MODULE FOR AN AIRCRAFT TURBOMACHINE
The module with axial retaining elements addresses the oil leakage issue by securing bearing flanges with non-shear screws, ensuring controlled flange separation and preventing contamination in aircraft turbomachines.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- SAFRAN AIRCRAFT ENGINES SAS
- Filing Date
- 2024-05-24
- Publication Date
- 2026-06-05
Abstract
Description
Title of the invention: MODULE FOR AN AIRCRAFT TURBOMACHINE Technical field of the invention
[0001] The present invention relates to a module for an aircraft turbomachine, as well as a turbomachine comprising such a module. Technical background
[0002] The prior art includes in particular document EP-B1-2 721 260.
[0003] An aircraft turbomachine includes a gas generator which conventionally comprises, from upstream to downstream, with reference to the flow of gases in the turbomachine, at least one compressor, an annular combustion chamber and at least one turbine.
[0004] In the case of a twin-spool turbofan engine, with low-pressure and high-pressure components respectively, the gas generator comprises successively a low-pressure compressor, a high-pressure compressor, the combustion chamber, a high-pressure turbine, and a low-pressure turbine. The gas generator defines a first annular flow path of gas, called the primary flow, which passes through the compressors, the combustion chamber, and the turbines.
[0005] The rotor of the high-pressure compressor is connected to the rotor of the high-pressure turbine by a high-pressure shaft. The rotor of the low-pressure compressor is connected to the rotor of the low-pressure turbine by a low-pressure shaft which passes through the high-pressure shaft and drives a shaft of a propulsion propeller generally located upstream of the gas generator.
[0006] When this propeller is enclosed and therefore surrounded by an annular casing, this propeller is called a blower and generates an airflow, called a secondary flow, which flows around the gas generator.
[0007] The propeller shaft and the low-pressure shaft are guided by bearings housed in a lubrication enclosure. This enclosure is surrounded by the first channel and is at least partially delimited by bearing supports. A first rolling bearing located upstream is supported by a first bearing support, and a second rolling bearing located downstream is supported by a second bearing support. These bearing supports have annular flanges that are radially oriented and axially applied to each other and to an annular flange of a stator housing.
[0008] The lubrication chamber is designed to lubricate the bearings and maintain an oily atmosphere around them. The oil is supplied to the chamber via a supply circuit.
[0009] The propeller includes blades that are susceptible to breakage, although this phenomenon is extremely rare. In such a case, a significant imbalance appears on the propeller shaft, generating cyclic loads and vibrations that the upstream bearing transmits to the stator, with a considerable risk of damage.
[0010] To limit the forces transmitted to the stator in the presence of significant imbalance, a shear screw decoupling device is known from document FR-A1-2 831 624. In practice, the second bearing support is fixed to the stator housing by non-shear screws, and the first bearing support is fixed to the second bearing support by shear screws to form a connection that can be broken. These so-called "fuse" screws, whose operation is fully described in the aforementioned document, have a reduced cross-section portion that is likely to break beyond a predetermined mechanical tensile force and thus achieve the decoupling of the bearing supports. In this situation of shear screw failure, the first bearing support is no longer axially restrained. It moves axially upstream and therefore moves axially away from the second bearing support. This is especially true when the bearing supported by the first bearing support is a roller bearing, which does not provide axial restraint to the bearing support when it is separated from the second bearing support.
[0011] This phenomenon is problematic because the housing continues to be supplied with oil by the aforementioned circuit, and the oil that accumulates in the housing is likely to pass through the annular passage formed between the bearing support flanges, which have moved axially apart. The oil then spills into the engine, generating contamination. This oil can reach the first air intake from which air is drawn to supply air to the aircraft equipped with the turbomachine. There is therefore a risk that the aircraft will be supplied with polluted air, or even with unpleasant fumes and odors.
[0012] The invention relates to a technical solution aimed at eliminating the risk of oil leakage into the primary channel after decoupling the bearing supports from the lubrication chamber. Summary of the invention
[0013] The invention relates to a module for an aircraft turbomachine, this module comprising:
[0014] - a first annular bearing support which extends around an axis and which comprises a first annular fixing flange,
[0015] - a second annular bearing support which extends around the axis and which comprises a second annular fixing flange, the first and second flanges being suitable for to be applied axially against each other and to be fixed together by shear screws,
[0016] - an annular housing that extends around the axis, the flange of the second bearing support being applied axially against an annular flange of the casing and fixed to this flange by non-shear screws,
[0017] - a lubrication chamber which is at least partly delimited by the first bearing support, this lubrication enclosure containing a first bearing supported by the first bearing support and a second bearing supported by the second bearing support, and
[0018] - an oil supply circuit for the enclosure, and
[0019] - axial retaining elements of the first and second flanges vis-à-vis each other the other in case of breakage of the fusible screws, each of these elements having an orifice for the passage of one of the non-fusible screws and being axially clamped by this screw against the second flange, each of these elements further having a retaining rim which is axially spaced from the first flange when the fusible screws are not broken, and which is able to axially bear against the first flange when the fusible screws have broken and the first and second flanges move axially apart from each other.
[0020] Under normal operating conditions, the shear screws provide axial retention of the first bearing support relative to the second bearing support. If the shear screws break, the bearing supports separate and move axially apart. The non-shear screws remain intact and hold the second flange against the housing. The retaining elements are also held against the second flange by the non-shear screws and are capable of axially retaining the first flange to prevent it from moving too far away from the second flange. It is therefore understood that the axial distance between the retaining edge of each retaining element and the first flange corresponds to the maximum axial displacement of the first flange relative to the second flange in the event of shear screw failure. The axial retention of the flanges relative to each other helps to limit the risk of oil leakage into the engine's oil passage between these flanges.
[0021] The module according to the invention may comprise one or more of the following features, taken individually or in combination with each other: • the retaining elements are cylindrical cups; • the cups each comprise a cylindrical wall, one axial end of which is connected to a radially internal annular rim defining said orifice for the passage of the non-fusible screw, and to an opposite axial end a radially external annular rim which forms the retaining rim; • the inner rim of each cup has a disc shape; • the outer rim of each cup has a non-axisymmetric shape; • the outer rim of each cup includes two non-lateral sides parallels; • the cylindrical walls of the cups surround the heads of said non-consumable screws; • the cylindrical walls of the cups have an axial length or dimension greater than or equal to 1.5 times, or even twice, an axial length or dimension of the heads of said non-consumable screws; • each of the retaining elements is sandwiched between two stiffening ribs projecting on the first flange; • the retaining elements are axially supported against a cylindrical shoulder of the second flange and pass axially through openings in the first flange; • the retaining rim of each of the elements is located at an axial distance from the first flange which represents less than half, and preferably less than one third, of an axial thickness or dimension of the first flange; • the flange of the second bearing support is axially interposed between the flange of the first bearing support and the flange of the housing;
[0022] — the fusible screws have a weakening or thinning whereas the Non-fusible screws do not contain them; fusible screws are thus different from non-fusible screws;
[0023] — the number of retaining elements is less than or equal to the number of fusible screws and therefore less than the total number of screws (fusible and non-fusible);
[0024] — the retaining elements are distributed, preferably regularly, around the axis.
[0025] The present invention also relates to an aircraft turbomachine, comprising at least one module as described above. Brief description of the figures
[0026] Other features and advantages of the invention will become apparent upon reading the detailed description that follows, for an understanding of which reference should be made to the accompanying drawings in which:
[0027] [Fig-1] [Fig.1] is a schematic half-view in axial section of a part of a aircraft turbomachine,
[0028] [Fig.2] [Fig.2] is a partial schematic axial cross-sectional view of a bearing lubrication chamber,
[0029] [Fig.3] [Fig.3] is a larger-scale view of part of [Fig.2] and shows a decoupling device comprising fusible screws which are here unbroken,
[0030] [Fig.4] [Fig.4] is a view similar to that of [Fig.3] and shows the device of decoupling with fusible screws, which are broken here.
[0031] [Fig.5] [Fig.5] is a schematic perspective view of bearing support mounting flanges,
[0032] [Fig.6] [Fig.6] is a perspective and axial cross-sectional view of a retaining element for a module according to the invention, and shows this module in normal operation,
[0033] [Fig.7] [Fig.7] is a perspective view of the retaining element of [Fig.6], and
[0034] [Fig.8] [Fig.8] is a view similar to that of [Fig.6] and shows the device after the fuse screws have broken. Detailed description of the invention
[0035] Fig. 1 shows a turbomachine 10 for an aircraft, this turbomachine 10 being here a twin-spool turbojet.
[0036] Axis A designates the longitudinal axis of the turbomachine.
[0037] The turbomachine 10 comprises a gas generator 12 which includes, from upstream to downstream with reference to the gas flow along axis A, a low-pressure (LP) compressor 14, a high-pressure (HP) compressor, an annular combustion chamber, a high-pressure (HP) turbine, and a low-pressure (LP) turbine. The turbomachine 10 is partially shown, and only the LP compressor 14 is depicted in the drawing.
[0038] Although not visible in [Fig.1], the HP compressor rotor is connected to the HP turbine rotor by a high-pressure shaft, and the LP compressor rotor 14 is connected to the LP turbine rotor by a low-pressure shaft which passes through the high-pressure shaft and drives a propulsion propeller, called a blower 16, located upstream of the gas generator 12 and which is surrounded by an annular casing called a blower casing 18.
[0039] The blower housing 18 is connected to the gas generator 12 by an intermediate housing 20 which includes a central hub 22 and a series of radial arms 24 connecting the hub 22 to the blower housing 18.
[0040] The gas generator 12 defines a main annular flow channel V1 of a first air flow, called primary flow FL. The gas generator 12 is surrounded by a secondary annular flow channel V2 of a second air flow, called secondary flow F2.
[0041] The airflow F entering the blower 16 splits into a portion forming the primary flow FL. The air from this primary flow FL is compressed in the compressors BP 14 and HP, then mixed with fuel and burned in the combustion chamber. The gases primary combustion flow are then expanded in the HP and LP turbines and finally flow into an exhaust nozzle.
[0042] The other part of the airflow entering the blower 16 forms the secondary flow F2 and is intended to be mixed with the primary flow Fl downstream of the nozzle.
[0043] Fig. 1 further shows a module 30 of the turbomachine, this module 30 comprising annular bearing supports 32, 34, an annular housing 36, a lubrication chamber 38 and an oil supply circuit 40 for the chamber 38.
[0044] A first annular bearing support 32 extends around the axis A and includes a first annular fixing flange 32a, more clearly visible in [Fig.2].
[0045] A second annular bearing support 34 extends around the axis A and includes a second annular mounting flange 34a. The flanges 32a, 34a extend radially outwards and are suitable for being applied axially against each other and fixed together by screws 42 which are shear-off and more clearly visible in figures 2 to 4.
[0046] An annular housing 36 extends around the axis A, and the second bearing support 34 is fixed to this housing 36 by screws 42' which are non-felt and which are shown schematically in [Fig. 5]. The shear screws 42 and non-felt screws 42' may be located on the same circumference centered on the axis A. The housing 36 may be the intermediate housing 20 of [Fig. 1] or another housing fixed to or integral with this intermediate housing 20.
[0047] The housing 36 includes a flange 36a onto which the flange 34a is applied and fixed by the aforementioned non-sheathable screws 42'. The flange 34a of the second bearing support 34 is axially interposed between the flange 32a of the first bearing support 32 and the flange 36a of the housing 36, as illustrated in Figures 2 to 5.
[0048] The number of fusible screws 42 can be equal to the number of non-fusible screws 42. The screws 42, 42' can be regularly distributed around the axis A so that each screw 42 is intercalated between two screws 42', and each screw 42' is intercalated between two screws 42.
[0049] The lubrication enclosure 38 is at least partly delimited by the first bearing support 32 and contains a first bearing 44, or upstream bearing, carried by the first bearing support 32, and a second bearing 46, or downstream bearing, carried by the second bearing support 34.
[0050] In the example shown, the upstream bearing 44 is a roller bearing and the downstream bearing 46 is a ball bearing.
[0051] Furthermore, in the example shown, the first bearing support 32 has a generally annular and elongated shape along the axis A, and comprises an upstream end carrying the rolling bearing 44, and a downstream end connected to the flange 32a. The second bearing support 34 has a generally annular and radial shape, and comprises a radially internal end carrying the downstream bearing 46, and a radially external end connected to the flange 34a.
[0052] The oil supply circuit 40 of the enclosure 38 is more clearly visible in [Fig.2] and includes an oil distributor 48 and at least one oil line 50. The oil distributor 48 is integral with the housing 36 and includes at least one oil inlet 48a and at least one first oil outlet 48b.
[0053] The oil inlet 48a is suitable for being connected to an oil reservoir not shown.
[0054] The oil line 50 is integral with the first bearing support 32 and has an end 40a, here downstream, connected to the first oil outlet 48b of the distributor 48 for the purpose of circulating oil from said inlet 48a to said at least one outlet 48b.
[0055] In the example shown, the distributor 48 comprises two oil outlets 48b, 48c, the first oil outlet 48b mentioned above and a second oil outlet 48c. The second oil outlet 48c can be connected to another line or to an oil nozzle 52 as illustrated in the drawing. The nozzle 52 sprays oil onto the downstream bearing 46, while the line 50 connected to the first outlet 48b of the distributor 48 supplies oil to the upstream bearing 44 for lubrication.
[0056] Preferably, the first outlet 48b is oriented axially, in particular towards the first bearing support 32, i.e. here upstream. The second outlet 48c can be oriented radially inwards.
[0057] Figures 2 to 4 further show that the conduit 50 includes a part which extends axially and which passes through an axial orifice 54 of the second bearing support 34. The conduit 50 is radially interposed between the downstream bearing 46 and the flanges 32a, 34a of the bearing supports 32, 34.
[0058] Fig. 3 shows the default and normal operating case in which the flanges 32a of the bearing supports 32 are applied axially to each other and fixed together by the shear screws 42.
[0059] As mentioned above, in the event of imbalance and vibrations, the shear screws 42 are liable to break as illustrated in [Fig. 4]. The flange 32a of the first bearing support 32, and in particular the first bearing support 32 as a whole, is then no longer axially restrained and moves axially away from the second bearing support 32. The first bearing support 32 then moves upstream, creating an annular passage 56 between the flanges 32a, 34a of the bearing supports 32, 34.
[0060] The oil supplied by the distributor 48 continues to flow into the enclosure and accumulates there. This oil is then liable to flow by gravity through the passage 56 and can reach the primary vein VI, which is problematic as mentioned above.
[0061] The present invention offers a simple, effective and economical solution to this problem.
[0062] The invention proposes, in the event of breakage of the fusible screws 42, to provide elements 60 for axial retention of the flanges 32a, 34a vis-à-vis each other in order to limit the axial separation of the flanges 32a, 34a to avoid any oil leakage between these flanges 32a, 34a.
[0063] Figures 6 to 8 illustrate one embodiment of the retaining elements 60.
[0064] Each of these elements 60 has an opening 62 for the passage of one of the screws 42' not fuses and is axially tightened by means of this screw 42' against the flange 34a.
[0065] Each of these elements 60 further comprises a retaining rim 64 which is axially spaced from the flange 32a when the fusible screws 42 are not broken, and which is able to axially bear against the flange 32a when the screws 42 have broken and the flanges 32a, 34a have moved axially apart from each other.
[0066] In the example shown, the retaining elements 60 are cylindrical cups.
[0067] Each cup comprises a cylindrical wall 66, one axial end of which is connected to a radially internal annular rim 68 defining the orifice 62 for the passage of the screw 42'.
[0068] The cylindrical wall 66 includes at an opposite axial end a radially external annular rim 70 which forms the retaining rim 64.
[0069] The inner rim 68 of each cup may have a disc shape.
[0070] The outer rim 70 of each cup may have a non-axisymmetric shape. This external rim 70 may include two non-parallel lateral flanks 72.
[0071] The cylindrical walls 66 of the cups preferably surround the heads 42a' of said non-fusible screws 42'.
[0072] The cylindrical walls 66 of the cups have a length L1 or axial dimension greater than or equal to 1.5 times, or even twice, a length L2 or axial dimension of the heads 42a'. The length L1 may be less than three times or even four times the length L2.
[0073] Each of the retaining elements 60 can be intercalated between two stiffening ribs 74 projecting on the flange 32a.
[0074] As in the example shown, the retaining elements 60 can be axially supported against a cylindrical shoulder 76 of the flange 34a and can axially pass through orifices 78 of the flange 32a.
[0075] Preferably, the retaining rim 64 of each of the elements 60 is located at an axial distance L3 from the flange 32 which represents less than half, and preferably less than one third, of a thickness L4 or axial dimension of the flange 32a.
[0076] In normal operation as illustrated in [Fig. 6], the shear screws 42 are unbroken and the flanges 32a, 34a are axially pressed against each other. The retaining edges 64 of the elements 60 are at a distance from the flange 32. These elements of The retaining elements 60 are in this case non-functional and "on standby". In the event of breakage of the shear screws 42, the retaining elements 60 remain fixed to the flange 34a by the screws 42' and their edges 64 are capable of axially retaining the flange 34a, and therefore the bearing support 34, which bears axially on these edges 60, as illustrated in [Fig. 8]. It is therefore understood that the distance L3 corresponds to the maximum axial distance of separation of the flanges 32a, 34a after breakage of the shear screws 42, and thus to the maximum axial thickness or dimension of the aforementioned passage 56 between the flanges 32a, 34a. Limiting the axial displacement stroke of flange 32a and therefore of bearing support 32 with respect to flange 34a and bearing support 34 reduces the risk of oil leakage from enclosure 38 to the engine vein through passage 56.
[0077] It can also be seen in [Fig. 6] that the flange 32a comprises an internal cylindrical surface 32a1 which cooperates by radial support with an external cylindrical bearing surface 34a1 of the flange 34a, and that the flange 32a further comprises an external cylindrical surface 32a2 which cooperates by radial support with an internal cylindrical bearing surface 34a2 of the flange 34a. These interactions allow, in normal operation, the centering of the bearing supports 32, 34 and their radial connection to each other.
[0078] The radial supports also ensure a seal, in particular against oil, of the assembly of the flanges 32a, 34a even if an annular seal can be interposed between these flanges.
[0079] The radial support of the surface 32al on the span 34al has an axial extent Hl, and the radial support of the surface 32a2 on the span 34a2 has an axial extent H2.
[0080] L3 is preferably greater than H2 to ensure decoupling of flanges 32a, 34a in case of breakage of shear screws 42. Hl is preferably greater than H2 to prevent oil leaks through flanges 32a, 34a.
[0081] Alternatively, Hl can be equal to H2. When there is decoupling of the flanges 32a, 34a, radial movement is permitted, inducing a possibility of leakage. This leakage will be limited due to the limited and controlled decoupling, if necessary by providing, for example, a gasket between the flanges 32a, 34a.
Claims
Demands
1. A module (30) for an aircraft turbomachine (10), said module (30) comprising: - a first annular bearing support (32) extending about an axis (A) and including a first annular mounting flange (32a), - a second annular bearing support (34) extending about the axis (A) and including a second annular mounting flange (34a), the first and second flanges (32a, 34a) being adapted to be axially pressed against each other and fastened together by shear screws (42), - an annular housing (36) extending about the axis (A), the flange (34a) of the second bearing support (34) being axially pressed against an annular flange (36a) of the housing (36) and fastened to this flange (36a) by non-shear screws (42'), - an enclosure lubrication (38) which is at least partly delimited by the first bearing support (32),this lubrication chamber (38) containing a first bearing housing (44) supported by the first bearing support (32) and a second bearing housing (46) supported by the second bearing support (34), - an oil supply circuit (40) for the chamber (38), and - axial retaining elements (60) for the first and second flanges (32a, 34a) relative to each other in the event of failure of the shear screws (42), each of these elements (60) having an opening (62) for the passage of one of the non-shear screws (42') and being axially clamped by this screw (42') against the second flange (34a), each of these elements (60) further having a retaining rim (64) which is axially spaced from the first flange (32a) when the shear screws (42) are not broken, and which is adapted to bear axially against the first flange (32a) when the fusible screws (42) have broken and the first and second flanges (32a, 34a) move axially apart from each other.
2. Module (30) according to claim 1, wherein the retaining elements (60) are cylindrical cups.
3. Module (30) according to claim 2, wherein the cups each comprise a cylindrical wall (66) having an axial end connected to a radially internal annular rim (68) defining said orifice (62) for the passage of the non-fusible screw (42'), and at an opposite axial end a radially external annular rim (70) which forms the retaining rim (64).
4. Module (30) according to claim 3, wherein the inner rim (68) of each cup has a disc shape.
5. Module (30) according to claim 3 or 4, wherein the outer rim (70) of each cup has a non-axisymmetric shape.
6. Module (30) according to any one of claims 3 to 5, wherein the outer rim (70) of each cup comprises two non-parallel lateral flanks (72).
7. Module (30) according to any one of claims 3 to 6, wherein the cylindrical walls (66) of the cups surround heads (42a') of said non-fusible screws (42').
8. Module (30) according to claim 7, wherein the cylindrical walls (66) of the cups have a length (L1) or axial dimension greater than or equal to 1.5 times, or even twice, a length (L2) or axial dimension of the heads of said non-fusible screws (42').
9. Module (30) according to any one of the preceding claims, wherein each of the retaining elements (60) is interposed between two stiffening ribs (74) projecting on the first flange (32a).
10. Module (30) according to any one of the preceding claims, wherein the retaining elements (60) are axially supported against a cylindrical shoulder (76) of the second flange (34a) and axially pass through orifices (78) of the first flange (32a).
11. Module (30) according to any one of the preceding claims, wherein the retaining rim (64) of each of the elements (60) is located at an axial distance (L3) from the first flange (32a) which is less than half, and preferably less than one third, of a thickness (L4) or axial dimension of the first flange (32a).
12. Module (30) according to any one of the preceding claims, wherein the flange (34a) of the second bearing support (34) is axially interposed between the flange (32a) of the first bearing support (32) and the flange (36a) of the housing (36).
13. Turbomachine (10) for an aircraft, comprising at least one module (30) according to any one of the preceding claims.