Fluid pump for an aircraft turbomachine, lubrication circuit and aircraft turbomachine

Abstract

The invention relates to a fluid pump (1) for an aircraft turbomachine, the pump comprising an immobile crown (10) having a wall (13) and having a pipe (12) pass therethrough along a central axis (101), a rotor (20) capable of rotating relative to the crown (10) on a main axis (100) which is offset relative to the central axis (101), cavities between the crown and the rotor, the volume of the cavities varying depending on the angular position of the rotor relative to the crown, a radial inlet space (16) passing through the wall (13) for intaking fluid into the cavities and a radial outlet space (11) for discharging fluid from the cavities, the pressure in the outlet space being higher than the pressure in the inlet space, and a groove (15) subjecting the cavities to the pressure of the outlet space when the rotor rotates, which groove passes through the wall and opens into the outlet space (11). The invention also relates to a lubrication circuit with such a pump, as well as to an aircraft turbomachine with such a circuit.

Description

technical field

[0001] The present invention relates to a fluid pump for an aircraft turbomachine, a lubrication circuit with such a pump and an aircraft turbomachine with such a lubrication circuit. Previous art

[0002] Aircraft turbojet engines have numerous mechanical components that require lubrication and cooling, including shafts, bearings, and gears. To meet these needs, these turbojets are equipped with a lubrication system that supplies oil to each of these components. A feed pump generates a flow of oil that is then divided into several lines to supply the various engine components.

[0003] To save oil, this lubrication circuit operates in a closed loop, with the oil delivered to each piece of equipment being recovered and then reinjected into the lubrication circuit by recovery pumps.

[0004] The increase in flow rates and outlet pressures of the pumps providing the supply function (oil tank to engine compartments) implies new hydraulic phenomena to be controlled.

[0005] One of the phenomena to control is the pressure pulsation at the outlet of the lubrication unit. Since aircraft pumps are positive displacement pumps, they deliver a flow rate. The outlet pressure is the result of pressure losses in the downstream circuit and the imposed flow rate.

[0006] Therefore, pressure pulsations become flow pulsations. If the discharged flow rate is not constant, then there will also be pressure variations (or pulsations) at the outlet of the lubrication unit. These pulsations can be caused, in particular, by the compressibility of the fluid.

[0007] Pulsations are detrimental in several respects, including the integrity of the lubrication unit housing and the integrity of the oil circuit equipment downstream of the lubrication unit (such as filters, valves, heat exchangers, pipes, ...).

[0008] The drawback of current lubrication systems is that they are prone to premature failure (pulsation fatigue) of one or more components. To prevent such failure, some current lubrication systems have oversized components – which leads to an overall increase in engine mass.

[0009] US patent 2017 / 009776 describes a turbine engine comprising two rotating shafts and a lubrication unit. The lubrication unit includes at least one pump whose casing is mounted internally and is driven by one of the rotating shafts. US patent 6030191 describes a suction pump suitable for use in a fuel dispensing system or other fluid dispensing system for volatile liquids. The suction pump includes a pump body that defines a pump chamber with inlet and outlet ports. A rotor with vanes is housed within the pump chamber. The vanes define fluid cavities that rotate between the inlet and outlet ports.

[0010] There is therefore a need to reduce, or even eliminate, pressure pulsations. Description of the invention

[0011] To this end, the invention proposes a fluid pump for an aircraft turbomachine, comprising a ring through which a conduit passes along a central axis, a rotor driven in rotation relative to the ring along a main axis offset from the central axis, cavities between the ring and the rotor, the volume of the cavities varying according to the angular position of the rotor relative to the ring, an inlet space for the admission of the fluid into the cavities and a discharge space for the discharge of the fluid from the cavities, the pressure in the discharge space being higher than the pressure in the inlet space, a groove being formed to bring the cavities to the pressure of the discharge space during the rotation of the rotor.

[0012] According to the invention, the ring is fixed and comprises a wall, the discharge and admission spaces being radial and passing through the wall and the groove passes radially through the wall and opens into the discharge space.

[0013] According to one variant, the groove has an elongated shape along a circumference of the wall.

[0014] According to one variant, groove 15 has a length and a height, the length being greater than 110% of the height.

[0015] According to one variant, the pump further includes a sealing area between the fluid inlet space and the fluid discharge space, with the groove extending over part of the sealing area.

[0016] According to one variant, the groove opens into the discharge space, upstream or downstream of the discharge space, in the direction of rotation of the rotor.

[0017] According to one variant, the wall has a sealing zone between the fluid inlet space and the fluid outlet space, with the groove extending over part of the sealing zone.

[0018] According to one variant, the pump comprises a plurality of discharge spaces, each with a groove radially traversing the wall of the crown and opening into the respective discharge space; the cumulative height of the grooves along the axial direction of the crown is between 1 and 15% of the height of the crown along the direction of the central axis.

[0019] Depending on one variant, the groove(s) are obtained by a milling, electro-erosion or wire cutting process.

[0020] According to one variant, the pump includes movable vanes on the rotor in a radial direction of the rotor, and extending to the crown, the vanes defining the cavities between them.

[0021] The invention also relates to an aircraft turbomachine lubrication circuit, comprising at least one pump as described above, the groove bringing the cavities to the pressure of the discharge space and to the pressure of the circuit downstream of the pump.

[0022] The invention also relates to an aircraft turbomachine, including the lubrication circuit as described above.

[0023] The use of the verb "comprendre" (to understand), its variants, and its conjugations in this document does not in any way preclude the presence of elements other than those mentioned. The use of the indefinite article "un" (a / an) or the definite article "le" (the / it) to introduce an element does not preclude the presence of multiple such elements.

[0024] The terms "first", "second", "third", etc., are used in this document exclusively to differentiate different elements, without implying any order between these elements.

[0025] All preferred embodiments and all advantages of the crown are applicable mutatis mutandis to the pump, lubrication circuit, and turbomachine – and vice versa. The various embodiments can be considered individually or in combination. Brief description of the figures

[0026] Other features and advantages of the present invention will become apparent upon reading the detailed description that follows, for understanding of which reference should be made to the accompanying figures which show: there figure 1 A schematic view of a lubrication circuit; the figure 2 , a perspective view of an example of a fluid pump design; the figure 3, a perspective view of an example of the construction of a pump crown figure 2 ; there figure 4 , another perspective view of an example of the construction of a pump crown figure 2 .

[0027] The drawings in the figures are not to scale. Similar features are generally denoted by similar reference numerals in the figures. Within the scope of this document, identical or analogous features may bear the same reference numerals. Furthermore, the presence of reference numerals or letters in the drawings shall not be considered limiting, even when such numerals or letters are specified in the claims. Detailed description of embodiments of the invention

[0028] The invention relates to a fluid pump for an aircraft turbomachine, comprising a ring through which a conduit passes along a central axis, a rotor driven in rotation relative to the ring about a principal axis offset from the central axis, cavities between the ring and the rotor, the volume of the cavities varying according to the angular position of the rotor relative to the ring, an inlet space for the intake of fluid into the cavities, and a discharge space for the discharge of fluid from the cavities, the pressure in the discharge space being higher than the pressure in the inlet space. The pump also includes a groove that brings the cavities to the pressure of the discharge space during rotor rotation. Such a groove allows the pump cavities to be brought to the outlet pressure, thereby reducing, or even eliminating, pressure pulsations at the pump outlet.In the long run, the lifespan of the pump parts increases.

[0029] There figure 1Figure 2 illustrates an aircraft turbomachine lubrication circuit 2. Circuit 2 cools and / or lubricates the various components of the turbomachine. Within circuit 2, oil is sent from reservoir 3 to turbomachine components 4, such as bearings or housings. Circuit 2 includes a lubrication unit 5 comprising circulation pumps 1, the technology of which may vary. In this description, these are, for example, desmodromic vane pumps 1 or gerotor pumps 1. The pumps 1 supply oil to the components 4 via supply lines 6. Downstream of the components 4, recovery lines 7 allow the oil to be recovered and recirculated into circuit 2. One pump 1 can be used for each component 4 upstream and downstream of the components 4, or one pump 1 for several components 4 upstream and downstream of the components 4. Depending on the embodiment of the figure 1As an example, one pump 1 is provided per equipment 4 upstream and only one pump 1 downstream for all the equipment 4.

[0030] There figure 2This shows a perspective view of an example of a pump 1, which is a desmodromic vane pump. Pump 1 is a positive displacement pump, which imposes a flow rate. Pump 1 comprises a ring 10 (or cam for such a pump) with an external shape that is generally cylindrical of revolution. The ring 10 includes an axial cylindrical conduit 12 passing through the ring 10 along a central axis 101. The ring 10 is stationary. The ring 10 is radially bounded by a wall 13. The ring 10 also includes a fluid inlet space 16 (or inlet port) and a fluid discharge space 11 (or discharge port) – particularly for lubricating fluid – the spaces 11 and 16 being radial and passing through the wall 13.The pressure in the discharge space 11 is higher than the pressure in the inlet space 16; in other words, the discharge space 11 is at high pressure, to discharge the fluid towards the pump outlet, and the inlet space 16 is at low pressure to admit the fluid from the pump inlet. The ring 10 may include one or more inlet spaces 16 and discharge spaces 11, distributed along the main axis 100. Two inlet spaces 16 and two discharge spaces 11 are shown as examples in the figures; in another example, the ring 10 may include two inlet spaces 16 – from different lines – and one discharge space 11 – returning the fluid to a single line. Spaces 11 and 16 extend along a certain angular sector, so as to connect different cavities of conduit 12 with the outside.

[0031] The pump 1 also includes a rotor 20 (or shaft) that rotates about a main axis 100 parallel to, but eccentric with respect to, the central axis 101. The rotor 20 extends along the main axis 100 and passes longitudinally through the conduit 12 of the ring 10. The rotor 20 includes a drum 21 supporting vanes 30. The rotor 20 is supported by trunnions 22 on either side of the drum 21 along the axis 100. The trunnions 22 are each rotatably mounted on bearings 40. The vanes 30 are radial, extending along a radius of the rotor 20, in a plane containing the main axis 100. The vanes 30 are inserted into slots 17 in the drum 21, extending radially within the drum 21, in a plane containing the main axis 100. There are four pallets, 30 of them, on the figure 2 and this is just an example; the 30 pallets can be more numerous, for example six or eight.

[0032] The pallets 30 delimit the cavities of the conduit 12 in communication with the outside, through the spaces 11 and 16. A cavity is delimited between two consecutive pallets, according to an angular sector of the conduit 12 centered on the main axis 100. A cavity admits the fluid when the cavity is opposite an inlet space 16; a cavity discharges the fluid when the cavity is opposite a discharge port 11.

[0033] The internal surface of the conduit 12 of the crown 10 forms a cam surface 18, which, as the rotor 12 rotates, acts on the vanes 30 - due to the offset between the main axis 100 of rotation of the rotor 20 and the central axis 101 of the conduit 12. For a certain vane 30, when the distance between the rotor 12 and the cam surface 18 decreases, the cam surface 18 pushes the vane 30 towards the inside of the drum 21, thus maintaining the seal at the end of the vane 30, between two consecutive cavities. Then, for a certain paddle 30, when the distance between the rotor 12 and the cam surface 18 increases, the paddle 30 is forced outwards from the drum 21 against the crown surface 18, also maintaining the seal at the end of the paddle 30. The paddles 30 are forced against the cam surface 18 by various possible means, for example by springs not shown.Thus, the volume of the cavities varies according to the angular position of the rotor 20 relative to the ring 10.

[0034] As the rotor 20 rotates around the main shaft 100, fluid such as oil enters through an inlet space 16 into a cavity within the conduit 12, delimited by two consecutive vanes 30. The rotation of the rotor 20 drives the cavity towards a discharge space 11, increasing the fluid pressure due to the reduction in the cavity's volume.

[0035] THE figures 3 and 4They show a perspective view of an example embodiment of the pump ring 10. Between two inlet spaces 16 and discharge spaces 11 located on the same circumference of the ring, the ring 10 includes a sealing zone 19 defined by the wall 13. Thus, when fluid is admitted into a cavity through an inlet space 16, the fluid cannot leak from the cavity when the latter is driven in rotation by the rotor and is opposite the sealing zone 19; the fluid is only discharged when the cavity is opposite the discharge space 11. Due to the offset between the axes 100 and 101, the ring 10 has a thicker wall 13 portion 23 and a thinner wall 13 portion 22; each of the portions 23 and 22 has a sealing zone 19.Similarly, between two inlet spaces 16 and between two discharge spaces 11 along the main axis 100, the ring 10 includes a sealing zone 19 defined by the wall 13. Thus, the fluid admitted into a cavity opposite an inlet space 16 cannot leak towards a neighboring cavity along the main axis 100.

[0036] When the fluid is discharged from the conduit through a discharge space 11, a pressure pulsation occurs. Since pump 1 is a positive displacement pump, it delivers a flow rate. The outlet pressure is the result of pressure losses in the downstream circuit and the imposed flow rate. Consequently, the pressure pulsations become flow pulsations. If the discharged flow rate is not constant, then there will also be pressure variations (pulsations) at the outlet of the lubrication unit 5. These pulsations can be due, in particular, to the compressibility of the fluid. To reduce, or even eliminate, the pressure pulsations, the ring 10 includes a groove 15, visible in the figures, which pressurizes the cavities to the pressure of the discharge space 11 during the rotation of the rotor 20. This groove 15 ensures a gradual pressurization of the conduit cavity 12 before the fluid is discharged.This helps to avoid premature failure of one or more pieces of equipment in the oil circuit and also to avoid oversizing equipment to prevent breakage.

[0037] Since the cavity is already at high pressure when it discharges, the reduction in cavity volume during the rotation of rotor 20 allows the fluid to be discharged directly. Without the grooves 15, the initial moments of cavity volume reduction serve only to pressurize the fluid (by compressing / reducing the cavity volume). There is therefore a delay during which the cavity does not discharge, which induces flow rate variations (and thus pressure pulsations) at the outlet of pump 1. The presence of the grooves 15 therefore allows for initiating discharge and reducing, or even eliminating, pressure pulsations.

[0038] More specifically, the groove 15 passes radially through the wall 13 and opens into the discharge space 11, following the circumference of the ring 10. The groove 15 extends over a portion of the sealing zone 19 defined in the wall 13 between a fluid inlet space 16 and a fluid discharge space 11. The presence of the groove 15 in the sealing zone breaks the seal of a fluid cavity between the inlet and outlet but allows the cavity to be pressurized before discharge, towards the discharge space 11.In other words, depending on the direction of rotation of the rotor 20 in the conduit 12, the fluid is admitted through an inlet space 16 into a cavity between two vanes 30 and then the cavity is directed towards a discharge space 11; the groove 15 being in the sealing zone between the inlet spaces 16 and discharge space 11, upstream of the discharge space 11, the groove allows the pump cavity to be brought to the outlet pressure while limiting leakage and backflow of the fluid.

[0039] According to the figures 3 and 4The grooves 15 are located at one end 14 of the discharge spaces 11, upstream of the discharge spaces 11. This is the end first reached by the conduit cavity during the rotation of the rotor 20. Alternatively, or in combination, the grooves 15 may also be located at one end of the discharge spaces 11, downstream of the discharge spaces 11. The presence of the grooved shape opening into the discharge space allows for gradual pressure variations within the discharge space. The presence of the groove(s) upstream and / or downstream allows for a gradual pressure variation in the cavity and reduces the mechanical loads on the lubrication circuit components caused by sudden pressure changes.

[0040] The dimensions of a groove 15 are small enough to limit leakage (or backflow) while ensuring gradual pressurization of the cavity before discharge. A groove that is too large would lead to unacceptable leakage, while a groove that is too small would have no effect on pressurizing the cavity. For this reason, the cumulative height of the grooves 15 is between 1 and 15% of the height of the ring 10. The groove 15 has an elongated shape. The groove 15 is an elongated orifice. The groove 15 has an elongated shape along the circumference of the ring 10 (and the wall 13). The groove 15 is a longitudinal notch in the wall 13. The groove 15 is a longitudinal notch in the wall 13, along the circumference of the ring 10.The groove 15 has a dimension in one direction (circumferential to the ring 10 and the wall 13) that is greater than a dimension in another direction (along the central axis 101 of the ring 10). The groove 15 has a length and a height, the length being greater than 110% of the height. The length of the groove 15 is a dimension along the circumference of the ring 10 (and the wall 13). In other words, the length of the groove 15 is along a directrix of the cylindrical ring 10. The height of the groove 15 is a dimension along the central axis 101 of the ring 10. In other words, the height of the groove 15 is along a generatrix of the cylindrical ring 10. The groove 15 crosses radially the wall 13 and opens at one end of its largest dimension into the displacement space 11, according to the circumference of the ring 10. The groove is a long orifice in one direction and narrow in another direction.The shape and arrangement of the groove through the wall and relative to the discharge space 11 ensure a gradual pressurization of the cavity before discharge. Alternatively, or in combination, the shape and arrangement of the groove through the wall and relative to the discharge space 11 ensure a gradual pressure variation in the cavity after discharge.

[0041] The grooves 15 are positioned at the end of the sealing zone 19 upstream of the discharge space 11, in the direction of rotation of the rotor 20. This sealing zone 19 can, depending on the design of the ring 10, correspond to the thinner part 22 of the wall 13 (as can be seen on the figures 3 and 4 ) but can also be in the thicker part 23 of the wall 13. The grooves 15 can also be positioned at the beginning of the sealing zone 19, downstream of the discharge space 11, in the direction of rotation of the rotor 20.

[0042] The grooves 15 can, for example, be obtained by a milling, electrical discharge machining (EDM) or wire cutting process, allowing control over the groove dimensions and ensuring appropriate sizes. A groove that is too large would lead to unacceptable leaks, while a groove that is too small would not pressurize the cavity.

[0043] The elements of the pump 1 such as the rotor 20, the trunnions 22, the drum 21, the vanes 30 and the ring 10 can be made of steel; the bearings 40 can be made of bronze.

[0044] The invention also relates to the lubrication circuit 2, which includes the pump 1 and an aircraft turbomachine. The grooves 15 reduce, or even eliminate, pressure pulsations in the lubrication circuit. This has no impact on the interfaces with the pump. This also improves fluid circulation and prevents premature failure of one or more components of the oil circuit. This extends the lifespan of the equipment. It also avoids oversizing the equipment and thus prevents an overall increase in the mass of the turbomachine.

[0045] The present invention has been described in relation to specific embodiments, which are purely illustrative and should not be considered limiting. Generally, it will be obvious to a person skilled in the art that the present invention is not limited to the examples illustrated and / or described above.

Claims

1. Fluid pump for an aircraft turbomachine, comprising: - A ring (10) through which a duct (12) passes along a central axis (101), the ring (10) being immobile and having a wall (13), - A rotor (20) driven in rotation relative to the ring (10) along a main axis (100) offset from the central axis (101), - Cavities between the ring (10) and the rotor (20), the volume of the cavities varying according to the angular position of the rotor (20) relative to the ring (10), - An inlet space (16) for admitting the fluid into the cavities and a discharge space (11) for discharging fluid from the cavities, the pressure in the discharge space (11) being higher than the pressure in the inlet space (16), the discharge (11) and inlet (16) spaces being radial and passing through the wall (13), - A groove (15) radially passing through the wall (13), characterized in that the groove (15) is shaped to expose the cavities to the pressure of the discharge space (11) as the rotor (20) rotates, and the groove (15) opens into the discharge space (11).

2. Pump (1) according to claim 1, wherein the groove has an elongate shape along a circumference of the wall (13).

3. Pump (1) according to claim 1 or 2, wherein the groove 15 has a length and a height, the length being greater than 110% of the height.

4. Pump (1) according to any one of the preceding claims, further comprising a sealing area (19) between the fluid inlet space (16) and the fluid discharge space (11), the groove (15) extending over a portion of the sealing area (19).

5. Pump (1) according to any one of the preceding claims, wherein the groove (15) opens into the discharge space (11), upstream or downstream of the discharge space (11), in the direction of rotation of the rotor (20).

6. Pump (1) according to any one of the preceding claims, wherein the wall (13) comprises a sealing area (19) between the fluid inlet space (16) and the fluid discharge space (11), the groove (15) extending over a portion of the sealing area.

7. Pump (1) according to any one of the preceding claims, comprising a plurality of discharge spaces (11) each with a groove (15) passing radially through the wall (13) of the ring and opening into the respective discharge space (11), the cumulative height of the grooves (15) along the axial direction of the ring (10) is between 1 and 15% of the height of the ring in the direction of the central axis (101).

8. Pump (1) according to any one of the preceding claims, wherein the groove(s) (15) are obtained by a milling, electro erosion or wire-cutting method.

9. Pump (1) according to any one of the preceding claims, comprising pallets (30) movable on the rotor along a radial direction of the rotor, and extending to the ring, the pallets defining the cavities between them.

10. Circuit (2) for lubricating an aircraft turbomachine, comprising at least one pump (1) according to any one of the preceding claims, the groove exposing the cavities to the pressure of the discharge space (11) and to the pressure of the circuit downstream of the pump.

11. Aircraft turbomachine, comprising the lubrication circuit (2) according to the preceding claim.

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