Inter-turbine casing comprising mounted splitter blades

The invention relates to an inter-turbine casing (1) comprising: an inner shell (10), an outer shell (20), and an assembly of arms (2) extending radially between the timer (10) and outer (20) shells; and an assembly of splitter blades (30) positioned between the arms (2), each splitter blade (30) comprising an inner platform (33) and an outer platform (36). The inner shell (10) comprises at least one inner groove (11) for slidably receiving one or more inter platforms (33). The outer shell (20) comprises at least one outer groove (21) for slidably receiving one or more outer platforms (36). The inter-turbine casing further comprises locking means (4, 5) for locking the splitter blades (30) in the inner (11) and outer (21) grooves. The splitter blades are arranged using multiple tenons (39) that extend in corresponding ribs (12, 22).

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No. PCT/FR2019/050164 filed Jan. 25, 2019, claiming priority based on French Patent Application No. 1850672 filed Jan. 29, 2018, the entire contents of each of which incorporated by reference herein in their entireties.

FIELD OF THE INVENTION

The invention generally relates to a turbomachine, in particular a bypass turbomachine, and more particularly to an inter-turbine casing of the turbine vane frame type performing the function of turbine distributor in such a turbomachine.

TECHNOLOGICAL BACKGROUND

A bypass turbomachine generally comprises, from upstream to downstream in the gas flow direction, a fan, an annular primary flow path and an annular secondary flow path. The mass of air suctioned by the fan is thus divided into a primary flow, which circulates in the primary flow path, and a secondary flow, which is concentric with the primary flow and circulates in the secondary flow path.

The primary flow path passes through a primary body comprising one or more stages of compressors, for example a low pressure compressor and a high pressure compressor, a combustion chamber, one or more stages of turbines, for example a high pressure turbine and a low pressure turbine, and a gas exhaust nozzle.

In a manner known per se, the turbomachine also comprises an inter-turbine casing, the hub of which is arranged between the high-pressure turbine casing and the low-pressure turbine casing. The inter-turbine hub comprises a fairing including an inner shroud and an outer shroud, which together delimit the flow path between the high-pressure turbine and the low-pressure turbine, as well as arms which radially extend between the inner shroud and the outer shroud.

The fairing may have a single profile configuration and only include arms. Alternatively, the fairing may have a multi-profile configuration and include, in addition to the arms, splitter blades (or splitters). In this case, one or more splitter blades are interposed between the arms and have a small cord compared to the arms, which are thicker and have a long cord. It is understood by cord here that the segment connecting the leading edge and the trailing edge of the arm or the splitter blade at its junction with the outer shroud.

The single profile configuration is more conventional and easier to manufacture. However, the integration of the arms can be difficult since the need for deflection of the gas flow by the arms can lead to strongly curved aerodynamic profiles. In the multi-profile configuration, the deflection of the gas flow is performed via the downstream part of the arms and the splitter blades, which allows maintaining an almost symmetrical profile in the upstream part of the arms. In addition, the multi-profile configuration has significant aerodynamic optimization potential since it includes a large number of parameters that can be adjusted as required. However, a fairing having a multi-profile configuration is more difficult to achieve. Generally, it is obtained either from casting or by, mounting the splitter blades.

Documents EP 2 860 354, EP 2 835 503 and GB 1 058 759 describe an inter-turbine casing for a turbomachine comprising an inner shroud, an outer shroud, a set of arms and a set of splitter blades mounted on the inner shroud and the outer shroud downstream of the arms.

SUMMARY OF THE INVENTION

A purpose of the invention is to provide an inter-turbine casing for a multi-profile type turbomachine which is easy to produce at a moderate cost and whose maintenance is facilitated in comparison with conventional inter-turbine casings.

For this purpose, the invention proposes an inter-turbine casing for a turbomachine comprising:an inner shroud, an outer shroud and a set of arms extending radially between the inner shroud and the outer shroud, the inner shroud and the outer shroud extending coaxially around a longitudinal axis,a set of splitter blades positioned circumferentially between the arms, each splitter blade comprising a root provided with an inner platform fixed to the inner shroud and a head provided with an outer platform fixed to the outer shroud.

The inner shroud comprises at least one inner groove configured to slidingly receive one or more inner platforms. The outer shroud comprises at least one outer groove configured to slidingly receive one or more outer platforms. Moreover, the inter-turbine casing further comprises means for blocking the splitter blades in the inner and outer grooves.

Some preferred but non-limiting features of the inter-turbine casing described above are the following, taken individually or in combination:at least one rib is formed in each inner groove and each outer groove, each inner platform and each outer platform comprising a stud protruding from said platforms configured to penetrate into the rib of the inner groove or of the corresponding outer groove in order to radially block the splitter blades in said inner and outer grooves.each inner platform and each outer platform has an upstream face and a downstream face and comprises two studs, a first one of the studs extending from the upstream face while the second one of the studs extends from the downstream face, and in which each inner groove and each outer groove has an upstream border and a downstream border, a rib being formed in each upstream border and in each downstream border and being configured to receive an associated stud.the blocking means comprise: a set of orifices formed in the inner shroud and the inner platforms and a set of anti-rotation pins, each anti-rotation pin being inserted, on the one hand, into an orifice of the inner shroud and into an orifice of an inner platform, and a set of orifices formed in the outer shroud and the outer platforms and a set of anti-rotation pins, each anti-rotation pin being inserted, on the one hand, into an orifice of the outer shroud and into a orifice in an outer platform.the arms are formed integrally and in one-piece with the inner shroud and the outer shroud.the arms extend over a greater length than the splitter blades in the direction of the longitudinal axis.each arm and each splitter blade has a cord, the cord of the arms being larger than the cord of the splitter blades.the inter-turbine casing is sectored so that the inner shroud and the outer shroud each comprise a plurality of ring sectors.each ring sector of the inner shroud and of the outer shroud includes axial edges, each axial edge being configured to be fixed opposite an associated axial edge of another ring sector of the inner shroud or of the outer shroud, and in which the inner grooves and the outer grooves of each ring sector of the inner shroud and of the outer shroud open onto an axial edge of said ring sector. And/orthe inter-turbine casing comprises a single arm formed integrally and in one-piece with one of the ring sectors of the inner shroud and one of the ring sectors of the outer shroud and at least two splitter blades, preferably three splitter blades.

DETAILED DESCRIPTION OF AN EMBODIMENT

An inter-turbine casing1according to the invention comprises:an inner shroud10, an outer shroud20and a set of arms2extending radially between the inner shroud10and the outer shroud20. The inner shroud10and the outer shroud20extend coaxially around a longitudinal axis X.a set of splitter blades30comprising a root31fixed to the inner shroud10and a head32fixed to the outer shroud20.

The splitter blades30are positioned circumferentially between the arms2. Particularly, one or more splitter blades30can extend between two adjacent arms2. It will be noted that, conventionally, the cord of each splitter blade30is shorter than the cord of each arm2. Moreover, each splitter blade30comprises an inner platform33fixed on its root31and an outer platform36fixed on its head32.

The inner shroud10comprises at least one inner groove11configured to slidingly receive one or more inner platforms33and the outer shroud20comprises at least one outer groove21configured to slidingly receive one or more outer platforms36.

In this description, a part will be designated by “inner” as opposed to “outer” when this part is close to the longitudinal axis X (as opposed to far from the longitudinal axis X). An axis or a direction extending in a plane normal to the longitudinal axis X and intersecting this longitudinal axis X will be designated by “radial”. An axis or a direction which is parallel to the longitudinal axis X will be designated by “axial”.

Finally, the upstream and downstream are defined relative to the direction of gas flow in the inter-turbine casing.

The splitter blades30are therefore mounted and fixed on the rest of the inter-turbine casing1via their inner platform33and their outer platform36, which allows simplifying the manufacture of the inter-turbine casing1as well as the maintenance operations.

Indeed, it suffices to slide the splitter blades30into the inner and outer grooves11,21associated with the inner and outer shrouds10,20in order to position said splitter blades30, then to fix them in this position to the rest of the inter-turbine casing1using the blocking means4,5.

Once the splitter blades30in place in the inner and outer grooves11,21, the radially outer face33aof the inner platforms33and the radially inner face36aof the outer platforms36extend in the continuation of the inner shroud10and the outer shroud20so as to reconstitute the flow path. Furthermore, the inner and outer platforms33,36completely fill the inner and outer grooves so as not to leave a cavity capable of creating pressure drops.

In order to facilitate the production of the inter-turbine casing1, the latter can be sectored, that is to say that the inner shroud10and the outer shroud20can each be formed of several ring sectors, each ring sector carrying one or more arms2. Then, each ring sector comprises two axial edges3and are fixed together in pairs at their axial edges3in order to form the inner shroud10and the outer shroud20.

The inner and outer grooves11,21each open onto one of the axial edges3of the ring sectors forming the inner and outer shrouds10,20in order to allow the insertion of the inner and outer platforms33,36into the associated inner and outer11,21grooves.

Preferably, each ring sector includes only one arm2. However, each ring sector can comprise two inner grooves11(respectively, two outer grooves21) extending on either side of the associated arm2(see for exampleFIG. 3b). Each groove then opens into the associated axial edge3. It will be noted that the same groove can, however, receive several splitter blades30. For example,FIGS. 1 and 2illustrate an example of an inter-turbine casing sector comprising an arm surrounded on one side by a splitter blade30and on the other side by two splitter blades30.

At least one rib12,22is formed in each inner groove11and each outer groove21while each inner platform33and each outer platform36comprises an associated stud39.

More specifically, each inner groove11(respectively, each outer groove21) is delimited by an inner wall13(respectively an outer wall23) and a peripheral border including an upstream border14,24and a downstream border15,25. A rib12,22is formed both in the upstream border14,24and in the downstream border15,25of the inner groove11(respectively, of the outer groove21) by opening at one of the axial edges3of the inner groove11(respectively, of the outer groove21).

Moreover, the inner platform33(respectively, the outer platform36) of the splitter blades30has an upstream face34,37configured to be opposite the upstream border14of the inner groove11(respectively, of the outer groove21) and a downstream face35,38configured to be opposite its downstream border15. It further includes a stud39protruding from the upstream face34of the inner platform (respectively, the upstream face37of the outer platform36) and configured to slide in the rib12,22of the upstream border14,24, as well as a stud39protruding from the downstream face35of the inner platform33(respectively, the downstream face38of the outer platform36) and configured to slide in the rib12,22of the downstream border15,25. The studs39and the associated ribs12,22thus allow guiding the splitter blades30in the inner and outer grooves11,21and preventing their radial displacement.

In order to allow the sliding of the splitter blades30relative to the inner shroud10and the outer shroud20, the radial section of the inner and outer grooves11,21is constant between the axial edges3of the ring sectors forming said shrouds10,20.

The blocking means4,5are configured to block the splitter blades30in position once the latter are in place in the inner and outer grooves11,21.

For this purpose, the blocking means can comprise:a set of orifices4formed in the inner shroud10and the inner platforms33and a set of anti-rotation pins5, each anti-rotation pin being inserted, on the one hand, into an orifice4of the inner shroud10and into an orifice4of an inner platform33, anda set of orifices formed in the outer shroud20and the outer platforms36and a set of anti-rotation pins, each anti-rotation pin5being inserted, on the one hand, into an orifice4of the outer shroud20and into an orifice4of an outer platform36.

In the exemplary embodiment illustrated in the figures, an orifice4is formed in the inner shroud10and in the outer shroud20for each splitter blade30. The inter-turbine casing1therefore comprises as many anti-rotation pins5as there are splitter blades30.

In one embodiment, the orifices5are circular and have an axis of symmetry which is normal to the inner shroud10(respectively, to the outer shroud20).

The arms2are in turn integrally formed with the inner shroud10and the outer shroud20(or at least with the ring sector of the inner shroud10and the outer shroud20to which they are fixed). For this purpose, the arms2can be integrally cast with the inner shroud10and the outer shroud20. Alternatively, the arms2can be mounted and fixed on the inner shroud10and the outer shroud20.

Where appropriate, the radially inner face of the inner platform33and the radially outer face of the outer platform36can be locally hollowed out in order to reduce the overall weight of the inter-turbine casing1, except in the area in which is formed the orifice (seeFIG. 4).