FR3062677A1 - DOUBLE FLOW TURBOREACTOR COMPRISING A PREVIOUS DISTRIBUTOR TWO FLOORS OF LOW PRESSURE TURBINES WHICH ARE VENTILATED BY COOLING AIR OF THE DISTRIBUTOR - Google Patents

Abstract

The invention relates to a turbojet engine (1) comprising an inner envelope (2) surrounded by an intermediate envelope (3) jointly delimiting a primary vein which is surrounded by a secondary vein, - this turbojet engine (1) comprising in the primary vein a turbine low pressure (4) comprising a distributor (6) and a first and a second rotary stage (7, 9); the distributor comprising fixed vanes (11) traversed by cooling air collected at a high-pressure compressor; the first rotary stage (7) comprising a first disk (14) carrying first blades (13) and the second rotary stage (9) comprising a second disk (17) bearing second blades (16), these disks (14, 17) being carried by a low pressure journal (22); - The blades (13) of the first rotary stage (7) and the blades (16) of the second rotary stage (9) being cooled by cooling air having passed through the vanes (11) of the distributor (6).

Description

DESCRIPTION

TECHNICAL AREA

The invention relates to the cooling of the blades of a two-stage low pressure turbine in a turbofan engine.

PRIOR STATE OF THE ART

A dual-flow turbojet engine has an inlet sleeve that receives air which is drawn in by a low-pressure compressor and then divided into a central primary flow and a secondary flow surrounding the primary flow.

The primary flow circulates in a space called primary vein which extends between an internal envelope delimited by a succession of fixed and rotating internal elements, and externally by an intermediate envelope surrounding these elements. The fixed internal elements include rectifiers, distributors, and inner casing ferrules, and the rotary internal elements include padded rotor wheels.

The intermediate casing is successively delimited by different casings comprising in particular a high pressure compressor casing, a primary stream casing, a high pressure turbine casing, and an exhaust casing.

The secondary flow circulates in a space called secondary vein which extends radially between the intermediate envelope and an external envelope also called the engine hull, which surrounds this intermediate envelope.

After passing through the low pressure compressor, this secondary flow is propelled backwards to directly generate a thrust by being blown around the primary flow.

After passing through the low pressure compressor, the primary flow passes through a high pressure compressor, then reaching a combustion chamber. After combustion, it is expanded in a high pressure turbine linked in rotation with the high pressure compressor, then in a low pressure turbine linked in rotation with the low pressure compressor, before being expelled backwards to generate a thrust.

Each turbine and each compressor is formed of stages each comprising a disc carrying a series of rotary vanes regularly spaced around a longitudinal central axis of the motor, optionally followed by a distributor or a rectifier constituted by a series of 'fixed blades.

A distributor is interposed between the high pressure turbine and the low pressure turbine, and the vanes of this distributor are traversed by cooling air which is taken from an intermediate stage of the high pressure compressor by being supplied by a conduit.

After passing through the distributor vanes, the air passes through a central region before passing through a low-pressure turbine disc which directs this air into the rotary vanes which this disc carries to cool them.

The object of the invention is to provide a solution for air cooling a low pressure turbine comprising two stages.

STATEMENT OF THE INVENTION

To this end, the subject of the invention is a low pressure turbojet turbine comprising an inner envelope surrounded by an intermediate envelope to jointly delimit a primary stream:

- This low pressure turbine comprising a distributor followed by a first rotary stage and a second rotary stage;

the distributor comprising fixed vanes extending radially from the intermediate casing to the inner casing, these fixed vanes being traversed by cooling air collected at the level of a high pressure compressor;

the first rotary stage comprising a first disc carrying first vanes and the second rotary stage comprising a second disc carrying second vanes;

- The first disc and the second disc being carried jointly by a pin;

- the blades of the first rotary stage and the blades of the second rotary stage being ventilated respectively by a first flow and by a second flow both coming from a main flow coming from a high pressure compressor, the second flow passing through a barrier formed by the first disc and the journal carrying this first disc, by corresponding holes formed in this barrier.

With this arrangement, the vanes of the distributor, which are the most thermally exposed, are traversed by a main flow whose flow is the greatest, and this same main flow is subdivided into two flows ventilating the first stage and the second rotary stage whose the thermal exposure is less important. The invention thus makes it possible to control the ventilation flow rate cooling the second rotary stage and possibly purges, thanks to the holes present in the barrier formed by the pin and the first disc.

The invention also relates to a turbine thus defined, in which the second disc has holes for passage of the second flow towards a space located downstream of the second disc to supply a purge located downstream of the second disc.

The invention also relates to a turbine thus defined, in which the first disc is fixed to a flange of the journal by bolts comprising screws drilled in the direction of their length to be traversed by the second flow, and in which the second disc comprises through holes for the second flow to the blades of the second rotary stage.

The invention also relates to a turbine thus defined, comprising a second distributor interposed between the first rotary stage and the second rotary stage, and in which this second distributor comprises blades cooled by a flow collected at a high pressure compressor.

The invention also relates to a turbine thus defined, in which the cooling flow from the second distributor ends up in an interdisc space situated between the first disk and the second disk to supply two purges situated respectively upstream and downstream of this second distributor.

The invention also relates to a turbomachine comprising a turbine thus defined.

The invention also relates to a turbojet engine comprising a turbomachine thus defined.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a half-sectional view of a rear part of a turbojet engine according to the invention showing its low pressure turbine and its exhaust;

FIG. 2 is a view in local half-section showing a journal carrying two discs of low pressure turbines in a turbojet engine according to a variant of the invention.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

In FIG. 1, a rear part 1 of an engine according to the invention located immediately downstream of a high pressure turbine, not shown, comprises an internal envelope 2 surrounded by an intermediate envelope 3 which jointly delimit a primary stream. An outer casing 5, also called a secondary vein casing or engine hull delimits with the intermediate casing 3 the secondary vein of this turbojet engine.

The inner casing 2 is delimited by a succession of rotary internal elements comprising the platforms of the paddlewheel vanes of the rotor, and by a succession of fixed internal elements which include rectifiers, distributors and internal casing ferrules.

The intermediate casing 3 is successively delimited along the engine by a high pressure compressor casing, by a primary stream casing, by a high pressure turbine casing and by an exhaust casing.

This rear part comprises a low pressure turbine 4, comprising a first distributor 6 followed by a first rotary stage 7, followed by a second distributor 8 which is followed by a second rotary stage 9.

The first distributor 6 is formed of stationary vanes 11 oriented radially and each extending from the inner casing 2 to the intermediate casing 3. Similarly, the second distributor 8 is formed of stationary vanes identified by 12 .

The first rotary stage 7 comprises a series of vanes 13 extending radially in the primary stream from the inner envelope 2 to the intermediate envelope 3, these blades 13 being carried by a first rotary disk 14 located at the inside of the inner envelope 2.

Similarly, the second rotary stage 9 comprises a series of blades 16 carried by a second rotary disc 17 also located in the inner casing 2 downstream of the first disc 14.

Downstream of this low-pressure turbine is located an exhaust casing 19 comprising an internal ferrule and an external ferrule as well as radial arms 18 joining these ferrules to one another. The external shell defines a portion of the intermediate envelope 3, the internal shell defines a portion of the internal envelope, the radial arms radially crossing the primary vein. This exhaust casing 19 carries in its central region a bearing support 21 situated inside the interior envelope 2.

This bearing support 21 located inside the inner casing 2, carries a low pressure pin 22, also extending inside the inner casing, and to which the first and second turbine discs are fixed low pressure 14.17.

The first disc 14 is rigidly secured to an upstream face of a circumferential flange 23 of the pin 22, and the second disc 17 is secured to a downstream face of this flange 23. Concretely, this fixing is ensured by bolts 24 each passing through the first disc 14 at its internal periphery, the flange 23 and the second disc 17 at its internal periphery.

The fixed blades 11 of the first distributor are traversed radially by a main flow of ventilation Fp which comes from the high pressure compressor while being conveyed by a pipe terminated by an elbow 26 projecting externally from the intermediate envelope 3.

This main ventilation flow Fp, passes through the fixed vanes 11 in a centripetal radial direction, from the intermediate envelope 3 to the interior envelope 2 to reach an internal space E surrounded by the interior envelope 2, in a region of this internal space E located upstream of the first disc 14.

By crossing the fixed blades 11, the flow Fp ensures their cooling by winding in internal conduits not shown to increase convection, and by crossing the wall of each fixed blade 11 by micro perforations to create an external air film. The part of the flow Fp leaving the blade through the micro perforations is identified by Fp '.

The flow Fp reaches the internal space E via a distributor 27 by splitting into a portion distributing upstream AM and a portion distributing downstream AV of this space E. In the example of the figures, this separation is relatively strict, but it is an example of an embodiment, this separation possibly being more diffuse.

The portion of the main flow Fp distributed upstream mainly supplies the high pressure turbine of the engine. The portion of the main flow Fp distributed downstream becomes a first ventilation flow f1 which ventilates the rotary blades 13 of the first stage 7, and a second ventilation flow f2 which ventilates the rotary blades 16 of the second stage 9.

The stationary vanes 12 of the second distributor 8 are cooled by another ventilation flow identified by Fv, which also comes from the high pressure compressor via the pipe terminated by the elbow 26, the flow conveyed by this pipe dividing to constitute the flow Fp and flow Fv when it leaves the elbow 26.

This flow Fv flows like the main flow Fp in a centripetal radial direction, in the stationary vanes 12, from the intermediate casing 3 to the inner casing 2 to cool these vanes. This flow Fv also passes through the interior envelope 2 to then contribute to the cooling of this interior envelope 2.

By crossing the fixed blades 12, the flow Fv ensures their cooling by winding in internal pipes not shown to increase convection, and by crossing each wall of fixed blade 12 by micro perforations to create an external air film. The part of the flow Fv leaving the blade by the micro perforations is identified by Fv '.

As visible in FIG. 1, the first ventilation flow fl travels from a downstream nozzle of the distributor ΊΊ to reach a peripheral edge 28 of the first disc 14 which carries the blades 13 by their feet 29. The first ventilation flow fl engages thus in the inlet ports of the feet 29 so as to then circulate in the blades to ventilate them.

Similarly, the second ventilation flow f2 travels from an upstream nozzle of the distributor 27 downstream, passing through corresponding openings or bores 31 of the first disc 14, so as to reach interdisc regions El, E2 and E3 of l internal space E which are located between the first and second disc 14,

17.

This second ventilation flow f2 then reaches a peripheral edge 32 of the second disc 17 which carries the blades 16 by their feet 33 to engage in the inlet openings of these feet so as to then circulate in the corresponding blades in order to cool.

As can be seen in FIG. 1, a part fl ′ of the first ventilation flow fl is deflected to supply a purge ensuring that hot air from the primary vein does not enter the internal space E at the level of the small spacing located at the junction between the feet of the fixed blades 11 and the feet of the rotary blades 13. Thus, at this junction spacing between stator and rotor, the pressurized air of the flow fl 'is expelled radially towards the primary vein whose pressure is less, to ensure that there is no circulation from the primary vein to the internal space E.

Similarly, a part f2 'of the second ventilation flow f2 is deflected to constitute another purge where it is expelled radially, at the junction between the feet of the rotary vanes 16 and the inner shroud of the exhaust casing 19 located downstream of these rotary blades. The part f2 'is deflected from the flow f2 in the interdisc region E3, and it crosses the second disc 17 by holes 34 to leave this region E3, before crossing the second disc by other holes 35 located downstream of the holes 34 , to then reach the junction between the feet of the rotary blades 16 and the inner shell of the exhaust casing 19 which is downstream of these rotary blades.

In addition, the air from stream Fv having passed through the fixed blades 12 of the second distributor 8 is split in regions El and E2 into two streams Fv '' and Fv 'constituting two other purges. The flow Fv feeds a purge corresponding to the junction between the feet of the rotary blades 13 is the feet of the fixed blades 12. The flow Fv 'which passes through the region E2 feeds a purge corresponding to the junction between the feet of the fixed blades 12 and the feet of the rotary blades 16.

In general, the assembly formed by the first disc 14 and the pin 22 which carries it constitutes a barrier opposing the passage of the second ventilation flow f2. In the example of FIG. 1, this second ventilation flow f2 passes from the upstream region to an intermediate region located between the two discs 14 and 17, through holes 31 of the first disc, which allows this second flow to be brought into the intake openings of the blades 16 of the second rotary stage 9.

In the variant of FIG. 2, the second ventilation flow f2 reaches the feet of the vanes 16 of the second rotary stage 9 by first passing through the pin 22 via the bolts 24 whose screws are drilled in the direction of their length, and then crossing the second disc 17 through corresponding holes 34.

More particularly, by crossing the bolts 24, the second flow f2 jointly crosses the first disc 14, the flange 23 of the journal, and the second disc

17, so that it is then in a region of the internal space E extending beyond the first disc 14 and the second disc 17.

To reach the intermediate region located between the discs 14 and 17 in order to supply ventilation air to the blades 16 of the second rotary stage, the flow fl passes through corresponding holes 34 of the second disc 17.

In the example of FIG. 1, the flow f2 crosses the barrier formed by the first disc 14 and the pin 22 by holes 31 formed in the first disc. More generally, such holes can also be formed in the pin 22 and possibly in the second disc 17, or even in the assembly.

When these holes are formed in the disc, they are formed in the part of the disc ensuring the mechanical connection with the pin. When they are formed in the pin they are located in the vicinity of the connection with the disc. When these holes are formed in the drilled screws, they extend through the connection as such of the disc with the journal.

As regards their positioning, these holes are formed in a region of the barrier constituted by the pin and the disc which is located radially between the radius of an internal edge of the disc reduced by 20% and the radius of a radial end external of the trunnion flange increased by 20%.

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Claims (7)

1. Low pressure turbine of a turbojet engine (1) comprising an internal envelope (2) surrounded by an intermediate envelope (3) to jointly delimit a primary stream: - This low pressure turbine (4) comprising a distributor (6) followed by a first rotary stage (7) and a second rotary stage (9); - the distributor (6) comprising fixed vanes (11) extending radially from the intermediate envelope (3) to the inner envelope (2), these fixed vanes (11) being traversed by air from cooling of a main flow (Fp) from a high pressure compressor; - the first rotary stage (7) comprising a first disc (14) carrying first blades (13) and the second rotary stage (9) comprising a second disc (17) carrying second blades (16); - the first disc (14) and the second disc (17) being carried jointly by a pin (22); - the vanes (13) of the first rotary stage (7) and the vanes (16) of the second rotary stage (9) being ventilated respectively by a first flow (fl) and by a second flow (f2) coming from one and l other of the main flow (Fp), the second flow (f2) passing through a barrier formed by the first disc (14) and the journal (22) carrying this first disc (14), by corresponding holes (31, 24) formed in this barrier. 2. A turbine according to claim 1, in which the second disc (17) has holes (34) for the passage of the second stream (f2) to a space located downstream of the second disc (17) to supply a purge located downstream of the second disc (17). 3. Turbine according to claim 1, in which the first disc (14) is fixed to a flange (33) of the journal (22) by bolts (24) comprising screws drilled in the direction of their length to be traversed by the second flow (f2), and in which the second disc comprises holes (34) for passage of the second flow (f2) towards the blades (16) of the second rotary stage (9). 4. Turbine according to one of claims 1 to 3, comprising a second distributor (8) interposed between the first rotary stage (7) and the second rotary stage (9), and in which this second distributor (8) comprises blades (12) cooled by a flow (Fv) from a high pressure compressor. 5. A turbine according to claim 4, in which the cooling flow (Fv) of the second distributor (8) ends in an interdisc space (El, E2) situated between the first disc (14) and the second disc (17) for supply two purges located respectively upstream and downstream of this second distributor (8). 6. Turbomachine comprising a turbine according to one of the preceding claims. 7. A turbojet engine comprising a turbomachine according to claim 6. S61697 1/2 23 22 24