FR2961257A1 - Method for mounting discharge valve on hub of intermediate casing of e.g. twin spool turbojet engine of aircraft, involves fixing end-fitting on structure of door for defining air guiding conduit in opening position - Google Patents

Abstract

The method involves transporting a door (30) through an air passage orifice (28) managed in an annular collar (12) of a hub (10) so as to define an annular space (24) for flow of air in a turbojet engine, where a supporting unit is integrated to the hub and allows pivoting of the door between a closing position and an opening position of the orifice. An end-fitting (50) is fixed on a structure (39) of the door for defining an air guiding conduit in the opening position such that the end-fitting allows the conduit to extend toward downstream. Independent claims are also included for the following: (1) a discharge valve comprising a door (2) a intermediate casing comprising a deflector (3) a turbojet engine comprising an intermediate casing.

Description

FIELD OF THE INVENTION The present invention relates to an aircraft turbojet engine, in particular of the type comprising at least two bodies mechanically. independent. In a double-body turbojet engine, an intermediate casing is usually designated as a casing whose hub is arranged between a low-pressure compressor casing and a high-pressure compressor casing. The present invention relates more particularly to a method of mounting a discharge valve, of the type sometimes referred to as the VBV (Variable Bleed Valve), on an intermediate crankcase hub in an aircraft turbojet engine. Valves of this type are intended to regulate the inlet flow of the high-pressure compressor in order, in particular, to limit the risks of pumping the low-pressure compressor by allowing part of the air to escape from the annular space of the compressor. flow of the primary flow. In addition, in case of accidental penetration into this flow space, water, especially in the form of rain or hail, or various debris, which are likely to affect the operation of the turbojet, these valves can recover this water or debris which is centrifuged in the above-mentioned flow space and ejected outwardly thereof. In the case of turbofan engines, these valves are thus configured to allow the passage of fragments or debris from the flow space of the primary flow to an annular flow space of a secondary flow. In what follows, the term "debris" refers to any type of debris likely to affect the operation of the turbojet engine, whether it is water in liquid or solid form or fragments of various materials. STATE OF THE PRIOR ART As illustrated in FIG. 1, which is a partial diagrammatic view in axial section of a double-body and dual-flow aircraft turbojet engine of known type, the hubs 10 of the intermediate casings 11 of the aforementioned type usually comprise a plurality of annular coaxial ferrules, among which an intermediate shell 12 and an outer shell 14 interconnected by two transverse flanges, respectively upstream 16 and downstream 18. The upstream flange 16 is arranged downstream of a low pressure compressor 20 of the turbojet while the downstream flange 18 is arranged upstream of a high-pressure compressor 22 of this turbojet engine. The intermediate shell 12 delimits externally an annular space 24 of flow of the primary flow of the turbojet, and is generally connected by structural arms 26 passing through this space 24 to an inner shell 27 internally defining said space 24. In addition, the ferrule intermediate 12 includes air passages 28 each of which is closed by the pivoting valve 29 of a corresponding discharge valve 30 for regulating the flow of the high-pressure compressor 22 and, where appropriate, the evacuation of debris as explained above.

Such a discharge valve usually takes the form of a door which has the valve 29 at its radially inner end and which is pivotally mounted about an axis 31 so that in the closed position of the air passages 28 , the valve 29 extends the intermediate ring 12 of the housing substantially continuously to reduce the risk of aerodynamic disturbances of the primary flow by this valve 29, and in the open position of said openings 28, the valve 29 protrudes radially. inwardly relative to the intermediate ferrule 12 above and thus forms a scoop for taking part of the primary flow. Patent Application EP 2,060,746 A1 describes in more detail an example of a discharge valve.

When the outer shell 14 of the hub 10 of the intermediate casing 11 carries structural arms which extend in a flow space 32 of a secondary flow of the turbojet and which are relatively spaced from each other, the evacuation of the air or debris can be done through the outer shell 14. 4 On the other hand, when as in the example shown in Figure 1, the outer shell 14 carries guide vanes 34 relatively close to each other, the latter obstruct the aforementioned evacuation through the outer shell 14. In this case, and more generally when it is of interest, it may therefore be desirable to allow this evacuation further downstream, through the annular wall 36 of an extension 38 of the hub 10 of the intermediate casing 11. Here is meant by extension 38 a structural part which is sometimes used to support at its downstream end of the thrust reverser elements such as pa fairing units.

A known solution to this problem is to integrate in the door of each discharge valve 30 a structure 39 forming air guide duct when the valve is in the open position, and to provide in the transverse flange downstream 18 a plurality air passage holes 40, respectively arranged downstream of each of the discharge valves 30 and intended to receive air and any debris from these valves 30, this air and these debris can then continue their trajectory within ducts 41 connected to corresponding air passages 42 provided in the annular wall 36 of the extension 38 of the hub 10 and opening into the flow space 32 of the secondary flow.

Figure 2 illustrates the door of a discharge valve 30 and shows in particular the structure 39 forming air guide duct which is part of this door. However, the way in which the doors of the discharge valves are mounted in the intermediate casing 5 can lead to a limitation of the extent of these doors in the direction of the axis 44 of the turbojet, and thus to impose a relatively large distance between the exit the air guide duct of each door and the corresponding air passage 40 of the downstream transverse flange 18. In fact, when it is not possible to bring the doors of the discharge valves 30 radially from the outside in the internal space 46 of the hub 10 of the intermediate casing 11 between its outer shell 14 and its intermediate shell 12 and wherein these doors are intended to be installed, as is the case when the outer shell 14 door guide vanes 34 relatively close to each other, each door is brought into this inner space 46 radially from the inside, by the space 24 of flow of the primary flow and then through the orifice of corresponding air passage 28 of the intermediate shell 12, as symbolized by the arrow 48 of FIG. 3 which schematically illustrates the mounting of a discharge valve door 30 in the hub 10 of the intermediate casing 11. The respective sections of the The flow space 24 of the primary flow and the aforementioned orifices 28 thus limit the axial extent of the doors of the discharge valves 30, and more particularly of their respective structures 39 forming the air guide duct. However, the spacing between the outlet of the air guide duct of each discharge valve 30 and the corresponding air passage 40 of the downstream transverse flange 18 induces the risk that a part of possible debris will strike the duct. flange 18 next to the air passages 40 of the latter and remains in the intermediate casing, the risk of interfering with the operation of the valves and the evacuation of additional debris. In order to limit this risk, the air passage orifices 40 of the downstream transverse flange 18 may be positioned near the flow space 24 of the primary flow, substantially at the same level radially as the passage openings 28. of the intermediate shell 12, so that the debris captured by each discharge valve 30 naturally continue their stroke from the outlet of the structure 39 forming the air guide duct of the valve to the air passage holes 40 of the flange This configuration has disadvantages, however.

On the one hand, it does not sufficiently reduce the aforementioned risk that debris does not reach one of the air passages 40 provided for this purpose in the downstream transverse flange 18 and then accumulate in the air. internal space 46 of the hub 10 of the intermediate casing. On the other hand, this solution implies a removal of the air passage orifices 40 from the downstream transverse flange 18 with respect to the air passage orifices 42 of the downstream extension 38 of the hub 10, of a nature to increase the congestion and the mass of ducts 41 interconnecting the above-mentioned orifices, which is undesirable. DISCLOSURE OF THE INVENTION The invention aims in particular to provide a simple, economical and effective solution to these problems, to avoid at least partly the aforementioned drawbacks. To this end, the invention proposes a method of mounting a discharge valve comprising a pivoting door on an intermediate case hub for an aircraft turbojet engine, this method comprising the routing of the door through a passage orifice. of air formed in an annular shell of the hub intended to define externally an annular flow space of a primary flow of the turbojet, into an internal space of the hub, then the installation of the door on support means integral with this hub and allowing a pivoting of the door between a closed position and an open position of said orifice. According to the invention, the method then comprises attaching a nozzle to a structure of the door delimiting, in the open position, an air guide duct, so that said tip extends said duct downstream. It should be noted that the upstream and downstream directions are defined in relation to the flow of the primary flow of gas in a turbojet engine equipped with said intermediate casing.

The mounting method according to the invention allows the mounting of a discharge valve door whose axial extent is greater than the limit allowed by the assembly methods known from the prior art. The tip allows to extend the air guide duct structure and thus improve the guiding of air and any debris passing through the discharge valve. When the intermediate casing hub has a downstream transverse flange provided with air passages for receiving air and any debris from each discharge valve fitted to this hub, the tip of each valve mounted by means of the In particular, the aforementioned method makes it possible to reduce the axial spacing between the downstream end of the air guide duct structure of the valve and the corresponding air passage orifice of the downstream transverse flange. In this case, the improvement of the guiding of the air and debris also allows a spacing, in the radial direction, between the air passage holes of the annular ring of the hub and the air passages of the transverse flange downstream of the latter. The orifices of this flange can thus in particular be arranged radially outwardly relative to the orifices of the annular shell of the hub. In general, the nozzle also has the advantage of allowing air and possible debris to be guiding as soon as an opening operation of the discharge valve equipped with this nozzle is initiated. during all this opening operation, as well as during a closing maneuver of the valve. Fixing the nozzle on the air guide duct structure of the door of the discharge valve is advantageously carried out by force engagement or by means of screws. This allows easy disassembly of the tip, which can be advantageous to replace it in case of wear of it.

Alternatively, this attachment of the tip can be made by gluing or by soldering, welding or the like. In all cases, the tip may advantageously be made of a lighter material and / or less expensive than that in which is made the door of the discharge valve on which the tip is mounted. The mounting method according to the invention can be applied to an intermediate casing previously mounted in an aircraft turbojet engine. Alternatively, this method can be applied to an intermediate casing before mounting the latter in an aircraft turbojet engine. The invention also relates to a discharge valve for an aircraft turbojet intermediate casing hub, comprising a door intended to be pivotally mounted between a closed position and an open position of an air passage orifice. formed in an annular shell of an intermediate casing hub intended to define externally an annular space flow of a primary flow in a turbojet engine comprising such a hub, this door comprising a structure which delimits an air duct, and a tip attached to this structure so as to extend downstream the aforementioned conduit. The invention also relates to an intermediate casing for an aircraft turbojet engine, comprising at least one discharge valve of the type described above mounted on an annular shell of a hub of this intermediate casing, said shell being intended to externally define a space annular flow of a primary turbojet flow. Preferably, the hub of the aforementioned intermediate housing further comprises, downstream of each discharge valve of this hub, a baffle for guiding the air from the outlet of the valve to a corresponding air passage opening provided in a transverse flange downstream of the hub and for receiving the air from the valve.

Such a deflector is particularly advantageous when the orifices of the transverse flange downstream of the hub are spaced radially outwardly relative to the orifices of the annular shell of this hub.

The tip extending the door of the aforesaid discharge valve (s) allows the use of 11 deflectors of smaller axial extent than the deflectors which could be used with discharge valves without tip. The limitation of the axial extent of these deflectors reduces the risk of excessive vibration of the latter in operation. The invention also relates to an aircraft turbojet engine comprising an intermediate casing of the type described above.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood, and other details, advantages and characteristics thereof will appear on reading the following description given by way of nonlimiting example and with reference to the appended drawings in which: FIG. 1, already described, is a partial schematic view in axial section of an aircraft turbojet of a known type; Figure 2, already described, is a schematic perspective view of a relief valve of the turbojet engine of Figure 1, shown isolated from its immediate environment; FIG. 3, already described, is a partial schematic view in axial section of the turbojet engine of FIG. 1, illustrating a mounting method, of a known type, of the relief valve of FIG. 2; Figure 4 is a schematic perspective view of a discharge valve according to the invention; 12

Figure 5 is a partial schematic view in axial section of an aircraft turbojet comprising the relief valve of Figure 4; Figure 6 is a partial schematic view in axial section of the turbojet engine of Figure 5, illustrating a method of mounting the relief valve of Figure 4 according to the invention. In all of these figures, identical references designate identical or similar elements. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS FIG. 4 illustrates a discharge valve door 30 similar to that of FIG. 2, but also comprising a nozzle 50 attached to the structure 39 forming an air guide duct of the door. to extend it downstream. The tip 50 is fixed to the structure 39 by gluing. Alternatively, the end piece 50 can be fixed to the structure 39 by means of screws, or be welded to this structure 39. As a further variant, the end piece 50 can be forcibly engaged in the structure 39 or vice versa. In the particular example described in Figure 4, the tip 50 takes the form of a cylinder of rectangular section with rounded edges. In general, the shape of the tip may be adapted to match the geometry of the discharge valves of various known types or the geometry of new upcoming discharge valves. FIG. 5 illustrates an aircraft turbojet engine which differs from the turbojet engine of FIGS. 1 and 3, especially in that it comprises discharge valves 30 of the type described in FIG. 4 and one of which is visible in FIG. a partial opening position. In addition, the air passage orifices 40 formed in the downstream transverse flange 18 of the hub 10 of the intermediate casing 11 of this turbojet engine are positioned near the radially outer end of this flange 18 and thus also close to the air passage 42 of the annular wall 36 of the extension 38 of the hub 10. The guiding of the air and any debris from the outlet of the tip 50 of the discharge valves 30 to the orifices passing through Corresponding air 40 of the downstream transverse flange 18 is provided by deflectors 52 each of which extends upstream and radially inwardly from a radially inner edge of a corresponding air passage 40. In addition, each of these air passage holes 40 is provided with a deflector 54 extending upstream opposite the deflector 52 corresponding and of smaller extent than the latter to channel the air and any debris in the orifice 40.

Furthermore, the air passages 40 of the downstream transverse flange 18 are connected to the 14 air passage holes 42 of the extension 38 of the hub 10 by means of scoops 56 of geometry considerably more compact radially than the ducts. 41 known turbojets of the type illustrated in Figure 1.

It should be noted that the combination of a tip 50 and a deflector 52 allows efficient guidance of the air and any debris while allowing the use of a deflector 52 of axial extent sufficiently small to limit risks of vibration problems during operation of the turbojet engine. Each discharge valve 30 may, according to the invention, be mounted on the hub 10 of the intermediate casing 11 of the turbojet engine by a mounting method illustrated in FIG. 6 and in which: the door forming the valve 30, without a nozzle 50 , is first conveyed into the flow space 24 of the primary flow; this door 30 is then introduced into the internal space 46 of the hub 10 through an air passage orifice 28 housed in the intermediate shell 12 of the hub 10 and intended to be closed by this door; the door 30 is then mounted on support and control means integral with the hub 10 and for operating the door between an open position and a closed position of the air passage opening 28 above; a tip 50 is then brought into the internal space 46 above, radially from the outside, possibly passing through openings 15 formed in the outer shell 14 of the hub 10 or in the transverse flange upstream 16 or downstream 18; the end piece 50 is then fixed to the structure 39 forming the air guide duct of the door 30.

The first two steps of supply of the door 30 without endpiece 50 are symbolized by the arrow 48 in FIG. 6 while the fourth step of supplying the endpiece 50 is symbolized by the arrow 58.

According to the method described above, the intermediate casing 11 has been mounted in the turbojet engine before the implementation of the method of mounting the discharge valves 30. As a variant, the discharge valves 30 may nevertheless be mounted on the hub 10 of the intermediate casing 11 by the method described above before the intermediate casing 11 is assembled to the other components of a turbojet engine. The mounting method according to the invention is particularly advantageous when it is not possible to pass the discharge valves 30 radially from the outside to their mounting position, because the space available for their passage through the internal space 46 of the hub 10 is insufficient, or that the outer shell 14 of the hub 10 carries guide vanes relatively close to each other and thus preventing the passage of these valves. In general, the mounting method according to the invention makes it possible to increase the axial extent of the discharge valves, and therefore their ability to guide the air and any debris towards the air passage orifices. 40 dedicated to the reception of this air and debris, beyond the limits authorized by the assembly methods known from the prior art.

Claims (10)

CLAIMS1, A method of mounting a discharge valve (30), comprising a pivoting door, on a hub (10) of intermediate casing (11) for an aircraft turbojet engine, said method comprising the routing of said door through an air passage opening (28) formed in an annular shroud (12) of said hub for externally delimiting an annular space (24) for flow of a primary flow of said turbojet engine into an internal space (46) of said hub, then the installation of said door on support means integral with this hub and allowing a pivoting of the door between a closed position and an open position of said orifice (28), said method being characterized in that it then comprises the fixing of a tip (50) on a structure (39) of the door delimiting, in the open position, an air guide duct, so that said tip (50) extends said duct downstream. 2. Method according to claim 1, characterized in that the attachment of said tip (50) on said structure (39) of the door is achieved by a forced engagement. 3. Method according to claim 1, characterized in that the fixing of said tip (50) on said structure (39) of the door is made by means of screws or the like. 18 4. Method according to claim 1, characterized in that the attachment of said tip (50) on said structure (39) of the door is made by brazing, welding or the like. 5. Method according to claim 1, characterized in that the attachment of said tip (50) on said structure (39) of the door is made by gluing. 6. Method according to any one of claims 1 to 5, characterized in that said intermediate casing (11) is previously mounted in an aircraft turbojet engine. 15 7. Discharge valve (30) for an aircraft turbojet engine intermediate casing hub (10), comprising a door intended to be pivotally mounted between a shut-off position and an orifice opening position. air passage (28) formed in an annular shell (12) of a hub (10) of intermediate casing (11) intended to delimit externally an annular space (29) for flow of a primary flow in a turbojet engine comprising such a hub (10), said gate comprising a structure (39) defining an air guide duct, and said door being characterized in that it comprises an end piece (50) attached to said structure (39) so as to extend downstream said conduit. 30 8. Intermediate casing for an aircraft turbojet, characterized in that it comprises at least 10 19 a discharge valve (30) according to claim 7 mounted on an annular shell (12) of a hub (10) of said intermediate casing (11), said ferrule (12) being intended to delimit externally an annular space (24) for flow of a primary turbojet flow. 9. Intermediate casing according to claim 8, characterized in that the hub (10) of said intermediate casing (11) further comprises, downstream of each discharge valve (30) above, a deflector (52) for guiding the air from the outlet of said valve (30) to a corresponding air passage (40) in a downstream transverse flange (18) of said hub (10) for receiving air from said valve (30). 10. Aircraft turbojet, characterized in that it comprises an intermediate casing according to claim 8 or 9.