AIRCRAFT TURBOMACHINE COMPRISING A LIMITED PRESSURE LOSS LUBRICATION UNIT

Abstract

The invention relates to an aircraft turbomachine (1) comprising a bladed rotating wheel (40), a stator structure (44) defining a flow channel (14a), a purge air circulation chamber (46), and a lubrication chamber (60) delimited by a seal (62) exposed to pressurized air circulating in a pressurized air circuit (66). According to the invention, a passive system (90) is provided for regulating a purge air passage section, comprising a movable seal element (92) and a static seal element (94). The turbomachine is configured so that, in a first engine speed, the seal elements adopt a first relative position, and in a second engine speed higher than the first, the seal elements adopt a second relative position in which the purge air passage section is larger than that defined in the first relative position. Figure 2.

Description

Title of the invention: TURBOMACHINE AIRCRAFT INCLUDING AN ENCLOSURE OF LUBRICATION WITH LIMITED PRESSURE LOSS technical field

[0001] The invention relates to the field of aircraft turbomachinery, and more specifically to the management of lubricant pressure within lubrication chambers.

[0002] The invention applies in particular to turbojet engines, and even more particularly to twin-spool, twin-flow turbojet engines. PRIOR TECHNOLOGY

[0003] In the prior art, it is known that turbomachinery exists in which one or more bearings are arranged in a lubrication chamber. An example is known, for instance, from document FR 2 985 766 AL

[0004] In order to keep the lubricant within such a lubrication chamber, pressurized air is channeled around the chamber. This prevents or greatly limits lubricant leakage through the seal(s) delimiting the chamber.

[0005] For various reasons, a minimum lubricant pressure is required within the enclosure to ensure proper operation. For example, when the lubricant circulates through the enclosure via a lubricant recovery pump, the pump may require a minimum lubricant pressure inside the enclosure to achieve satisfactory lubricant recovery capacity.

[0006] If the minimum pressure is not reached, the pump is at risk of damage. Furthermore, if the pump is unable to extract sufficient lubricant from the chamber, it is at risk of lubricant leaking into the pressurization air circuit surrounding the chamber.

[0007] However, at certain engine operating points, the lubricant pressure within the housing may be low, exposing the turbomachine to the aforementioned risks. This is the case, for example, at idle speed during flight, typically adopted at the beginning of the aircraft's descent. In this regime, the lubricant pressure within the housing may be low, consequently implying risks of lubricant leakage outside the housing, as well as risks of damage to the lubricant recovery pump. Description of the invention

[0008] To overcome the drawbacks mentioned above, relating to prior embodiments, the invention relates to an aircraft turbomachine comprising:

[0009] - a turbine, comprising a bladed rotating wheel with a rotor, as well as a structure of stator arranged axially opposite the bladed rotating wheel, the rotating wheel and the stator structure jointly defining a gas circulation channel, as well as a purge air circulation chamber arranged radially inwards relative to the gas circulation channel, and separated from it by a purge device;

[0010] - a drive shaft, driving the bladed rotating wheel;

[0011] - a lubrication chamber, in which at least one bearing is arranged of rotational guidance of the drive shaft, the lubrication chamber being delimited in part by a sealing gasket limiting or preventing the extraction of lubricant outside the lubrication chamber, by being exposed to pressurization air circulating in a pressurization air circuit communicating with the purge air circulation chamber.

[0012] According to the invention, the purging device comprises a passive system for regulating a purging air passage section through the purging device, the passive regulation system comprising a movable seal element integral with the bladed rotating wheel, and a static seal element integral with the stator structure, the turbomachine being configured such that in a first engine operating regime, the movable and static seal elements adopt a first relative position, and that in a second engine operating regime, higher than the first regime, the movable and static seal elements adopt a second relative position in which the purging air passage section is greater than that defined in the first relative position.

[0013] Thus, the turbomachine is designed so that the purge air passage cross-section is passively modified following a simple change in engine operating speed. More precisely, the thermomechanical displacements and deformations of the parts, observed during changes in engine speed, are used to passively modify the state of the control system, and more specifically the relative position of the movable and static sealing elements of this system, which define the purge air passage cross-section. Consequently, it is easy to design the turbomachine so that the first relative position of these two sealing elements is occupied when the turbomachine is operating at the first speed, which would usually result in low lubricant pressure in the housing containing the bearing(s). This is preferably an idle operating speed during flight.However, in this initial relative position of the two sealing elements, the purge air passage area is reduced, so that the air pressure in the purge air circulation chamber is increased, as well as in the pressurization air circuit that communicates with this chamber. This indirectly results in... Advantageously, an increase in lubricant pressure within the housing is achieved. The risks described above are thereby reduced, using a simple, passive, and reliable solution that does not compromise the operation of the turbomachine at other engine speeds.

[0014] Indeed, the turbomachine is also designed so that the second relative position of the two sealing elements is occupied when the turbomachine is operating under the second operating regime, which would normally lead to a suitable lubricant pressure in the lubrication chamber. This is preferably a full-throttle operating regime. However, in the second relative position of the two sealing elements, the purge air passage area is larger, thus reducing its impact on the pressurization of the purge air circulation chamber, and therefore on the pressurization of the lubrication chamber, or even having no impact on either.

[0015] The invention also has at least one of the following optional features, taken individually or in combination.

[0016] Preferably, the movable sealing element is a platform, and the static sealing element is a slat, or vice versa, and the purge air passage section is defined between the platform and the slat, the latter extending preferably radially inwards.

[0017] Preferably, in the first relative position, the lick is located radially opposite the platform, and in the second relative position, the lick is located axially and radially spaced from the platform.

[0018] Preferably, the stator structure is a fixed turbine housing, comprising a fixed bladed runner, and the bladed rotating runner belongs to a final turbine stage. However, other applications are possible for the stator structure, such as a turbine distributor located further upstream than the fixed turbine housing, also called a turbine rear frame or TRF housing (from the English "Turbine Rear Frame").

[0019] Preferably, the purging device comprises a static portion of revolution belonging to the stator structure, as well as a radially internal platform spoiler of the bladed rotating wheel, the static portion of revolution and the platform spoiler extend axially in the direction of each other, being arranged radially outwards with respect to the moving and static sealing elements of the passive system for regulating the purging air passage section.

[0020] Preferably, the static joint element extends radially inwards from the static portion of revolution.

[0021] Preferably, the turbomachine includes a lubricant recovery pump communicating with the lubrication chamber.

[0022] Preferably, as mentioned previously, the first engine operating regime is an idle regime in flight, and the second engine operating regime is a full throttle regime.

[0023] Preferably, the turbomachine comprises a low-pressure body and a high-pressure body, and the turbine preferably belongs to the low-pressure body.

[0024] Finally, the turbomachine is preferably a turbojet. Other types of turbomachines, such as turboprops, remain conceivable, however, without departing from the scope of the invention.

[0025] Other advantages and features of the invention will become apparent in the detailed, non-limiting description below. Brief description of the drawings

[0026] This description will be made with reference to the attached drawings, among which;

[0027] [Fig.1] represents a schematic longitudinal cross-sectional view of a turbojet engine according to the invention;

[0028] [Fig.2] represents a longitudinal cross-sectional view of part of the turbojet engine shown in [Fig.1], according to a preferred embodiment of the invention, and showing in particular a lubrication chamber belonging to this turbomachine, as well as a purging device;

[0029] [Fig.3] represents an enlarged longitudinal sectional view of a part of that shown in the preceding figure, specifically illustrating the passive regulation system for a purge air passage section, the configuration of the parts as adopted in a first engine operating regime is shown in dashed lines, and the configuration of these same parts in a second engine operating regime, higher than the first, is shown in solid lines. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0030] With reference first to [Fig. 1], an aircraft turbomachine 1, according to the invention, is shown. This is a twin-spool, turbofan engine. However, it could be a turbomachine of another type, for example a turboprop, without departing from the scope of the invention.

[0031] The turbojet 1 has a longitudinal axis 3 around which its various components extend. It comprises, from upstream to downstream along a main direction of gas flow through this turbomachine, a fan 2, a low-pressure compressor 4, a high-pressure compressor 6, a combustion chamber 8, a high-pressure turbine 10 and a low-pressure turbine 12.

[0032] Conventionally, these elements define a primary channel 14a through which a primary flow 16a circulates, and a secondary channel 14b through which a secondary flow 16b circulates. In this dual-flow design, a casing is provided intermediate 20 arranged downstream of the blower 2. The intermediate housing includes a hub 22, radial arms 24, and an external ferrule 26 extending downstream a blower housing.

[0033] Here, the high-pressure turbine 10 and the high-pressure compressor 6 are connected by a high-pressure shaft 30, while the low-pressure turbine 12 and the low-pressure compressor 4 are connected by a low-pressure shaft 32, preferably passing through the high-pressure shaft 30. A rotating blower shaft 34 is also provided, driving the blower blades in rotation around the axis 3, on which the three shafts 30, 32, 34 are centered.

[0034] In the configuration shown, the blower shaft 34 is driven by means of a reducer 36, which is itself driven by the low-pressure shaft 32. However, driving the blower directly by the low-pressure body remains possible, without departing from the scope of the invention.

[0035] With more specific reference to [Fig. 2], a rear portion of the turbojet engine is shown, comprising the low-pressure turbine 12, which has one or more stages, each stage including a bladed rotor wheel 40 and a bladed stator wheel 42, also called a turbine distributor. These wheels 40 and 42 are thus arranged axially in alternating positions, and in [Fig. 2], two rotor wheels 40 and one static wheel 42 are visible. At the rear of the last rotor wheel 40 of the last stage of this low-pressure turbine 12, a stator structure is provided, formed by a fixed turbine casing 44, corresponding to a rear turbine casing, or TRF casing. This turbine casing 44 includes a bladed fixed wheel 45, which is located axially opposite the last rotor wheel 40.

[0036] The last rotating wheel 40 and the rear turbine housing 44 jointly define, with their radially external portions, the primary gas flow 14a. They also define, with their radially internal portions, a purge air circulation chamber 46, which is therefore arranged radially inwards with respect to the primary flow 14a, and separated from it by a purge device 50 specific to the invention.

[0037] More specifically, the purge air circulation chamber 46 is delimited radially outwards by the purge device 50. It is also delimited axially on one side by a disc 52 of the last turbine wheel 40, and on the other side by a wall of revolution 54 of the rear turbine casing 44, this wall 54 being of predominantly radial orientation.

[0038] The drive shaft of the low-pressure turbine 12, namely the low-pressure shaft 32, extends axially rearward to, or near, these elements 40, 44. It is guided in rotation by one or more guide bearings 58, arranged in a lubrication housing 60. In the mode of [Fig. 2], these are two bearings 58 which are arranged in the housing 60 containing lubricant, and which serve to guide the rotation of the low pressure shaft 32.

[0039] This enclosure 60 is delimited by fixed walls and movable walls rotating around the axis 3, and also delimited by one or more sealing joints 62 arranged at the interface between these fixed and movable walls.

[0040] Each lubricant seal 62 is configured, in a known manner, to limit or prevent the extraction of lubricant from the lubrication chamber 60. To achieve this, on the side opposite the chamber 60, the seal 62 is exposed to pressurized air 64, conventionally drawn from a fresh air intake on one of the compressors, or from outside the turbomachine. This pressurized air 64, which can therefore travel along the low-pressure shaft 32 before externally pressurizing the seal 62, circulates in a pressurized air circuit 66, bypassing the chamber 60. Downstream in the direction of pressurized air flow 64, the circuit 66 communicates at its downstream end with the purge air circulation chamber 46, described previously.The pressurization air 64, which has therefore contributed to the sealing of the lubricant container 60 at its contact with the seal 62, then becomes purge air 68 circulating in the chamber 46. It is then this purge air 68, with a pressure higher than that of the primary flow 16a, which passes through the purge device 50 to join the primary vein 14a.

[0041] Due to the high rotational speed of the low-pressure housing, the bearings 58 are continuously lubricated in the housing 60 by a liquid lubricant. This lubricant continuously supplies each bearing 58 in the housing and is then collected via a conduit 70 connected to a lubricant recovery pump 74, which returns the oil to a reservoir 72 supplying the engine's lubrication circuit. This pump 74 allows the lubricant to be recovered from the housing 60, preventing it from becoming excessively full.

[0042] In the event of a possible failure of this lubrication circuit, the chamber 60 gradually fills, eventually reaching the level of the chamber's sealing gasket, which is not perfectly sealed. In this case, a small amount of lubricant may flow out of the chamber through the gasket 62, and then be channeled by a rotating flange 76 designed to bypass the turbine's rotating wheel discs 40. This same rotating flange 76 defines a path for the air flowing between the pressurization circuit 66 and the purge chamber 46.

[0043] One of the distinctive features of the invention lies in the design of the purging device 50, which nevertheless incorporates certain conventional elements. Indeed, this device 50 comprises a static portion of revolution 80 belonging to the rear turbine casing 44 and extending axially upstream. It also includes a downstream spoiler 82, belonging to the radially internal platform 86 of the latter The bladed rotating wheel 40. These two elements 80, 82, shaped like ferrules centered on the axis 3, extend axially towards each other, and they may have a slight radial offset between them. In the preferred embodiment shown, the spoiler 82 is located radially outwards with respect to the static portion of revolution 80, although a reversed arrangement could be adopted without departing from the scope of the invention.

[0044] These conventional elements 80, 82, which participate in the delimitation of the primary vein 14a, are arranged radially outwards with respect to the elements of a passive system 90 for regulating the purge air passage cross-section. This system 90, belonging to the purge device 50 and specific to the present invention, will now be described in more detail with reference to [Fig. 3].

[0045] First, in this [Fig. 3], it is noted that the elements of the purge device 50 are shown in two distinct configurations. The dashed lines represent the first configuration adopted when the turbojet is operating at a first engine operating speed, preferably a low speed such as idle in flight. Furthermore, the solid lines represent the elements of the purge device 50 in a second configuration adopted when the turbojet is operating at a second, higher engine operating speed, such as full throttle. The relative positions of the parts, as well as any deformations they may undergo, thus differ between the two configurations, and the turbojet is designed to control these thermomechanical displacements and deformations observed simply due to a change in engine speed, in order to passively control the purge air passage cross-section through the purge device 50.

[0046] To this end, the passive system 90 for regulating the purge air passage section comprises a movable seal element 92, integral with the last bladed impeller, and extending downstream from it. This movable seal element 92 is preferably located radially inward with respect to the spoiler 82, being concentric with it, and it extends downstream beyond it. It is preferably a platform 92, in the shape of a ferrule. The platform 92 can be attached by fixing it to the disc of the last impeller 40.

[0047] Furthermore, the passive system 90 includes a static sealing element 94, integral with the rear turbine casing 44. This is preferably a flap 94, of revolutionary shape, which extends radially inward from the static portion of revolution 80 of the casing 44. The radially internal free end of the flap 94, which is preferably unique within the passive system 90, defines, together with the radially external surface of the platform 92, a section for purging air passage through the device 50. Regardless of the operating regime of the turbojet, it is this section between the two elements 92, 94 that corresponds to the greatest restriction important, and which therefore conditions the flow of purge air 68 through the whole device 50. In particular, it is preferentially ensured that the gap between the two elements 80, 82 is always greater than this section between the elements 92, 94.

[0048] Thus, in the first engine operating regime, the platform and the slat 92, 94 adopt a first relative position leading to a first purge air passage section SI, just as in the second engine operating regime, the platform and the slat 92, 94 adopt a second relative position leading to a second purge air passage section S2, strictly greater than the first.

[0049] More precisely, in the first relative position, the slat 94 is radially aligned with the platform 92, and the cross-section S1 corresponds to the small radial gap between these elements. Furthermore, in the second relative position, the observed thermomechanical displacements and deformations cause the slat 94 to be axially and radially separated from the platform 92. In other words, the slat 94 is axially offset relative to the platform 92, so that there is no longer a radial overlap between the two, but an axial offset. This significantly increases the value of the cross-section S2, which, in half-section, comprises a radial component and an axial component.

[0050] It follows from the above that the turbojet is configured so that the purge air passage cross-section SI, S2 is passively modified following a simple substantial change in engine speed. More precisely, the thermomechanical displacements and deformations of the turbojet components are used to modify, as desired, the purge air passage cross-section SI, S2 defined between the nozzle 94 and the platform 92.

[0051] However, when the turbojet is operating at its first speed, the conditions are such that they usually generate low lubricant pressure in the chamber 60, with the associated risks described above. By providing such a reduction in the purge air passage cross-section at this first speed, the air pressure in the purge air circulation chamber 46 is increased, as is the pressure in the pressurization air circuit 66 which communicates with this chamber. This indirectly, but advantageously, results in an increase in the air pressure in the chamber 60. Indeed, when the pressure outside the chamber increases, the air flow entering the chamber through the seal 62 is increased due to the increased pressure differential across the seal.The enclosure is preferably ventilated, meaning that air from the enclosure is evacuated through a degassing circuit typically including an oil separator in order to release into the atmosphere air as free as possible of oil droplets. The evacuation. Air from the enclosure via a degassing circuit ensures that the air pressure in the enclosure 60 always remains lower than the pressure of the pressurization air circuit 66 adjacent to the outer terminal of the sealing joint 62. This maintains a pressure differential across the terminals of the joint, and the resulting incoming airflow prevents oil leakage through the joint 62.

[0052] The air pressure in the chamber 60 is therefore linked to the pressure of the pressurization air circuit 66. When the latter increases, the air pressure in the chamber 60 increases accordingly, which in turn increases the lubricant pressure at the inlet of the lubricant recovery pump 74. The risks of insufficient air pressure in the chamber 60, and therefore insufficient lubricant pressure at the inlet of the pump 74, are thus advantageously reduced by means of a simple, passive, and reliable solution that does not compromise the operation of the turbomachine at other engine speeds.Indeed, when the turbojet operates according to the second regime, which would usually lead to a suitable pressure in the lubrication chamber 60, the widening of the purge air passage section reduces its impact on the pressurization of chamber 46, and therefore indirectly on the pressurization of the lubrication chamber 60, which thus remains within a range of desired values.

[0053] Of course, various modifications can be made by a person skilled in the art to the invention just described, solely by way of non-limiting examples, and the scope of which is defined by the attached claims.

Claims

Demands

1. Aircraft turbomachine (1) comprising: - a turbine (12), having a bladed rotor wheel (40), and a stator structure (44) arranged axially opposite the bladed wheel, the wheel and the stator structure (40, 44) jointly defining a gas flow channel (14a), and a purge air circulation chamber (46) arranged radially inwards with respect to the gas flow channel, and separated from it by a purge device (50); - a drive shaft (32), driving the bladed wheel (40) in rotation; - a lubrication chamber (60), in which is arranged at least one bearing (58) for guiding the rotation of the drive shaft (32), the lubrication chamber (60) being partially delimited by a sealing gasket (62) limiting or preventing the extraction of lubricant outside the lubrication chamber,by being exposed to pressurized air circulating in a pressurized air circuit (66) communicating with the purge air circulation chamber (46), characterized in that the purge device (50) comprises a passive system (90) for regulating a purge air passage section through the purge device, the passive regulation system comprising a movable seal element (92) integral with the bladed impeller (40), and a static seal element (94) integral with the stator structure (44), in that the turbomachine is configured such that in a first engine operating regime, the movable and static seal elements (92, 94) adopt a first relative position, and in that in a second engine operating regime, higher than the first regime, the movable and static seal elements (92, 94) adopt a second relative position in which the purge air passage section (SI,S2) is greater than that defined in the first relative position.

2. Turbomachine according to claim 1, characterized in that the movable sealing element is a platform (92), and the static sealing element is a flap (94), or vice versa, and in that the purge air passage section (S1, S2) is defined between the platform (92) and the lick (94), the latter extending in projection preferably radially inwards.

3. Turbomachine according to claim 2, characterized in that in the first relative position, the blade (94) is located radially opposite the platform (92), and in that in the second relative position, the blade (94) is located axially and radially spaced from the platform (92).

4. Turbomachine according to any one of the preceding claims, characterized in that the stator structure is a fixed turbine casing (44), comprising a fixed bladed wheel (45), and in that the movable bladed wheel (40) belongs to a final turbine stage.

5. Turbomachine according to any one of the preceding claims, characterized in that the purge device (50) comprises a static portion of revolution (80) belonging to the stator structure (44), as well as a radially internal platform spoiler (82) of the bladed wheel (40), the static portion of revolution (80) and the platform spoiler (82) extend axially in the direction of each other, being arranged radially outwards with respect to the moving and static seal elements (92, 94) of the passive system (90) for regulating the purge air passage section.

6. Turbomachine according to claim 5, characterized in that the static seal element (94) extends radially inwards from the static portion of revolution (80).

7. Turbomachine according to any one of the preceding claims, characterized in that it comprises a lubricant recovery pump (74) communicating with the lubrication chamber (60).

8. Turbomachine according to any one of the preceding claims, characterized in that the first engine operating regime is an idle-in-flight regime, and in that the second engine operating regime is a full-throttle regime.

9. Turbomachine according to any one of the preceding claims, characterized in that it comprises a low-pressure body as well as a high-pressure body, and in that the turbine (12) belongs preferentially to the low-pressure body.

10. Turbomachine according to any one of the preceding claims, characterized in that it is a turbojet.

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