RU2788264C2 - Aviation gas-turbine engine with at least two cases and with power takeoff - Google Patents

Abstract

FIELD: aviation.

SUBSTANCE: aviation gas-turbine engine (10) contains at least low-pressure case (12a) and high-pressure case (12b), as well as power takeoff means (54) on the mentioned low-pressure case, which include first power takeoff shaft (54a), on a radial inner end of which first conical gear (54b) is installed, engaging with first conical wheel (54c) of angular transmission, rotated with the mentioned low-pressure case. At the same time, the gas-turbine engine additionally contains first annular support (76) of a bearing, located around the mentioned axis and rigidly connected to a stator. In this case, the mentioned first support of the bearing contains first essentially cylindrical section (76b), which is located coaxially with second essentially cylindrical section (54ca) of the mentioned wheel of angular transmission. At the same time, these first and second sections are guided, one inside the other, with support bearings (78, 80), and the mentioned wheel of angular transmission is rotated with the mentioned low-pressure case through annular damping part (86, 86’), which is made independent of the mentioned first support of the bearing.

EFFECT: invention allows for obtainment of compact engagement for power takeoff, independent of movements and case dimensions.

11 cl, 6 dwg

Description

FIELD OF TECHNOLOGY

The present invention relates to an aircraft gas turbine engine with at least two housings, equipped with power take-offs.

BACKGROUND OF THE INVENTION

The prior art is represented by documents EP-A1-1 701 019, WO-A1-99/47799, US-A1-2012/213629, FR-A1-2 645 907, FR-A1-3 026 775 and WO-A1-2015 /166187.

In the field of aircraft construction, many tasks are currently being set related to the possibility of using hybrid engines for civil aviation. The use of electrical energy is currently being considered not only to provide the functions of an aircraft, but also to electrify the functions of a gas turbine engine.

This conclusion leads to the study of hybrid engine architecture solutions that combine hydrocarbon fuel energy and electrical energy to provide rotation of the moving part (gas turbine engine fans) and power some drive and/or aircraft functions.

These architectures can be based in particular on high bypass and geared architectures, as well as multiple housings (2 or 3 housings). In these architectures, the gas turbine engine comprises a low pressure housing and a high pressure housing, each housing containing a shaft connecting the compressor rotor to the turbine rotor.

It is known to take power from one of these housings and supply this power to an electric generator for the production of electric energy, and this generator can additionally provide the function of a starter, that is, an electric drive when starting a gas turbine engine.

The power take-off means on the casing of a gas turbine engine classically include a power take-off shaft, at one end of which is mounted a bevel gear meshing with a bevel gear that is driven by the casing.

With currently known technologies, the application of a high power take-off on the low-pressure casing of a gas turbine engine, in particular with a high bypass ratio and with a gearbox, turns out to be very difficult. The size and dimension of the power take-offs are too large to allow for a use similar to that of the power take-offs on the pressure vessel. Thus, it is not possible to mount the bevel gear wheel directly on the shaft of the low pressure housing.

One solution would be to add a gear between the low pressure housing shaft and the power take-off shaft. However, the selection means will in this case be more complex and larger due to the greater number of necessary parts.

In this case, the gear system will include several gears, one of which will be mounted directly on the shaft of the low pressure housing. The guide block bearings of the housing will be axially spaced from this gear, which can create clearance problems when meshing between the gears.

In addition, the gas turbine engine with a high bypass ratio is characterized, in particular, by a small engine diameter (which has the appearance of a wasp waist). The primary flow path in the engine thus has a small internal diameter, which reduces in particular the free annular space between the housings and this flow path located around the housings. Here it is not possible to install the power take-offs, and in particular the aforementioned gear train, since they would take up too much space in the radial direction and would interfere with the flow path.

Finally, it has been noted that power take-offs typically transmit vibrations and dynamic stresses to journal bearings through the bearing mounts. These vibrations can adversely affect the operation and life of the support bearings as well as the gas turbine engine.

The present invention provides a solution to at least part of the above problems.

DISCLOSURE OF THE INVENTION

The invention proposes an aircraft gas turbine engine, wherein this gas turbine engine comprises at least a low-pressure housing and a high-pressure housing, as well as power take-off means at least on said low-pressure housing, while said power take-off means comprise a first power take-off shaft passing along essentially radially with respect to the longitudinal axis of rotation of said housings, wherein the first selection shaft has a radially inner end, on which the first bevel gear is mounted, meshing with the first bevel gear of the angular transmission driven by said low pressure housing, while the gas turbine engine additionally comprises the first annular bearing support located around said axis and rigidly connected to the stator,

characterized in that said first bearing support comprises a first substantially cylindrical section, which is located coaxially with the second essentially cylindrical section of said angular transmission wheel, wherein these first and second sections are guided one inside the other by support bearings, and said angular transmission wheel is driven into rotation said low-pressure housing through an annular damping piece, which is made independently of said first bearing support.

Thus, the present invention proposes a power take-off solution on a low pressure or LP casing.

It will be understood that the bevel gear wheel is driven by the housing through a damping piece configured to absorb vibrations and/or dynamic stresses due to its elastic deformability. In addition, the bearing pedestal is independent of this damping part, which thus does not transmit vibrations and/or dynamic stresses to the bearing pedestal as well as to the journal bearings to which the bearing pedestal is associated. This ensures optimum operation of the journal bearings and in particular the optimum guidance of centered parts by these journal bearings, such as the power take-off shaft, for example.

The claimed gas turbine engine may have one or more of the following features, considered separately from each other or in combination with each other:

said first and second portions are guided by two adjacent and axially spaced support bearings such as a ball bearing and a roller bearing,

- said first bearing support is fixed or connected to the guide casing of said selection shaft,

- said first bearing support has an overall L-shape in axial half-section, the radially inner periphery of which contains said first section and is designed to be at least partially covered by said angular gear wheel,

- said bevel gear wheel has an overall L-shape in axial half-section, the radially inner periphery of which contains said second section and is designed to be at least partially enclosed by said bearing support,

- said bevel gear wheel is driven by said low-pressure housing through an annular damping piece capable of elastic torsion deformation around said axis and/or in the radial direction.

- said bevel gear wheel is driven by said low-pressure housing through an annular damping piece having an annular row of through holes and/or having an annular section with a C-shaped axial half-section, the opening of which is oriented in the axial direction towards the inlet or the outlet,

- said first bevel gear and said first bevel gear wheel are located in the lubrication chamber of the pressure housing guide support bearing,

- the gas turbine engine also comprises power take-off means on said high-pressure housing, said power take-off means including a second power take-off shaft extending substantially radially with respect to said axis and containing a radially inner end on which a second bevel gear is mounted, engaging with the second bevel an angle gear wheel driven by said high pressure housing, wherein said second gear and said second angle gear wheel are located in said lubrication chamber,

- gas turbine engine contains an intermediate crankcase having an annular shell, around which there is an annular row of tubular racks, and this shell separates the mentioned lubrication chamber from the annular flow gas path located around this chamber, and is located in the axial direction between the mentioned first bearing support and the mentioned guide support bearing of the high-pressure housing, while said first and second selection shafts pass through various racks of this intermediate crankcase.

The subject of the present invention is also a method for modular assembly of the gas turbine engine described above, comprising the steps of:

(a) installing the first module of the gas turbine engine, and this first module contains at least part of the high pressure housing, at least part of the intermediate crankcase, part of the low pressure housing, including its main shaft, as well as the second power take-off means,

(b) installing the second module of the gas turbine engine and connecting it in axial translation, starting from the entrance, on and around the part of the mentioned first module, and this second module contains the mentioned first bearing support, as well as the mentioned first power take-off means, and

(c) installing the third module of the gas turbine engine and connecting it with axial translational movement, starting from the input, and this third module contains a part of the low pressure housing, including the output shaft, as well as said damping part, and this third module contains a part entering into in the radial direction between the parts of the mentioned first and second modules, and this assembly allows you to connect through the splines, on the one hand, the main and secondary shafts of the low-pressure housing and, on the other hand, through the other splines, the damping part mounted on the mentioned output shaft, with the mentioned wheel corner drive or with an intermediate piece already connected to this corner drive wheel.

DESCRIPTION OF FIGURES

The invention, its other details, features and advantages will be more apparent from the following description, presented as a non-limiting example with reference to the accompanying drawings, in which:

Fig. 1 is a schematic axial sectional view of an aircraft gas turbine engine with a high bypass ratio and with a reduction gear.

Fig. 2 is a schematic view of the power take-off means on the low pressure and high pressure casings of a gas turbine engine.

Fig. 3 is a partial schematic half-length view in axial section of power take-offs according to an embodiment of an aircraft gas turbine engine.

Fig. 4 is a view similar to FIG. 3 illustrating the steps for modularizing the gas turbine engine shown in this FIG. 3.

Fig. 5 is a partial schematic axial sectional view of power take-offs according to a version of an aircraft gas turbine engine.

Fig. 6 is a view similar to FIG. 5 illustrating the steps for modularizing the gas turbine engine shown in this FIG. five.

DETAILED DESCRIPTION

Referring first to FIG. 1, which schematically shows a double-casing and by-pass aircraft gas turbine engine 10.

Classically, the gas turbine engine 10 comprises a gas generator 12, at the inlet of which is a fan 14. The fan 14 is surrounded by a fan housing 16, which is part of a nacelle 18 located around and along the main part of the gas generator 12.

In this case, the gas generator 12 comprises two housings, namely a low pressure or LP housing 12a and a high pressure or HP housing 12b. Each housing includes a compressor and a turbine.

The terms "inlet" and "outlet" should be considered with respect to the main direction F of the flow of gases in the gas turbine engine 10, and this direction F runs parallel to the longitudinal axis A of the gas turbine engine.

From inlet to outlet, gas generator 12 comprises a low pressure compressor 20, a high pressure compressor 22, a combustor 24, a high pressure turbine 26 and a low pressure turbine 28.

The fan 14 contains an annular row of blades 30 driven by a fan shaft 32, which is connected to the rotor of the low pressure housing 12a through a reducer 33. The gas flow passing through the fan (arrow F) is divided at the inlet of the gas generator 12 by an annular nose 34 into a radially inner a stream, called primary stream 36, which feeds gas generator 12, and to a radially outer annular stream, called secondary stream 38, which passes between gas generator 12 and nacelle 18 and provides the bulk of the turbine engine thrust.

Between the low and high pressure compressors 20, 22 there is an intermediate crankcase 40, which structurally connects the gas generator 12 with the fan crankcase 16 and with the nacelle 18. The intermediate crankcase 40 contains an annular row of radially internal racks 42 passing in the primary flow 36 between the flow paths of the low and high pressure 20, 22, and an annular row of radially outer struts 44 passing in the secondary flow 38. The struts 42, 44 are usually made in a limited number (less than ten), are tubular, and various auxiliary pipelines and networks pass through them.

The rotor of the low pressure casing 12a as well as the fan shaft 32 are guided by support bearings 46. The rotor of the high pressure casing 12b is guided by support bearings 48. The support bearings 46, 48 are ball bearings or roller bearings and each contain an inner ring mounted on a guided shaft, an outer ring mounted on an annular bearing support and a rolling element between the rings.

The bearing supports are located around axis A and are fixed parts connected to the stator and, for example, to the intermediate housing 40 in the case of support ball bearings 46a, 48a guiding the input ends of the LP and HP rotors. Each of the LP and HP rotors contains a main shaft and possibly attached annular parts such as trunnions, etc.

The gas turbine engine 10 includes power take-off means 50 on the HP housing 12b, which include a power take-off shaft 50a having a substantially radial orientation with respect to axis A. The radially inner end of the shaft 50a is located near the HP housing and includes a bevel gear 50b mounted on it, which engages with the bevel gear wheel 50c connected to the input end of the shaft 12ba of the ID housing 12b. The radially outward end of the shaft 50a is connected to the gears of an accessory box 52, commonly referred to as an AGB, short for Accessory Gear Box (FIGS. 1 and 2). The box 52 of the units is located in the annular space located around the gas generator 12 between the flow paths of the primary and secondary flows 36, 38. The shaft 50a passes through the flow path of the primary flow and through one of the racks 42 of the intermediate crankcase 40.

In addition, the gas turbine engine 10 includes power take-off means 54 on the LP housing 12a, including a power take-off shaft 54a, which has a substantially radial orientation with respect to axis A. The radially inner end of the shaft 54a is located near the LP housing and contains a bevel gear mounted thereon. 54b, which engages with the bevel gear wheel 54c connected to the input end of the shaft 12aa of the ID housing 12a. The radially outer end of the shaft 54a is connected to the gears of another assembly box 56, commonly referred to as the AGB (FIGS. 1 and 2). The box 56 of the units is in the above annular space, and the shaft 54a passes through the flow path of the primary flow and through another of the racks 42 of the intermediate casing 40.

As shown more clearly in FIG. 3, the guide support bearing 48a of the shaft 12ba of the HP housing 12b is located in the annular lubrication chamber E of this support bearing. The axial half-section of this chamber E has a general triangular shape. In this case, it is limited on its inner periphery by the input end of the shaft 12ba of the HP housing 12b and the portion of the shaft 12aa of the ID housing 12a extending axially through the shaft 12ba of the HP housing 12b. In addition, on the inlet side, chamber E is limited by an annular hood 60 and, on the outlet side, by a truncated conical shell 62 of the intermediate crankcase 40, the radially outer peripheral surface 62a of which limits the flow path of the primary flow 36 from the inside.

Hood 60 has a general shape of a truncated cone, in which the input end of the smaller diameter surrounds the aforementioned section of the shaft 12aa of the housing ND 12a, and the output end of the larger diameter is fixed, for example, by bolts 74, at the input end of the larger diameter of the shell 62. At the output end of the smaller diameter of the shell 62 an outer ring 48aa of the thrust bearing 48a is mounted, with its inner ring 48ab rotatably connected to the input end of the shaft 12ba of the HP housing 12b.

Thus, the chamber E is limited by the parts of the rotor and the parts of the stator. Chamber E is sealed with O-rings at the level of the gaps between the parts of the rotor and the stator. This applies to the gap between the hood 60 and the trunnion 61, connected in rotation with the ND body 12a, where the labyrinth seals are located, indicated by the position 64. This also applies to the gap between the intermediate housing 40 and the shafts 12aa, 12ba of the LP and HP housings, while the labyrinth seals 66, 67 are located between the sealing ring 68 fixed on the crankcase 40 and these housings 12a, 12b. The ring 68 is fixed with its radially outer end on the crankcase 40, and at its radially inner end there are abradable elements, of which the first, input element interacts with the protruding annular scallops of the gasket 66 located on the annular part 69 of the ND 12a housing, and the second, output element interacts with protruding annular gasket scallops 67 located at the input end of the shaft 12ba of the HP 12b housing.

With regard to the power take-off means 50 on the HP shaft 12b, the bevel wheel 50c, the pinion 50b, as well as the radially inner end of the shaft 50a (not shown here) are located in chamber E.

Similarly, with regard to the power take-off means 54 on the OD shaft 12a, the bevel wheel 54c, pinion 54b as well as the radially inner end of the shaft 54a are located in chamber E.

The shafts 50a, 54a may be inclined with respect to a plane perpendicular to the axis A of the gas turbine engine and may have similar angles of inclination as in the example shown.

As mentioned above and shown in FIG. 2, the shafts 50a, 54a do not pass through the same struts of the intermediate casing 40 and thus form an angle with each other. For example, they are located respectively in the racks located between 6 o'clock and 8 o'clock in analogy with the clock face. Gear 50b is shown in FIG. 3 with a dotted line for a better understanding of the invention, but it is not in the sectional plane of the drawing.

The engagement between the gear 50b and the bevel gear wheel 50c is substantially on a circle C1 whose diameter is smaller than the diameter of the engagement circle C2 of the gear 54b with the wheel 54c.

The ring 68 includes a through hole 70 through which a gear 50b passes which can rotate in the hole. As noted above, this opening 70 is shown to facilitate understanding of the invention, but it is not in the sectional plane of the drawing.

The radially inner end of the shaft 54a is guided by a casing 72 fixed to the hood 60 and to the intermediate casing 40. In this case, the casing 72 comprises two coaxial support bearings, respectively a roller bearing and a ball bearing, and includes a radially outer annular flange 72a of attachment to the radially outer annular flange 60a of the hood 60.

The flanges 72a, 60a are fastened together and even fixed on the intermediate casing 40 by means of bolts 74, and in this case, between these flanges 72a, 60a, a radially outer annular flange 76a of the annular bearing 76 is inserted.

Mounted on the support 76 are guide support bearings 78, 80 of the wheel 54c of the angular gear. The wheel 54c comprises a cylindrical wall 54a connected to outer races 78a, 80a of support bearings 78, 80, which in this case are adjacent and axially spaced apart. A roller bearing 78 is at the inlet and the other support bearing 80 at the outlet is a ball bearing. The inner rings 78b, 80b of the support bearings 70, 80 are rigidly connected to the substantially cylindrical wall 76b of the bearing support 76. Here, on the contrary, the support bearing 78 is a roller bearing and can be located at the output, and the other support bearing 80, in this case at the input, is a ball bearing.

Thus, it is understood that the wall 76b of the bearing support 76 extends radially within the wall 54ca of the wheel. Wall 76b is connected to flange 76a via a truncated tapered wall 76c that expands radially outward from inlet to outlet. As shown in FIG. 3, wall 76c extends along cowling 60 and forms an annular space with it, in which an oil line 82 can pass. a series of oil jets 84 communicating with a line 82. The jets 84 are configured to spray oil onto the support bearings 78, 80, which oil is sprayed onto the radially inner surface of the wall 76b and passes to the support bearings 78, 80 through the holes 76ba of the wall 76b.

Thus, it is understood that the bearing support 76 is rigidly connected to the cowl 60 and is part of the stator of the gas turbine engine. The wheel 54c of the angular gear is connected in rotation with the body ND 12a through the annular damping piece 86.

In the example shown, item 86 is fixed to the housing ND 12a. It comprises a substantially cylindrical inlet section 86a which is clamped in the axial direction between the trunnion 61 and the piece 69. In addition, it comprises an outlet section 86b of larger diameter, which contains, on the one hand, an annular row of through holes 88 and, on the other hand, an annular row of outer splines 90. Holes 88 are positioned and sized to give component 86 some torsional flexibility and to allow the component to dampen vibrations and/or dynamic stresses during operation. The splines 90 co-operate with the corresponding splines of the inner periphery of the annular coupling 92, the outer periphery of which is fixed on the corner gear wheel 54c and, for example, is sandwiched between the outer ring 80a of the support bearing 80 and the nut 94 mounted and screwed radially inside the wall 54ca of the corner gear wheel 54c. A spacer 96 is inserted between the outer races 78a, 80a of the support bearings 78, 80 to hold them in position and apart. Similarly, a spacer 98 is inserted between the inner races 78b, 80b of the support bearings 78, 80, and a nut 100 is mounted and screwed radially outside the cylindrical wall 76b of the bearing support 76.

Sets of slots 102 are also provided for connecting in rotation the trunnion 61, the damping part 86 and the part 69 with the rest of the housing ND 12a. The trunnion 61, the damping piece 86 and the piece 69 contain internal splines that interact with the outer splines of the shaft 104 of the LP body, which, in turn, interacts with another set of splines 106 with the shaft 12aa of the ND body 12a.

The shaft 104 may be the input shaft of the gearbox 33 or the fan shaft 14 if the gas turbine engine does not include a gearbox.

In FIG. 4 shows very schematically the modular assembly of the gas turbine engine 10. In this case, three modules are shown, which are assembled in translation towards each other and intersect each other in the axial direction.

Preferably, the modules are connected to each other in advance and then mounted on top of each other. The first module B, shown on the right in the drawing, comprises at least part of the high pressure housing 12b, at least part of the intermediate casing 40, part of the low pressure housing 12a with its main shaft 12aa, and the second power take-off means 50.

The second module C, shown in the center, includes a hood 60, a bearing support 76, a casing 72, a power take-off means 54, and a connecting piece 92. It should be noted that the support 76 is provided with guide support bearings 78, 80 of the bevel gear wheel 54c, as was stated above.

The third module D, on the left, contains a shaft 104, a trunnion 61 and parts 86, 69. This third module is inserted axially inside the second module C until the splines 90 of the damping part 86 and the connecting part 92 begin to interact with each other.

Thereafter, the assembly containing the second and third modules C, D is mounted on the first module B by means of an axial translational movement from the inlet to the outlet until the splines 106 of the shafts 104, 12aa begin to interact with each other.

Fig. 5 and 6 are similar to Figs. 3 and 4 and illustrate an embodiment of the invention. This version basically has the same features as those described above for the first embodiment.

The main difference is that the cylindrical portion 54ca of the bevel wheel 54c is in this case radially inside (and not outside) the cylindrical wall 76b of the bearing support 76 .

It will be understood that the outer rings 78a, 80a of the support bearings 78, 80 are fixed in this case to the wall 76b, and the inner rings 78b, 80b are fixed to the wall 54ca.

The radially outer flange 76a of the bearing support 76 is fixed to the radially inner annular flange 72a' of the casing 72. The wall 76c of the bearing support 76 includes a through hole 76d for the passage and rotation of the gear 54b, since the wall 76 in this case extends radially inside the radially inner end of the selection shaft 54a power.

The wall 54ca of the bevel wheel 54c is disposed around the OD body 12a, with the bevel wheel rotatably connected to the BE body through a single annular piece which is the damping piece 86'. This part 86' is in this case clamped in the axial direction between the pin 61 at the inlet and the nut 108 at the outlet. The assembly is mounted on shaft 104.

Part 86' includes a radially inner cylindrical section 86a' located between the trunnion 61 and the nut 108 and connected through internal splines 86aa' with the corresponding outer splines of the shaft 104, and a radially external flexible section 86b'. This section 86b' has an axial C-shaped half-section, the opening of which is oriented in the axial direction, in this case towards the entrance. This section 86b' has, on its outer periphery, outer splines 90 which co-operate with corresponding inner splines of the bevel wheel wall 54ca.

The oil for lubricating the support bearings 78, 80 in this case does not enter through the inlet of the bevel gear wheel 54c, but through the outlet. In this case, the oil jets 84' are located in the annulus located between the wall 54ca of the bevel gear wheel 54c and the ring 68.

The labyrinth-type seals 64, 64' in this case are, on the one hand, between the hood 60 and the trunnion 61 and, on the other hand, between the outlet end of the part 86' and the inlet end of the sealing ring 68. Another labyrinth seal 67 is located between this sealing ring 68 and the input end of the shaft 12ba of the HP housing 12b.

In FIG. 6 shows very schematically the modular assembly of this version of the gas turbine engine 10. In this case, three modules are shown, which are assembled in translation towards each other and intersect each other in the axial direction.

Preferably, the modules are connected to each other in advance and then mounted on top of each other. The first module B, shown on the right in the drawing, comprises at least part of the high pressure housing 12b, at least part of the intermediate casing 40, part of the low pressure housing 12a with its main shaft 12aa, and the second power take-off means 50.

The second module C, shown in the center, includes a hood 60, a bearing support 76, a casing 72, and power take-offs 54.

The third module D, on the left, contains shaft 104, trunnion 61 and part 86'. This third module is inserted axially inside the second module C until the splines 90 of the damping piece 86 and the bevel gear wheels 54c begin to interact with each other.

Thereafter, the assembly containing the second and third modules C, D is installed at least partially around the first module B by means of an axial translational movement from the inlet to the outlet until the splines 106 of the shafts 104, 12aa begin to interact with each other.

EFFECT: invention makes it possible to perform power take-off on LP and HP housings in the same zone and, in particular, in the same chamber. The axial locking of each of these housings is provided by a thrust ball bearing. One of these bearings, namely the HP shaft thrust bearing (indicated 48a) is located in this chamber E, and the other bearing, namely the HP housing thrust bearing, is located at the inlet of this chamber and, therefore, at a distance (it is surrounded in Fig. 1) . This situation results in a distance between the LP housing ball bearing and the power take-off on this housing. This removal is compensated for by splined connection and fastening of the bearing support 76 and casing 72 on the same crankcase.

EFFECT: invention makes it possible to obtain a compact engagement for power take-off, independent of movements and dimensions of the LP body. Gear 54b is driven by an intermediate piece 86, 86' which uses a flexible portion to isolate the engagement from the rest of the motor. Chamber E is common for engagement and support bearings, which are lubricated by jets 84, 84'.

Claims (15)

1. Aircraft gas turbine engine (10), moreover, this gas turbine engine contains at least a low pressure housing (12a) and a high pressure housing (12b), as well as power take-off means (54) on at least the mentioned low pressure housing, while said power take-off means comprise a first power take-off shaft (54a) extending substantially radially relative to the longitudinal axis (A) of rotation of said housings, wherein the first take-off shaft has a radially inner end carrying a first bevel gear (54b) meshing with the first bevel wheel (54c) an angular gear driven by said low-pressure housing, wherein the gas turbine engine further comprises a first annular bearing support (76) extending around said axis and rigidly connected to the stator, characterized in that said first bearing support comprises a first substantially cylindrical section (76b) which is located coaxially with a second essentially cylindrical section (54ca) of said bevel gear wheel, these first and second sections being guided one inside the other by bearings (78, 80 ), and said bevel gear wheel is driven by said low pressure housing through an annular damping piece (86, 86') which is made independent of said first bearing support. 2. The gas turbine engine (10) according to claim 1, wherein said first and second portions (76b, 54ca) are guided by two adjacent and axially spaced bearings (78, 80), such as a ball bearing and a roller bearing. 3. Gas turbine engine (10) according to claim 1 or 2, in which said first bearing support (76) is fixed or connected to the guide casing (72) of said selection shaft (54a). 4. Gas turbine engine (10) according to one of paragraphs. 1-3, in which said first bearing support (76) has an overall L-shape in axial half-section, the radially inner periphery of which contains said first section (76b) and is designed to be at least partially covered by said angular gear wheel (54c). 5. Gas turbine engine (10) according to one of paragraphs. 1-3, in which said bevel gear wheel (54c) has an overall L-shape in axial half-section, the radially inner periphery of which contains said second section (54ca) and is designed to be at least partially enclosed by said bearing support (76). 6. Gas turbine engine (10) according to one of paragraphs. 1-5, wherein said bevel gear wheel (54c) is driven by said low pressure housing (12a) through an annular damping piece (86,86') capable of elastically deforming torsion around said axis (A) and/or in a radial direction. 7. Gas turbine engine (10) according to one of paragraphs. 1-6, wherein said bevel gear wheel (54c) is driven by said low pressure housing (12a) through an annular damping piece (86, 86') having an annular row of through holes (88) and/or having an annular section (86b ') with a C-shaped axial half-section, the opening of which is oriented in the axial direction towards the entrance or towards the exit. 8. Gas turbine engine (10) according to one of paragraphs. 1-7, in which said first bevel gear (54b) and said first bevel gear (54c) are located in the lubrication chamber (E) of the pilot bearing (48a) of the high pressure housing (12b). 9. Gas turbine engine (10) according to claim 8, which also contains power take-off means (50) on said high pressure housing (12b), moreover, these selection means comprise a second power take-off shaft (50a) extending essentially radially with respect to said axis (A) and comprising a radially inner end carrying a second bevel gear (50b) meshing with a second bevel gear (50c) of an angular gear driven by said pressure housing, wherein said second gear and said second bevel gear are located in said lubrication chamber (E). 10. Gas turbine engine (10) according to claim 9, which contains an intermediate crankcase (40) having an annular shell (62), around which an annular row of tubular racks (44) is located, and this shell separates the said lubrication chamber (E) from the annular a gas flow path passing around this chamber and passing in the axial direction between said first bearing support (76) and said guide bearing (48a) of the high pressure housing (12b), while said first and second selection shafts (50a, 54a) pass through various racks of this intermediate crankcase. 11. A method for modular assembly of a gas turbine engine (10) according to claim 10, comprising steps in which (a) install the first module (B) of the gas turbine engine, and this first module contains at least part of the high pressure housing (12b), at least part of the intermediate crankcase (40), part of the low pressure housing (12a), including its the main shaft (12aa), as well as the second power take-off means (50), (b) install the second module (C) of the gas turbine engine and connect it with axial translational movement, starting from the inlet, on and around the part of the mentioned first module (B), and this second module contains the mentioned first support (76) of the bearing, as well as the mentioned first means (54) of power take-off, (c) install the third module (D) of the gas turbine engine and connect it with axial translational movement, starting from the input, and this third module contains a part of the low pressure housing, including the secondary shaft (104), as well as the said damping part (86, 86 '), and this third module contains a part that extends in the radial direction between the parts of the mentioned first and second modules (B, C), and this assembly allows you to connect through splines (106), on the one hand, the main and secondary shafts (12aa, 104 ) of the low-pressure housing (12a) and, on the other hand, through other splines (90) a damping piece (86, 86') carried on said output shaft (104), with said angular gear wheel (54c) or with an intermediate piece ( 92) already connected to this corner gear wheel.

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