Roller bearing arrangement for a gas turbine engine

A roller bearing arrangement for a gas turbine engine. The roller bearing arrangement includes a fan shaft, and a stub shaft connected to the fan shaft. The roller bearing arrangement further includes a plurality of roller bearing elements positioned between a first axial bearing surface created on a radially outer surface of the stub shaft and a second axial bearing surface of a static structure, the roller bearing arrangement further including a first snubber positioned between the radially outer surface of the fan shaft and a radially inner surface of the stub shaft, the first snubber being spaced apart from the radially inner surface of the stub shaft or the radially outer surface of the fan shaft so as to limit a radial movement range of the stub shaft.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority pursuant to 35 U.S.C. 119(a) to from United Kingdom patent Application No. 2110451.8, filed Jul. 21, 2021, which application is incorporated herein by reference in its entirety.

BACKGROUND

The present disclosure relates to a roller bearing arrangement, and in particular to a roller bearing arrangement for a gas turbine engine.

The trend towards more fuel-efficient and environmentally friendly engines has led to an increase in the diameter of fans and fan blades. However, the diameter of the fan is constrained by the space available on the airframe between the wing and the ground. This leads to a design challenge, whereby it is desirable to increase the diameter of the fan whilst minimizing the increase of the diameter of the engine.

A gas turbine engine generally includes a roller bearing arrangement including a plurality of roller bearing elements for transferring loads from a fan shaft to a static structure of the gas turbine engine. In some cases, the roller bearing arrangement may include a stub shaft connected to the fan shaft and positioned radially between the plurality of roller bearing elements and the fan shaft.

In conventional roller bearing assemblies, the stub shaft may be connected to the fan shaft by an interference fit that is axially aligned with the plurality of roller bearing elements. The interference fit in such conventional roller bearing assemblies may be axially aligned with the plurality of roller bearing elements in order to enable the conventional roller bearing assemblies to withstand ultimate loads from the fan shaft due to a failure event (e.g., a fan blade-off event). However, such conventional roller bearing assemblies may require the fan shaft and the stub shaft to have large diameters in order to withstand the ultimate loads. Also, if the interference fit of the stub shaft is axially aligned with the plurality of roller bearing elements, it becomes difficult to deliver lubrication to the stub shaft, meaning further radial space is required to allow room for an lubrication distribution system to deliver oil to the interior surface of the stub shaft. Therefore, the conventional roller bearing assemblies may be large, space consuming, and heavy, due to the large diameters of the fan shaft and the stub shaft, thus limiting the space available for larger, more efficient fan blades.

SUMMARY OF THE DISCLOSURE

According to a first aspect, there is provided a roller bearing arrangement for a gas turbine engine. The roller bearing arrangement includes a fan shaft, a stub shaft, a static structure, a plurality of roller bearing elements, and a first snubber. The fan shaft defines an axis of rotation. The stub shaft is connected to the fan shaft and extends radially away therefrom so as to create a first axial bearing surface on a radially outer surface of the stub shaft. The first axial bearing surface is parallel with the axis of rotation and at a greater radial distance from the axis of rotation than a radially outer surface of the fan shaft. The static structure has a second axial bearing surface parallel with and opposite to the first axial bearing surface. The plurality of roller bearing elements is positioned between the first axial bearing surface and the second axial bearing surface. The first snubber is positioned between the radially outer surface of the fan shaft and a radially inner surface of the stub shaft. The first snubber is spaced apart from the radially inner surface of the stub shaft or the radially outer surface of the fan shaft so as to limit a radial movement range of the stub shaft.

The roller bearing arrangement may be compact and lightweight while being capable of transferring loads from the fan shaft to the static structure. Furthermore, the roller bearing arrangement may be capable of withstanding ultimate loads from the fan shaft due to a failure event (e.g., a fan blade-off event). Such a roller bearing arrangement takes up less radial space than known arrangements, allowing for an increase in fan blade/fan diameter whilst minimising the increase in the overall diameter of the engine.

Further, the stub shaft may be designed to independently withstand normal running loads. When the stub shaft is subjected to the ultimate loads by the fan shaft, the first snubber may provide a secondary load path and additional support to the stub shaft. The secondary load path may limit a maximum stress experienced by the stub shaft to an acceptable level. In other words, the stub shaft may not need to be designed to independently withstand the ultimate loads. Thus, the stub shaft may be designed to be lightweight and compact, thereby reducing a weight of the gas turbine engine.

As discussed above, the first snubber may provide additional support to the stub shaft when the stub shaft is subjected to the ultimate loads. This may allow a design of the fan shaft that is capable of withstanding the ultimate loads with a smaller diameter. Thus, the fan shaft may be designed to be lightweight and compact, thereby further Reducing the weight of the gas turbine engine.

In some embodiments, the stub shaft is connected to the fan shaft via an interference fit.

The interference fit may be a diametrical interference fit that may be a simple, low-cost, low-weight, and an accurate means of connecting the stub shaft to the fan shaft.

In some embodiments, the first axial bearing surface is axially spaced apart from the interference fit.

The first axial bearing surface being axially spaced apart from the interference fit may reduce deformation or coning of raceway surfaces of the plurality of roller bearing elements. This may result in an even load distribution across the plurality of roller bearing elements and a reduction of a peak stress experienced by the plurality of roller bearing elements. Furthermore, the first axial bearing surface being axially spaced apart from the interference fit may facilitate lubrication of the plurality of roller bearing elements.

In some embodiments, the first snubber is an extension of the fan shaft extending radially outward towards the radially inner surface of the stub shaft.

In some embodiments, the first snubber is an extension of the stub shaft extending radially inward towards the radially outer surface of the fan shaft.

In some embodiments, the first snubber is an extension of an output shaft from a power gear box extending radially outward towards the radially inner surface of the stub shaft.

In some embodiments, the output shaft is in contact with the radially outer surface of the fan shaft opposite to the first snubber.

Therefore, in some cases, the fan shaft may provide additional support to the output shaft including the first snubber.

In some embodiments, the first snubber is axially aligned with the plurality of roller bearing elements.

Therefore, the first snubber may provide the secondary load path that is axially aligned with the plurality of roller bearing elements. This may further prevent coning of the raceway surfaces of the plurality of roller bearing elements.

In some embodiments, the roller bearing arrangement includes the second snubber being at an axially distinct position from the first snubber.

In some embodiments, the second snubber is an extension of the fan shaft extending radially outward towards the radially inner surface of the stub shaft.

In some embodiments, the second snubber is an extension of the stub shaft extending radially inward towards the radially outer surface of the fan shaft.

In some embodiments, the second snubber is an extension of an output shaft from a power gear box extending radially outward towards the radially inner surface of the stub shaft.

In some embodiments, the second snubber is a continuous extension having a circumferential extent of 360 degrees.

In some embodiments, the second snubber includes a plurality of second snubber segments circumferentially spaced apart from each other.

In some embodiments, the first axial bearing surface is axially located between the plurality of roller bearing elements.

In some embodiments, the first snubber is a continuous extension having a circumferential extent of 360 degrees.

In some embodiments, the first snubber includes a plurality of first snubber segments circumferentially spaced apart from each other.

In some embodiments, the roller bearing arrangement includes an inner race at least partially disposed on the first axial bearing surface and an outer race at least partially disposed on the second axial bearing surface. The plurality of roller bearing elements is at least partially received between the inner race and the outer race.

The roller bearing arrangement may reduce deformation or coning of the inner race and the outer race. Therefore, the roller bearing arrangement may provide an even load distribution across the plurality of roller bearing elements and a reduction of a peak stress experienced by the plurality of roller bearing elements.

In some embodiments, the stub shaft includes a plurality of scallops on the radially inner surface of the stub shaft and a plurality of channels fluidly communicating the plurality of scallops with the first axial bearing surface. Each scallop is configured receive a lubricant from a lubricant supply. Each channel is configured to supply the lubricant to the first axial bearing surface.

Therefore, the plurality of scallops and the plurality of channels may effectively lubricate and cool the plurality of roller bearing elements.

According to a second aspect, there is provided a gas turbine engine for an aircraft. The gas turbine engine includes the roller bearing arrangement of the first aspect.

The gearbox may be a reduction gearbox (in that the output to the fan is a lower rotational rate than the input from the core shaft). Any type of gearbox may be used. For example, the gearbox may be a “planetary” or “star” gearbox, as described in more detail elsewhere herein. The gearbox may have any desired reduction ratio (defined as the rotational speed of the input shaft divided by the rotational speed of the output shaft), for example greater than 2.5, for example in the range of from 3 to 4.2, or 3.2 to 3.8, for example on the order of or at least 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1 or 4.2. The gear ratio may be, for example, between any two of the values in the previous sentence. Purely by way of example, the gearbox may be a “star” gearbox having a ratio in the range of from 3.1 or 3.2 to 3.8. In some arrangements, the gear ratio may be outside these ranges.

The radius of the fan may be measured between the engine centreline and the tip of a fan blade at its leading edge. The fan diameter (which may simply be twice the radius of the fan) may be greater than (or on the order of) any of: 220 cm, 230 cm, 240 cm, 250 cm (around 100 inches), 260 cm, 270 cm (around 105 inches), 280 cm (around 110 inches), 290 cm (around 115 inches), 300 cm (around 120 inches), 310 cm, 320 cm (around 125 inches), 330 cm (around 130 inches), 340 cm (around 135 inches), 350 cm, 360 cm (around 140 inches), 370 cm (around 145 inches), 380 (around 150 inches) cm, 390 cm (around 155 inches), 400 cm, 410 cm (around 160 inches) or 420 cm (around 165 inches). The fan diameter may be in an inclusive range bounded by any two of the values in the previous sentence (i.e., the values may form upper or lower bounds), for example in the range of from 240 cm to 280 cm or 330 cm to 380 cm.

The overall pressure ratio of a gas turbine engine as described and/or claimed herein may 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 combustor). By way of non-limitative example, the overall pressure ratio of a gas turbine engine as described and/or claimed herein at cruise may be greater than (or on the order of) any of the following: 35, 40, 45, 50, 55, 60, 65, 70, 75. The overall pressure ratio may be in an inclusive range bounded by any two of the values in the previous sentence (i.e. the values may form upper or lower bounds), for example in the range of from 50 to 70.

Specific thrust of an engine may be defined as the net thrust of the engine divided by the total mass flow through the engine. At cruise conditions, the specific thrust of an engine described and/or claimed herein may be less than (or on the order of) any of the following: 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 bounded by any two of the values in the previous sentence (i.e., the values may form upper or lower bounds), for example in the range of from 80 Nkg−1s to 100 Nkg−1s, or 85 Nkg−1s to 95 Nkg−1s. Such engines may 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 non-limitative example, a gas turbine as described and/or claimed herein may be capable of producing a maximum thrust of at least (or on the order of) any of the following: 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 bounded by any two of the values in the previous sentence (i.e., the values may form upper or lower bounds). Purely by way of example, a gas turbine as described and/or claimed herein may be capable of producing a maximum thrust in the range of from 330 kN to 420 kN, for example 350 kN to 400 kN. 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.), with the engine static.

In use, the temperature of the flow at the entry to the high-pressure turbine may be particularly high. This temperature, which may be referred to as TET, may be measured at the exit to the combustor, for example immediately upstream of the first turbine vane, which itself may be referred to as a nozzle guide vane. At cruise, the TET may be at least (or on the order of) any of the following: 1400K, 1450K, 1500K, 1550K, 1600K or 1650K. The TET at cruise may be in an inclusive range bounded by any two of the values in the previous sentence (i.e., the values may form upper or lower bounds). The maximum TET in use of the engine may be, for example, at least (or on the order of) any of the following: 1700K, 1750K, 1800K, 1850K, 1900K, 1950K or 2000K. The maximum TET may be in an inclusive range bounded by any two of the values in the previous sentence (i.e., the values may form upper or lower bounds), for example in the range of from 1800K to 1950K. The maximum TET may occur, for example, at a high thrust condition, for example at a maximum take-off (MTO) condition.

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 may allow the exit area of the bypass passage to be varied in use. The general principles of the present disclosure may 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 14, 16, 18, 20, 22, 24 or 26 fan blades.

As used herein, cruise conditions have the conventional meaning and would be readily understood by the skilled person. Thus, for a given gas turbine engine for an aircraft, the skilled person would immediately recognise cruise conditions to mean the operating point of the engine at mid-cruise of a given mission (which may be referred to in the industry as the “economic mission”) of an aircraft to which the gas turbine engine is designed to be attached. In this regard, mid-cruise is the point in an aircraft flight cycle at which 50% of the total fuel that is burned between top of climb and start of descent has been burned (which may be approximated by the midpoint—in terms of time and/or distance—between top of climb and start of descent. Cruise conditions thus define an operating point of the gas turbine engine that provides a thrust that would ensure steady state operation (i.e., maintaining a constant altitude and constant Mach Number) at mid-cruise of an aircraft to which it is designed to be attached, taking into account the number of engines provided to that aircraft. For example, where an engine is designed to be attached to an aircraft that has two engines of the same type, at cruise conditions the engine provides half of the total thrust that would be required for steady state operation of that aircraft at mid-cruise.

In other words, for a given gas turbine engine for an aircraft, cruise conditions are defined as the operating point of the engine that provides a specified thrust (required to provide—in combination with any other engines on the aircraft—steady state operation of the aircraft to which it is designed to be attached at a given mid-cruise Mach Number) at the mid-cruise atmospheric conditions (defined by the International Standard Atmosphere according to ISO 2533 at the mid-cruise altitude). For any given gas turbine engine for an aircraft, the mid-cruise thrust, atmospheric conditions and Mach Number are known, and thus the operating point of the engine at cruise conditions is clearly defined.

Purely by way of example, the cruise conditions may correspond to an operating point of the engine that provides a known required thrust level (for example a value in the range of from 30 kN to 35 kN) at a forward Mach number of 0.8 and standard atmospheric conditions (according to the International Standard Atmosphere) at an altitude of 38000 ft (11582 m). Purely by way of further example, the cruise conditions may correspond to an operating point of the engine that provides a known required thrust level (for example a value in the range of from 50 kN to 65 kN) at a forward Mach number of 0.85 and standard atmospheric conditions (according to the International Standard Atmosphere) at an altitude of 35000 ft (10668 m).

According to an aspect, there is provided an aircraft comprising a gas turbine engine as described and/or claimed herein. The aircraft according to this aspect is the aircraft for which the gas turbine engine has been designed to be attached. Accordingly, the cruise conditions according to this aspect correspond to the mid-cruise of the aircraft, as defined elsewhere herein.

According to an aspect, there is provided a method of operating a gas turbine engine as described and/or claimed herein. The operation may be at the cruise conditions as defined elsewhere herein (for example in terms of the thrust, atmospheric conditions, and Mach Number).

According to an aspect, there is provided a method of operating an aircraft comprising a gas turbine engine as described and/or claimed herein. The operation according to this aspect may include (or may be) operation at the mid-cruise of the aircraft, as defined elsewhere herein.

DETAILED DESCRIPTION OF THE DISCLOSURE

As used herein, a component extends “axially” relative to an axis if the component extends along the axis. A component extends “circumferentially” relative to an axis if the component extends in a circumferential direction defined around the axis. A component extends “radially” relative to an axis if the component extends radially inward or outward relative to the axis.

As used herein, the term “axis of rotation” refers to a straight line around which a component performs, at least in working condition, rotation and/or revolution.

As used herein, “a radially inner surface” and “a radially outer surface” of a component may be defined as an innermost, circumferentially extending surface and an outermost, circumferentially extending surface of the component, respectively, relative to the axis of rotation.

FIG.1illustrates a gas turbine engine10having a principal rotational axis9. The engine10comprises an air intake12and a propulsive fan23that generates two airflows: a core airflow A and a bypass airflow B. The gas turbine engine10comprises a core11that receives the core airflow A. The engine core11comprises, in axial flow series, a low-pressure compressor14, a high-pressure compressor15, a combustor section16, a high-pressure turbine17, a low-pressure turbine19and a core exhaust nozzle20. A nacelle21surrounds the gas turbine engine10and defines a bypass passage22and a bypass exhaust nozzle18. The bypass airflow B flows through the bypass passage22. The propulsive fan23is attached to and driven by the low-pressure turbine19via a shaft26(interchangeably referred to as a fan shaft26, or an input shaft26) and an epicyclic gearbox30.

In use, the core airflow A is accelerated and compressed by the low-pressure compressor14and directed into the high-pressure compressor15where further compression takes place. The compressed air exhausted from the high-pressure compressor15is directed into the combustor section16where it is mixed with fuel and the mixture is combusted. The resultant hot combustion products then expand through, and thereby drive, the high-pressure and low-pressure turbines17,19before being exhausted through the core exhaust nozzle20to provide some propulsive thrust. The high-pressure turbine17drives the high-pressure compressor15by a suitable interconnecting shaft27. The propulsive fan23generally provides the majority of the propulsive thrust. The epicyclic gearbox30is a reduction gearbox.

Note that the terms “low-pressure turbine” and “low-pressure compressor” as used herein may be taken to mean the lowest pressure turbine stages and lowest pressure compressor stages (i.e., not including the propulsive fan23) respectively and/or the turbine and compressor stages that are connected together by the interconnecting shaft26with the lowest rotational speed in the engine (i.e., not including the gearbox output shaft that drives the propulsive fan23). In some literature, the “low-pressure turbine” and “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 propulsive fan23may be referred to as a first, or lowest pressure, compression stage.

In addition, the present disclosure is equally applicable to aero gas turbine engines, marine gas turbine engines and land-based gas turbine engines.

FIG.4Aillustrates a sectional side view of a roller bearing arrangement100for a gas turbine engine10(shown inFIG.1). The roller bearing arrangement100includes a fan shaft26.FIG.4Billustrates a detailed view of a portion A ofFIG.4A.

The fan shaft26defines an axis of rotation29. In some embodiments, the axis of rotation29may coincide with the principal rotational axis9of the gas turbine engine10(shown inFIG.1). The fan shaft26includes a radially outer surface50. The radially outer surface50and the axis of rotation29of the fan shaft26define a maximum radial distance55therebetween.

The roller bearing arrangement100further includes a stub shaft110. The stub shaft110includes a radially inner surface112and a radially outer surface114parallel with and opposite to the radially inner surface112.

The stub shaft110is connected to the fan shaft26and extends radially away therefrom so as to create a first axial bearing surface118on the radially outer surface114of the stub shaft110. The first axial bearing surface118is parallel with the axis of rotation29. The first axial bearing surface118and the axis of rotation29define a maximum radial distance116therebetween.

The stub shaft110may be connected to the fan shaft26by any suitable method, such as, bolting, welding, and the like. In the illustrated embodiment ofFIG.4A, the stub shaft110is connected to the fan shaft26via an interference fit120. Specifically, in the illustrated embodiment ofFIG.4, the interference fit120is provided between a portion of a fan disk70and the fan shaft26.

The first axial bearing surface118is axially spaced apart from the interference fit120. Specifically, in the illustrated embodiment ofFIG.4, the first axial bearing surface118is positioned axially downstream from the interference fit120relative to the axis of rotation29. The first axial bearing surface118being axially spaced apart from the interference fit120may ensure that the first axial bearing surface118remains concentric with the axis of rotation29of the fan shaft26, at least during normal operating conditions (e.g., cruise conditions of an aircraft).

The first axial bearing surface118is at a greater radial distance from the axis of rotation29than the radially outer surface50of the fan shaft26. In other words, the first axial bearing surface118is radially spaced apart from the radially outer surface50of the fan shaft26. That is, the maximum radial distance116between the first axial bearing surface118and the axis of rotation29is greater than the maximum radial distance55between the radially outer surface50of the fan shaft26and the axis of rotation29.

The roller bearing arrangement100further includes a static structure127. The static structure127may be designed to be capable of withstanding ultimate loads (e.g., loads during a fan blade-off event) from the fan shaft26. The static structure127has a second axial bearing surface128parallel with and opposite to the first axial bearing surface118.

The roller bearing arrangement100further includes a plurality of roller bearing elements130positioned between the first axial bearing surface118and the second axial bearing surface128. The plurality of roller bearing elements130may be configured to transfer loads from the fan shaft26to the static structure127of the roller bearing arrangement100.

In the illustrated embodiment ofFIG.4A, the roller bearing arrangement100further includes an inner race132at least partially disposed on the first axial bearing surface118and an outer race134at least partially disposed on the second axial bearing surface128. Furthermore, in the illustrated embodiment ofFIG.4A, the plurality of roller bearing elements130is at least partially received between the inner race132and the outer race134.

The inner race132and the outer race134may be disposed substantially parallel to each other in order to ensure an even load distribution across the plurality of roller bearing elements130. However, the inner and outer races132,134may deform if an interference fit, such as the interference fit120is within close proximity of the inner and outer races132,134. This deformation (also known as “coning”) may result in a poor load distribution and a greater peak stress experienced by the plurality of roller bearing elements130. To reduce or prevent deformation of the inner race132and the outer race134, the first axial bearing surface118may be axially spaced apart from the interference fit120. Therefore, the interference fit120being axially spaced apart from the interference fit120may minimize coning of the inner race132and the outer race134, and ensure even load distribution across the plurality of roller bearing elements130.

In the illustrated embodiment ofFIG.4A, the stub shaft110further includes a plurality of scallops122(best shown inFIGS.5A and5B) on the radially inner surface112of the stub shaft110. In the illustrated embodiment ofFIG.4A, the stub shaft110further includes a plurality of channels126(best shown inFIGS.5A and5B) fluidly communicating the plurality of scallops122with the first axial bearing surface118. Furthermore, each scallop122is configured receive a lubricant75from a lubricant supply80. In some embodiments, the lubricant supply80may be configured to provide the lubricant75as an oil jet to each scallop122. Thus, in some embodiments, each scallop122may receive the lubricant75as the oil jet from the lubricant supply80.

The plurality of channels126may feed the lubricant75to the plurality of roller bearing elements130, thereby providing lubrication and cooling to the plurality of roller bearing elements130. In some embodiments, the plurality of channels126may be configured to create an annular film of the lubricant75on either axial side of the plurality of roller bearing elements130, such that the annular film lubricates and cools the plurality of roller bearing elements130. Such lubrication of the plurality of roller bearing elements130may be facilitated due to the interference fit120being axially spaced apart from the first axial bearing surface118.

However, the first axial bearing surface118being axially spaced apart from the interference fit120may create a cantilever effect in the stub shaft110. The stub shaft110may be subjected to the ultimate loads by the fan shaft26during a structural failure of the gas turbine engine10. An example of such structural failure includes a blade-off event, in which at least one blade of the propulsive fan23breaks off within the gas turbine engine10. In some cases, the stub shaft110may be deflected radially inwards towards the fan shaft26due to the cantilever effect and the ultimate loads. In extreme cases, this could damage the stub shaft110.

To prevent damage to the stub shaft110from ultimate loads, the roller bearing arrangement100further includes a first snubber140positioned between the radially outer surface50of the fan shaft26and the radially inner surface112of the stub shaft110. Shape and dimensions of the first snubber140may depend upon various factors, such as magnitudes of the ultimate loads, and designs of the stub shaft110and the fan shaft26.

The first snubber140is spaced apart from the radially inner surface112of the stub shaft110or the radially outer surface50of the fan shaft26so as to limit a radial movement range of the stub shaft110. In other words, the first snubber140is spaced apart from one of the radially inner surface112of the stub shaft110and the radially outer surface50of the fan shaft26so as to limit the radial movement range of the stub shaft110.

During events inducing the ultimate loads, the stub shaft110may radially deflect inwards such that the first snubber140contacts one of the radially inner surface112of the stub shaft110or the radially outer surface50of the fan shaft26so as to limit the radial movement range of the stub shaft110. Therefore, a secondary load path may be temporarily formed for time periods of the ultimate loads. As a result, the stub shaft110may be configured to independently support only normal operating loads and limit loads rather than also having to independently withstand ultimate loads. Thus, the stub shaft110may be designed to be compact and lightweight.

Furthermore, in the illustrated embodiment ofFIG.4A, the first snubber140is axially aligned with the plurality of roller bearing elements130. The first snubber140being axially aligned with the plurality of roller bearing elements130may ensure even load distribution across the plurality of roller bearing elements130when the stub shaft110contacts the first snubber140and may prevent coning of the inner race132and the outer race134.

In the illustrated embodiment ofFIG.4A, the first snubber140is an extension142of an output shaft102from a power gear box104extending radially outward towards the radially inner surface112of the stub shaft110. In other words, in the illustrated embodiment ofFIG.4A, the roller bearing arrangement100further includes the output shaft102of the power gear box104including the first snubber140. In some embodiments, the first snubber140may be integrally formed with the output shaft102.

In the illustrated embodiment ofFIG.4A, the first snubber140is spaced apart from the radially inner surface112of the stub shaft110. Further, the first snubber140includes a radially outer surface144. The radially outer surface144of the first snubber140and the radially inner surface112of the stub shaft110define a first radial clearance146therebetween. The first radial clearance146may depend upon design attributes and a material of the stub shaft110. The first radial clearance146may further depend upon loads to be experienced by the stub shaft110. In some embodiments, the first radial clearance146may be less than or equal to about 1 millimetre (mm).

The output shaft102includes a radially inner surface106and a radially outer surface108generally parallel with and opposite to the radially inner surface106. In the illustrated embodiment ofFIG.4A, the fan shaft26further includes an extension60extending radially outwards from the radially outer surface50of the fan shaft26and aligned with the first snubber140. In some other embodiments, the fan shaft26may include more than one extension60extending from the radially outer surface50of the fan shaft26and aligned with the first snubber140.

In the illustrated embodimentFIG.4A, the output shaft102is in contact with the radially outer surface50of the fan shaft26opposite to the first snubber140. Specifically, in the illustrated embodimentFIG.4A, the radially inner surface106of the output shaft102is in contact with the radially outer surface50of the fan shaft26at the extension60, opposite to the first snubber140. However, this is not essential, with a gap between the radially inner surface106of the output shaft102and the radially outer surface50of the fan shaft26being possible whilst maintain the functionality of the roller bearing arrangement100.

In some embodiments, the extension60may be integrally formed with the fan shaft26. However, in some other embodiments, the extension60may be separately formed from the fan shaft26and coupled to the fan shaft26. The extension60of the fan shaft26may be configured to radially locate the output shaft102. Furthermore, the extension60may support the output shaft102, while allowing reduction of a diameter of a major portion of the fan shaft26, thereby decreasing a weight of the fan shaft26.

While the first snubber140is the extension142of the output shaft102in the illustrated embodiment ofFIG.4A, in some embodiments, the first snubber140may be an extension of the fan shaft26extending radially outward towards the radially inner surface112of the stub shaft110. In some other embodiments, the first snubber140may be an extension of the stub shaft110extending radially inward towards the radially outer surface50of the fan shaft26. In some embodiments, the first snubber140may include two snubber portions. In such embodiments, one snubber portion of the two snubber portions may be an extension of the fan shaft26extending radially outward towards the radially inner surface112of the stub shaft110, and another snubber portion of the two snubber portions may be an extension of the stub shaft110extending radially inward towards the radially outer surface50of the fan shaft26. It may be noted that various configurations of the first snubber140may be contemplated and are intended to be within the scope of the present disclosure.

Referring toFIGS.4A and4B, the output shaft102includes an end portion103having a radial thickness greater than a radial thickness of a rest of the output shaft102. A surface portion109of the radially outer surface108of the output shaft102corresponding to the end portion103is located at a radially outward position relative to the radially outer surface108of the rest of the output shaft102. The first snubber140is disposed on the end portion103. Further, the first snubber140defines a radial height H relative to the surface portion109of the radially outer surface108of the end portion103of the output shaft102. The first snubber140further defines an axial length L along the axis of rotation29. The radial height H and the axial length L of the first snubber140may depend on various parameters, such as expected loads on the first snubber140, the first radial clearance146, a material of the output shaft102, and so forth. The radial height H may be equal to zero, such that the first snubber140effectively extends along the entire length of the end portion103.

FIG.5Aillustrates a portion of the stub shaft110including the plurality of scallops122, andFIG.5Billustrates a schematic side view of a portion of the radially inner surface112of the stub shaft110.

Referring toFIGS.4A,5A, and5B, the scallops122are circumferentially spaced apart from each other. In some embodiments, the plurality of scallops122may include about 20 scallops on the radially inner surface112of the stub shaft110. Further, the scallops122include corresponding channels126. As discussed above, each scallop122is configured to receive the lubricant75from the lubricant supply80. Further, each channel126is configured to supply the lubricant75to the first axial bearing surface118. In some embodiments, the lubricant75from the lubricant supply80may be used as a lubricating agent and/or a cooling agent for the plurality of roller bearing elements130.

FIG.6Aillustrates a schematic sectional front view of the output shaft102ofFIG.4Aaccording to an embodiment of the present disclosure. In the illustrated embodiment ofFIG.6A, the output shaft102includes a first snubber140A similar to the first snubber140ofFIG.4A. Specifically, the first snubber140A extends radially outward from the outer surface108of the output shaft102. However, the first snubber140A is a continuous extension142A having a circumferential extent of 360 degrees. In other words, the first snubber140A continuously extends in the circumferential direction. The circumferential direction relative to the axis of rotation29is indicated by an arrow CD inFIG.6A.

FIG.6Billustrates a sectional front view of the output shaft102ofFIG.4Aaccording to another embodiment of the present disclosure. In the illustrated embodiment ofFIG.6B, the output shaft102includes a first snubber140B similar to the first snubber140ofFIG.4A. Specifically, the first snubber140B extends radially outward from the outer surface108of the output shaft102. However, the first snubber140B includes a plurality of first snubber segments142B circumferentially spaced apart from each other. In other words, the first snubber140B discontinuously extends in the circumferential direction indicated by the arrow CD.

FIG.7illustrates a sectional side view of a roller bearing arrangement200according to another embodiment of the present disclosure. The roller bearing arrangement200is similar to the roller bearing arrangement100ofFIG.4A. Accordingly, similar features between the roller bearing arrangement100and the roller bearing arrangement200are designated by the same reference numbers. However, the roller bearing arrangement200includes a first snubber240having a different configuration from the first snubber140ofFIG.4A.

Specifically, in the illustrated embodiment ofFIG.7, the first snubber240is an extension242of the fan shaft26extending radially outward towards the radially inner surface112of the stub shaft110. The first snubber240is positioned between the radially outer surface50of the fan shaft26and the radially inner surface112of the stub shaft110. The first axial bearing surface118is axially spaced apart from the interference fit120.

Further, the first snubber240includes a radially outer surface244. The first snubber240is spaced apart from the radially inner surface112of the stub shaft110so as to limit the radial movement range of the stub shaft110. Therefore, the radially outer surface244of the first snubber240and the radially inner surface112of the stub shaft110define a first radial clearance246therebetween. In some embodiments, the first radial clearance246may be less than or equal to about 1 mm.

FIG.8Aillustrates a sectional front view of the fan shaft26ofFIG.7according to an embodiment of the present disclosure. In the illustrated embodiment ofFIG.8A, the fan shaft26includes a first snubber240A similar to the first snubber240ofFIG.7. Specifically, the first snubber240A extends radially outward from the radially outer surface50of the fan shaft26. However, the first snubber240A is a continuous extension242A having a circumferential extent of 360 degrees. In other words, the first snubber240A continuously extends in the circumferential direction (indicated by the arrow CD).

FIG.8Billustrates a sectional front view of the fan shaft26ofFIG.7according to another embodiment of the present disclosure. In the illustrated embodiment ofFIG.8B, the fan shaft26includes a first snubber240B similar to the first snubber240ofFIG.7. Specifically, the first snubber240B extends radially outward from the radially outer surface50of the fan shaft26. However, the first snubber240B includes a plurality of first snubber segments242B circumferentially spaced apart from each other. In other words, the first snubber240B discontinuously extends in the circumferential direction (indicated by the arrow CD).

FIG.9illustrates a sectional side view of a roller bearing arrangement300according to another embodiment of the present disclosure. The roller bearing arrangement300is similar to the roller bearing arrangement100ofFIG.4A. Accordingly, similar features between the roller bearing arrangement100and the roller bearing arrangement300are designated by the same reference numbers. However, the roller bearing arrangement300includes a first snubber340having a different configuration from the first snubber140ofFIG.4A.

Specifically, in the illustrated embodiment ofFIG.9, the first snubber340is an extension342of the stub shaft110extending radially inward towards the radially outer surface50of the fan shaft26. The first snubber340is positioned between the radially outer surface50of the fan shaft26and the radially inner surface112of the stub shaft110.

Further, the first snubber340includes a radially inner surface344. The first snubber340is spaced apart from the radially outer surface50of the fan shaft26so as to limit the radial movement range of the stub shaft110. Therefore, the radially inner surface344of the first snubber340and the radially outer surface50of the fan shaft26define a first radial clearance346therebetween. In some embodiments, the first radial clearance346may be less than or equal to about 1 mm.

FIG.10Aillustrates a sectional front view of the stub shaft110ofFIG.9according to an embodiment of the present disclosure. In the illustrated embodiment ofFIG.10A, the stub shaft110includes a first snubber340A similar to the first snubber340ofFIG.9. Specifically, the first snubber340A extends radially inward from the radially inner surface112of the stub shaft110. However, the first snubber340A is a continuous extension342A having a circumferential extent of 360 degrees. In other words, the first snubber340A continuously extends in the circumferential direction (indicated by the arrow CD).

FIG.10Billustrates a sectional front view of the stub shaft110ofFIG.9according to another embodiment of the present disclosure. In the illustrated embodiment ofFIG.10B, the stub shaft110includes a first snubber340B similar to the first snubber340ofFIG.9. Specifically, the first snubber340B extends radially inward from the radially inner surface112of the stub shaft110. However, the first snubber340B includes a plurality of first snubber segments342B circumferentially spaced apart from each other. In other words, the first snubber340B discontinuously extends in the circumferential direction (indicated by the arrow CD).

FIG.11illustrates a sectional side view of a roller bearing arrangement400according to another embodiment of the present disclosure. The roller bearing arrangement400is similar to the roller bearing arrangement100ofFIG.4A. Accordingly, similar features between the roller bearing arrangement100and the roller bearing arrangement400are designated by the same reference numbers. The roller bearing arrangement400includes a first snubber440similar to the first snubber140ofFIG.4A. Specifically, the first snubber440is positioned between the radially outer surface50of the fan shaft26and the radially inner surface112of the stub shaft110. Furthermore, the first snubber440is an extension442of the output shaft102from the power gear box104extending radially outward towards the radially inner surface112of the stub shaft110. The first snubber440is spaced apart from the radially inner surface112of the stub shaft110so as to limit the radial movement range of the stub shaft110. However, the roller bearing arrangement400further includes a second snubber450. The second snubber450is at an axially distinct position from the first snubber440.

Specifically, in the illustrated embodiment ofFIG.11, the second snubber450is an extension452of the output shaft102from the power gear box104extending radially outward towards a radially inner surface112of the stub shaft110. In the illustrated embodiment ofFIG.11, the first and second snubbers440,450are axially aligned with the plurality of roller bearing elements130. Further, the first and second snubbers440,450are disposed on the end portion103of the output shaft102. However, in some other embodiments, the first and second snubbers440,450may not be axially aligned with the plurality of roller bearing elements130, and may be spaced further axially apart from each other. In some embodiments, either or both of the first and second snubbers440,450may be axially spaced apart from the plurality of roller bearing elements130. For example, the first snubber440may be spaced to one side of the axial location of the roller bearing elements130, and the second snubber450may be spaced to the other side of the axial location of the roller bearing elements130, such that the roller bearing elements130are positioned axially between the first440and second450snubbers. In some embodiments, shape and dimensions of the first and second snubbers440,450may be substantially similar.

Furthermore, the second snubber450includes a radially outer surface454. In the illustrated embodiment ofFIG.11, the second snubber450is spaced apart from the radially inner surface112of the stub shaft110so as to limit the radial movement range of the stub shaft110. Therefore, the radially outer surface454of the second snubber450and the radially inner surface112of the stub shaft110define a second radial clearance456therebetween. In some embodiments, the second radial clearance456is substantially equal to a first radial clearance446defined between a radially outer surface444of the first snubber440and the radially inner surface112of the stub shaft110. In some embodiments, the second radial clearance456is less than or equal to about 1 mm.

FIG.12Aillustrates a sectional front view of the output shaft102ofFIG.11according to an embodiment of the present disclosure. In the illustrated embodiment ofFIG.12A, the output shaft102includes a second snubber450A similar to the second snubber450ofFIG.11. Specifically, the second snubber450A extends radially outward from the radially outer surface108of the output shaft102. However, the second snubber450A is a continuous extension452A having a circumferential extent of 360 degrees. In other words, the second snubber450A continuously extends in the circumferential direction (indicated by the arrow CD).

It will be understood that the first snubber440and second snubber450can have different configurations. For example, one of the first440or second450snubber may be a continuous extension having a circumferential extent of 360 degrees, whilst the other of the first440or second450snubber may comprise a plurality of snubber segments circumferentially spaced apart from each other.

FIG.12Billustrates a sectional front view of the output shaft102ofFIG.11according to another embodiment of the present disclosure. In the illustrated embodiment ofFIG.12B, the output shaft102includes a second snubber450B similar to the second snubber450ofFIG.11. Specifically, the second snubber450B extends radially outward from the radially outer surface108of the output shaft102. However, the second snubber450B includes a plurality of second snubber segments452B circumferentially spaced apart from each other. In other words, the second snubber450B discontinuously extends in the circumferential direction (indicated by the arrow CD).

FIG.13illustrates a sectional side view of a roller bearing arrangement500according to another embodiment of the present disclosure. The roller bearing arrangement500is similar to the roller bearing arrangement200ofFIG.7. Accordingly, similar features between the roller bearing arrangement200and the roller bearing arrangement500are designated by the same reference numbers. The roller bearing arrangement500includes a first snubber540similar to the first snubber240ofFIG.7. Specifically, the first snubber540is an extension542of the fan shaft26extending radially outward towards the radially inner surface112of the stub shaft110. Furthermore, the first snubber540is positioned between the radially outer surface50of the fan shaft26and the radially inner surface112of the stub shaft110. The first snubber540is spaced apart from the radially inner surface112of the stub shaft110so as to limit the radial movement range of the stub shaft110. However, the first snubber540is not axially aligned with the plurality of roller bearing elements130. Moreover, the roller bearing arrangement500further includes a second snubber550. The second snubber550is at an axially distinct position from the first snubber540.

Specifically, in the illustrated embodiment ofFIG.13, the second snubber550is an extension552of the fan shaft26extending radially outward towards the radially inner surface112of the stub shaft110. Further, the second snubber550is not axially aligned with the plurality of roller bearing elements130. In other words, in the illustrated embodiment ofFIG.13, each of the first and second snubbers540,550are not axially aligned with the plurality of roller bearing elements130. In some embodiments, shape and dimensions of the first and second snubbers540,550may be substantially similar.

The second snubber550includes a radially outer surface554. The second snubber550is spaced apart from the radially inner surface112of the stub shaft110so as to limit the radial movement range of the stub shaft110. Therefore, the radially outer surface554of the second snubber550and the radially inner surface112of the stub shaft110define a second radial clearance556therebetween. In some embodiments, the second radial clearance556is substantially equal to a first radial clearance546defined between a radially outer surface544of the first snubber540and the radially inner surface112of the stub shaft110. In some embodiments, the second radial clearance556is less than or equal to about 1 mm.

FIG.14Aillustrates a sectional front view of the fan shaft26ofFIG.13according to an embodiment of the present disclosure. In the illustrated embodiment ofFIG.14A, the fan shaft26includes a second snubber550A similar to the second snubber550ofFIG.13. Specifically, the second snubber550A extends radially outward from the radially outer surface50of the fan shaft26. However, the second snubber550A is a continuous extension552A having a circumferential extent of 360 degrees. In other words, the second snubber550A continuously extends in the circumferential direction (indicated by the arrow CD).

FIG.14Billustrates a sectional front view of the fan shaft26ofFIG.13according to another embodiment of the present disclosure. In the illustrated embodiment ofFIG.14B, the fan shaft26includes a second snubber550B similar to the second snubber550ofFIG.13. Specifically, the second snubber550B extends radially outward from the radially outer surface50of the fan shaft26. However, the second snubber550B includes a plurality of second snubber segments552B circumferentially spaced apart from each other. In other words, the second snubber550B discontinuously extends in the circumferential direction (indicated by the arrow CD).

It will be understood that the first snubber540and second snubber550can have different configurations. For example, one of the first540or second550snubber may be a continuous extension having a circumferential extent of 360 degrees, whilst the other of the first540or second550snubber may comprise a plurality of snubber segments circumferentially spaced apart from each other.

FIG.15illustrates a sectional side view of a roller bearing arrangement600according to another embodiment of the present disclosure. The roller bearing arrangement600is similar to the roller bearing arrangement300ofFIG.9. Accordingly, similar features between the roller bearing arrangement300and the roller bearing arrangement600are designated by the same reference numbers. Specifically, the first snubber640is an extension642of the stub shaft110extending radially inward towards the radially outer surface50of the fan shaft26. Furthermore, the first snubber640is positioned between the radially outer surface50of the fan shaft26and the radially inner surface112of the stub shaft110. The first snubber640is spaced apart from the radially outer surface50of the fan shaft26so as to limit the radial movement range of the stub shaft110. However, the first snubber640is not axially aligned with the plurality of roller bearing elements130. Moreover, the roller bearing arrangement600further includes a second snubber650. The second snubber650is at an axially distinct position from the first snubber640.

In the illustrated embodiment ofFIG.15, the second snubber650is an extension652of the stub shaft110extending radially inward towards the radially outer surface50of the fan shaft26. Further, the second snubber650is axially aligned with the plurality of roller bearing elements130. In some embodiments, shape and dimensions of the first and second snubbers640,650may be substantially similar.

Further, in the illustrated embodiment ofFIG.15, the second snubber650includes a radially inner surface654. In the illustrated embodiment ofFIG.15, the second snubber650is spaced apart from the radially outer surface50of the fan shaft26so as to limit the radial movement range of the stub shaft110. Therefore, the radially inner surface654of the second snubber650and the radially outer surface50of the fan shaft26define a second radial clearance656therebetween. In some embodiments, the second radial clearance656is substantially equal to a first radial clearance646defined between a radially inner surface644of the first snubber640and the radially outer surface50of the fan shaft26. In some embodiments, the second radial clearance656is less than or equal to about 1 mm.

FIG.16Aillustrates a sectional front view of the stub shaft110ofFIG.15according to an embodiment of the present disclosure. In the illustrated embodiment ofFIG.16A, the stub shaft110includes a second snubber650A similar to the second snubber650ofFIG.15. Specifically, the second snubber650extends radially inward from the radially inner surface112of the stub shaft110. However, the second snubber650A is a continuous extension652A having a circumferential extent of 360 degrees. In other words, the second snubber650A continuously extends radially in the circumferential direction (indicated by the arrow CD).

FIG.16Billustrates a sectional front view of the stub shaft110ofFIG.15according to an embodiment of the present disclosure. In the illustrated embodiment ofFIG.16B, the stub shaft110includes a second snubber650B similar to the second snubber650ofFIG.15. Specifically, the second snubber650B extends radially inward from the radially inner surface112of the stub shaft110. However, the second snubber650B includes a plurality of first snubber segments652B circumferentially spaced apart from each other. In other words, the second snubber650B discontinuously extends radially inward from the radially inner surface112of the stub shaft110in the circumferential direction (indicated by the arrow CD).

It will be understood that the first snubber640and second snubber650can have different configurations. For example, one of the first640or second650snubber may be a continuous extension having a circumferential extent of 360 degrees, whilst the other of the first640or second650snubber may comprise a plurality of snubber segments circumferentially spaced apart from each other.

In one aspect, the gas turbine engine10is for an aircraft (not shown) and includes any one of the roller bearing arrangements100,200,300,400,500,600ofFIGS.4A,7,9,11,13,15, respectively.