Aircraft turbomachine with mechanical reducer and contrarotative turbine

Abstract

Aircraft turbomachine with mechanical reducer and counter-rotating turbine are described. The turbomachine includes a fan driven in rotation by a fan shaft, a mechanical reducer with epicyclic gear train, a gas generator comprising a counter-rotating turbine, a first turbine shaft of which is coupled to an input shaft of the reducer and to a pin, and a second turbine shaft of which is coupled to the fan shaft. The guidance of the reducer input shaft is provided by a first ball bearing, the guidance of the pin is provided by a second roller bearing, and the guidance of the first shaft is provided by a third roller bearing axially interposed between the first and second bearings.

Claims

1. An aircraft turbomachine with a mechanical reducer and a counter-rotating turbine, comprising: a fan driven in rotation by a fan shaft; the mechanical reducer with an epicyclic gear train; a gas generator including the counter-rotating turbine, a first turbine shaft coupled to an input shaft of the reducer and to a pin of a low-pressure compressor of the gas generator, and a second turbine shaft coupled to the fan shaft and to an output shaft of the reducer; a first ball bearing located downstream of the reducer between the input shaft and an input casing, the first ball bearing guiding the input shaft of the reducer; a second roller bearing mounted between the pin and an intermediate casing of the turbomachine, the second roller bearing guiding the pin; and a third roller bearing axially interposed between the first and second bearings and radially located at an intermediate position between the first shaft and the input shaft, the third roller bearing guiding the first shaft.

2. The turbomachine according to claim 1, further comprising an upstream roller bearing and a downstream ball bearing, the upstream roller bearing and downstream ball bearing located upstream of the reducer, between the fan and output shafts and the input casing, the upstream roller bearing and downstream ball bearing guiding the fan shaft and the output shaft.

3. The turbomachine according to claim 1, wherein the first bearing has an average diameter greater than the average diameter of the second bearing, which is itself greater than the average diameter of the third bearing.

4. The turbomachine according to claim 1, wherein the pin is engaged on the first shaft and axially fixed thereto by a first nut screwed on the first shaft.

5. The turbomachine according to claim 4, wherein the fan shaft and the output shaft are axially fixed on the second shaft by a second nut screwed on the second shaft.

6. The turbomachine according to claim 1, wherein the first shaft is connected at a downstream end to a first rotor of the counter-rotating turbine, and the second shaft is connected at a downstream end to a second rotor of the counter-rotating turbine, the first turbine rotor comprising wheels interposed between wheels of the second turbine rotor.

7. The turbomachine according to claim 6, wherein the first and second turbine rotors are surrounded by a casing; and a downstream end of the casing includes a flange for fixing to an exhaust casing of the turbomachine.

8. The turbomachine according to claim 1, wherein the first turbine shaft is coupled to an input shaft of the reducer such that the first shaft is integral in rotation with the input shaft.

9. An aircraft turbomachine with a mechanical reducer and a counter-rotating turbine, comprising: a fan driven in rotation by a fan shaft; the mechanical reducer with an epicyclic gear train; a gas generator including the counter-rotating turbine, a first turbine shaft coupled to an input shaft of the reducer and to a pin of a low-pressure compressor of the gas generator, and a second turbine shaft coupled to the fan shaft and to an output shaft of the reducer; a first ball bearing located downstream of the reducer between the input shaft and an input casing, the first ball bearing guiding the input shaft of the reducer; a second roller bearing mounted between the pin and an intermediate casing of the turbomachine, the second roller bearing guiding the pin; and a third roller bearing axially interposed between the first and second bearings and radially located at an intermediate position between the first shaft and the input shaft, the third roller bearing being mounted between the second shaft and the first shaft.

10. An aircraft turbomachine with a mechanical reducer and a counter-rotating turbine, comprising: a fan driven in rotation by a fan shaft; the mechanical reducer with an epicyclic gear train; a gas generator including the counter-rotating turbine, a first turbine shaft coupled to an input shaft of the reducer and to a pin of a low-pressure compressor of the gas generator, and a second turbine shaft coupled to the fan shaft and to an output shaft of the reducer; a first ball bearing located downstream of the reducer between the input shaft and an input casing, the first ball bearing guiding the input shaft of the reducer; a second roller bearing mounted between the pin and an intermediate casing of the turbomachine, the second roller bearing guiding the pin; and a third roller bearing axially interposed between the first and second bearings and radially located at an intermediate position between the first shaft and the input shaft, the third roller bearing being located in between the second shaft and the input shaft.

Description

DESCRIPTION OF THE DRAWINGS

(1) The disclosure shall be better understood and other details, characteristics and advantages of the disclosure shall appear more clearly when reading the following description by way of non-limiting example and with reference to the annexed drawings in which:

(2) FIG. 1 is a schematic axial cross-sectional view of a turbomachine with reducer and counter-rotating turbine according to an embodiment of the disclosure,

(3) FIG. 1a is a schematic axial cross-sectional view in a larger scale and more detailed of a part of the exemplary turbomachine in FIG. 1,

(4) FIGS. 2a and 2b are schematic axial cross-sectional views and on a larger scale of a fixing system according to an embodiment of the disclosure,

(5) FIGS. 3 to 9 are similar views to that of FIG. 1 and illustrate steps in a disassembly method according to embodiments of the disclosure,

(6) FIGS. 4a, 7a, 8a and 9a are similar views to that of FIG. 1a as part of the method steps.

DETAILED DESCRIPTION

(7) FIG. 1 shows a very schematic representation of a turbomachine 10 with counter-rotating turbine and reducer for an aircraft.

(8) This turbomachine 10 includes, from upstream to downstream, in the direction of flow of gases, a fan 12, a low-pressure compressor 14, a high-pressure compressor 16, an annular combustion chamber 18, a high-pressure turbine 20 and a counter-rotating turbine 22.

(9) The reference 23 refers to an input casing located between the fan 12 and the compressor 14. The reference 24 refers to an intermediate casing located between the compressors 14 and 16, and the reference 26 refers to a turbine casing (TVF type) located between the turbines 20 and 22. Finally, the reference 28 refers to an exhaust casing (TRF type).

(10) The rotor of the high-pressure turbine 20 drives the rotor of the high-pressure compressor 16 in rotation by a high-pressure shaft 30 which is centered and guided in rotation by bearings, such as an upstream ball bearing 32 and a downstream roller bearing 34. The bearing 32 is mounted between an upstream end of the shaft 30 and the intermediate casing 24, and the bearing 34 is mounted between a downstream end of the shaft 30 and the turbine casing 26.

(11) The counter-rotating turbine 22 comprises a first rotor 22a, the wheels 22aa of which are configured to rotate in a first direction of rotation and are connected to a first turbine shaft 36, and a second rotor 22b, the wheels 22ba of which are configured to rotate in an opposite direction of rotation and are connected to a second turbine shaft 38. The wheels 22ba are interposed between the wheels 22aa.

(12) The first and second rotors 22a, 22b are surrounded by a casing 29 the downstream end of which includes a flange for fixing to the exhaust casing 28.

(13) The first shaft 36 extends axially inside the shaft 30 and drives the rotor of the low-pressure compressor 14 in rotation. This first shaft 36 is also coupled to an input shaft 36a which is engaged with a solar or planetary mechanical reducer 42 with an epicyclic gear train. The input shaft 36a is thus integral in rotation with the shaft 36.

(14) The second shaft 38 extends axially inside the shaft 36 and drives the fan 12 in rotation. This shaft 38 is coupled to a fan casing 39 as well as an output shaft 38a which is engaged with the ring of the reducer 42.

(15) The reducer 42 also includes satellites engaged respectively with the solar and the ring and carried by a satellite carrier 42a which is fixed to the input casing 23.

(16) The first shaft 36 is centered and guided upstream by a bearing 48 mounted between the first shaft 36 and the intermediate casing 24, and downstream by a bearing 50 shown between the first shaft 36 and the turbine casing 26.

(17) The second shaft 38 is centered and guided upstream by a bearing 52 mounted between the second shaft 38 and the first shaft 36, and downstream by a bearing 54 shown between the second shaft 38 and the exhaust casing 28.

(18) The bearings 50 and 54 are roller bearings in the example shown.

(19) The fan shaft 39 and the output shaft 38a are guided by an upstream roller bearing 56 and a downstream ball bearing 58. These bearings 56, 58 are located upstream of the reducer 42, between the fan 39 and output 38a shafts, on the one hand, and the input casing 23, on the other hand. Downstream of the reducer 42, a bearing 60 guides the input shaft 36a in rotation and is mounted between this shaft and the input casing 23.

(20) FIG. 1a is a larger and more detailed view of the area Z of FIG. 1 and provides a better view of the bearings 48, 52 and 60 and their respective positions.

(21) The second shaft 38 comprises at an upstream end an upstream screwing portion 62 with outer thread and a downstream coupling portion 64 with outer straight splines.

(22) The fan shaft 39 and output shaft 38a are fixed to each other or formed in one piece and comprise of a downstream end that comprises of a downstream coupling portion 66 with inner straight spline. The portions 64, 66 are configured to cooperate together by complementarity of shapes in order to secure the shafts 38a, 39 and 38 in rotation.

(23) This downstream end of the fan 39 and output 38a shafts comprises an annular edge 68 oriented radially inward and intended to be clamped axially (directly or indirectly) against a cylindrical shoulder of the shaft 38, by means of a nut 70 with inner thread screwed on the portion 62 from upstream. This nut 70 is called “second” nut because it is attached to the second shaft 38.

(24) The portion 66 further comprises a downstream wall 72 extending radially outward and carrying on its outer periphery an inner ring 52a of the roller bearing 52.

(25) The first shaft 36 comprises an upstream end which includes a downstream coupling portion 84 with outer straight splines, a screwing intermediate portion 86 with outer thread, and a substantially cylindrical upstream retaining portion 88, these portions 84, 86, 88 being better visible in FIGS. 2a and 2b.

(26) A pin 90 of the low-pressure compressor 14 is mounted on the upstream end of the first shaft 36 and comprises inner straight splines configured to cooperate with the coupling portion 84 to be rotationally integral with the first shaft 36.

(27) A nut 92 for blocking the pin 90 called “first” nut because it is attached to the first shaft 36, comprises an upstream gripping section 92a configured to be engaged with a screwing/unscrewing tool of the nut, a screwing intermediate section 92b with inner thread configured to cooperate with the intermediate portion 86, and a downstream retaining section 92c which is here substantially cylindrical (FIGS. 2a and 2b).

(28) FIG. 2a shows the nut 92 in its screwed and tightened position for blocking the pin 90. The nut 92 is supported axially on the pin 90 and fixes it axially on the shaft 36. FIG. 2b shows the nut 92 in its fully unscrewed position, when the threads of the nut and portion 86 are not engaged with each other. In this position, the nut 92 is retained radially by supporting its downstream section 92c on the pin 90 and/or the first shaft 36. In the example shown, the nut 92 is further retained radially by supporting its section 92b on the portion 88 of the shaft 36.

(29) The nut 92 comprises outer ring lips 92d from a first labyrinth seal. In the clamping position of FIG. 2a, the lips 92d are surrounded by an annular layer 94 of abradable material and its ability to cooperate by friction in operation with it. In the example shown, the layer 94 is supported by a cylindrical edge 52aa oriented downstream of the inner ring 52a of the bearing 52.

(30) The pin 90 comprises a cylindrical coupling wall 90a comprising inner splines for coupling to the shaft 36, as well as a radial wall 90b which extends radially outward from the upstream end of the wall 90a and which comprises or carries a first downstream oriented cylindrical edge 90ba and internally delimiting an annular space E1 configured to receive oil from at least one nozzle 96 (FIG. 1a).

(31) The radial wall 90b has a series of orifices 90bb1 passing through the bottom of this space E1 to allow oil to pass from downstream to upstream, inside a lubrication enclosure of the bearing 52.

(32) The orifices 90bb1 open upstream into another annular space E2 which is part of the lubrication enclosure and which is internally delimited by a second cylindrical edge 90bc upstream oriented of the wall 90b, or an element attached to the wall 90b.

(33) As is best seen in FIG. 2b, the upstream end of this edge 90bc surrounds the downstream end of the edge 52aa of the inner ring 52a and is itself surrounded by the downstream end of another downstream cylindrical edge 52ab of the inner ring 52a. The edges 52aa, 52ab define another annular space E3 between them.

(34) The oil sprayed by the nozzle into the space E1 is intended to flow through the orifices 90bb1 to reach the space E2. This oil then flows due to centrifugal forces along the edge 90bb and then the edge 52ab into the space E3. It then reaches channels 52ac of the inner ring 52a visible in FIG. 2b, in order to join the bearings 52 and ensure their lubrication.

(35) The first seal formed by the lips 92d and the layer 94 seals the lubrication enclosure of the bearing 52, which is further sealed by a second seal visible in FIG. 1a and provided between another cylindrical edge 90bc upstream oriented of the radial wall 90b, which extends around the edge 90bb, and an outer ring 52b of the bearing 52. This second seal includes outer annular lips carried by the edge 90bc and cooperating with a layer of abradable material carried by the outer ring 52b.

(36) On its outer periphery, the pin 90 comprises a first annular ferrule 97 of generally frustoconical shape, flared downstream, and carrying or forming on its outer periphery an inner ring of the bearing 48, the outer ring of which is carried by or formed on the inner periphery of an annular bearing support 98 fixed to the intermediate casing 24. In addition, a labyrinth seal 99 can be provided between the ferrule 97 and the intermediate casing 24.

(37) On its outer periphery, the pin 90 also comprises a second annular ferrule 100 of generally frustoconical shape, flared upstream, and carrying a radially outer annular flange for fixing to the rotor of the low-pressure compressor 14, on the one hand, and to the input shaft 36a of the reducer, on the other hand.

(38) The input shaft 36a comprises a downstream end which is configured, on the one hand, to form or carry the inner ring 60a of the bearing 60, and the outer ring 52b of the bearing 52, and on the other hand, to be fixed to the pin 90, and to the above-mentioned ferrule 100. This downstream end of the shaft 36a is overthickened and may resemble a pin.

(39) In the example shown, the input shaft 36a comprises an outer cylindrical track 36aa for mounting the inner ring 60a of the bearing 60, the outer ring of which is fixed to an annular bearing support 101 integral with the input casing 23, and an inner cylindrical track receiving or forming the outer ring 52b of the bearing 52.

(40) FIG. 1a shows that the bearings 60, 52 and 48 are close to each other and arranged in relation to each other to optimize the dimensions of the assembly.

(41) The bearing 60 has an average diameter greater than the average diameter of the bearing 48, which is itself greater than the average diameter of the bearing 52. The average diameter is measured at the geometric center of the rolling members of the bearing. The bearing 52 is axially interposed between the bearing 60, located upstream, and the bearing 48, located downstream.

(42) The first nut 70 is located upstream of the bearing 60 and the second nut 92 is located between the bearings 52, 48.

(43) FIG. 3 and following illustrate the steps of a method according to the disclosure of disassembly of the turbomachine 10.

(44) A first step illustrated in FIG. 3 is to remove an inlet cone 104 (visible in FIG. 1) from the turbomachine 10. This inlet cone 104 is centered on the axis of the turbomachine 10 and is fixed on the hub of the fan 12, by screws. These screws are unscrewed and the cone 104 is removed from the upstream, allowing access to the inside of the second shaft 38 and the second nut 70.

(45) The next step illustrated in FIGS. 4 and 4a is to unscrew and remove the second nut 70. Removing this nut 70 makes it possible to separate the shaft 38, on the one hand, from the fan shaft 39 and the output shaft 38a, on the other hand, and thus to consider a removing of the shaft 38 by axial translation from the downstream part of the turbomachine.

(46) Before considering removing the shaft 38, the exhaust casing 28 is removed. The latter is therefore disconnected from the casing 29 and removed (FIG. 5).

(47) The removal of shaft 38 can be carried out at the same time as the last wheel 22ba of the rotor 22b of the turbine 22b, or independently of this wheel. This wheel 22ba is separated from the rest of the rotor 22b and then removed in FIG. 6, to allow the shaft 38 to be removed (FIGS. 7 and 7a).

(48) Removing the shaft 38 gives access to the nut 92. This nut 92 is unscrewed and remains on the first shaft 36 due to its captive nature or trapped in a cavity during an assembly/disassembly phase. Unscrewing the nut 92 disengages the shaft 36 from the pin 90 (FIGS. 8 and 8a).

(49) The next step is to remove the shaft 36 by axial translation from downstream of the turbomachine (FIGS. 9 and 9a). The nut 92 can then be supported radially on the cylindrical edge 52aa of the inner ring 52a of the bearing, which ensures its radial retention and ensures correct positioning of the nut for re-mounting the turbomachine 10. Alternatively, the nut 92 can also be left radially supported on the edge of the pin 90 opposite the splines 84, and the shaft 36 can still be removed.