Low-pressure turbine of a turbojet engine including a nozzle guide vane axially retained by a plurality of retaining ring sectors

Abstract

The invention relates to a turbine engine turbine including a casing (12) supporting a nozzle guide vane (13) extending circumferentially around an axial direction, wherein: - the nozzle guide vane is formed by several bladed sectors (22, 23, 24) each including a radially outer platform (26, 27, 28) and a radially inner platform with several blades (14) extending radially from the inner platform to the outer platform (26, 27, 28); - the casing (12) includes a rotationally symmetrical inner groove (29), with several separate ring sectors (32, 33, 34) each inserted into this inner groove (29) and protruding radially towards the inside of the casing (12); and - each ring sector (32, 33, 34) axially retains at least one bladed sector (22, 23, 24).

Description

[0001] DESCRIPTION

[0002] Title of the invention: Low pressure turbojet turbine comprising a distributor retained axially by several locking ring sectors

[0003] TECHNICAL FIELD

[0004] The invention relates to the axial locking of a low-pressure turbine distributor equipping a turbomachine such as a turbojet.

[0005] STATE OF THE PRIOR ART

[0006] A turbofan engine has an inlet sleeve through which air is drawn into a low-pressure compressor by means of a fan before being split into a central primary flow and a secondary flow surrounding the primary flow.

[0007] The primary flow circulates in a space called the primary vein delimited by a rotor and by an internal revolution structure surrounding this rotor, and it passes through rotating elements comprising bladed wheels carried by the rotor and fixed elements of the rectifier and distributor type carried by the internal structure.

[0008] The internal structure is delimited by casings including in particular a high pressure compressor casing, a primary vein casing, a high pressure turbine casing, and an exhaust casing.

[0009] The secondary flow circulates in a space called a secondary vein which extends radially between the internal structure and an external structure called the engine fairing or nacelle, which surrounds the internal structure.

[0010] After being set in motion by the fan, this secondary flow is propelled backward to generate thrust.

[0011] The primary flow, which also comes from the flow set in motion by the fan, passes successively through a high-pressure compressor, a combustion chamber, then high-pressure and low-pressure turbines, and drives the fan before being propelled out of the engine. The high-pressure turbine is linked in rotation with the high-pressure compressor, and the low-pressure turbine is linked in rotation with the low-pressure compressor.

[0012] The low pressure turbine is surrounded by a portion of casing, called the low pressure casing, and comprises several stages which include at least one distributor formed of fixed blades rigidly secured to the portion of casing, and surrounding a rotor.

[0013] This distributor is formed of several bladed sectors, each comprising several contiguous blades, and these sectors are mounted on the internal face of the low pressure casing and form a crown or bladed wheel which is fixed.

[0014] These sectors are held longitudinally by a ring engaged in an internal groove of the low pressure casing located immediately downstream of the distributor, this ring protruding radially towards the inside of the low pressure casing.

[0015] The bladed sectors are thus in longitudinal support on the rod, which thus opposes the aerodynamic forces exerted on the distributor from upstream to downstream, to prevent the distributor from moving back towards the bladed wheel located immediately downstream.

[0016] For assembly purposes, the two ends of the ring are spaced apart from each other by a certain distance along the circumference of the internal groove in which this ring is mounted.

[0017] In practice, the thermal cycles and mechanical deformation cycles that the low-pressure ring and casing undergo during the life of the engine cause a reduction in the circumferential length of this ring, due to creep. Consequently, the distance separating the ends of the ring tends to increase during the life of the engine.

[0018] This situation induces a risk of recoil of the bladed sector located at the level of the space separating the two ends of the ring, which can cause this sector to interfere with the rotating bladed wheel located immediately downstream, and cause degradation or even destruction of the low pressure turbine.

[0019] The aim of the invention is to provide a solution for improving the axial locking of a distributor. PRESENTATION OF THE INVENTION

[0020] To this end, the invention relates to a turbomachine turbine comprising a casing carrying a distributor extending circumferentially around an axis, in which:

[0021] - the distributor is formed of several bladed sectors mounted circumferentially end-to-end around the axis, each bladed sector comprising a radially external platform and a radially internal platform with one or more blades extending radially from the radially internal platform to the radially external platform;

[0022] - the casing comprises an annular internal groove which is open by opening radially inwards with respect to the casing, and in which several separate locking ring sectors arranged circumferentially end-to-end are each engaged in this internal groove and protrude radially towards the inside of the casing;

[0023] - each locking ring sector axially blocks at least one bladed sector.

[0024] With this arrangement, the length of the locking elements formed by the ring sectors is reduced, so that the creep experienced by each locking element results in a lesser reduction in its circumferential length, compared with a snap ring or split ring type locking member extending around the entire circumference of the distributor.

[0025] A bladed sector is no longer likely to be located opposite a void extending between two ends of ring sectors, so that there is no longer a risk of a bladed sector no longer being axially retained after a significant series of turbine operating cycles.

[0026] The invention also relates to a turbine thus defined, in which each locking ring sector comprises a lug, and in which each radially external platform comprises a downstream end edge in which a notch is formed receiving the lug of a locking ring sector. The invention also relates to a turbine thus defined, in which the lugs of the locking ring sectors and the notches of the external platforms extend parallel to the axis.

[0027] The invention also relates to a turbine thus defined, in which each lug comprises a portion extending radially relative to the axis extended by a portion extending parallel to the axis, each lug having the shape of a hook on which a platform rests.

[0028] The invention also relates to a turbine thus defined, comprising the same number of locking ring sectors as bladed sectors, and in which each ring sector ensures the axial locking of a bladed sector.

[0029] The invention also relates to a turbine thus defined, comprising the same number of locking ring sectors as bladed sectors, in which the locking ring sectors are circumferentially offset relative to the bladed sectors, and in which each ring sector contributes to the axial locking of two circumferentially adjacent bladed sectors.

[0030] The invention also relates to a turbine thus defined, comprising a greater number of bladed sectors than locking ring sectors, and in which each ring sector ensures the axial locking of several bladed sectors.

[0031] The invention also relates to a turbine thus defined, in which the casing comprises radial studs projecting radially inwards with respect to its radially internal face, and in which each radially external platform comprises at its upstream end edge which comprises a locking notch receiving a radial stud.

[0032] The invention also relates to a turbine thus defined, in which the casing comprises radial studs projecting radially inwards with respect to its radially internal face, each radial stud engaging in a notch of a radially external upstream edge of the platform which also receives a locking ring sector lug.

[0033] The invention also relates to a turbomachine comprising a turbine thus defined. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is an overview of a turbojet engine shown in longitudinal section;

[0035] Figure 2 is a partial longitudinal sectional view of a low pressure turbine;

[0036] Figure 3 is a partial view showing the spacing of the ends of a locking ring after creep;

[0037] Figure 4 is a view of a distributor locking ring according to the state of the art shown alone;

[0038] Figure 5 is a partial view showing the blocking of three bladed sectors by three blocking ring sectors in accordance with the invention;

[0039] Figure 6 is a perspective view of a locking ring sector according to the invention;

[0040] Figure 7 is another perspective view of a locking ring sector according to the invention;

[0041] Figure 8 is a local longitudinal sectional view showing the blocking of a bladed sector by the ring sectors according to the invention;

[0042] Figure 9 is a cross-sectional view showing the blocking of several bladed sectors by several ring sectors in accordance with the invention.

[0043] DETAILED DESCRIPTION OF THE INVENTION

[0044] In the turbojet 1 shown in Figure 1, the outside air is admitted into an inlet sleeve 2 then passes through a fan 3 comprising a series of rotating blades before splitting into a central primary flow and a secondary flow surrounding the primary flow.

[0045] The primary flow is then compressed in a low-pressure compressor 4 and a high-pressure compressor 6 before arriving in a combustion chamber 7, after which it expands by passing through a high-pressure turbine 8 and a low-pressure turbine 9 before being discharged towards the rear, generating thrust. The secondary flow is propelled directly towards the rear by the fan in a vein delimited by a set of casings 11 to generate additional thrust.

[0046] The moving parts of the high-pressure turbine and high-pressure compressor are carried by a high-pressure body, and the low-pressure turbine and low-pressure compressor are carried by a central rotor surrounded by the high-pressure body.

[0047] As seen in Figure 2, the low pressure turbine 9 which is surrounded by a portion of casing called low pressure casing 12, comprises several stages including a distributor 13 formed of a series of fixed blades 14 carried by the casing 12.

[0048] The rotor, marked 16, comprises a disc 17 carrying vanes 18, located immediately downstream of the distributor 13. Another disc 19 carrying vanes 21 is located upstream of the distributor 13 and is also carried by the rotor 16.

[0049] The distributor 13 is formed of several bladed sectors such as the three bladed sectors 22, 23 and 24 visible in figures 3 and 5.

[0050] Each bladed sector more particularly comprises a radially external platform 26, T1, 28 and a radially internal platform between which several blades 14 extend to form a whole consisting of a single piece.

[0051] Each bladed sector is connected by its external platform to the internal face of revolution of the low pressure casing 12, these bladed sectors being mounted circumferentially end-to-end so as to jointly constitute a fixed bladed crown.

[0052] Additionally, the casing 12 comprises, at the downstream face of the distributor 13, an internal groove of revolution 29 receiving a locking member to axially retain the external platforms of the bladed sectors in order to prevent their movement downstream under the effect of the aerodynamic forces to which they are subjected.

[0053] If this locking member is a snap ring 31, that is to say a split ring as shown in FIG. 4, it turns out that over the operating cycles of the engine, the circumferential length of this snap ring decreases due to creep. Consequently, and as illustrated in FIG. 3, the circumferential ends of this snap ring become spaced apart, so that the bladed sector 23 located at these circumferential ends can no longer be retained axially.

[0054] According to the invention, the blocking of the bladed sectors is ensured not by a ring, but by several blocking ring sectors arranged circumferentially end-to-end, identified by 32, 33, 34 in figure 5, to retain the platforms 26, T1, 28 in the axial direction AX.

[0055] Each ring sector 32, 33, 34 is engaged in a portion of the groove 29, opposite a corresponding bladed sector platform. More particularly, each platform has a shape of a portion of wall of revolution delimited downstream by an edge extending in a plane normal to the axis AX.

[0056] These downstream edges, marked 36, 37 and 38, extend in the same plane normal to the axis AX which is located at right angles to the upstream edge of the groove 29, and each ring sector 32, 33, 34 protrudes radially towards the inside of the internal face of the casing 12. Each downstream platform edge thus bears axially on the upstream flank of the corresponding ring sector, to axially retain the bladed sector of which this platform is a part.

[0057] As visible in Figures 5 to 7, the ring sector 33 is provided with a lug 39 which protrudes axially from its upstream face to engage axially in a corresponding notch 41 formed on the downstream face of the downstream edge 37 of the platform 27. The ring sector 33 is thus indexed circumferentially relative to the platform T1, so as to be blocked circumferentially opposite the platform T1 to retain it circumferentially in all circumstances.

[0058] In the example of the figures, the lug 39 has a generally parallelepiped shape protruding from the upstream face of the ring sector 33. The notch 41 has a parallelepiped shape which opens in the face of the downstream edge 37 of the platform T1, and in the radially internal face of this platform 27.

[0059] Under these conditions, the locking ring sector 33 can be inserted after positioning the bladed sector 23 on the internal face of the casing 12, the ring sector 33 can then be moved radially from the inside to the outside to engage its body in the groove 29 and its lug 39 in the notch 41. The other ring sectors and the other bladed sectors have the same morphologies, so that the installation of the distributor 13 consists of firstly placing the bladed sectors on the internal face of the casing 12, then inserting the locking ring sectors in the groove 29. Thanks to the lugs, engaged in the notches of each platform, each locking ring sector is held opposite the bladed sector which it retains when the engine is in operation.

[0060] In the example of Figure 5, the distributor has as many ring sectors as there are bladed sectors, the ring sectors being circumferentially offset relative to the bladed sectors. Each ring sector is mainly opposite a platform to retain it, while having one end opposite a circumferentially adjacent platform.

[0061] Each ring sector thus contributes to the axial retention of two platforms. Thus, ring sector 33 contributes to the axial retention of platforms T1 and 26, and platform T1 is axially retained by ring sectors 33 and 34.

[0062] It is also possible to provide that the ring sectors are not circumferentially offset relative to the bladed sectors for which they ensure axial retention, each ring sector then ensuring the retention of a single bladed ring sector.

[0063] The number of blocking ring sectors can also be provided to be less than the number of bladed sectors, each ring sector then ensuring the blocking of at least two bladed sectors.

[0064] Furthermore, the lugs 39 can be provided to have a hook shape: each lug 39 then comprises a radially extending portion extended by an axially extending portion, each lug 39 then being able to protrude radially from the ring sector which carries it, a platform coming to bear on this hook shape to be blocked.

[0065] To prevent rotation of the distributor 13 around the axis AX during operation of the turbine, which may occur due to the vibrations to which the system is subjected, the bladed sectors are furthermore angularly indexed relative to the casing 12 which carries them. For this purpose, as shown in FIGS. 8 and 9, the casing 12 is provided with studs 42, 43 projecting radially inwards from its internal face, and which engage in corresponding notches 44, 46 formed in the upstream edges 47, 48 of the platforms when the bladed sectors are placed in the casing 12.

[0066] As visible in Figure 8, the notch 44 opens in the upstream face of the platform T1, that is to say in its upstream edge 47, and also in the radially external face of this platform T1, so as to facilitate the engagement of the stud 42 during the positioning of the bladed sector 23.

[0067] The different bladed sectors have the same morphology as sector 23, so that each bladed sector is circumferentially indexed to the internal face of the casing 12 by a corresponding stud.

[0068] Alternatively, the platforms are devoid of notches at their upstream edges, and the studs 42 and 43 are located at right angles to the notches 41 formed in the downstream edges of the platforms. In this case, each notch 41 formed in an upstream edge of the platform extends over the entire height of this edge, that is to say over the entire radial thickness of the platform.

[0069] Each notch 41 then has a face opening in the downstream edge of the platform and a face opening in the radially internal face of the platform but also a face opening in the radially external face of the platform.

[0070] Under these conditions, each notch 41 receives on the one hand a stud 42 for indexing the bladed sector relative to the casing 12 and also a lug 39 for indexing the ring sectors 33 axially retaining the bladed sector comprising the platform provided with this notch.

Claims

CLAIMS 1. Turbomachine turbine comprising a casing (12) carrying a distributor (13) extending circumferentially around an axis (AX), in which: - the distributor is formed of several bladed sectors (22, 23, 24) mounted circumferentially end-to-end around the axis (AX), each bladed sector (22, 23, 24) comprising a radially external platform (26, Tl, 28) and a radially internal platform with one or more blades extending radially from the radially internal platform to the radially external platform (26, Tl, 28); - the casing (12) comprises an annular internal groove (29) which is open by opening radially inwards with respect to the casing (12), and in which several distinct locking ring sectors (32, 33, 34) arranged circumferentially end-to-end are each engaged in this internal groove (29) and protrude radially inwards with respect to the casing (12); - each locking ring sector (32, 33, 34) axially blocks at least one bladed sector (22, 23, 24).

2. Turbine according to claim 1, in which each locking ring sector (32, 33, 34) comprises a lug (39), and in which each radially external platform (26, T1, 28) comprises a downstream end edge (36, 37, 38) in which a notch (41) is formed receiving the lug (39) of a locking ring sector (32, 33, 34).

3. Turbine according to claim 2, in which the lugs (39) of the locking ring sectors (32, 33, 34) and the notches (41) of the external platforms (26, T1, 28) extend parallel to the axis (AX).

4. Turbine according to claim 2, in which each lug (39) comprises a portion extending radially relative to the axis (AX) extended by a portion extending parallel to the axis (AX), each lug (39) having the shape of a hook on which a platform rests.

5. Turbine according to one of the preceding claims, comprising the same number of locking ring sectors (32, 33, 34) as bladed sectors (22, 23, 24), and in which each locking ring sector (32, 33, 34) ensures the axial locking of a bladed sector (22, 23, 24).

6. Turbine according to one of the preceding claims, comprising the same number of locking ring sectors (32, 33, 34) as bladed sectors (22, 23, 24), in which the locking ring sectors (32, 33, 34) are circumferentially offset relative to the bladed sectors (22, 23, 24), and in which each locking ring sector (32, 33, 34) contributes to the axial locking of two circumferentially adjacent bladed sectors (22, 23, 24).

7. Turbine according to one of the preceding claims, comprising a greater number of bladed sectors (22, 23, 24) than locking ring sectors (32, 33, 34), and in which each locking ring sector (32, 33, 34) ensures the axial locking of several bladed sectors (22, 23, 24).

8. Turbine according to one of the preceding claims, in which the casing (12) comprises radial studs (42, 43) projecting radially inwards with respect to its radially internal face, and in which each radially external platform (26, T1, 28) comprises an upstream end edge which comprises a notch (44, 46) receiving a radial stud (42, 43).

9. Turbine according to any one of the preceding claims, in which the casing (12) comprises radial studs (42, 43) projecting radially inwards with respect to its radially internal face, each radial stud (42, 43) engaging in a notch (41) of a radially external upstream edge of the platform (26, T1, 28) which also receives a lug (39) of the locking ring sector (32, 33, 34).

10. Turbomachine comprising a turbine according to one of the preceding claims.

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