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

[0001] Fluid pump for aircraft turbomachine, lubrication circuit and aircraft turbomachine

[0002] Technical field

[0003] 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.

[0004] Prior art

[0005] Aircraft turbojet engines have a large amount of mechanical equipment that needs to be lubricated or cooled, including shafts, bearings, and gears. To achieve this, these turbojet engines are equipped with a lubrication circuit that supplies oil to each of these components. A feed pump generates an oil flow that is then divided between several lines to supply the engine's various components.

[0006] In order to save oil, this lubrication circuit operates in a closed circuit, the oil delivered to each piece of equipment being recovered and then reinjected into the lubrication circuit by recovery pumps.

[0007] The increase in flow rates and output pressures of the pumps providing the supply function (oil tank to engine enclosures) involves new hydraulic phenomena to be controlled.

[0008] One of the phenomena to be controlled is the pressure pulsation at the outlet of the lubrication unit. Since aeronautical pumps are positive displacement pumps, they provide a flow rate. The outlet pressure is the result of the pressure losses in the downstream circuit and the imposed flow rate.

[0009] Therefore, pressure pulsations return to 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 due in particular to the compressibility of the fluid.

[0010] Pulsations are detrimental in several ways, including the performance of the lubrication unit housing and the performance of the oil circuit equipment downstream of the lubrication unit (such as filters, valves, exchangers, pipes, etc.). The disadvantage of current lubrication units is that they are prone to premature failure (pulsation fatigue) of one or more of the units' equipment. To avoid such failure, some current lubrication units have oversized equipment - which leads to an overall increase in engine mass.

[0011] There is therefore a need to reduce, or even eliminate, pressure pulsations.

[0012] Statement of the invention

[0013] To this end, the invention proposes a fluid pump for an aircraft turbomachine, comprising a crown crossed by a conduit along a central axis, a rotor driven in rotation relative to the crown along a main axis offset relative to the central axis, cavities between the crown and the rotor, the volume of the cavities varying according to the angular position of the rotor relative to the crown, an intake 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 intake space, a groove putting the cavities at the pressure of the discharge space during rotation of the rotor.

[0014] Preferably, the crown is stationary and has a wall, the discharge and intake spaces being radial and passing through the wall and the groove passing radially through the wall and opening into the discharge space.

[0015] According to one variant, the groove has an elongated shape along a circumference of the wall.

[0016] According to one variant, the groove 15 has a length and a height, the length being greater than 110% of the height.

[0017] According to a variant, the pump further comprises a sealing zone between the fluid inlet space and the fluid discharge space, the groove extending over a portion of the sealing zone.

[0018] 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. According to one variant, the wall comprises a sealing zone between the fluid inlet space and the fluid discharge space, the groove extending over a portion of the sealing zone.

[0019] According to one variant, the pump comprises a plurality of discharge spaces, each with a groove passing radially through the wall of the crown and opening into the respective discharge space, the cumulative height of the grooves in the axial direction of the crown is between 1 and 15% of the height of the crown in the direction of the central axis.

[0020] According to one variant, the groove(s) are obtained by a milling, electroerosion or wire cutting process.

[0021] According to one variant, the pump comprises vanes movable on the rotor in a radial direction of the rotor, and extending to the crown, the vanes defining the cavities between them.

[0022] The invention also relates to a lubrication circuit for an aircraft turbomachine, comprising at least one pump as described above, the groove putting the cavities at the pressure of the discharge space and at the pressure of the circuit downstream of the pump.

[0023] The invention also relates to an aircraft turbomachine, comprising the lubrication circuit as described previously.

[0024] The use in this document of the verb "to understand", its variants, and its conjugations, cannot in any way exclude the presence of elements other than those mentioned. The use in this document of the indefinite article "un", "une", or of the definite article "le", "la" or "I'", to introduce an element does not exclude the presence of a plurality of these elements.

[0025] The terms "first", "second", "third", etc. are used in this document exclusively to differentiate between different elements, without implying any order between these elements.

[0026] All of the preferred embodiments and all of the advantages of the crown are transposed mutatis mutandis to the pump, the lubrication circuit and the turbomachine - and vice versa. The different embodiments can be considered alone or in combination. Brief description of the figures

[0027] Other characteristics and advantages of the present invention will appear on reading the detailed description which follows, for the understanding of which reference will be made to the appended figures which show:

[0028] - figure 1, a schematic view of a lubrication circuit;

[0029] - figure 2, a perspective view of an exemplary embodiment of a fluid pump;

[0030] - figure 3, a perspective view of an exemplary embodiment of a crown of the pump of figure 2;

[0031] - figure 4, another perspective view of an exemplary embodiment of a crown of the pump of figure 2.

[0032] The drawings of the figures are not to scale. Like elements are generally denoted by like references in the figures. For the purposes of this document, identical or similar elements may bear the same references. Furthermore, the presence of reference numbers or letters in the drawings cannot be considered as limiting, including when these numbers or letters are indicated in the claims.

[0033] Detailed description of embodiments of the invention

[0034] The invention relates to a fluid pump for an aircraft turbomachine, comprising a crown crossed by a conduit along a central axis, a rotor driven in rotation relative to the crown along a main axis offset from the central axis, cavities between the crown and the rotor, the volume of the cavities varying according to the angular position of the rotor relative to the crown, an inlet space for the admission 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 comprises a groove putting the cavities at the pressure of the discharge space during rotation of the rotor. Such a groove makes it possible to put the cavities of the pump at the outlet pressure, which makes it possible to reduce, or even cancel, the pressure pulsations at the outlet of the pump.In the long term, the life of the pump parts increases.

[0035] Figure 1 illustrates a lubrication circuit 2 for an aircraft turbomachine. Circuit 2 allows the various equipment of the turbomachine to be cooled and / or lubricated. Within circuit 2, the oil is sent from the reservoir 3 to equipment 4 of the turbomachine, such as bearings or enclosures. Circuit 2 comprises a lubrication group 5 comprising circulation pumps 1 whose technology may vary. In the present description, these are, for example, desmodromic vane pumps 1 or gerotor pumps 1. Pumps 1 supply oil to equipment 4 via supply lines 6. Downstream of equipment 4, recovery lines 7 allow the oil to be recovered and recirculated in circuit 2. It is possible to envisage one pump 1 per equipment 4 upstream and downstream of equipment 4, or one pump 1 for several equipment 4 upstream and downstream of equipment 4.According to the embodiment of figure 1 given as an example, one pump 1 is provided per piece of equipment 4 upstream and a single pump 1 downstream for all of the equipment 4.

[0036] Figure 2 shows a perspective view of an exemplary embodiment of a pump 1 which is a desmodromic vane pump. The pump 1 is a positive displacement pump, which imposes a flow rate. The pump 1 comprises a crown 10 (or cam for such a pump) with a generally cylindrical outer shape of revolution. The crown 10 comprises an axial cylindrical conduit 12 passing through the crown 10 along a central axis 101. The crown 10 is stationary. The crown 10 is delimited radially by a wall 13. The crown 10 also comprises an inlet space 16 (or inlet port) for fluid and a discharge space 11 (or discharge port) for fluid - in particular 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 outlet of the pump, and the inlet space 16 is at low pressure to admit the fluid from the inlet of the pump. The crown 10 may comprise one or more inlet 16 and discharge 11 spaces, distributed along the main axis 100. Two inlet spaces 16 and two discharge spaces 11 are shown as an example in the figures; according to another example, the crown 10 may comprise two inlet spaces 16 - coming from different lines - and a discharge space 11 - returning the fluid to a single line. The spaces 11 and 16 extend along a certain angular sector, so as to put different cavities of the conduit 12 into communication with the exterior.

[0037] The pump 1 also comprises a rotor 20 (or shaft) movable in rotation around a main axis 100 parallel but eccentric with respect to the central axis 101. The rotor 20 extends along the main axis 100 and longitudinally passes through the duct 12 of the crown 10. The rotor 20 comprises a drum 21 supporting vanes 30. The rotor 20 is supported by journals 22 on either side of the drum 21 along the axis 100. The journals 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 of the drum 21, extending radially in the drum 21, in a plane containing the main axis 100. The vanes 30 are four in number in FIG. 2, and this, by way of example; the 30 pallets can be more numerous, for example six or eight.

[0038] The vanes 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 vanes, 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.

[0039] The inner surface of the duct 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 duct 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 vane 30, when the distance between the rotor 12 and the cam surface 18 increases, the vane 30 is urged towards the outside of the drum 21 against the crown surface 18, also maintaining the seal at the end of the vane 30. The vanes 30 are urged 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 crown 10.

[0040] As the rotor 20 rotates about the main axis 100, fluid such as oil enters through an inlet space 16 into a cavity inside 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 pressure of the fluid due to the reduction in the volume of the cavity.

[0041] Figures 3 and 4 show a perspective view of an exemplary embodiment of the crown 10 of the pump 1. Between two inlet 16 and discharge 11 spaces located on the same circumference of the crown, the crown 10 comprises a sealing zone 19 defined by the wall 13. Thus, when the fluid is admitted into a cavity through an inlet space 16, the fluid cannot leak from the cavity when the latter is rotated 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 crown 10 comprises a thicker part 23 of wall 13 and a thinner part 22 of wall 13; each of the parts 23 and 22 comprises a sealing zone 19.Likewise, between two intake spaces 16 and between two discharge spaces 11 along the main axis 100, the crown 10 comprises a sealing zone 19 defined by the wall 13. Thus, the fluid admitted into a cavity opposite an intake space 16 cannot leak towards a neighboring cavity along the main axis 100.

[0042] When the fluid is discharged from the conduit through a discharge space 11, a pressure pulsation occurs. Since the pump 1 is a positive displacement pump, it ensures a flow rate. The outlet pressure is the result of the pressure losses of the downstream circuit and the imposed flow rate. Consequently, the pressure pulsations return to flow rate pulsations. If the discharged flow rate is not constant, then there will also be variations (pulsations) in pressure at the outlet of the lubrication group 5. These pulsations may in particular be due to the compressibility of the fluid. To reduce, or even cancel, the pressure pulsations, the crown 10 comprises a groove 15 visible in the figures putting the cavities under the pressure of the discharge space 11 during the rotation of the rotor 20. Such a groove 15 ensures a progressive pressurization of the cavity of the conduit 12 before the discharge of the fluid.This prevents premature failure of one or more pieces of equipment in the oil circuit and also prevents oversizing of the equipment to avoid breakage.

[0043] By already being at high pressure at the time when the cavity discharges, the reduction in the volume of the cavity during the rotation of the rotor 20 makes it possible to discharge the fluid directly. Without the grooves 15, the first moments of reduction in the volume of the cavity serve only to put the fluid under pressure (by compression / reduction of the volume of the cavity). There is therefore a delay during which the cavity does not discharge which induces variations in flow rate (and therefore pressure pulsations) at the outlet of the pump 1. The presence of the grooves 15 therefore makes it possible to initiate a discharge and reduce, or even cancel, the pressure pulsations.

[0044] More specifically, the groove 15 passes radially through the wall 13 and opens into the discharge space 11, along the circumference of the crown 10. The groove 15 extends over a portion of the sealing zone 19 defined in the wall 13 between an 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 the outlet but allows the cavity to be pressurized before it is discharged, in the direction of 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 then the cavity is directed towards a discharge space 11; the groove 15 being in the sealing zone between the inlet 16 and discharge 11 spaces, upstream of the discharge space 11, the groove makes it possible to put the cavity of the pump at the outlet pressure while limiting leaks and the discharge of the fluid.

[0045] According to Figures 3 and 4, the grooves 15 are at one end 14 of the discharge spaces 11, upstream of the discharge spaces 11. This is the end first reached by the cavity of the conduit during the rotational movement of the rotor 20. Alternatively or in combination, the grooves 15 may also be at one end of the discharge spaces 11, downstream of the discharge spaces 11. The presence of the groove shape opening into the discharge space allows for progressive pressure variations in the discharge space. The presence of the groove(s) upstream and / or downstream allows for a progressive pressure variation in the cavity and to reduce the mechanical loads in the components of the lubrication circuit due to sudden pressure variations.

[0046] The dimensions of a groove 15 are small enough to limit leaks (or a return flow) while ensuring a progressive pressurization of the cavity before its discharge. A groove that is too large would lead to unacceptable leaks while a groove that is too small would not have any effect of pressurizing the cavity. For this, the cumulative height of the grooves 15 is between 1 and 15% of the height of the crown 10. The groove 15 has an elongated shape. The groove 15 is an orifice of elongated shape. The groove 15 has an elongated shape along the circumference of the crown 10 (and of 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 crown 10.The groove 15 has a dimension in one direction (circumferential of the crown 10 and the wall 13) greater than a dimension in another direction (along the central axis 101 of the crown 10). The groove 15 has a length and a height, the length being greater than 1 10% of the height. The length of the groove 15 is a dimension along the circumference of the crown 10 (and of the wall 13). In other words, the length of the groove 15 is along a directrix of the cylindrical crown 10. The height of the groove 15 is a dimension along the central axis 101 of the crown 10. In other words, the height of the groove 15 is along a generatrix of the cylindrical crown 10. The groove 15 passes radially through the wall 13 and opens at one end of its largest dimension into the discharge space 11, along the circumference of the crown 10. The groove is an orifice which is long 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 ensures a progressive pressure build-up 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 ensures a progressive pressure variation of the cavity after discharge.

[0047] 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 may, depending on the design of the crown 10, correspond to the thinner part 22 of the wall 13 (as can be seen in FIGS. 3 and 4) but may also be in the thicker part 23 of the wall 13. The grooves 15 may also be positioned at the start of the sealing zone 19, downstream of the discharge space 11, in the direction of rotation of the rotor 20.

[0048] The grooves 15 can for example be obtained by a milling, electroerosion or wire cutting process, making it possible to control the dimensions of the grooves and to obtain appropriate dimensions. A groove that is too large would lead to unacceptable leaks while a groove that is too small would not have any effect of pressurizing the cavity.

[0049] The elements of the pump 1 such as the rotor 20, the journals 22, the drum 21, the vanes 30 and the crown 10 can be made of steel; the bearings 40 can be made of bronze.

[0050] The invention also relates to the lubrication circuit 2 comprising the pump 1 and an aircraft turbomachine. The grooves 15 make it possible to reduce, or even cancel, the pressure pulsations in the lubrication circuit. This has no impact on the interfaces with the pump. This also allows for better circulation of the fluid and avoids premature breakage of one or more pieces of equipment in the oil circuit. This provides a longer service life for the equipment. Oversizing of the equipment and therefore an overall increase in the mass of the turbomachine are also avoided. The present invention has been described in relation to specific embodiments, which have a purely illustrative value and should not be considered limiting. In general, 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

Demands 1. Fluid pump for aircraft turbomachinery, comprising - A ring (10) traversed by a conduit (12) along a central axis (101), the ring (10) being stationary and comprising a wall (13), - A rotor (20) driven in rotation relative to the ring (10) along a main axis (100) offset relative to 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 the admission of the fluid into the cavities and a discharge space (11) for the discharge of the fluid from the cavities, the pressure in the discharge space (11) being higher than the pressure in the inlet space (16), the discharge spaces (11) and the inlet space (16) being radial and passing through the wall (13), - A groove (15) that puts the cavities under the pressure of the discharge space (11) during the rotation of the rotor (20), the groove radially passing through the wall (13) and opening into the discharge space (11).

2. Pump (1) according to claim 1, wherein the groove has an elongated 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 1 10% of the height.

4. Pump (1) according to any one of the preceding claims, further comprising a sealing zone (19) between the fluid inlet space (16) and the fluid discharge space (11), the groove (15) extending over a part of the sealing zone (19). 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). Pump (1) according to any one of the preceding claims, wherein the wall (13) comprises a sealing zone (19) between the fluid inlet space (16) and the fluid discharge space (11), the groove (15) extending over a portion of the sealing zone. Pump (1) according to any one of the preceding claims, comprising a plurality of discharge spaces (11) each with a groove (15) radially traversing 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 along the direction of the central axis (101).A pump (1) according to any one of the preceding claims, wherein the groove(s) (15) are obtained by a milling, electrical discharge machining (EDM), or wire cutting process. A pump (1) according to any one of the preceding claims, comprising vanes (30) movable on the rotor in a radial direction of the rotor and extending to the ring, the vanes defining the cavities between them. An aircraft turbomachine lubrication circuit (2), comprising at least one pump (1) according to any one of the preceding claims, the groove bringing 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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