the gas generator 3 so as to be of the pusher type or at the front of the gas generator 3 so as to be of the tractor type.Alternatively, the propulsion system 1 may include a single unshod blower rotor 9 and a blower stator.

[0057] 16 unfaired (straightener). 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

[0058] The blades 17 of the rectifier 16 are fixed in rotation relative to the X-axis of rotation of the upstream blower rotor 9 and therefore do not experience centrifugal force. The blades 17 of the rectifier 16 also have variable pitch.

[0059] 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 casings 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.

[0060] Attaching the propulsion system to an aircraft

[0061] We will present an example of implementation applied to a propulsion system illustrated in Figure 4 and which can be of the type of that of Figures 1 and 2. Figure 4 is a schematic cross-sectional view of the internal structure of propulsion system 1.

[0062] This propulsion system 1 is here of the type of that of figure 2. It has a main longitudinal axis X and includes in particular a blower 2 and a gas generator 3, which includes, from upstream to downstream in the direction of the flow of the gases 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.

[0063] In an alternative design not shown, the fan 2 can be enclosed. Figure 5 illustrates a partial schematic profile view of the gas generator 3 of the propulsion system 1, in which structural housings can be seen around the gas generator 3.

[0064] The propulsion system 1 thus includes a compressor housing 30 extending around the low-pressure compressor 4. The compressor housing 30 includes an upstream section 30a, an intermediate section 30b and a downstream section 30c adjacent to each other along the longitudinal axis X.

[0065] Extending axially along the X-axis of the compressor housing 30, the propulsion system 1 includes 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.

[0066] Furthermore, the propulsion system 1 comprises, within the structural cowling 35, a turbine blade center frame extending around the blades of the low-pressure turbine 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 as 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.

[0067] The propulsion system 1 is here an aircraft turbomachine configured to be fixed to an aircraft via a pylon (or mast) 101 schematically illustrated in Figure 5.

[0068] Pylon 101 has an elongated general shape along a direction parallel to the longitudinal axis X. It is designed to extend above the propulsion system 1 in a vertical direction. A vertical direction is defined as a direction from bottom to top, perpendicular to the longitudinal axis X, and a horizontal direction as a direction perpendicular to the vertical direction. A vertical plane is therefore a plane containing a vertical axis, and a horizontal plane is a plane perpendicular to a vertical plane. In particular, a median horizontal plane H containing the longitudinal axis X and a median vertical plane V containing the longitudinal axis X are thus defined and coincide at the longitudinal axis X. Finally, a lateral direction is defined as a direction from left to right, that is, a direction perpendicular to the vertical direction and parallel to the horizontal direction.

[0069] The pylon 101 includes attachment members 33 for attaching the propulsion system 1 to the aircraft 100. In this case, the pylon 101 comprises an upstream attachment member 33a and a downstream attachment member 33b. To attach the propulsion system 1 to the pylon 101, the propulsion system 1 includes attachment elements 34 to which the attachment members 33 of the pylon can be attached. In particular, the propulsion system 1 includes an upstream attachment element 34a and a downstream attachment element 34b.

[0070] The upstream fixing member 33a to the upstream fixing element 34a is fixed in an upstream fixing plane which is perpendicular to the longitudinal axis X. Similarly, the downstream fixing member 33b to the downstream fixing element 34b is fixed in a downstream fixing plane which is perpendicular to the longitudinal axis X.

[0071] 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 configured, for example, to allow displacement of the propulsion system 1 in the vertical direction within the upstream fastening plane.

[0072] The downstream fixing element 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.

[0073] It can be assumed 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.

[0074] 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 a portion of the structural hood 35 surrounding the turbine blade frame or the exhaust housing 31b.

[0075] Structural cover around the gas generator 3

[0076] 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 housing, 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.

[0077] The downstream ring 38 extends for example around the turbine blade frame and / or the exhaust casing 31 b.

[0078] 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.

[0079] 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, the hood body 37 may include 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 and 37d are opposite each other on either side of the longitudinal axis X.

[0080] It can be predicted 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.

[0081] 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 assumed 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.

[0082] It can be predicted that, in any plane perpendicular to the longitudinal axis X between the upstream fixing element 34a and the downstream fixing 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.

[0083] The dimensions of the structural cover 35 contribute to its significant stiffness. It is thus configured to form a predominant load path C between the upstream fixing element 34a and the downstream fixing element 34b. This load path C is represented by dashed lines in Figures 4 and 5. It does not pass through the gas generator 3. It bypasses it, passing primarily through beam 37a, and secondarily through the lateral structural panels 37c, 37d and beam 37b. The high-pressure body is therefore no longer located on the predominant load path C and is thus protected.

[0084] This configuration protects the gas generator 3, and more specifically the high-pressure body and in particular the low-pressure turbine 8, significantly reducing the impact of the 1P and gravity loads. The addition of the large-radius, high-stiffness structural cowling 35, which creates a predominant load path bypassing the gas generator 3, allows for better management of the 1P loads and minimizes problems related to the cantilevered position of the second part of the propulsion system 1.

[0085] Gas generator centering device

[0086] The propulsion system 1 further includes 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 Figure 7 and in a front or end view in Figure 8. It is also visible in Figure 6. The centering device 50 is, however, suitable for any type of propulsion system, including 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 section of the propulsion system 1, in a position centered around 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.

[0087] 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 a single connecting rod when mechanically feasible. The connecting rods 51 may all be identical.

[0088] It can be anticipated 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.

[0089] 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 latter). In Figure 7, the structural cover 35 is not shown in order to make the connecting rods 51 visible. Furthermore, in the example illustrated in this Figure 7, the second ends 51b of the connecting rods 51 are connected to the exhaust casing 31b.

[0090] The structural hood 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 hood 35, and the second ends 51b of the connecting rods 51 can be fixed to the outer wall 53 of the exhaust housing 31b.

[0091] As illustrated in Figure 8, the outer wall 53 of the exhaust housing 31b is an annular circumferential wall, comprising 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 Figure 8.

[0092] 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 Figure 8. The two lateral portions 53c and 53d are thus opposite each other and symmetrical with respect to this vertical plane V.

[0093] 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 foreseen 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 foreseen that the second ends 51b fixed to the first lateral portion 53c are uniformly distributed circumferentially around 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 around this second lateral portion 53d.

[0094] 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. In this way, the connecting rods 51 are distributed so as to effectively take over the tilting of the propulsion system 1 at any time during 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 compressive 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.

[0095] 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.

[0096] 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.

[0097] 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 cowling 35. This threshold can, for example, be at least 10 centimeters.

[0098] The connecting rods 51 extend tangentially to the exhaust housing 31b, or, where applicable, to the turbine blade frame when the downstream mounting 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 through radial extension. This also allows for better adaptation to displacements or thermal expansions of the propulsion system 1.

[0099] In this sense in particular, it can be foreseen that each connecting rod 51 includes a ball joint at each of its ends 51 a and 51 b, 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.

[0100] It can be assumed that the first end 51a is an upstream end and the second end 51b is a downstream end; that is, 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 assumed that, when the propulsion system 1 is cold-started, each of the connecting rods 51 forms a non-zero positive angle α of less than 10°, in particular less than 5°, for example 1.9°, with a plane P perpendicular to the longitudinal axis X. This angle is visible in Figure 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, Figure 7 further illustrates, in dashed lines, as an 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 followed 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.

[0101] In another possible embodiment, the first end 51a is a downstream end and the second end 51b is an upstream end, meaning that each of the connecting rods 51 extends between the structural cover 35 and the gas generator 3 at a non-zero negative angle with plane P, greater than -5°. In this configuration, the connecting rods 51 exert slightly more stress 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 stressing the exhaust housing 31b.

[0102] 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 P of 10° to 45°, in particular 20° to 30°, possibly 24° to 28°, for example 26°. Thus, the projection of each connecting rod 51 onto a plane perpendicular to the longitudinal axis X, for example onto the plane including the upstream end 51a of the connecting rod 51, forms an angle with the vertical direction of 10° to 45°, possibly 20° to 30°, in particular 24° to 28°, for example 26°. This angle P is visible in Figure 8.

[0103] 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 radially with respect to the longitudinal axis X. Indeed, when the propulsion system 1, and more specifically the exhaust housing 31b, undergoes outward radial thermal displacement, the connecting rods 51 accommodate this thermal expansion by pivoting around an axis passing through their first end 51a and 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 inward radial thermal contraction, 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 an outward radial thermal expansion of 3 millimeters, the connecting rods 51 accommodate this thermal expansion by pivoting around an axis passing through their first end 51a and parallel to the longitudinal axis X, forming a greater angle of up to 2 degrees with the vertical direction. Thus, the connecting rods 51 adapt without stress to the deformations of the exhaust housing 31b during the thermal displacement of the gas generator 3.

[0104] The centering device 50 may 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.

[0105] 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.

[0106] The connecting rods 51 are dimensioned at least under limit loads, and for example under ultimate loads.

[0107] The centering device 50 therefore ensures centering of the gas generator 3 relative to the structural hood 35, whether under gravity, under inertial loads and / or under 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 one 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 a portion of the exhaust casing (31b), the propulsion system (1) comprising a first portion having means for attachment to a pylon (101) and a second portion intended to be cantilevered from the pylon (101), the propulsion system (1) further comprising a centering device (50) for the gas generator relative to the structural hood, the centering device (50) comprising at least one connecting rod (51), the connecting rod or rods (51) extending between the structural hood (35) and the second portion 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, in which, 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 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 of 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 (V) of the propulsion system (1).

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

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