Turbine engine comprising a contrarotating propeller receiver supported by a structural casing attached to the intermediate housing

An open rotor type aircraft turbine engine including a contrarotating propeller receiver and a dual-body gas generator having a low-pressure compressor and a high-pressure compressor separated by an intermediate housing, in which the gas generator is arranged upstream from the receiver is provided. The turbine engine includes a structural casing for supporting the receiver, surrounding the gas generator and having a downstream end attached to the receiver and an upstream end attached to the intermediate housing; and a connection device between the structural supporting casing and the gas generator, arranged between the upstream and downstream ends of the casing.

FIELD OF THE INVENTION

The present invention relates to the field of aircraft turbine engines comprising a contrarotating propeller receiver arranged downstream from a gas generator.

The invention particularly applies to a turbine engine having non-streamlined propellers, referred to as an open rotor turbine engine, wherein a free power turbine drives the two contrarotating propellers, directly or indirectly via a mechanical transmission device acting as a reduction gear.

STATE OF THE RELATED ART

FIG. 1shows an open rotor type aircraft turbine engine1, according to a known embodiment of the prior art, comparable to that described in the document FR 2 944 155.

In this figure, direction A consists of the longitudinal direction or axial direction, parallel to the longitudinal axis2of the turbine engine. Direction B consists of the radial direction of the turbine engine, and direction C of the tangential direction. Furthermore, the arrow4represents the direction of progression of the aircraft under the action of the thrust of the turbine engine1, this direction of progression going against the main gas flow direction4′ within the turbine engine. The terms “upstream” and “downstream” used hereinafter are to be interpreted with respect to the main gas flow direction4′.

At the front, the turbine engine has an air inlet6extending to the rear by means of a pod8, globally comprising an outer shell10and an inner shell12, both centred on the axis2and radially offset with respect to each other.

The inner shell12forms an external radial housing for a gas generator14, conventionally comprising, upstream to downstream, a low-pressure compressor16, a high-pressure compressor18, a compression chamber20, a high-pressure turbine22, and an intermediate-pressure turbine24. The compressor16and the turbine24are mechanical connected by a shaft26, thus forming a low-pressure body, whereas the compressor18and the turbine22are mechanically connected by a shaft28, forming a higher pressure body. Consequently, the gas generator14has a conventional, dual-body, design, wherein the compressors16and18are separated by an intermediate housing27, acting as an important structural component of the turbine engine. Indeed, this housing27, traversed by the outflowing air from the compressor16before it enters the compressor18, has an upper end equipped with an engine mount29connecting the turbine engine1to a coupling strut31, preferably intended to be mounted on the aircraft wing unit.

Downstream from the intermediate-pressure turbine24, a contrarotating propeller receiver30is situated, the receiver acting as the propulsion component of the turbine engine.

The receiver30comprises at the upstream end thereof a free power turbine32, acting as a low-pressure turbine. This turbine comprises a rotor34mechanically connected to a mechanical transmission device13, acting as a reduction gear and particularly comprising a planetary gear15. The stator part thereof comprises an outer housing36wherein one upstream flange38is attached to a downstream flange40of the casing12, situated at the end of the intermediate turbine24. The attachment is performed conventionally, by bolting.

Furthermore, downstream from the turbine32, the receiver30incorporates a first propeller7or downstream propeller, bearing blades7a. Similarly, the system30comprises a second propeller9or upstream propeller, bearing blades9a. In this way, the propellers7,9are offset with respect to each other along the direction4, and both situated downstream from the free turbine32.

The two propellers7,9are intended to rotate in opposite directions about the axis2whereon they are centred, the rotations being performed with respect to the stator which remains immobile. The rotation of these two propellers7,9, devoid of outer radial streamlining surrounding same, is performed using the mechanical transmission device13to which they are connected.

The receiver30is thus arranged overhanging the downstream end of the gas generator, which gives rise to stress causing distortions thereof, particularly of the outer housing thereof. This may give rise to significant play-related consumptions at the end of gas generator module blades, particularly on the high-pressure compressor blades. These play-related consumptions are liable to degrade the overall efficiency and surge margin of the turbine engine.

DESCRIPTION OF THE INVENTION

The aim of the invention is thus that of remedying, at least partially, the drawbacks mentioned above, in relation to embodiments of the prior art.

To this end, the invention relates to an aircraft turbine engine comprising a contrarotating propeller receiver and a dual-body gas generator comprising a low-pressure compressor and a high-pressure compressor separated by an intermediate housing, said gas generator being arranged upstream from said receiver.

According to the invention, the turbine engine further comprises a structural casing for supporting the receiver, said casing surrounding the gas generator and having a downstream end attached to said receiver and an upstream end attached to said intermediate housing. Furthermore, it comprises additional connection means between said structural supporting casing and the gas generator, arranged between the upstream and downstream ends of the casing.

The invention is thus characterised in that it enables at least part of the stress, resulting from the overhanging position of the receiver, to no longer transit through the portion of the gas generator situated downstream from the intermediate housing. Indeed, this stress transits via the structural casing to be subsequently introduced directly into the intermediate housing separating the two compressors. The solution provided thus advantageously makes it possible to remove the direct mechanical connection between the downstream end of the gas generator, and the upstream end of the receiver. Preferably, in addition, no direct mechanical connection is envisaged between the receiver and the outer housing of the gas generation situated downstream from the intermediate housing.

This gives rise to a reduction in the distortions of the gas generator, particularly of the outer housing thereof, downstream from the intermediate housing. This induces a noteworthy limitation of the play-related consumption at the end of the blades of the generator modules, particularly at the end of the blades of the high-pressure compressor. The overall efficiency and the surge margin of the turbine engine are thus substantially enhanced.

Also according to the invention, said additional connection means are designed to enable relative movement between said structural support casing and the gas generator. This makes it possible not only to handle the differential heat expansion between the two elements connected by these additional means in a satisfactory manner, but also to increase the portion of the stress resulting from the overhanging position transiting to the intermediate housing substantially, without loading the outer housing of the gas generator. It is even possible to ensure that the all the stress in question transits via this casing, without loading the part of the gas generator situated downstream from the intermediate housing. The overall efficiency of the turbine engine is thus perfectly optimised by means of the flexibility provided by the additional connection means, thus enabling the casing to be deformed while limiting/preventing the transmission of stress to the gas generator.

Preferably, said additional connection means comprise a plurality of connecting rods distributed circumferentially with respect to each other, about the longitudinal axis of the turbine engine, these connecting rods being preferentially mounted at the ends thereof with ball joints.

Preferably, said additional connection means are arranged downstream from the combustion chamber of the gas generator, and more preferentially, in the vicinity of a downstream end of the gas generator.

Finally, the turbine engine preferably comprises means for extracting an air flow at the low-pressure compressor outlet and routing same to an annular space defined externally by the structural support casing, the turbine engine being designed such that said air flow is introduced into a power turbine of the receiver. The structural casing is then moved to channel a secondary air flow through the turbine engine, which is usually devoid thereof in this type of non-streamlined contrarotating propeller design. The extracted air flow is then reinjected into the power turbine, making it possible to reduce the fuel consumption, cool the gas generator elements situated in contact with and in the vicinity of the diverted air flow and control the thermodynamic aspects of the low-pressure compressor, particularly the surge margin thereof.

The air may be extracted using fixed or controllable flaps, preferably mounted on the intermediate housing.

Further advantages and features of the invention will emerge in the non-limiting description detailed hereinafter.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 2represents an open rotor type turbine engine, according to a preferred embodiment of the present invention. The elements bearing the same reference numbers as the elements of the turbine engine inFIG. 1consist of identical or similar elements.

In this way, it can be noted that the specificity of the present invention lies in the presence of a structural casing50for supporting the receiver30.

This casing50extends around the gas generator14, centred on the axis2, between a downstream end50aand an upstream end50b. The upstream end50bis attached to the intermediate housing via an attachment flange52provided on the casing, and an attachment flange54of the intermediate housing27. The two flanges are attached conventionally by bolting. The flange54extends radially outwards from an outer downstream end of the intermediate housing, this flange54has a contact surface with the flange52, situated in a plane corresponding to the interface plane between the intermediate housing27and the portion of the outer housing12surrounding the high-pressure compressor18. In this way, the casing50extends from the intermediate housing27around and away from the outer housing12, downstream towards the end50athereof bearing an attachment flange56. The flange is attached conventionally by bolting to the upstream attachment flange38of the receiver30, the latter flange38thus no longer being attached directly on the downstream part of the gas generator14, as in the case in the prior art.

On the other hand, additional connection means between the casing50and the downstream end of the gas generator14are provided, these means being preferentially mounted close to the downstream end50a, and connected to the part of the outer housing12surrounding the turbine24, on or in the vicinity of a downstream end thereof.

These means are in the form of a plurality of connecting rods60distributed circumferentially with respect to each other, about the longitudinal axis2. Each connecting rod60is preferably inscribed in a plane incorporating this axis2, slightly inclined with respect to the vertical direction such that the radially inward end thereof is offset downstream with respect to the radially outward end thereof. This arrangement makes it possible to accompany the heat expansion of the gas generator downstream in a satisfactory manner, with said generator tending to undergo more expansion than the casing50, which is less exposed to temperature stress.

In this way, the connecting rods advantageously enable a relative movement between the structural casing50and the gas generator14, in the three directions, longitudinal A, radial B and tangential C. To facilitate these relative movements, the connecting rods60are mounted at the ends thereof with ball joints62.

With this design, the stress resulting from the overhanging position of the reciever30transit almost exclusively via the casing50, which may then be deformed without loading the gas generator arranged at a distance, radially inward.

The casing50is preferentially produced using two half-shells attached longitudinally onto each other. They are made of metal or a composite material, according to the level of temperature stress to which they are subjected.

This casing50may advantageously be used so as to circulate a cool secondary flow inside the turbine engine. To this end, it comprises means for extracting an airflow (not shown), wherein the means for extracting the airflow are flaps for extracting an air flow70at the outlet of the low-pressure compressor16. The flaps, mounted on the intermediate casing, are fixed or controllable. The air flow70diverted from flow from the compressor16thus transits via the intermediate housing27wherein the flow70is extracted, to reach an annular space72defined externally by the inner surface of the casing50, and defined internally by the outer housing12of the generator. The flow70is routed downstream until it reaches an annular passage78between the downstream ends of the housing12and the casing50, and is thus introduced into the free power turbine36, as represented inFIG. 2In this turbine, it joins the primary flow74from the turbine24, from which it was separated by the flaps in the intermediate housing27.

According to an alternative embodiment shown inFIG. 3, the downstream end50aof the casing50is connected by the flange56thereof to the downstream end of the outer housing36of the turbine32, via a flange80intended for this purpose.

Obviously, various modifications may be made to the invention described above, merely as non-limiting examples, by those skilled in the art.