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, PARTICULARLY FOR AIRCRAFT Technical field of the invention

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

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

[0003] A turbomachine, particularly an aircraft turbomachine, generally extends along and around a longitudinal axis. It comprises a gas generator which typically includes, from upstream to downstream in the direction of gas flow 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, on the other hand, is connected to the rotor of the high-pressure turbine via a high-pressure shaft.

[0005] The turbomachine further comprises a fan located upstream of the gas generator and 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 operation. Also, the speed reducer has gears and must also be lubricated to ensure its proper operation.

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

[0008] Each lubrication chamber is connected to a lubrication circuit that supplies oil to the lubrication chamber. Each chamber therefore contains a mixture of air and lubricating oil that must be contained to To prevent oil leaks outside the enclosures and limit the risk of fire or the generation of an imbalance, 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 elements of the stator and rotor.

[0009] This sealing is ensured by dynamic seals mounted between the stator elements or walls and the rotor elements or walls, which hermetically seal the lubrication chambers. To limit oil leakage outside the chamber through these seals, it is necessary to adjust the pressures between the inside and outside of the lubrication chambers to achieve a predetermined pressure differential. For this purpose, pressurized air must be supplied to the seals. The air pressure outside the chamber must be higher than the pressure inside the chamber. The pressurized air outside the chamber will therefore naturally pass through the seals and enter the chamber, thus preventing oil leakage from the chamber to the outside through these seals.Air is typically drawn from the upstream stages of the high-pressure compressor and directed to the seals of this chamber through a pressurization circuit for the lubrication chambers.

[0010] Since the seals are not completely airtight, air enters the lubrication chamber through these seals. The air that has entered the lubrication chamber is typically vented outside each chamber through a degassing circuit. The degassing circuit typically comprises a vent pipe with an inlet connected to the lubrication chamber and an outlet located outside the lubrication chamber, this outlet possibly leading to an oil separator. The degassing circuit is sized so that the outgoing air flow rate maintains a pressure in the lubrication chamber close to atmospheric pressure to preserve the pressure differential between the inside and outside of the chamber necessary for sealing the lubrication chamber.

[0011] During certain operating phases of the turbomachine, it is difficult to maintain the pressure differential across the seals, which limits oil leakage at these seals. Indeed, during these operating phases, the pressure differential is insufficient or even reversed, which can lead to oil leaks. For example, an obstruction in the degassing circuit can lead to a significant increase in pressure within the lubrication chamber, resulting in a decrease or even a reversal of the pressure differential. Similarly, a fuel leak within the lubrication circuit of the lubrication chamber can saturate the main degassing circuit and cause an increase in pressure within the lubrication chamber.

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

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

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

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

[0016] - a main degassing circuit for the lubrication chamber, 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 chamber, the circuit secondary degassing unit comprising:

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

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

[0023] a valve comprising:

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

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

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

[0027] The secondary degassing circuit according to the invention allows the pressurized air and oil mixture to be evacuated from the lubrication chamber when this pressure differential is lower than the threshold pressure. Indeed, in such a situation, the body The valve's moving part moves into the open position, allowing the mixture to circulate and be evacuated through the secondary degassing circuit.

[0028] Thanks to such a secondary degassing circuit, the pressure in the lubrication chamber 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 chamber in the event of malfunction of the main degassing circuit or in the event of fuel leakage into the lubrication chamber are limited.

[0030] The invention may comprise one or more of the following features, taken individually or in combination with each other:

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

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

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

[0034] - the valve further includes 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 enclosure of lubrication and transmitting a signal to a valve actuator to control the movement of the moving body from the first position to the second position,

[0036] - the secondary degassing circuit further includes 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 includes a drain duct connecting the secondary inlet to the secondary outlet, the valve being located in the drain pipe,

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

[0040] Other features and advantages will become apparent from the following description of non-limiting embodiments of the invention with reference to the accompanying drawings in which:

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

[0042] [Fig.2] [Fig.2] is a schematic longitudinal cross-sectional view of part of the aircraft turbomachine of the [Fig.1];

[0043] [Fig.3] [Fig.3] is a schematic representation of a valve according to an 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 degassing circuit equipped with a non-return valve according to an 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. 1]. The turbomachine 1 is, for example, a turbofan engine. The turbomachine 1 may have any other architecture and may, for example, be in the form of a turboprop engine.

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

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

[0050] Furthermore, the terms "longitudinal", "longitudinally", "radial", "radially" are understood in relation to the longitudinal axis X of the turbomachine 1. The terms "external", "internal" are understood in relation 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 blower 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 the 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 shafts 8 and high pressure shafts 9 are centered on the longitudinal axis X and are free to rotate 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 splits into a primary air flow Fl passing through a primary stream v1 and a secondary air flow F2 passing through a secondary stream v2 surrounding the primary stream. The primary air flow Fl passes through the low-pressure compressor 3 and the high-pressure compressor 4. The compressed primary air flow Fl then passes through the combustion chamber 5 where it is mixed with fuel. The combustion gases thus pass through the high-pressure turbine 6 and the low-pressure turbine 7. The energy of the gases is transformed by the turbine rotor 7a of the low-pressure turbine 7 into mechanical energy, which drives the low-pressure shaft 8 and, consequently, the low-pressure compressor 3.

[0057] The fan 2 comprises a rotating disk about the longitudinal axis X and blades 2a evenly distributed on the disk. In the example of [Fig. 1], the fan 2 is surrounded by a fan housing 2b. The fan 2 is of the enclosed type. The fan housing 2b carries a nacelle 2c and together they define a fan compartment 2d.

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

[0059] The blower disc 2 is driven in rotation by a blower shaft 10. Advantageously, the blower shaft 10 is connected to the low-pressure shaft 8 via a speed reducer 11. The speed reducer 11 is mechanical. For example, it may be an epicyclic or planetary gear train. While not shown, the speed reducer 11 conventionally comprises a sun gear and a ring gear centered on the longitudinal axis X. It also includes planet gears that mesh with the sun gear and the ring gear. Furthermore, it includes a planet carrier s.

[0060] The solar element is rotationally fixed to the low-pressure shaft 8 and forms the input of the speed reducer 11, while one or the other of the ring and the satellite carrier, depending on the configuration of the reducer 11, is rotationally fixed to the blower shaft 10 and forms the output of the speed reducer 11.

[0061] The speed reducer 11 allows the blower shaft 10 to be driven at a rotational speed lower than the rotational speed of the low-pressure shaft 8. This makes it possible to increase the dilution ratio of the turbomachine 1.

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

[0063] The turbomachine 1 may further include an inlet housing 13. The inlet housing 13 is arranged axially between the fan 2 and the low-pressure compressor 3. The inlet housing 13 includes, 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.

[0064] The turbomachine 1 may further include 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 include an inter-vein compartment v3 located between the primary vein vl and the secondary vein v2.

[0066] The blower 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 blower shaft 10 and the inlet housing 13. Each first and second bearing 15a, 15b comprises, for example, a bearing arranged between an outer ring and an inner ring. The outer ring is supported by a first bearing support 16a extending radially inward from the inlet housing 13. The inner ring is supported by the blower shaft 10. The bearing is, for example, a row of balls. Advantageously, the 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 housing 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 supported by a second bearing support 16b connected to the inlet housing 13. The inner ring is supported by the low-pressure shaft 8. The fourth bearing 15d is arranged radially between the inter-compressor housing 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 supported by a third bearing support 16c connected to the inter-compressor housing 12. The inner ring is supported 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 housing 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 supported by the high-pressure shaft 9 and the outer ring is supported by a fourth bearing support 16d connected to the inter-turbine housing 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 housing 14 for example.

[0070] The bearings 15a, 15b, 15c, 15d, 15e, 15f and the speed reducer 11 must be lubricated with oil to ensure their proper operation. To prevent contamination of the associated components of the turbomachine 1 by the oil, the bearings 15a, 15b, 15c, 15d, 15e and the speed reducer 11 are arranged in lubrication chambers.

[0071] For this purpose, the turbomachine 1 further comprises at least one lubrication chamber, in particular a first upstream chamber 17 in which the first, second and third bearings 15a, 15b, 15c and the speed reducer 11 are arranged, a second upstream lubrication chamber 18 in which the fourth bearing 15d is arranged and a downstream lubrication chamber 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 chamber 17, 18, 19 is annular. Each lubrication chamber 17, 18, 19 is delimited externally by a fixed part such as a housing and internally by a rotating part such as a shaft.

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

[0075] In the following description, the upstream and downstream lubrication chambers 17, 18, 19 will be referred to interchangeably as "lubrication chamber".

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

[0077] In order to limit oil leakage outside the lubrication chamber 17, 18, 19, upstream and downstream dynamic seals 21a, 21b, such as labyrinth seals, are arranged at the axial ends of the lubrication chamber 17, 18, 19. A dynamic seal is understood as an assembly that limits fluid leakage between the stationary part and the rotating part. For example, the rotating part carries flaps that cooperate with the stationary part, which is, for example, coated.

[0078] To limit oil leakage through the seals 21a, 21b, the turbomachine 1 typically includes a pressurization circuit C2 for the lubrication chamber 17, 18, 19. The pressurization circuit C2 includes an air intake device (not shown) configured to draw air from the high-pressure compressor 4, for example. The pressurized air Al drawn from the high-pressure compressor 4 is routed to the lubrication chambers 17, 18, 19. A portion of the pressurized air Al passes through the upstream and downstream seals 21a, 21b and enters the lubrication chamber 17, 18, 19.

[0079] The pressurization circuit C2 further includes at least one air outlet opening into the pressurization chamber 17, 18, 19. Preferably, the pressurization circuit C2 includes an upstream air outlet 22a and a downstream air outlet 22b opening into the lubrication chamber 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 chamber 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 includes an oil recovery circuit C3 connected to the lubrication chamber 17, 18, 19. The oil recovery circuit C3 has an oil inlet C3a opening into the lubrication chamber 17, 18, 19 and an oil passage C3b passing outside the lubrication chamber 17, 18, 19. The oil passage C3b can be connected to an oil reservoir for example.

[0082] In operation, the interior of the lubrication chamber 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 chamber 1, 18, 19, a second pressure P2 prevails, which is higher than the first pressure PL. This second pressure P2 can be measured at the terminals of the lubrication chamber 17, 18, 19, for example, at the sealing points 21a, 21b. The pressure differential between the outside and inside of the lubrication chamber 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 allows the oil to be contained within the chamber. lubrication 17, 18, 19 and therefore to avoid oil leaks from the lubrication chamber 17, 18, 19.

[0084] To maintain such a pressure differential, it is necessary to evacuate air from the lubrication chamber 17, 18, 19 in order to keep the initial pressure PI close to atmospheric pressure and prevent this initial pressure PI from increasing. This prevents the pressure differential from reversing and thus prevents oil leaks outside the lubrication chamber. In order to evacuate this air from the lubrication chambers 17, 18, 19, the turbomachine 1 further includes a main degassing circuit C4 for the air from the lubrication chamber 17, 18, 19.

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

[0086] The main degassing circuit C4 includes a main discharge conduit 23 of the mixture M from the lubrication chamber 17, 18, 19. The main discharge conduit 23 includes a main inlet 24 of the mixture M which opens into the lubrication chamber 17, 18, 19 and a main outlet 25 of the mixture M which opens outside the lubrication chamber 17, 18, 19.

[0087] Since the air in the lubrication chamber 17, 18, 19 is mixed with oil particles H, the main degassing circuit C4 further includes an oil removal device 26 connected to the main discharge conduit 23. The oil removal device 26 is arranged for example in the inter-vein compartment v3.

[0088] Not shown in the illustration, the oil removal device 26 comprises, for example, a centrifugal separation chamber mounted around a drive shaft which is driven in rotation by the high-pressure shaft 9, for example. The separation chamber has an inlet for the mixture M and an outlet for oil-free air and an outlet for oil.

[0089] The main degassing circuit C4 allows the pressurized air to be evacuated from the lubrication chamber 17, 18, 19 and maintains a pressure inside the lubrication chamber 17, 18, 19 equal to the first pressure PL

[0090] During operation, the main venting circuit C4 may become obstructed and fail to adequately vent pressurized air from the lubrication chamber 17, 18, 19, resulting in a significant increase in the first pressure PI in the lubrication chamber 17, 18, 19. Fuel may also enter the lubrication chamber 17, 18, 19. Under certain conditions, this fuel may vaporize, also generating an increase in the first pressure PI in the lubrication chamber 17, 18, 19. An increase in the first pressure PI can result in a decrease or even a reversal of the pressure differential. When the pressure differential decreases below the threshold pressure, the risk of oil leakage from the lubrication chamber 17, 18, 19 is significant.

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

[0092] Furthermore, according to the invention, the secondary degassing circuit C5 includes 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 more clearly 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 less than the threshold pressure.

[0095] Figure 3 illustrates an example of an 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] Figure 4 illustrates an example of an embodiment in which the pressure differential is less than the threshold pressure. In this condition, the movable body 33 is in the open position. The inlet port 31 communicates fluidly 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 nominal operating condition 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 oil-charged pressurized air mixture M is not evacuated through the secondary degassing circuit C5 because 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 air and lubricating oil mixture M.

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

[0099] The secondary degassing circuit C5 thus makes it possible to reduce the first pressure PI in the lubrication chamber 17, 18, 19 in order to restore a pressure differential above the threshold pressure allowing the sealing of the lubrication chamber 17, 18, 19 to be preserved.

[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 moving body 33.

[0101] The valve 30 advantageously includes a return spring 36 connected to the moving body 33. The return spring 36 forces the moving body into the open position of the valve 30 when the pressure differential is less than the threshold pressure. The valve 30 is thus a passive valve.

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

[0103] According to a second embodiment illustrated in [Fig. 5], the return spring 36 works in tension. According to this first example, when the pressure differential is less than the threshold pressure, the return spring 36 pulls the moving body 33 under the effect of the increase in the first pressure PI to move the moving 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 threshold pressure value. Indeed, the nut 37 allows adjustment of the threshold pressure value below which the movable body 33 is driven into the open position. The nut 37 thus allows the valve 30 to be positioned in the open position only when the pressure differential becomes less than the predetermined pressure alone.

[0105] According to another embodiment not shown, the turbomachine 1 includes a sensor configured to detect the presence of fuel in the lubrication chamber 17, 18, 19 and transmit a signal to a valve actuator 30, thereby controlling the movement of the movable body 33 to the open position. The sensor is, for example, of the optical type, enabling the identification of the presence of fuel in the lubrication chamber 17, 18, 19. The fuel in the lubrication chamber 17, 18, 19 increases the pressure PI in the lubrication chamber 17, 18, 19 such that the pressure differential becomes lower than the predetermined threshold pressure.

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

[0107] According to an advantageous embodiment of the invention illustrated in [Fig. 6], the secondary degassing circuit C5 further comprises a check valve 38. The check valve 38 is mounted between the valve 30 and the secondary outlet 28. It is advantageously mounted in the secondary discharge conduit 29. The check 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 even though 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 chamber 17, 18, 19 is limited and maintained close to atmospheric pressure even in the event of failure of the main degassing circuit C4 or fuel leakage inside the lubrication chamber 17, 18, 19. The pressure differential between the pressurization circuit C2 and the inside of the lubrication chamber 17, 18, 19 is thus maintained at least equal to the threshold pressure necessary for the sealing of the lubrication chamber 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 chamber 17, 18, 19.

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

Claims

Demands

1. Turbomachine (1), in particular for an aircraft, the turbomachine (1) comprising: - a lubrication chamber (17, 18, 19) for containing a mixture (M) of air and oil (H), - a lubrication circuit (C1) of the lubrication chamber (17, 18, 19), this lubrication circuit (C1) having an oil outlet (20) opening into the lubrication chamber (17, 18, 19), - a main degassing circuit (C4) of the lubrication chamber (17, 18, 19), the main degassing circuit (C4) comprising: a main inlet (24) opening into the lubrication chamber (17, 18, 19), and a main outlet (25) located outside the lubrication chamber (17, 18, 19), characterized in what the turbomachine (1) further comprises: - a secondary degassing circuit (C5) of 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 (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 chamber (17, 18, 19) and the inside of the lubrication chamber (17, 18, 19) is less than a predetermined threshold pressure.

2. Turbomachine according to the preceding claim, characterized in that the secondary inlet (27) opens into the lubrication chamber (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 chamber (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 strain the moving 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 value of the predetermined threshold pressure.

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 chamber (17, 18, 19) and transmit a signal to a valve actuator (30) to control the movement of the moving body (33) from the closed position of the valve (30) to the open position of the valve (30).

7. Turbomachine according to any one of the preceding claims, characterized in that the secondary degassing circuit (C5) further comprises a check 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 a discharge conduit (29) connecting the secondary inlet (27) to the secondary outlet (28), the valve (30) being located in the discharge conduit (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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