TURBOMACHINE DISTRIBUTOR COMPRISING A GAS REINTRODUCTION DUCT WITH A TANGENTIAL COMPONENT

A distributor for a turbine of a turbomachine. The distributor includes a radially inner platform, a blade and a root which is coated with a track made of an abradable material. According to the invention, the distributor includes a leakage gas reintroduction duct. The duct includes an inlet through the track made of an abradable material, an outlet opening through a downstream surface of the root, and a duct intermediate portion which extends from the inlet up to the outlet. The duct intermediate portion is orientated with a tangential component.

TECHNICAL FIELD

The invention relates to the general technical field of aircraft turbomachines such as turbojet engines and turboprop engines. More specifically, the invention belongs to the technical field of turbines for turbomachines. In particular, it relates to a distributor of a turbomachine high-pressure turbine.

PRIOR ART

Turbomachine turbines are conventionally formed by movable wheels and distributors, alternately arranged according to the axial direction of the turbomachine. For example, an example of the design of such a turbine is known from the document FR 3 034 129 A1.

At the junction between a movable wheel and a distributor located downstream, a leakage gas flow is often observed which escapes from a gas flow path of the turbomachine, to join a leakage gas cavity arranged radially under the root of the distributor. This leakage gas flow is usually reinjected into the flow path downstream of the distributor, after having circulated through a labyrinth seal. The leakage flow is reinjected into the flow path with a generally radial direction which is different from the flow direction of a primary flow in the flow path.

Thus, this reintroduction of the gas leak rate generates aerodynamic disturbances on the primary flow, causing losses in efficiency.

DISCLOSURE OF THE INVENTION

The invention aims to at least partially solve the problems encountered in the solutions of the prior art.

In this respect, an object of the invention is a distributor for a turbomachine turbine. The distributor extends around a longitudinal axis. The distributor comprises a radially inner platform, at least one blade extending between the radially inner platform which is configured to delimit a gas flow path radially inwardly, and a root extending radially inwards from the radially inner platform. The root is coated with a track made of an abradable material of a turbomachine rotating seal.

The distributor comprises a duct for reintroducing leakage gas into the turbomachine gas flow path. According to the invention, the duct comprises an inlet opening radially inwards the distributor through the track made of an abradable material, an outlet opening through a downstream surface of the root of the distributor, and a duct intermediate portion which extends from the inlet up to the outlet. The duct intermediate portion is oriented with a tangential component with respect to the longitudinal axis.

Thanks to the leakage gas reintroduction duct of the distributor according to the invention, the reintroduction of the leakage gas at the outlet of the duct disturbs the gas flow less in the gas flow path of the turbine. Thus, the efficiency of the turbomachine is increased.

In particular, the outlet of the duct opens under the inner platform into a region in which the pressure of the gas is low, which promotes mixing with the gas having passed through the rotating seal, while limiting the aerodynamic disturbances of the flow in the flow path.

The leakage gas at the outlet of the duct comes out of the duct with a flow tangential component which is close to that of the flow of the primary flow in the flow path. This results in a better mixing of the gas at the outlet of the duct and of the gas having passed along the blade of the distributor.

The relative position of the outlet of the duct with respect to that of the inlet of the duct tends to increase the pressure difference between the pressure of the gas at the inlet of the duct and the pressure of the gas at the outlet of the duct.

Moreover, the distributor may be manufactured easily, thanks to the relatively simple making of the leakage gas reintroduction duct.

Optionally, the invention may include one or more of the following features, combined or not.

According to a particular embodiment, the duct intermediate portion has an inner diameter which decreases from the inlet up to the outlet of the duct. The decrease in the diameter of the duct between the inlet and the outlet of the duct tends to accelerate the circulation of the leakage gas in the duct.

Preferably, the inner diameter of the duct intermediate portion decreases continuously from the inlet up to the outlet of the duct. The leakage gas tends to be further accelerated in the duct, while limiting pressure drops in the duct.

According to another particular embodiment, the duct intermediate portion is curved in the direction of the outlet of the duct. In particular, the intermediate portion is inclined tangentially in the direction of the outlet of the duct.

According to a particular embodiment, the duct intermediate portion extends with an axial component downstream from the inlet of the duct up to the outlet of the duct.

According to a particular embodiment, the duct intermediate portion is delimited radially by the track made of an abradable material and the distributor root. The duct intermediate portion is all the more easy to make, for example by means of a groove in the root of the distributor and/or in the track made of an abradable material.

According to a particular embodiment, the duct intermediate portion is substantially equidistant from the longitudinal axis from the inlet of the duct up to the outlet of the duct. The duct intermediate portion is all the more easy to make, for example by means of a groove in the root of the distributor and/or in the track made of an abradable material.

In particular, a longitudinal direction of the duct at the centre of the duct extends with an axial component and a tangential component but without a radial component with respect to the axis of the distributor.

According to a particular embodiment, the inlet of the duct extends through the abradable material from a radially inner surface of the track made of an abradable material up to the duct intermediate portion.

According to a particular embodiment, the outlet of the duct is a groove of the root extending from the duct intermediate portion up to the downstream surface of the distributor root which is radially inwards with respect to the inner platform.

According to a particular embodiment, the duct intermediate portion is a groove formed on an inner radial surface of the root to which the track made of an abradable material is fastened.

According to another particular embodiment, the inlet of the duct is oriented radially from the inner surface of the track made of an abradable material up to the duct intermediate portion.

According to another particular embodiment, the outlet of the duct is oriented radially from the duct intermediate portion up to the downstream surface of the root.

According to a particular embodiment, the outlet of the duct is substantially aligned with a trailing edge of the blade according to a gas flow direction along the trailing edge.

Preferably, the distributor includes as many leakage gas reintroduction ducts as there are blades.

The invention also relates to a turbine for a turbomachine, the turbine comprising a distributor as defined hereinabove.

Preferably, the turbine is a turbomachine high-pressure turbine. Alternatively, the turbine is a turbomachine low-pressure turbine.

Preferably, the distributor is a distributor of a second high-pressure turbine stage of a turbomachine which is located axially between a rotor wheel of a first high-pressure turbine stage and a rotor wheel of a second high-pressure turbine stage.

According to a particular embodiment, the turbine comprises a leakage gas cavity located radially inwards with respect to the distributor. The turbine comprises a rotating seal which includes the track made of an abradable material and at least two wipers which are configured to be in contact with the track made of an abradable material while being movable in rotation relative to the track made of an abradable material.

The invention also relates to a turbomachine comprising a turbine as defined hereinabove. Preferably, the turbomachine is an aircraft turbomachine. Quite preferably, the turbomachine is a twin-spool turbofan engine.

Furthermore, the invention relates to a method for manufacturing a distributor as defined hereinabove. The manufacturing method comprises drilling an inlet of the duct into the track made of an abradable material. The manufacturing method comprises making the duct intermediate portion by machining a groove along an inner radial surface of the distributor root. The manufacturing method comprises making the outlet of the duct by machining a groove along the downstream surface of the distributor root.

The manufacturing method comprises fastening the track made of an abradable material, preferably by brazing, to the distributor root, so that the inlet of the duct opens into the duct intermediate portion.

The order of the steps of drilling the inlet, making the outlet and the intermediate portion may vary. Nevertheless, they are made before fastening the track made of an abradable material to the distributor root.

Alternatively, the turbomachine distributor is for example made by additive manufacturing.

DETAILED DISCLOSURE OF PARTICULAR EMBODIMENTS

Identical, similar or equivalent parts of the various figures bear the same numerical references so as to facilitate the transition from one figure to the other.

FIG.1shows a twin-spool bypass turbomachine1. The turbomachine1is a turbojet engine which has an axisymmetric shape around a longitudinal axis AX.

The turbomachine1comprises, from upstream to downstream along the path of a primary flow, an air intake sleeve2, a fan3, a low-pressure compressor4, a high-pressure compressor6, a combustion chamber7, a high-pressure turbine8and a low-pressure turbine9. This primary flow flows in a primary flow path11of the turbomachine1.

The upstream and downstream directions are used in this document with reference to the overall gas flow in the turbojet engine, such a direction is substantially parallel to the direction of the longitudinal axis AX.

Unless stated otherwise, the adjectives “axial”, “radial” and “circumferential”, “inner” and “outer” are defined with respect to the longitudinal axis of revolution AX of the turbomachine. An axial direction is a direction substantially parallel to the longitudinal axis AX. A radial direction R-R is a direction substantially orthogonal to the longitudinal axis AX of the compressor6and secant with the longitudinal axis AX of the turbomachine. A circumferential or tangential direction T-T is a direction around the longitudinal axis AX. An “inner” element is closer to the longitudinal axis AX than an outer element.

The low-pressure compressor4, the high-pressure compressor6, the high-pressure turbine8and the low-pressure turbine9define a secondary flow path13for the circulation of a secondary flow that bypasses them.

The high-pressure compressor6and the high-pressure turbine8are mechanically linked by a drive shaft of the high-pressure compressor6, to form a high-pressure spool of the turbomachine1. Similarly, the low-pressure compressor4and the low-pressure turbine9are mechanically linked by a turbomachine shaft, so as to form a low-pressure spool of the turbomachine1.

The low-pressure compressor4, the high-pressure compressor6, the combustion chamber7, the high-pressure turbine8and the low-pressure turbine9are surrounded by an intermediate casing which extends from the inlet sleeve2up to the low-pressure turbine9.

FIG.2partially shows a high-pressure turbine8of the turbomachine. The high-pressure turbine8includes a plurality of stages each including a rotor wheel20and a distributor30.

The wheel20is movable in rotation around the longitudinal axis AX. It includes an annular row of movable blades28and a disc26in which the movable blades28are mechanically engaged while extending radially outwards from disc26. Each wheel20includes a downstream flange25which is fastened downstream of the disc26and downstream of the corresponding movable blades28.

Two axially adjacent wheels20are interconnected by an interdisc shroud24, which contributes to gas sealing between these wheels20, in particular in rotation around the longitudinal axis AX. The inter-disc shroud24is fastened by form-fitting to the downstream flange25of a wheel20of one stage and it includes an upstream portion24awhich is fastened by form-fitting to the upstream of the wheel20of the next stage.

The distributor30forms part of the stator of the turbomachine. In the embodiment that is shown, each distributor30is divided into bladed sectors according to the tangential direction T-T. Each distributor sector comprises an inner platform32, an outer platform, a plurality of fixed blades38which are spaced apart from each other according to a tangential direction T-T of the distributor, a root36and a track37made of an abradable material which coats a radially inner surface S2of the root36.

The blades38extend from upstream to downstream according to the flow direction of the gases in the turbomachine from a leading edge up to a trailing edge BF. They comprise an intrados wall38aand an extrados wall38F which interconnect the leading edge to the trailing edge BF. They extend radially from the inner platform32up to the outer platform.

The inner platform32is delimited radially downstream by a downstream edge34which projects downstream from a downstream surface S4of the root36of the distributor. The inner platform32is delimited radially outwards by an aerodynamic outer surface51which is in contact with the flow of the primary flow path11. The downstream edge34is delimited radially inwards by an inner surface S9which extends from the downstream surface S4of the root up to the downstream end of the inner platform32.

The root36is delimited axially upstream by an upstream surface S5and axially downstream by the downstream surface S4. It is delimited radially outwards by a lateral surface S6which laterally delimits the distributor30bladed sector. The root36is delimited radially outwards by the inner platform32and radially inwards by the radially inner surface S2to which the track37made of an abradable material is fastened.

In the embodiment that is shown, the distributor30is a distributor of a second high-pressure turbine stage8. It is located axially between a rotor wheel21of a first high-pressure turbine stage8and a rotor wheel22of a second high-pressure turbine stage8.

Referring toFIG.2, the high-pressure turbine8comprises a leakage gas cavity23is located radially inwards with respect to the distributor30and radially outwards with respect to the interdisc shroud24. The leakage gas cavity23is partially sealed by a rotating seal15.

The leakage gas cavity23comprises axially from upstream to downstream an upstream space23a, an inter-wiper space23band a downstream space23c. Leakage gas originating from the primary flow path11enters the upstream space23aupstream of the distributor30, then into the inter-wiper space23b, before returning back to the primary flow path downstream of the distributor30by circulating through the downstream space23c.

The upstream space23ais delimited axially upstream by a downstream flange25and axially downstream by the interdisc shroud24. It is delimited radially outwards by the track37made of an abradable material and by the root36and it is delimited radially inwards by the interdisc shroud24.

The inter-wiper space23bis delimited axially by two consecutive wipers of the rotating seal15. It is delimited radially inwards by the interdisc flange24and radially outwards by the track37made of an abradable material.

The downstream space23cis delimited axially upstream by the rotating seal15. It is delimited axially downstream by the wheel22of the second stage. It is sealed radially outwards by the track37made of an abradable material and by the upstream spoilers27of the movable blades28of the wheel22of the second stage. It is delimited radially inwards by the interdisc shroud24.

The rotating seal15is a labyrinth seal. It includes the track37made of an abradable material which is rigidly secured to the root36and to at least two wipers29which are rigidly secured to the interdisc shroud24. It limits the flow of leakage gas through the leakage gas cavity23, to improve the performances of the turbomachine1.

The wipers29of the rotating seal15are configured to be in contact with the track37made of an abradable material while being movable in rotation relative to the track37made of an abradable material. They are able to dig into the track37made of an abradable material, in particular in case of differential expansions during the operation of the turbomachine1.

Referring more specifically toFIGS.3to6, the distributor30comprises a duct40for reintroducing the leakage gas into the primary flow path11. The duct40is configured to make the gas circulate from the leakage gas cavity23up to the primary flow path11downstream of the distributor30. The leakage gas reintroduction duct40comprises, from upstream to downstream, an inlet42, a duct intermediate portion50and an outlet46.

Referring toFIGS.3and5in combination, the inlet42extends inside the distributor30up to an outlet orifice43which opens into the duct intermediate portion50.

To facilitate the manufacture of the inlet42, the inlet42of the duct40is formed by a cylindrical bore with a circular section around an axis of revolution X1-X1, in the first embodiment. In particular, the diameter d1of the inlet42is substantially constant. The inlet42is oriented radially from the inner surface of the track37made of an abradable material up to the duct intermediate portion50.

The inlet42opens onto the outside of the distributor30through a drawing orifice41which is formed in a radially inner surface S3of the track37made of an abradable material. The drawing orifice41is located axially between two wipers29of the rotating seal15.

Because of the position of the drawing orifice41at the level of the rotating seal15, the pressure of the gas at the inlet42of the duct is high, which facilitates the leakage gas circulation in the duct40in the direction from the outlet46. Moreover, the flow rate of the leakage gas that circulates in the duct40is limited.

Referring toFIGS.3and6in combination, the duct intermediate portion50extends from the inlet42up to the outlet46which it fluidly connects. In the embodiment that is shown, it is formed by a groove which is machined on the radially inner surface S2of the root36.

The duct intermediate portion50includes an inlet section51which is fluidly connected to the outlet orifice43of the inlet42. It includes an outlet section53which is fluidly connected to the outlet46.

In general, the duct intermediate portion50extends with an axial component T2downstream from the inlet42of the duct40up to the outlet46of the duct40. It is oriented with a tangential component T1with respect to the longitudinal axis AX, so as to bring the flow direction of the leakage gas closer to that of the gas having passed along the blade38in the primary flow path11.

The duct intermediate portion50is curved axially downstream with a tangential component T-T in the direction of the outlet46of the duct40. In particular, the centreline X2-X2of the duct intermediate portion50in axial section of the distributor through the duct intermediate portion50is curvilinear. The centreline X2-X2of the duct intermediate portion50is substantially equidistant from the longitudinal axis AX from the inlet42of the duct40up to the outlet46of the duct40.

In axial section through the root36, the duct intermediate portion50is delimited laterally by a first lateral wall52and a second lateral wall54. The first lateral wall52and the second lateral wall54are connected by a bottom wall56which delimits the duct intermediate portion50radially outwards. The first lateral wall52and the second lateral wall54define a variable inner diameter d2of the duct intermediate portion50.

The inner diameter d2decreases from the inlet42up to the outlet46of the duct40. More specifically, the inner diameter d2of the duct intermediate portion50according to the first embodiment decreases continuously uniformly from the inlet42up to the outlet46of the duct40. The decrease in the diameter d2of the duct tends to accelerate the circulation of the leakage gas in the duct40. The uniform decrease in the diameter d2of the duct intermediate portion50tends to limit the pressure drops in the duct40, compared to sudden changes in the inner diameter of the duct.

Referring toFIGS.3and4in combination, the outlet46of the duct40is formed by a groove through the downstream surface S4of the root. It extends radially from the duct intermediate portion50up to a junction region of the downstream surface S4and of the inner surface S9of the downstream edge34of the inner platform32. In this respect, the outlet46extends over a length I3which is substantially equal to the radial length of the root36. The width h3of the outlet46is substantially constant.

The outlet46opens into the primary flow path11under the inner platform32, in a gas low-pressure region, which promotes the flow of the leakage gas through the outlet46and which limits the aerodynamic disturbances of the flow in the primary flow path11downstream of the outlet46.

Moreover, mixing of the leakage gas at the outlet of the duct40with the gas having passed along the corresponding distributor blade38is delayed by the downstream edge34of the inner platform32which is located radially between the outlet46and the trailing edge BF of the corresponding blade38which physically separates it. The leakage gas at the outlet46of the duct may also mix with the leakage gas having passed through the rotating seal15along the inner surface S9of the downstream edge34of the inner platform32, before the leakage gas mixes downstream of the distributor30in the primary flow path11with the gas having passed along the blade38of the distributor.

The outlet46of the duct40is aligned with a trailing edge BF of the blade38according to a gas flow direction T3along the trailing edge BF, while being at a radial distance from the gas flow in the primary flow path11along the trailing edge BF. The outlet46of the duct40is also aligned circumferentially with the trailing edge BF of the blade38.

The leakage gas at the outlet46of the duct comes out of the duct40with a flow tangential component T-T which is locally parallel to that of the circulation of the flow in the primary flow path11. This results in a better mixing of the gas at the outlet46of the duct and of the gas having passed along the blade38of the distributor30.

The relative position of the outlet46of the duct with respect to that of the inlet42of the duct tends to increase the pressure difference between the pressure of the gas at the inlet42of the duct and the pressure of the gas at the outlet46of the duct, while limiting the pressure drops in the leakage gas reintroduction duct40. This tends to increase the speed of the leakage gas arriving in the primary flow path11so that this speed is closer to that of the gas flowing in the primary flow path11while having passed along the blade38. Mixing of the leakage gas and of the gas of the primary flow path11is thereby improved.

The method for manufacturing the distributor30is described hereinbelow with reference toFIGS.5to7.

The manufacturing method100comprises the prior manufacture of the root36of the distributor on the one hand and of the track37made of an abradable material on the other hand, before making the leakage gas reintroduction duct40.

Making of the duct40comprises drilling101the inlet42with reference toFIG.5, machining103the duct intermediate portion50with reference toFIG.6, and machining105the outlet46of the duct. These steps may be carried out successively, in different orders, or simultaneously.

The inlet42is drilled in the track37made of an abradable material from the inner surface S3of the track made of an abradable material up to the radially inner surface S2of the root36, in particular by electro-machining.

The duct intermediate portion50is made by machining a groove on the radially inner surface S2of the root36, in particular by electro-machining.

The outlet46of the duct is made by machining a groove on the downstream surface S4of the root, in particular by electro-machining.

Afterwards, the manufacturing method100comprises a step107of fastening the track37made of an abradable material to the distributor30root36, so that the inlet42of the duct40opens into the inlet section51of the duct intermediate portion50and that the outlet section53of the duct intermediate portion50opens into the outlet46of the duct. The track37made of an abradable material is fastened to the root36by brazing.

Thanks to the leakage gas reintroduction duct40of the distributor30according to the invention, the mixture of the gas having passed through the rotating seal15, of the gas at the outlet46of the gas reintroduction duct and of the gas having passed along the blade38in the primary flow path11is improved. The reintroduction of the leakage gas at the outlet46of the duct40disturbs the gas flow in the primary flow path11lesser, and the efficiency of the turbomachine1is increased.

In particular, the outlet46of the duct opens into a region of the high-pressure turbine8in which the pressure of the gas is low, which promotes mixing of the leakage gas with the flow in the primary flow path11, while limiting the aerodynamic disturbances of the flow in the primary flow path11.

Moreover, the distributor30may be manufactured easily, thanks to the relatively simple making of the leakage gas reintroduction duct40.

Of course, various modifications may be made by a person skilled in the art to the invention that has just been described without departing from the scope of the disclosure of the invention.

The turbomachine1may have a different structure. Alternatively, the turbomachine1is for example a turboprop engine or a turbine engine.

The turbine according to the first embodiment may be a low-pressure turbine9of a turbomachine.

Alternatively, the rotating seal15includes other seals such as a brush seal or a segmented radial seal, between the track37made of an abradable material and the interdisc shroud24. The seal may include at least three wipers29rather than two wipers29.

Alternatively, the distributor30may be a distributor of the first high-pressure turbine stage8.

The distributor30may be made in one-piece or not. It may include one single blade38. The distributor30may be divided into bladed angular sectors or extend substantially over the entire circumferential length of the turbine around the longitudinal axis AX.

The structure of the distributor30may vary. For example, it may include a stagger between the root36and the radially inner platform32. In this case, the duct intermediate portion50passes in particular through the stagger.

The shape of the leakage gas reintroduction duct40may vary. In particular, the reduction in the diameter d2of the duct intermediate portion50may be non-uniform. The intermediate portion50may be made by machining a groove on a radially outer surface of the track37made of an abradable material.

The inlet42and/or the outlet46may include an axial component downstream. In addition or alternatively, the inlet42and/or the outlet46may include a tangential component. Nevertheless, the duct40of the distributor according to the first embodiment is particularly easy to make.

Alternatively, the outlet46may include a non-uniform width h3, for example by flaring when getting away from the duct intermediate portion50.

The distributor30may be made by additive manufacturing.