Structural assembly for a gas turbine engine

A structural subassembly which has a bearing which comprises a statically arranged outer ring and a rotatably arranged inner ring, wherein the inner ring is connected for conjoint rotation to a component that is rotatable about a longitudinal axis or said inner ring forms part of such a component, and wherein the longitudinal axis defines an axial direction of the bearing. The structural subassembly furthermore comprises a housing flange of a support structure, to which flange the statically arranged outer ring is connected. Provision is made for the outer ring to be of two-part design, wherein each part of the outer ring has a connecting element which is connected to the housing flange, wherein the housing flange is arranged between the two connecting elements in the axial direction.

This application claims priority to German Patent Application DE102020116785.7 filed Jun. 25, 2020, the entirety of which is incorporated by reference herein.

The invention relates to a structural subassembly for a gas turbine engine as per the present disclosure.

Bearings in which a statically arranged outer ring of the bearing forms a flange that is connected to a housing flange of a support structure are known.

It is the underlying object of the invention to provide a structural subassembly that has a bearing and allows favorable load transfer from the bearing to a support structure.

This object is achieved by a structural subassembly having features as disclosed herein. Refinements of the invention are also disclosed here.

Accordingly, the invention relates to a structural subassembly which can be part of a gas turbine engine. The structural subassembly comprises a bearing which has a statically arranged outer ring and a rotatably arranged inner ring. The inner ring is connected for conjoint rotation to a component that is rotatable about a longitudinal axis or said inner ring forms part of such a component. In this case, the longitudinal axis of the rotatable component defines an axial direction of the bearing. The bearing furthermore comprises a housing flange of a support structure, wherein the outer ring is connected to the housing flange.

In a structural subassembly of this kind, the invention envisages that the outer ring is of two-part design, wherein each part of the outer ring has a connecting element which is connected to the housing flange, wherein the housing flange is arranged between the two connecting elements in the axial direction.

The invention is based on the concept of providing symmetrical load transfer from the bearing to the support structure in a manner which is as uniform as possible and is largely without bending moments. For this purpose, the housing flange is arranged centrally in the axial direction between two connecting elements formed by two parts of the outer ring. The symmetrical arrangement of the housing flange between the two connecting elements allows uniform load transfer to the support structure and avoids the occurrence and transfer of bending moments which would occur in the case of unilateral connection of the outer ring to the housing flange.

Ideally, the situation is such that the center of mass of the connection between the two connecting elements and the housing flange lies in a plane perpendicular to the longitudinal axis in which the center of mass of the bearing also lies. Any bending moments during load transfer from the bearing to the support structure are thereby avoided.

Another advantage associated with the invention is that, owing to the fact that there is a connecting element of the outer ring secured on both sides of the housing flange, the contact area available for load transfer to the housing flange by friction is increased.

The support structure can be any fixed structure which can accept loads. For example, it is a fixed support structure of a gas turbine engine connected to an engine mounting. In another example, the support structure is a gear box housing arranged in a fixed manner.

The rotatable component to which the inner ring is connected or on which the inner ring is formed is a shaft or a rotating element of a gear box, for example. One embodiment associated therewith can provide for the rotating element to be formed by a planet carrier of a planetary gear box or to be connected to such a planet carrier.

According to one embodiment of the invention, the connecting elements of the two parts of the outer ring are likewise each designed as a flange and are flanged to the housing flange. Particularly effective and large-area connection between the housing flange and the connecting elements is thereby provided.

According to another embodiment, the outer ring is split radially. In this case, the outer ring forms a radially inner ring element and a radially outer ring element, which each form one of the connecting elements.

One embodiment associated therewith provides for the radially inner ring element to form a running surface of the bearing, for the radially outer ring element to adjoin the radially inner ring element radially on the outside, and for the two ring elements to have axial regions in which they overlap in the axial direction. In this case, provision can furthermore be made for the connecting elements to extend radially outward on axially opposite sides of the outer ring from the respective axial regions of the ring elements.

In the case of radial splitting of the outer ring, the radially inner ring element and the radially outer ring element overlap one another in the axial direction. One embodiment associated therewith provides for the radially outer ring element and the radially inner ring element to be connected to one another for conjoint rotation by means of an interference fit.

In another exemplary embodiment, the outer ring is split axially. In this case, the outer ring forms an axially forward ring element and an axially rearward ring element, which each form one of the connecting elements.

One embodiment associated therewith provides for one of the ring elements to form a running surface of the bearing, and for the other ring element to be connected at a distance from the running surface to the one ring element. Provision can furthermore be made for the connecting elements to extend radially outward on axially opposite sides of the outer ring from axial regions of the axially forward ring element and of the axially rearward ring element.

The axially forward ring element and the axially rearward ring element are connected to one another for conjoint rotation, e.g. by means of bolts or the like.

The bearing is a rolling bearing, for example, wherein rolling elements are arranged between the inner ring and the outer ring. However, the invention is not restricted thereto, and, as an alternative, the bearing can be designed as a sliding bearing, for example, wherein an inner surface of the outer ring and an outer surface of the inner ring form the sliding bearing.

Another embodiment provides for the structural subassembly to comprise a planetary gear box, wherein the inner ring is shrunk onto a planet carrier of the planetary gear box or onto an element connected to the planet carrier. The planet carrier can be part of a geared fan gas turbine engine.

In another aspect of the invention, the invention relates to a gas turbine engine having a structural subassembly according to the invention. Provision may be made here for the gas turbine engine to have:an engine core which comprises a turbine, a compressor and a core shaft connecting the turbine to the compressor and formed as a hollow shaft;a fan which is positioned upstream of the engine core, wherein the fan comprises a plurality of fan blades; anda planetary gear box, the input of which is connected to the turbine shaft and the output of which is connected to the fan shaft, wherein the planetary gear box comprises a planet carrier which is supported by a bearing as disclosed herein on a support structure of the gas turbine engine.

One design embodiment in this regard may provide thatthe turbine is a first turbine, the compressor is a first compressor, and the turbine shaft is a first turbine shaft;the engine core further comprises a second turbine, a second compressor, and a second turbine shaft which connects the second turbine to the second compressor; andthe second turbine, the second compressor, and the second turbine shaft are disposed with a view to rotating at a higher rotational speed than the first turbine shaft.

It is pointed out that the present invention is described with reference to a cylindrical coordinate system which has the coordinates x, r, and φ. Here, x indicates the axial direction, r indicates the radial direction, and φ indicates the angle in the circumferential direction. The axial direction is in this case identical to the machine axis of a gas turbine engine in which the structural subassembly is arranged. Proceeding from the x-axis, the radial direction points radially outward. Terms such as “in front of”, “behind”, “front”, and “rear” refer to the axial direction, or the flow direction in the engine. Terms such as “outer” or “inner” relate to the radial direction.

As noted elsewhere herein, the present disclosure may relate to a gas turbine engine. Such a gas turbine engine may comprise an engine core which comprises a turbine, a combustion chamber, a compressor, and a core shaft that connects the turbine to the compressor. Such a gas turbine engine may comprise a fan (having fan blades) which is positioned upstream of the engine core.

Arrangements of the present disclosure can be particularly, although not exclusively, beneficial for fans that are driven via a gear box. Accordingly, the gas turbine engine may comprise a gear box that receives an input from the core shaft and outputs drive for the fan so as to drive the fan at a lower rotational speed than the core shaft. The input to the gear box may be performed directly from the core shaft or indirectly from the core shaft, for example via a spur shaft and/or a spur gear. The core shaft may be rigidly connected to the turbine and the compressor, such that the turbine and the compressor rotate at the same rotational speed (wherein the fan rotates at a lower rotational speed).

In such an arrangement, the second compressor may be positioned so as to be axially downstream of the first compressor. The second compressor may be arranged so as to receive (for example directly receive, for example via a generally annular duct) flow from the first compressor.

The gear box may be arranged so as to be driven by that core shaft (for example the first core shaft in the example above) which is configured to rotate (for example during use) at the lowest rotational speed. For example, the gear box may be arranged so as to be driven only by that core shaft (for example only by the first core shaft, and not the second core shaft, in the example above) which is configured to rotate (for example during use) at the lowest rotational speed. Alternatively thereto, the gear box may be arranged so as to be driven by one or a plurality of shafts, for example the first and/or the second shaft in the example above.

In the case of a gas turbine engine as described and/or claimed herein, a combustion chamber may be provided axially downstream of the fan and of the compressor(s). For example, the combustion chamber can lie directly downstream of the second compressor (for example at the exit of the latter), if a second compressor is provided. By way of further example, the flow at the exit of the compressor may be supplied to the inlet of the second turbine, if a second turbine is provided. The combustion chamber may be provided upstream of the turbine(s).

The or each compressor (for example the first compressor and the second compressor as described above) may comprise any number of stages, for example multiple stages. Each stage may comprise a row of rotor blades and a row of stator vanes, which may be variable stator vanes (in the sense that the angle of incidence of said variable stator vanes may be variable). The row of rotor blades and the row of stator vanes may be axially offset from one another.

Each fan blade may be defined as having a radial span width extending from a root (or a hub) at a radially inner location flowed over by gas, or at a 0% span width position, to a tip at a 100% span width position. The ratio of the radius of the fan blade at the hub to the radius of the fan blade at the tip may be less than (or of the order of): 0.4, 0.39, 0.38, 0.37, 0.36, 0.35, 0.34, 0.33, 0.32, 0.31, 0.3, 0.29, 0.28, 0.27, 0.26 or 0.25. The ratio of the radius of the fan blade at the hub to the radius of the fan blade at the tip may be in an inclusive range delimited by two of the values in the previous sentence (that is to say that the values may form upper or lower limits). These ratios may be referred to in general as the hub-to-tip ratio. The radius at the hub and the radius at the tip can both be measured at the leading periphery part (or the axially frontmost periphery) of the blade. The hub-to-tip ratio refers, of course, to that portion of the fan blade which is flowed over by gas, that is to say the portion that is situated radially outside any platform.

The radius of the fan can be measured between the engine centerline and the tip of the fan blade at the leading periphery of the latter. The diameter of the fan (which can simply be double the radius of the fan) may be larger than (or of the order of): 250 cm (approximately 100 inches), 260 cm, 270 cm (approximately 105 inches), 280 cm (approximately 110 inches), 290 cm (approximately 115 inches), 300 cm (approximately 120 inches), 310 cm, 320 cm (approximately 125 inches), 330 cm (approximately 130 inches), 340 cm (approximately 135 inches), 350 cm, 360 cm (approximately 140 inches), 370 cm (approximately 145 inches), 380 cm (approximately 150 inches), or 390 cm (approximately 155 inches). The fan diameter may be in an inclusive range delimited by two of the values in the previous sentence (that is to say that the values may form upper or lower limits).

The rotational speed of the fan may vary during use. Generally, the rotational speed is lower for fans with a comparatively large diameter. Purely by way of non-limiting example, the rotational speed of the fan under cruise conditions may be less than 2500 rpm, for example less than 2300 rpm. Purely by way of a further non-limiting example, the rotational speed of the fan under cruise conditions for an engine having a fan diameter in the range from 250 cm to 300 cm (for example 250 cm to 280 cm) may also be in the range from 1700 rpm to 2500 rpm, for example in the range from 1800 rpm to 2300 rpm, for example in the range from 1900 rpm to 2100 rpm. Purely by way of a further non-limiting example, the rotational speed of the fan under cruise conditions for an engine having a fan diameter in the range from 320 cm to 380 cm may be in the range from 1200 rpm to 2000 rpm, for example in the range from 1300 rpm to 1800 rpm, for example in the range from 1400 rpm to 1600 rpm.

During use of the gas turbine engine, the fan (with associated fan blades) rotates about an axis of rotation. This rotation results in the tip of the fan blade moving with a velocity Utip. The work done by the fan blades on the flow results in an enthalpy rise dH in the flow. A fan tip loading can be defined as dH/Utip2, where dH is the enthalpy rise (for example the 1-D average enthalpy rise) across the fan and Utip is the (translational) velocity of the fan tip, for example at the leading periphery of the tip (which can be defined as the fan tip radius at the leading periphery multiplied by the angular velocity). The fan tip loading at cruise conditions may be more than (or of the order of): 0.3, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, or 0.4 (wherein all units in this passage are Jkg−1K−1/(ms−1)2). The fan tip loading may be in an inclusive range delimited by two of the values in the previous sentence (that is to say that the values may form upper or lower limits).

Gas turbine engines in accordance with the present disclosure can have any desired bypass ratio, where the bypass ratio is defined as the ratio of the mass flow rate of the flow through the bypass duct to the mass flow rate of the flow through the core at cruise conditions. In the case of some arrangements, the bypass ratio can be more than (or of the order of): 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, or 17. The bypass ratio may be in an inclusive range delimited by two of the values in the previous sentence (that is to say that the values may form upper or lower limits). The bypass duct may be substantially annular. The bypass duct may be situated radially outside the engine core. The radially outer surface of the bypass duct may be defined by an engine nacelle and/or a fan casing.

The overall pressure ratio of a gas turbine engine as described and/or claimed herein can be defined as the ratio of the stagnation pressure upstream of the fan to the stagnation pressure at the exit of the highest pressure compressor (before entry into the combustion chamber). As a non-limiting example, the overall pressure ratio of a gas turbine engine as described and/or claimed herein at cruising speed may be greater than (or of the order of): 35, 40, 45, 50, 55, 60, 65, 70, 75. The overall pressure ratio may be in an inclusive range delimited by two of the values in the previous sentence (that is to say that the values may form upper or lower limits).

The specific thrust of an engine can be defined as the net thrust of the engine divided by the total mass flow through the engine. The specific thrust of an engine as described and/or claimed herein at cruise conditions may be less than (or of the order of): 110 Nkg−1s, 105 Nkg−1s, 100 Nkg−1s, 95 Nkg−1s, 90 Nkg−1s, 85 Nkg−1s or 80 Nkg−1s. The specific thrust may be in an inclusive range delimited by two of the values in the previous sentence (that is to say that the values may form upper or lower limits). Such engines can be particularly efficient in comparison with conventional gas turbine engines.

A gas turbine engine as described and/or claimed herein may have any desired maximum thrust. Purely by way of a non-limiting example, a gas turbine as described and/or claimed herein may be capable of generating a maximum thrust of at least (or of the order of): 160 kN, 170 kN, 180 kN, 190 kN, 200 kN, 250 kN, 300 kN, 350 kN, 400 kN, 450 kN, 500 kN, or 550 kN. The maximum thrust may be in an inclusive range delimited by two of the values in the previous sentence (that is to say that the values may form upper or lower limits). The thrust referred to above may be the maximum net thrust at standard atmospheric conditions at sea level plus 15 degrees C. (ambient pressure 101.3 kPa, temperature 30 degrees C.) in the case of a static engine.

During use, the temperature of the flow at the entry to the high-pressure turbine can be particularly high. This temperature, which can be referred to as TET, may be measured at the exit to the combustion chamber, for example directly upstream of the first turbine blade, which in turn can be referred to as a nozzle guide blade. At cruising speed, the TET may be at least (or of the order of): 1400 K, 1450 K, 1500 K, 1550 K, 1600 K, or 1650 K. The TET at constant speed may be in an inclusive range delimited by two of the values in the previous sentence (that is to say that the values may form upper or lower limits). The maximum TET in the use of the engine may be at least (or of the order of), for example: 1700 K, 1750 K, 1800 K, 1850 K, 1900 K, 1950 K, or 2000 K. The maximum TET may be in an inclusive range delimited by two of the values in the previous sentence (that is to say that the values may form upper or lower limits). The maximum TET may occur, for example, under a high thrust condition, for example under a maximum take-off thrust (MTO) condition.

A fan blade and/or an airfoil portion of a fan blade described and/or claimed herein may be manufactured from any suitable material or a combination of materials. For example, at least a part of the fan blade and/or of the airfoil can be manufactured at least in part from a composite, for example a metal matrix composite and/or an organic matrix composite, such as carbon fiber. By way of further example, at least a part of the fan blade and/or of the airfoil can be manufactured at least in part from a metal, such as a titanium-based metal or an aluminum-based material (such as an aluminum-lithium alloy) or a steel-based material. The fan blade may comprise at least two regions which are manufactured using different materials. For example, the fan blade may have a protective leading periphery, which is manufactured using a material that is better able to resist impact (for example of birds, ice, or other material) than the rest of the blade. Such a leading periphery may, for example, be manufactured using titanium or a titanium-based alloy. Thus, purely by way of example, the fan blade may have a carbon-fiber-based or aluminum-based body (such as an aluminum-lithium alloy) with a titanium leading periphery.

A fan as described and/or claimed herein may comprise a central portion, from which the fan blades may extend, for example in a radial direction. The fan blades may be attached to the central portion in any desired manner. For example, each fan blade may comprise a fixing device which can engage with a corresponding slot in the hub (or disk). Purely by way of example, such a fixing device may be in the form of a dovetail that can be inserted into and/or engage with a corresponding slot in the hub/disk in order for the fan blade to be fixed to the hub/disk. By way of further example, the fan blades can be formed integrally with a central portion. Such an arrangement may be referred to as a blisk or a bling. Any suitable method may be used to manufacture such a blisk or such a bling. For example, at least a part of the fan blades can be machined from a block and/or at least a part of the fan blades can be attached to the hub/disk by welding, such as linear friction welding, for example.

The gas turbine engines described and/or claimed herein may or may not be provided with a variable area nozzle (VAN). Such a variable area nozzle can allow the exit cross section of the bypass duct to be varied during use. The general principles of the present disclosure can apply to engines with or without a VAN.

The fan of a gas turbine as described and/or claimed herein may have any desired number of fan blades, for example 16, 18, 20 or 22 fan blades.

As used herein, cruise conditions can mean cruise conditions of an aircraft to which the gas turbine engine is attached. Such cruise conditions can be conventionally defined as the conditions at mid-cruise, for example the conditions experienced by the aircraft and/or the engine between (in terms of time and/or distance) the top of climb and the start of descent.

Purely by way of example, the cruise conditions may correspond to standard atmospheric conditions at an altitude that is in the range from 10,000 m to 15,000 m, for example in the range from 10,000 m to 12,000 m, for example in the range from 10,400 m to 11,600 m (around 38,000 ft), for example in the range from 10,500 m to 11,500 m, for example in the range from 10,600 m to 11,400 m, for example in the range from 10,700 m (around 35,000 ft) to 11,300 m, for example in the range from 10,800 m to 11,200 m, for example in the range from 10,900 m to 11,100 m, for example of the order of 11,000 m. The cruise conditions may correspond to standard atmospheric conditions at any given altitude in these ranges.

Purely by way of example, the cruise conditions may correspond to the following: a forward Mach number of 0.8; a pressure of 23,000 Pa; and a temperature of −55 degrees C.

As used anywhere herein, “cruising speed” or “cruise conditions” may mean the aerodynamic design point. Such an aerodynamic design point (or ADP) may correspond to the conditions (including, for example, the Mach number, environmental conditions, and thrust requirement) for which the fan operation is designed. This may mean, for example, the conditions under which the fan (or the gas turbine engine) has the optimum efficiency in terms of construction.

In use, a gas turbine engine described and/or claimed herein can operate at the cruise conditions defined elsewhere herein. Such cruise conditions can be determined by the cruise conditions (for example the mid-cruise conditions) of an aircraft to which at least one (for example 2 or 4) gas turbine engine can be fastened in order to provide the thrust force.

It is self-evident to a person skilled in the art that a feature or parameter described in relation to one of the above aspects may be applied to any other aspect, unless these are mutually exclusive. Furthermore, any feature or any parameter described here may be applied to any aspect and/or combined with any other feature or parameter described here, unless these are mutually exclusive.

FIG.1illustrates a gas turbine engine10having a main axis of rotation9. The engine10comprises an air intake12and a thrust fan23that generates two air flows: a core air flow A and a bypass air flow B. The gas turbine engine10comprises a core11which receives the core air flow A. In the sequence of axial flow, the engine core11comprises a low-pressure compressor14, a high-pressure compressor15, a combustion device16, a high-pressure turbine17, a low-pressure turbine19, and a core thrust nozzle20. An engine nacelle21surrounds the gas turbine engine10and defines a bypass duct22and a bypass thrust nozzle18. The bypass air flow B flows through the bypass duct22. The fan23is attached to and driven by the low-pressure turbine19by way of a shaft26and an epicyclic gear box30.

During use, the core air flow A is accelerated and compressed by the low-pressure compressor14and directed into the high-pressure compressor15, where further compression takes place. The compressed air expelled from the high-pressure compressor15is directed into the combustion device16, where it is mixed with fuel and the mixture is combusted. The resulting hot combustion products then propagate through the high-pressure and the low-pressure turbines17,19and thereby drive said turbines, before being expelled through the nozzle20to provide a certain propulsive thrust. The high-pressure turbine17drives the high-pressure compressor15by means of a suitable connecting shaft27. The fan23generally provides the major part of the thrust force. The epicyclic gear box30is a reduction gear box.

An exemplary arrangement for a geared fan gas turbine engine10is shown inFIG.2. The low-pressure turbine19(seeFIG.1) drives the shaft26, which is coupled to a sun gear28of the epicyclic gear box assembly30. Multiple planet gears32, which are coupled to one another by a planet carrier34, are situated radially to the outside of the sun gear28and mesh therewith. The planet carrier34limits the planet gears32to orbiting around the sun gear28in a synchronous manner while enabling each planet gear32to rotate about its own axis. The planet carrier34is coupled by way of linkages36to the fan23so as to drive the rotation of the latter about the engine axis9. Radially to the outside of the planet gears32and meshing therewith is an annulus or ring gear38that is coupled, via linkages40, to a stationary support structure24.

It is noted that the terms “low-pressure turbine” and “low-pressure compressor” as used herein can be taken to mean the lowest pressure turbine stage and the lowest pressure compressor stage (that is to say not including the fan23) respectively and/or the turbine and compressor stages that are connected to one another by the connecting shaft26with the lowest rotational speed in the engine (that is to say not including the gear box output shaft that drives the fan23). In some documents, the “low-pressure turbine” and the “low-pressure compressor” referred to herein may alternatively be known as the “intermediate-pressure turbine” and “intermediate-pressure compressor”. Where such alternative nomenclature is used, the fan23can be referred to as a first compression stage or lowest-pressure compression stage.

The epicyclic gear box30is shown in an exemplary manner in greater detail inFIG.3. Each of the sun gear28, the planet gears32and the ring gear38comprise teeth about their periphery to mesh with the other gears. However, for clarity, only exemplary portions of the teeth are illustrated inFIG.3. Although four planet gears32are illustrated, it will be apparent to the person skilled in the art that more or fewer planet gears32may be provided within the scope of protection of the claimed invention. Practical applications of an epicyclic gear box30generally comprise at least three planet gears32.

The epicyclic gear box30illustrated by way of example inFIGS.2and3is a planetary gear box, in that the planet carrier34is coupled to an output shaft via linkages36, wherein the ring gear38is fixed. However, any other suitable type of epicyclic gear box30can be used. By way of further example, the epicyclic gear box30can be a star arrangement, in which the planet carrier34is held so as to be fixed, wherein the ring gear (or annulus)38is allowed to rotate. In the case of such an arrangement, the fan23is driven by the ring gear38. As a further alternative example, the gear box30can be a differential gear box in which both the ring gear38and the planet carrier34are allowed to rotate.

It will be appreciated that the arrangement shown inFIGS.2and3is by way of example only, and various alternatives are within the scope of protection of the present disclosure. Purely by way of example, any suitable arrangement can be used for positioning the gear box30in the engine10and/or for connecting the gear box30to the engine10. By way of a further example, the connections (such as the linkages36,40in the example ofFIG.2) between the gear box30and other parts of the engine10(such as the input shaft26, the output shaft and the fixed structure24) may have a certain degree of stiffness or flexibility. By way of a further example, any suitable arrangement of the bearings between rotating and stationary parts of the engine (for example between the input and output shafts of the gear box and the fixed structures, such as the gear box housing) may be used, and the disclosure is not limited to the exemplary arrangement ofFIG.2. For example, where the gear box30has a star arrangement (described above), the person skilled in the art would readily understand that the arrangement of output and support linkages and bearing positions would typically be different to that shown by way of example inFIG.2.

Accordingly, the present disclosure extends to a gas turbine engine having an arbitrary arrangement of gear box types (for example star-shaped or planetary), support structures, input and output shaft arrangement, and bearing positions.

Optionally, the gear box may drive additional and/or alternative components (e.g. the intermediate-pressure compressor and/or a booster compressor).

Other gas turbine engines in which the present disclosure can be used may have alternative configurations. For example, such engines may have an alternative number of compressors and/or turbines and/or an alternative number of connecting shafts. As a further example, the gas turbine engine shown inFIG.1has a split flow nozzle20,22, which means that the flow through the bypass duct22has a dedicated nozzle, which is separate from the engine core nozzle20and is radially on the outside with respect to the latter. However, this is not restrictive, and any aspect of the present disclosure can also apply to engines in which the flow through the bypass duct22and the flow through the core11are mixed or combined before (or upstream of) a single nozzle, which may be referred to as a mixed flow nozzle. One or both nozzles (whether mixed or split flow) can have a fixed or variable area. Although the example described relates to a turbofan engine, the disclosure can be applied, for example, to any type of gas turbine engine, such as, for example, an open rotor engine (in which the fan stage is not surrounded by an engine nacelle) or a turboprop engine. In some arrangements, the gas turbine engine10may not comprise a gear box30.

The geometry of the gas turbine engine10, and components thereof, is/are defined by a conventional axis system, comprising an axial direction (which is aligned with the axis of rotation9), a radial direction (in the bottom-to-top direction inFIG.1), and a circumferential direction (perpendicular to the view inFIG.1). The axial, radial and circumferential directions run so as to be mutually perpendicular.

It can be seen inFIG.2that the planet carrier34is supported on a bearing5. The bearing5has an outer ring, which is supported on a strut or wall structure45that is part of a load-bearing support structure of the gas turbine engine. In the context of the present invention, the configuration of the bearing5is important. It should be noted here that the following description of the bearing5is not restricted to its use in a gas turbine engine in connection with the support of a planetary gear box. In principle, the bearing5can be used in any context.

According to the exemplary embodiment inFIG.4, the bearing5comprises a rotating inner ring8connected to a rotatable component, a static outer ring6and rolling elements7, which are arranged in between and are designed, for example, as balls or rollers. However, this configuration of the bearing5should be understood as being merely by way of example.

The outer ring6of the bearing5is connected to a support structure45, which is part of a load-bearing support structure, e.g. of a gas turbine engine. The support structure45can be a fixing arm, a strut, a wall or a housing element, for example. For connection of the bearing5to the support structure45, the support structure forms a flange450, the lateral surfaces of which extend in the radial direction. The flange450is referred to below as the housing flange, although, as explained, it is not necessarily part of a housing but of a support structure in general.

The outer ring6is of two-part design and comprises a radially inner ring element61and a radially outer ring element62. The radially inner ring element61has an axial region611and a connecting element612, which projects perpendicularly from the axial region611. The radially outer ring element62likewise has an axial region621and a connecting element622, which projects perpendicularly from the axial region621.

With its inner surface, the axial region611of the radially inner ring element61forms a running surface of the bearing5. The axial region621of the radially outer ring element62adjoins the axial region611radially on the outside. In this arrangement, provision can be made for axial region611and axial region621of the two ring elements61,62to be connected to one another for conjoint rotation by an interference fit. As an alternative, a connection for conjoint rotation can be provided by way of positive-locking elements (not illustrated), or a connection is established only indirectly, via the connection of the connecting elements621,622to the housing flange.

The two connecting elements612,622of the two ring elements61,62extend radially outward on axially opposite sides of the outer ring6. They each form a flange, which is connected to the housing flange450by means of bolts91. Thus, provision is made for the connecting elements612,622to be arranged on both sides of the housing flange450, and hence for the housing flange450to be arranged between the two connecting elements612,622in the axial direction. This ensures that there is uniform load transfer from the bearing5to the housing flange450and the support structure45without bending moments being introduced into the support structure45.

It is envisaged here that both the center of mass of the connection of the two connecting elements612,622to the housing flange450and the center of mass of the bearing5lie in the same plane E. Here, the plane E is perpendicular to the axial direction of the bearing5, which is defined by the axis of rotation of a rotating element to which the inner ring8is connected. By arranging both centers of mass in the same plane, the introduction of bending moments or tilting moments into the support structure45is avoided. On the other hand, there is such introduction of bending moments if only one connecting element is provided and this is flanged to the housing flange450on one side.

FIG.5shows an exemplary embodiment of a bearing which differs from the exemplary embodiment inFIG.4in that the outer ring6is split axially and not split radially as in the exemplary embodiment inFIG.4.

According to the exemplary embodiment inFIG.5, the bearing5once again comprises a rotating inner ring8connected to a rotatable component, a static outer ring6and rolling elements7, which are arranged in between. The bearing5is connected to a support structure45, which is part of a load-bearing support structure, e.g. of a gas turbine engine. For connection of the outer ring6of the bearing5to the support structure45, the support structure forms a housing flange450, the lateral surfaces of which extend in the radial direction.

The outer ring6is of two-part design and comprises an axially forward ring element63and an axially rearward ring element64. The axially forward ring element63comprises an axial region631and a connecting element632, which projects perpendicularly from the axial region631. The axially rearward ring element64likewise has an axial region641and a connecting element642, which projects perpendicularly from the axial region641.

On its inner side, the axial region641of the axially rearward ring element64forms a running surface of the bearing5. The axially forward ring element63is situated axially ahead of the ring element64. The two ring elements63,64are connected to one another by means of bolts92.

The two connecting elements632,642of the two ring elements63,64extend on axially opposite sides of the outer ring6. As in the exemplary embodiment inFIG.4, they each form a flange that is connected to the housing flange450by means of bolts91, which are illustrated only schematically. The housing flange450is thus arranged between the two connecting elements632,642in the axial direction, and therefore there is uniform load transfer from the bearing5to the housing flange450and the support structure45, which is substantially free of bending moments. As in the exemplary embodiment inFIG.4, provision can be made here for the center of mass of the connection of the two connecting elements632,642to the housing flange450and the center of mass of the bearing5to lie in the same plane E.

It will be understood that the invention is not limited to the embodiments described above, and various modifications and improvements can be made without departing from the concepts described herein. For example, the bearing can be designed as a sliding bearing instead of a rolling bearing.

It should be noted that, except where mutually exclusive, any of the features described can be employed separately or in combination with any other features, and the disclosure extends to and includes all combinations and sub-combinations of one or more features that are described herein. If ranges are defined, said ranges thus comprise all of the values within said ranges as well as all of the partial ranges that lie in a range.