TURBOMACHINE, PARTICULARLY FOR AIRCRAFT

Abstract

The invention relates to a turbomachine (1) comprising: - a secondary degassing circuit (C5) for the lubrication chamber (17, 18, 19), the secondary degassing circuit (C5) comprising: a secondary inlet (27) connected to the lubrication chamber (17, 18, 19), a secondary outlet (28) located outside the lubrication chamber (17, 18, 19), and a valve (30) comprising: a movable body configured to move between a closed position of the valve (30) preventing fluid communication between the secondary inlet (27) and the secondary outlet (28) and an open position of the valve (30) in which the secondary inlet (27) is in fluid communication with the secondary outlet (28), the open position of the valve (30) being reached when a pressure differential between the outside of the lubrication chamber (17, 18, 19, 19) and the inside of the lubrication chamber (17, 18, 19) is below a predetermined threshold pressure.Abbreviation figure: 2.

Description

Title of the invention: TURBOMACHINE, IN PARTICULAR FOR AIRCRAFT Technical field of the invention

[0001] The invention relates to the field of turbomachines, in particular for aircraft.

[0002] The invention relates in particular to the field of turbomachines equipped with at least one lubrication enclosure and a degassing circuit for this lubrication enclosure. Technical background

[0003] A turbomachine, in particular an aircraft turbomachine, generally extends along and around a longitudinal axis. It comprises a gas generator which typically comprises, from upstream to downstream, in the direction of flow of the gases in the turbomachine, a low-pressure compressor, a high-pressure compressor, a gas combustion chamber, a high-pressure turbine and a low-pressure turbine.

[0004] The rotor of the low pressure compressor is typically connected to the rotor of the low pressure turbine via a low pressure shaft. The rotor of the high pressure compressor is connected to the rotor of the high pressure turbine via a high pressure shaft.

[0005] The turbomachine further comprises a fan which is located upstream of the gas generator and which is driven in rotation about the longitudinal axis by a fan shaft. The fan shaft can be connected to the low pressure shaft via a speed reducer.

[0006] The high and low pressure shafts are guided in rotation by means of guide bearings which must be lubricated to ensure their proper functioning. Also, the speed reducer has gears and must also be lubricated to ensure its proper functioning.

[0007] It is therefore known to spray lubricating oil onto the guide bearings and into the reducer. In order to protect the connected components of the turbomachine from this lubricating oil, the guide bearings and the reducer are typically arranged in lubrication enclosures. The guide bearings located upstream of the turbomachine are located in one or more upstream lubrication enclosures, and the guide bearings located downstream of the turbomachine are arranged in one or more downstream lubrication enclosures.

[0008] Each lubrication chamber is connected to a lubrication circuit which supplies the lubrication chamber with oil. Each chamber therefore contains a mixture of air and lubricating oil which must be contained to avoid oil leaks to the outside of the enclosures and limit the risk of fire or the generation of an unbalance, for example. The enclosures are generally delimited by walls or rotor elements and by walls or stator elements. During operation, it is therefore necessary to ensure a seal between the walls or stator and rotor elements.

[0009] This sealing is ensured by dynamic seals mounted between the stator elements or walls and the rotor elements or walls which tightly delimit the lubrication enclosures. To limit oil leaks outside the enclosure through these seals, it is necessary to adjust the pressures between the inside and the outside of the lubrication enclosures in order to achieve a predetermined pressure differential. For this purpose, it is necessary to bring pressurized air to the seals. The air pressure outside the enclosure must be greater than the pressure inside the enclosure. The pressurized air located outside the enclosure will therefore naturally pass through the seals and enter the enclosure, which prevents oil leaks from the enclosure to the outside through these seals.Air is typically taken from the upstream stages of the high pressure compressor and directed to the seals of this enclosure through a pressurization circuit of the lubrication enclosures.

[0010] Since the seals are not completely sealed, air is allowed to enter the lubrication enclosure through these seals. The air that has entered the lubrication enclosure is typically discharged to the outside of each enclosure through a degassing circuit. The degassing circuit typically comprises an evacuation conduit having an inlet connected to the lubrication enclosure and an outlet located outside the lubrication enclosure, this outlet being able to open onto an oil separator. The degassing circuit is sized so that the outgoing air flow makes it possible to maintain a pressure in the lubrication enclosure close to atmospheric pressure to preserve the pressure differential between the inside and the outside of the enclosure necessary for the sealing of the lubrication enclosure.

[0011] In certain operating phases of the turbomachine, it is difficult to comply with the pressure differential criteria at the terminals of the seals which make it possible to limit oil leaks at the level of these same seals. Indeed, in these operating phases, the pressure differential is insufficient or even reversed, which can lead to oil leaks. For example, an obstruction of the degassing circuit can lead to a significant increase in the pressure in the lubrication enclosure, which results in a reduction or even an inversion of the pressure differential. Also, a fuel leak within the lubrication circuit of the lubrication enclosure can result in saturation of the main degassing circuit and cause an increase in the pressure in the lubrication enclosure.

[0012] Consequently, there is a need to provide a turbomachine comprising a lubrication enclosure in which oil leaks are limited or even zero even in the event of a malfunction of the main degassing circuit or fuel leakage into the lubrication enclosure. Summary of the invention

[0013] To this end, the invention proposes a turbomachine, in particular for an aircraft, the turbomachine comprising:

[0014] - a lubrication enclosure intended to contain a mixture of air and oil,

[0015] - a lubrication circuit for the lubrication enclosure, this lubrication circuit comprising an oil outlet opening into the lubrication enclosure,

[0016] - a main degassing circuit for the lubrication enclosure, the main circuit of degassing including:

[0017] a main inlet opening into the lubrication enclosure, and

[0018] a main outlet located outside the lubrication enclosure.

[0019] The turbomachine is remarkable in that it further comprises:

[0020] - a secondary degassing circuit for the lubrication enclosure, the circuit degassing secondary unit comprising:

[0021] a secondary inlet connected to the lubrication enclosure,

[0022] a secondary outlet located outside the lubrication enclosure, and

[0023] a valve comprising:

[0024] a movable body configured to move between a closed position of the valve preventing fluid communication between the secondary inlet and the secondary outlet and an open position of the valve in which the secondary inlet is in fluid communication with the secondary outlet,

[0025] the opening position of the valve being reached when a pressure differential between the outside of the lubrication enclosure and the inside of the lubrication enclosure is less than a predetermined threshold pressure.

[0026] In the event of a malfunction of the main degassing circuit or in the event of fuel leakage into the lubrication enclosure, the pressure inside the lubrication enclosure increases. This pressure can increase until the pressure differential between the outside and the inside of the lubrication enclosure is lower than the threshold pressure which is necessary to prevent oil leakage outside the lubrication enclosure.

[0027] The secondary degassing circuit according to the invention makes it possible to evacuate the mixture of pressurized air and oil from the lubrication enclosure when this pressure differential is lower than the threshold pressure. Indeed, in such a situation, the movable body of the valve moves into the open position allowing circulation and the evacuation of the mixture through the secondary degassing circuit.

[0028] Thanks to such a secondary degassing circuit, the pressure in the lubrication enclosure is reduced and the pressure differential restored to be at least equal to the threshold pressure.

[0029] Thanks to the invention, the risks of leakage outside the lubrication enclosure in the event of malfunction of the main degassing circuit or in the event of fuel leakage into the lubrication enclosure are limited.

[0030] The invention may comprise one or more of the following features, taken in isolation from one another or in combination with one another:

[0031] - the secondary inlet opens into the lubrication enclosure,

[0032] - the valve further comprises a control port connected to the outside of the enclosure lubrication,

[0033] - the valve further comprises a return spring configured to bias the body movable towards the valve opening position,

[0034] - the valve further comprises a nut bearing against the return spring and configured to position the return spring so that the valve opening position is reached according to the predetermined threshold pressure value,

[0035] - a sensor configured to detect the presence of fuel in the lubrication enclosure and transmitting a signal to an actuator of the valve to control the movement of the movable body from the first position to the second position,

[0036] - the secondary degassing circuit further comprises a non-return valve mounted between the valve and the secondary outlet,

[0037] - the threshold pressure is between 10 mbar and 100 mbar,

[0038] - the secondary circuit comprises an evacuation conduit connecting the secondary inlet to the secondary outlet, the valve being located in the discharge duct,

[0039] - an oil separator connected to the main outlet. Brief description of the figures

[0040] Other characteristics and advantages will emerge from the following description of non-limiting embodiments of the invention with reference to the appended drawings in which:

[0041] [Fig-1] [Fig.l] is a longitudinal sectional view of an example of a tur- aircraft machine according to the invention;

[0042] [Fig.2] [Fig.2] is a schematic longitudinal sectional view of part of the aircraft turbomachine of [Fig.l];

[0043] [Fig.3] [Fig.3] is a schematic representation of a valve according to a mode of embodiment of the invention and equipping the secondary degassing circuit when the valve is in the closed position;

[0044] [Fig.4] [Fig.4] is a schematic representation of the valve of [Fig.3] when the valve is in the open position;

[0045] [Fig.5] [Fig.5] is a schematic representation of a valve according to another embodiment and equipping the secondary degassing circuit when the valve is in the closed position;

[0046] [Fig.6] [Fig.6] is a schematic representation of the secondary circuit of degassing equipped with a non-return valve according to one embodiment of the invention. Detailed description of the invention

[0047] An example of a turbomachine 1, in particular an aircraft turbomachine, according to the invention is shown in [Fig.l]. The turbomachine 1 is for example a dual-flow turbojet. The turbomachine 1 may have any other architecture and may be in the form of a turboprop for example.

[0048] The turbomachine 1 extends along a longitudinal axis X. A gas flow F flows in the turbomachine 1.

[0049] For the purposes of the present invention, the terms “upstream” and “downstream” are understood to mean relative to the direction of flow of the gas flow F in the turbomachine 1.

[0050] Furthermore, the terms “longitudinal”, “longitudinally”, “radial”, "radially" means relative to the longitudinal axis X of the turbomachine 1. The terms "external", "internal" mean relatively to the distance from the longitudinal axis X along a radial axis perpendicular to the longitudinal axis X.

[0051] The turbomachine 1 comprises, from upstream to downstream, a fan 2 and a gas generator. The gas generator comprises, from upstream to downstream, a low-pressure compressor 3, a high-pressure compressor 4, a combustion chamber 5, a high-pressure turbine 6 and a low-pressure turbine 7.

[0052] Each compressor 3, 4 comprises a compressor rotor 3a, 4a and each turbine 6, 7 comprises a turbine rotor 6a, 7a. The compressor rotors 3a, 4a and turbine rotors 6a, 7a are composed of a plurality of stages each comprising a bladed wheel.

[0053] The compressor rotor 3a of the low pressure compressor 3 is connected to the turbine rotor 7a of the low pressure turbine 7 by a low pressure shaft 8. They form a low pressure body.

[0054] The compressor rotor 4a of the high-pressure compressor 4 is connected to the turbine rotor 6a of the high-pressure turbine 6 by a high-pressure shaft 9. They form a high-pressure body.

[0055] The low pressure 8 and high pressure 9 shafts are centered on the longitudinal axis X and rotatable about the longitudinal axis X. The high pressure shaft 9 is arranged coaxially around the low pressure shaft 8.

[0056] The gas flow F passes through the blower 2 and is divided into a primary air flow F1 passing through a primary vein v1 and into a secondary air flow F2 passing through a secondary vein v2 surrounding the primary vein. The primary air flow F1 passes through the low pressure 3 and high pressure 4 compressors. The compressed primary air flow F1 then passes through the combustion chamber 5 in which it is mixed with a fuel. The gases resulting from the combustion thus pass through the high pressure 6 and low pressure 7 turbines. The energy of the gases is transformed by the turbine rotor 7a of the low pressure turbine 7 into mechanical energy making it possible to drive the low pressure shaft 8 in rotation and consequently the low pressure compressor 3.

[0057] The fan 2 comprises a mobile disc rotating around the longitudinal axis X and blades 2a regularly distributed on the disc. In the example of [Fig.l], the fan 2 is surrounded by a fan casing 2b. The fan 2 is of the ducted type. The fan casing 2b carries a nacelle 2c and together define a fan compartment 2d.

[0058] According to another example not shown, the fan 2 is of the non-ducted type.

[0059] The fan disc 2 is driven in rotation by a fan shaft 10. Advantageously, the fan shaft 10 is connected to the low pressure shaft 8 via a speed reducer 11. The speed reducer 11 is of the mechanical type. It is for example an epicyclic or planetary gear. In a manner not illustrated, the speed reducer 11 conventionally comprises a sun gear and a crown centered on the longitudinal axis X. It further comprises satellites meshing with the sun gear and the crown. It further comprises a planet carrier s.

[0060] The solar is integral in rotation with the low pressure shaft 8 and forms the input of the speed reducer 11, while one or the other of the crown and the planet carrier, depending on the configuration of the reducer 11, is integral in rotation with the fan shaft 10 and forms the output of the speed reducer 11.

[0061] The speed reducer 11 allows the fan shaft 10 to be driven at a rotational speed lower than the rotational speed of the low pressure shaft 8. This allows the bypass ratio of the turbomachine 1 to be increased.

[0062] The turbomachine 1 further comprises an inter-compressor casing 12 arranged axially between the low-pressure compressor 3 and the high-pressure compressor 4. The inter-compressor casing 12 comprises, for example, an inner shell and an outer shell which are centered on the longitudinal axis X. The inner and outer shells are, for example, connected by arms.

[0063] The turbomachine 1 may further comprise an inlet casing 13. The inlet casing 13 is arranged axially between the fan 2 and the low-pressure compressor 3. The inlet casing 13 comprises, for example, an inner shell and an outer shell which are centered on the longitudinal axis X. The internal and external ferrules are for example connected by arms.

[0064] The turbomachine 1 may further comprise an inter-turbine casing 14. The inter-turbine casing 14 is arranged axially between the high-pressure turbine 6 and the low-pressure turbine 7.

[0065] The turbomachine 1 may further comprise an inter-vein compartment v3 located between the primary vein v1 and the secondary vein v2.

[0066] The fan shaft 10 is guided in rotation by a first bearing 15a and advantageously a second bearing 15b. The first and second bearings 15a are arranged radially between the fan shaft 10 and the inlet casing 13. Each first and second bearing 15a, 15b comprises, for example, a rolling bearing arranged between an outer ring and an inner ring. The outer ring is carried by a first bearing support 16a extending radially inward from the inlet casing 13. The inner ring is carried by the fan shaft 10. The rolling bearing is, for example, a row of balls. Advantageously, the rolling bearing comprises two rows of balls.

[0067] The low pressure shaft 8 is guided in rotation by at least a third and fourth bearing 15c, 15d. The third bearing 15c is arranged radially between the inlet casing 13 and the low pressure shaft 8. The third bearing 15c comprises a bearing, for example a row of balls, arranged radially between an inner ring and an outer ring. The outer ring is carried by a second bearing support 16b connected to the inlet casing 13. The inner ring is carried by the low pressure shaft 8. The fourth bearing 15d is arranged radially between the inter-compressor casing 12 and the low pressure shaft 8. The fourth bearing 15d comprises a bearing, for example a row of balls, arranged radially between an inner ring and an outer ring. The outer ring is carried by a third bearing support 16c connected to the inter-compressor casing 12. The inner ring is carried by the low pressure shaft 8.

[0068] The high-pressure shaft 9 is guided in rotation by a fifth bearing 15e. The fifth bearing 15e is for example arranged radially between the high-pressure shaft 9 and the inter-turbine casing 14. The fifth bearing 15e comprises a bearing, for example a row of balls and a row of rollers arranged radially between an outer ring and an inner ring. The inner ring is carried by the high-pressure shaft 9 and the outer ring is carried by a fourth bearing support 16d connected to the inter-turbine casing 14.

[0069] The low pressure shaft 8 can be guided in rotation downstream by a sixth bearing 15f arranged radially between a downstream end of the low pressure shaft 8 and the inter-turbine casing 14 for example.

[0070] The bearings 15a, 15b, 15c, 15d, 15e, 15f as well as the speed reducer 11 must be lubricated with oil to ensure their proper operation. In order not to contaminate the related parts of the turbomachine 1 with oil, the bearings 15a, 15b, 15c, 15d, 15e as well as the speed reducer 11 are arranged in lubrication enclosures.

[0071] For this purpose, the turbomachine 1 further comprises at least one lubrication enclosure, in particular a first upstream enclosure 17 in which the first, second and third bearings 15a, 15b, 15c and the speed reducer 11 are arranged, a second upstream lubrication enclosure 18 in which the fourth bearing 15d is arranged and a downstream lubrication enclosure 19 in which the fifth and sixth bearings 15e, 15f are arranged.

[0072] Depending on the configuration of the turbomachine 1, the number of bearings and lubrication chambers may vary.

[0073] Each lubrication enclosure 17, 18, 19 is annular. Each lubrication enclosure 17, 18, 19 is delimited externally by a fixed part such as a casing and internally by a rotating part such as a shaft.

[0074] For example, the first upstream lubrication enclosure 17 is located in the internal shell of the inlet casing 13 and is delimited internally by the fan shaft 10. The second upstream lubrication enclosure 18 is located in the internal shell of the inter-compressor casing 12 and is delimited internally by the low pressure shaft 8 and the downstream lubrication enclosure 18 is located in the internal shell of the inter-turbine casing 14 and is delimited internally by the high pressure shaft 9.

[0075] In the remainder of the description, the upstream and downstream lubrication enclosures 17, 18, 19 will be referred to interchangeably by the terms “lubrication enclosure”.

[0076] With reference to [Fig. 2], the lubrication enclosure 17, 18, 19 is supplied with oil by at least one lubrication circuit C1. The lubrication circuit C1 comprises an oil outlet 20 opening into the lubrication enclosure 17, 18, 19. The lubrication circuit C1 further comprises an oil inlet connected for example to an oil reservoir for supplying oil to the lubrication circuit C1. The lubrication circuit C1 may comprise a supply pump allowing the circulation of oil in the lubrication circuit C1 to the lubrication enclosure 17, 18, 19. The lubrication oil from the oil reservoir is thus projected into the lubrication enclosure 17, 18, 19 through the oil outlet 20 for the lubrication of the bearings and / or meshes of the bearings. 15a, 15b, 15c, 15d, 15e, 15f and speed reducer 11.

[0077] In order to limit oil leaks outside the lubrication enclosure 17, 18, 19, upstream and downstream seals 21a, 21b of the dynamic type such as labyrinth seals are arranged at the axial ends of the lubrication enclosure 17, 18, 19. A dynamic type seal is understood as an assembly limiting leaks of a fluid between the fixed part and the rotating part. For example, the rotating part carries wipers cooperating with the fixed part, for example covered with a coating.

[0078] In order to limit oil leaks through the seals 21a, 21b, the turbomachine 1 typically comprises a pressurization circuit C2 for the lubrication enclosure 17, 18, 19. The pressurization circuit C2 comprises an air sampling member (not shown) configured to sample air from the high-pressure compressor 4, for example. The pressurized air Al sampled from the high-pressure compressor 4 is conveyed to the lubrication enclosures 17, 18, 19. A portion of the pressurized air Al passes through the upstream and downstream seals 21a, 21b and enters the lubrication enclosure 17, 18, 19.

[0079] The pressurization circuit C2 further comprises at least one air outlet opening into the pressurization enclosure 17, 18, 19. Preferably, the pressurization circuit C2 comprises an upstream air outlet 22a and a downstream air outlet 22b opening into the lubrication enclosure 17, 18, 19. The upstream and downstream air outlets 22a, 22b are respectively delimited by the upstream and downstream dynamic seals 21a, 21b which allow the passage of air within the lubrication enclosure 17, 18, 19.

[0080] The lubrication enclosure 17, 18, 19 thus comprises a mixture M of lubricating oil H and air.

[0081] In order to minimize oil consumption, the turbomachine 1 comprises an oil recovery circuit C3 connected to the lubrication enclosure 17, 18, 19. The oil recovery circuit C3 has an oil inlet C3a opening into the lubrication enclosure 17, 18, 19 and an oil passage C3b passing outside the lubrication enclosure 17, 18, 19. The oil passage C3b can be connected to an oil reservoir for example.

[0082] In operation, the interior of the lubrication enclosure 17, 18, 19 has a first pressure PL. The first pressure PI is substantially equal to atmospheric pressure, typically substantially greater than atmospheric pressure.

[0083] Outside the lubrication enclosure 1, 18, 19 there is a second pressure P2 greater than the first pressure PL. The second pressure P2 can be measured at the terminals of the lubrication enclosure 17, 18, 19, for example, at the seals 21a, 21b. The pressure differential between the outside and the inside of the lubrication enclosure 17, 18, 19 is greater than or equal to a threshold pressure, advantageously between 10 mbar and 100 mbar. Above or at this threshold pressure, the pressure differential makes it possible to contain the oil in the lubrication enclosure 17, 18, 19 and therefore to prevent oil leaks from the lubrication enclosure 17, 18, 19.

[0084] To maintain such a pressure differential, it is necessary to evacuate air from the lubrication enclosure 17, 18, 19 in order to maintain the first pressure PI close to atmospheric pressure and to avoid the increase of this first pressure PL. This makes it possible to prevent the reversal of the pressure differential and therefore leaks. of oil outside the lubrication enclosure. In order to evacuate this air from the lubrication enclosures 17, 18, 19, the turbomachine 1 further comprises a main degassing circuit C4 for the air from the lubrication enclosure 17, 18, 19.

[0085] There can be as many main degassing circuits C4 as there are lubrication enclosures.

[0086] The main degassing circuit C4 comprises a main evacuation conduit 23 for the mixture M from the lubrication enclosure 17, 18, 19. The main evacuation conduit 23 comprises a main inlet 24 for the mixture M which opens into the lubrication enclosure 17, 18, 19 and a main outlet 25 for the mixture M which opens outside the lubrication enclosure 17, 18, 19.

[0087] The air in the lubrication enclosure 17, 18, 19 being mixed with oil particles H, the main degassing circuit C4 further comprises a de-oiling device 26 connected to the main evacuation conduit 23. The de-oiling device 26 is for example arranged in the inter-vein compartment v3.

[0088] In a manner not illustrated, the de-oiling device 26 comprises for example a centrifugal separation chamber mounted around a drive shaft which is rotated by the high pressure shaft 9 for example. The separation chamber has an inlet for the mixture M and an outlet for de-oiled air and an outlet for oil.

[0089] The main degassing circuit C4 makes it possible to evacuate the pressurized air from the lubrication enclosure 17, 18, 19 and to maintain a pressure inside the lubrication enclosure 17, 18, 19 equal to the first pressure PL

[0090] In operation, it may happen that the main degassing circuit C4 is obstructed and does not sufficiently evacuate the pressurized air from the lubrication enclosure 17, 18, 19 so that a clear increase in the first pressure PI in the lubrication enclosure 17, 18, 19 is observed. Also, it may happen that fuel enters the lubrication enclosure 17, 18, 19. Under certain conditions, this fuel may vaporize, also generating an increase in the first pressure PI in the lubrication enclosure 17, 18, 19. An increase in the first pressure PI may result in a decrease or even an inversion of the pressure differential. When the pressure differential decreases until it becomes lower than the threshold pressure, the risks of oil leakage from the lubrication enclosure 17, 18, 19 are significant.

[0091] To reduce these risks of leakage and restore the pressure differential above or at the threshold pressure, the turbomachine 1 according to the invention further comprises a secondary degassing circuit C5. The secondary degassing circuit C5 comprises a secondary inlet 27 for the mixture M and a secondary outlet 28 for this mixture M. Advantageously, the secondary inlet 27 and the secondary outlet 28 are connected by a secondary evacuation conduit 29. The secondary inlet 27 is advantageously located at inside the lubrication enclosure 17, 18, 19. In other words, the secondary inlet 27 opens directly into the lubrication enclosure 17, 18, 19. The secondary outlet 28 is located outside the lubrication enclosure 17, 18, 19.

[0092] Furthermore, according to the invention, the secondary degassing circuit C5 comprises a valve 30. The valve 30 is advantageously mounted in the secondary evacuation conduit 29 between the secondary inlet 27 and the secondary outlet 28.

[0093] As best seen in [Fig. 3], the valve 30 comprises an inlet port 31 connected to the secondary inlet 27, an outlet port 32 connected to the secondary outlet 28 and a movable body 33 between a closed position and an open position of the valve 30. In the closed position, the movable body 33 prevents fluid communication between the secondary inlet 27 and the secondary outlet 28. In this position, the mixture M cannot circulate in the secondary degassing circuit C5. In the open position, the movable body 33 allows fluid communication between the secondary inlet 27 and the secondary outlet 28. In this position, the mixture M circulates in the secondary degassing circuit C5.

[0094] According to the invention, the position of the movable body 33 is determined by the value of the pressure differential between the second pressure P2 and the first pressure PL. The movable body 33 is moved from the closed position to the open position when the pressure differential is lower than the threshold pressure.

[0095] [Fig. 3] illustrates an exemplary embodiment in which the pressure differential is greater than or equal to the threshold pressure. In this condition, the movable body 33 is in the closed position. The movable body 30 obstructs the passage between the inlet port 31 and the outlet port 32 and therefore between the secondary inlet 27 and the secondary outlet 28.

[0096] [Fig.4] illustrates an exemplary embodiment in which the pressure differential is lower than the threshold pressure. In this condition, the movable body 33 is in the open position. The inlet port 31 communicates fluidically with the outlet port 32, thus allowing fluid communication between the secondary inlet 27 and the secondary outlet 28.

[0097] Thus, according to the invention, in the nominal operating state of the turbomachine 1, when the pressure differential between the second pressure P2 and the first pressure PI is greater than or equal to the threshold pressure, the secondary degassing circuit C5 is at rest. Indeed, the valve 30 is in the closed position, and the mixture M of pressurized air loaded with oil is not evacuated through the secondary degassing circuit C5 since the moving body 33 obstructs the passage between the secondary inlet 27 and the secondary outlet 28. In this nominal operating state of the turbomachine 1, it is the main degassing circuit C4 which ensures the evacuation of the mixture M of air and lubricating oil.

[0098] When the pressure differential between the second pressure P2 and the first pressure PI is lower than the threshold pressure, the secondary degassing circuit C5 is active. In fact, the movable body 33 of the valve 30 is moved to the open position of the valve 30 so that the mixture M circulates from the secondary inlet 27 to the secondary outlet 28 to be discharged outside the lubrication enclosure 17, 18, 19.

[0099] The secondary degassing circuit C5 thus makes it possible to reduce the first pressure PI in the lubrication enclosure 17, 18, 19 in order to re-establish a pressure differential above the threshold pressure making it possible to preserve the sealing of the lubrication enclosure 17, 18, 19.

[0100] According to one embodiment of the invention, the valve 30 comprises a control port 34 connected to the pressurization circuit C2 for example by means of a control line 35. The pressure in the control port which is equal to the second pressure P2 acts directly on the movable body 33.

[0101] The valve 30 advantageously comprises a return spring 36 connected to the movable body 33. The return spring 36 makes it possible to urge the movable body into the open position of the valve 30 when the pressure differential is lower than the threshold pressure. The valve 30 is thus a passive valve.

[0102] According to a first exemplary embodiment illustrated in [Fig. 3] and 4, the return spring 36 works in compression. According to this first example, when the pressure differential is lower than the threshold pressure as in [Fig. 4], the return spring 36 compresses the movable body 33 under the effect of the increase in the first pressure PI to move the movable body 33 to the open position.

[0103] According to a second embodiment illustrated in [Fig.5], the return spring 36 works in traction. According to this first example, when the pressure differential is lower than the threshold pressure, the return spring 36 pulls the movable body 33 under the effect of the increase in the first pressure PI to move the movable body 33 to the open position.

[0104] According to a particularly advantageous embodiment of the invention, the valve 30 further comprises a nut 37 bearing against the return spring 36 and configured to adjust the position of the return spring 36 according to the value of the threshold pressure. Indeed, the nut 37 makes it possible to adjust the value of the threshold pressure below which the movable body 33 is driven into the open position. The nut 37 thus makes it possible to place the valve 30 in the open position only when the pressure differential becomes lower than the predetermined pressure alone.

[0105] According to another embodiment not illustrated, the turbomachine 1 comprises a sensor configured to detect the presence of fuel in the lubrication enclosure 17, 18, 19 and transmit a signal to an actuator of the valve 30 making it possible to control the movement of the movable body 33 into the open position. sensor is for example of the optical type making it possible to identify the presence of fuel in the lubrication enclosure 17, 18, 19. The fuel in the lubrication enclosure 17, 18, 19 increases the pressure PI in the lubrication enclosure 17, 18, 19 so that the pressure differential becomes lower than the predetermined threshold pressure.

[0106] The valve 30 could, according to another embodiment, have a hydraulic or electrical type of actuation.

[0107] According to an advantageous embodiment of the invention illustrated in [Fig. 6], the secondary degassing circuit C5 further comprises a non-return valve 38. The non-return valve 38 is mounted between the valve 30 and the secondary outlet 28. It is advantageously mounted in the secondary discharge duct 29. The non-return valve 38 makes it possible to limit the entry of air when the movable body 33 of the valve 30 is in the open position although the outlet flow of the mixture M is low, for example during the start-up phases of the turbomachine 1.

[0108] Thanks to the secondary degassing circuit C5 of the invention, the pressure PI in the lubrication enclosure 17, 18, 19 is limited and maintained close to atmospheric pressure even in the event of a breakdown of the main degassing circuit C4 or a fuel leak inside the lubrication enclosure 17, 18, 19. The pressure differential between the pressurization circuit C2 and the inside of the lubrication enclosure 17, 18, 19 is thus maintained at least equal to the threshold pressure necessary for the sealing of the lubrication enclosure 17, 18, 19.

[0109] Furthermore, thanks to the invention, it is not necessary to oversize the main degassing circuit C4 to limit the pressure PI in the lubrication enclosure 17, 18, 19.

[0110] Also, thanks to the invention, the fire risk is reduced and the arrangements linked to the fire risk can be lightened.

Claims

Claims

1. Turbomachine (1), in particular for an aircraft, the turbomachine (1) comprising: - a lubrication enclosure (17, 18, 19) intended to contain a mixture (M) of air and oil (H), - a lubrication circuit (Cl) of the lubrication enclosure (17, 18, 19), this lubrication circuit (Cl) comprising an oil outlet (20) opening into the lubrication enclosure (17, 18, 19), - a main degassing circuit (C4) of the lubrication enclosure (17, 18, 19), the main degassing circuit (C4) comprising: a main inlet (24) opening into the lubrication enclosure (17, 18, 19), and a main outlet (25) located outside the lubrication enclosure (17, 18, 19), characterized in that the turbomachine (1) further comprises: - a secondary degassing circuit (C5) of the lubrication enclosure (17, 18, 19), the secondary degassing circuit (C5) comprising: a secondary inlet (27) connected to the lubrication enclosure (17, 18,19), a secondary outlet (28) located outside the lubrication enclosure (17, 18, 19), and a valve (30) comprising: a movable body (33) configured to move between a closed position of the valve (30) preventing fluid communication between the secondary inlet (27) and the secondary outlet (28) and an open position of the valve (30) in which the secondary inlet (27) is in fluid communication with the secondary outlet (28), the open position of the valve (30) being reached when a pressure differential between the outside of the lubrication enclosure (17, 18, 19) and the inside of the lubrication enclosure (17, 18, 19) is lower than a predetermined threshold pressure.,

2. Turbomachine according to the preceding claim, characterized in that the secondary inlet (27) opens into the lubrication enclosure (17, 18, 19).

3. Turbomachine according to any one of the preceding claims, characterized in that the valve (30) further comprises a control port (34) connected to the outside of the lubrication enclosure (17, 18, 19).

4. Turbomachine according to any one of the preceding claims, characterized in that the valve (30) further comprises a return spring (36) configured to urge the movable body towards the open position of the valve (30).

5. Turbomachine according to the preceding claim, characterized in that the valve (30) further comprises a nut (37) bearing against the return spring (36) and configured to position the return spring (36) so that the opening position of the valve (30) is reached according to the predetermined threshold pressure value.

6. Turbomachine according to any one of claims 1 or 2, characterized in that it comprises a sensor configured to detect the presence of fuel in the lubrication enclosure (17, 18, 19) and transmit a signal to an actuator of the valve (30) to control the movement of the movable body (33) from the first position to the second position.

7. Turbomachine according to any one of the preceding claims, characterized in that the secondary degassing circuit (C5) further comprises a non-return valve (38) mounted between the valve (30) and the secondary outlet (28).

8. Turbomachine according to any one of the preceding claims, characterized in that the threshold pressure is between 10 mbar and 100 mbar.

9. Turbomachine according to any one of the preceding claims, characterized in that the secondary circuit (C5) comprises an evacuation duct (29) connecting the secondary inlet (27) to the secondary outlet (28), the valve (30) being located in the evacuation duct (29).

10. Turbomachine according to any one of the preceding claims, characterized in that it further comprises an oil separator (26) connected to the main outlet (25).

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