WO2019110909A1

WO2019110909A1 - Pump comprising an axial balancing system

Info

Publication number: WO2019110909A1
Application number: PCT/FR2018/053093
Authority: WO
Inventors: Cyril LOISEAU; Sébastien BOUFFLERT; Thibaut LEMAIRE
Original assignee: Arianegroup Sas
Priority date: 2017-12-08
Filing date: 2018-12-03
Publication date: 2019-06-13
Also published as: EP3721093B1; FR3074859A1; FR3074859B1; EP3721093A1

Abstract

The present description relates to a pump (11) or compressor for the flow of a fluid, comprising a casing (13), a centrifugal impeller (15), configured to be rotationally driven with respect to the casing (13) about a main axis defining an axial direction (DA), a restrictive fluid-flow passage formed between the casing (13) and the centrifugal impeller (15) defining an axial balancing system (19), the casing (13) comprising a first balancing portion (23) and the centrifugal impeller (15) comprising a second balancing portion (29), the first and second balancing portions (23, 29) defining the inlet of the restrictive flow passage, the second balancing portion (29) of the centrifugal impeller (15) being configured to pass from a rest position, in which the external diameter of the second balancing portion (29) is less than the internal diameter of the first balancing portion (23), to an operating position in which the first and second balancing portions (23, 29) overlap in the axial direction (DA), under the effect of the centrifugal force applied to the rotating centrifugal impeller (15).

Description

Pump comprising an axial balancing system

FIELD OF THE INVENTION

The present invention relates to the field of axial balancing pumps or compressors, such as for example pumps for drawing liquefied gas for aerospace turbomachine.

TECHNOLOGICAL BACKGROUND

It is known that the pumps, or compressors, of the prior art comprise an axial balancing system for compensating all or part of the forces exerted on certain parts of the pump, when it is in operation. The axial balancing system is generally defined by a restrictive passage of fluid flow, provided between the housing and the rotor, for example a centrifugal wheel, of the pump. It is important to precisely calibrate the flow rate of the fluid in the restricting flow passage so as to optimize axial balancing of the pump. However, in order to be able to calibrate the flow rate of the fluid in the restrictive flow passage, and in order to limit the risk of contact between the casing and the rotor of the pump, it is necessary that the dimensions and the geometry of the restrictive passage flow are precisely defined. To ensure such accuracy, time-consuming and expensive calculations and tests are required. There is therefore a need in this sense.

PRESENTATION OF THE INVENTION

For this purpose the present disclosure relates to a pump or a compressor for the flow of a fluid, comprising:

- a housing, and a centrifugal wheel, configured to be rotated with respect to the housing around a main axis defining an axial direction,

a restrictive passage of fluid flow provided between the casing and the centrifugal wheel defining an axial balancing system, the casing comprising a first balancing portion and the centrifugal wheel comprising a second balancing portion, the first and second balancing portions; balancing portions defining the inlet of the flow restrictive passage,

the second balancing portion of the centrifugal wheel being configured to move from a rest position, in which the first and second balancing portions are at a distance, to an operating position in which the first and second balancing portions overlap in the axial direction under the effect of the force exerted on the rotating centrifugal wheel.

[0004] Main axis is the axis of rotation of the centrifugal wheel. The axial direction corresponds to the direction of main axis and a radial direction is a direction perpendicular to this main axis and intersecting this main axis. Similarly, an axial plane is a plane containing the main axis and a radial plane is a plane perpendicular to this main axis. A circumference is understood as a circle belonging to a radial plane and whose center belongs to the main axis. A tangential or circumferential direction is a direction tangent to a circumference; it is perpendicular to the main axis but does not go through the main axis.

Unless otherwise specified, the adjectives inside and outside are used with reference to a radial direction so that the inner part of an element is, in a radial direction, closer to the axis of the diffuser than the outer portion of the same element. Unless otherwise specified, the adjectives front and rear are used with reference to the axial direction, it being understood that the inlet of the centrifugal wheel is located on the front side of the centrifugal wheel, while its outlet is located on the rear side, in the normal direction of fluid flow through the centrifugal wheel.

[0007] The term "pump" means pumps, compressors or similar devices.

It is understood that the second balancing portion is displaced by the centrifugal force exerted on the centrifugal wheel when the latter is rotated.

The term "rest position", the position occupied by the second balancing portion when the centrifugal wheel is not rotated. In this position, the first and second balancing portions are at a distance from one another.

The term "operating position", the position occupied by the second balancing portion when the centrifugal wheel is rotated, for example, at its nominal rotational speed.

It is understood that the displacement of the second balancing portion under the effect of the centrifugal force is formed in a radial direction.

However, in operation, the flow of high pressure fluid passing through the restrictive flow passage could also cause a displacement of the second balancing portion in the axial direction.

Thus, the overall displacement of the second balancing portion may be the result of radial displacement and axial movement, in particular.

It is understood that the fluid flow is restricted by the restrictive flow passage, the input is defined by the first and second balancing portions. For example, the aerospace turbomachine is a cryotechnical turbine engine, that is to say, configured to compress a fluid, for example, at a temperature less than or equal to 120 K (Kelvin). For example, for a cryotechnical turbine engine using liquid dihydrogen as a fluid, the turbomachine is configured to compress the fluid at a temperature of less than or equal to 20 K. For example, for a cryotechnical turbine engine using liquid oxygen as a fluid, the turbomachine is configured to compress the fluid at a temperature of less than or equal to 90 K. For example, for a cryotechnical turbine engine using liquid methane as a fluid, the turbomachine is configured to compress the fluid to a temperature less than or equal to 110 K.

For example, the pump or compressor comprises a shaft configured to drive the centrifugal wheel in rotation about the main axis.

For example, the centrifugal wheel includes a mounting portion configured to be mounted to the shaft.

According to one embodiment, the outer diameter, or maximum, of the second balancing portion is smaller than the inner diameter, or minimum of the first balancing portion of the housing, in the rest position.

Thus, in the rest position, the first and second balancing portions not overlapping, the mounting of the centrifugal wheel relative to the housing is simpler to achieve. Indeed, the positioning of the parts does not have to be as precise as previously to limit the risk of contact between the centrifugal wheel and the housing. In addition, the pump or the compressor according to the present disclosure avoids the presence of an added nozzle.

When the centrifugal wheel is rotating, under the effect of the centrifugal force, the centrifugal wheel expands outwardly and the second balancing portion moves from the home position to the operating position.

In the operating position, the first and second balancing portions overlap, that is to say that the first and second balancing portions are at least partly opposite the one from the other, over an overlapping distance. In other words, the overlap distance is the length over which the pieces overlap. In other words, in the operating position, the first and second balancing portions overlap axially. The axial overlap of the first and second balancing portions makes it possible to better calibrate the flow rate, also called the leakage flow rate, in the restrictive flow passage. Indeed, as the centrifugal wheel is subjected to expansion when driven in rotation in the radial direction, it is difficult to control the radial play.

In contrast, the axial clearance is easily controllable, and can be calibrated. Thus, due to the axial overlap of the first and second balancing portions, a dimensionally controlled fluid passage is formed thereby calibrating the flow rate in the restricting flow passage. The axial clearance thus makes it possible to calibrate the flow rate of the fluid in the restrictive flow passage.

According to one aspect of the present disclosure, the overlap distance of the first and second balancing portions in a radial direction, in the operating position, is between 0.012% and 0.032% of the diameter of the centrifugal wheel. The overlap distance of the first and second balancing portions in a radial direction, in the operating position, may be between 0.03 mm and 0.08 mm, for example for a diameter of the wheel 250 mm centrifuge, a rotational speed of the centrifugal wheel of 40000 rpm (revolutions per minute) and a temperature of about 40 K.

With these provisions, the first and second balancing portions form a baffle, or a labyrinth to better restrict the fluid inlet in the restrictive passage of flow, and therefore to ensure better axial balancing pump or compressor.

According to one aspect of the present disclosure, the second balancing portion is configured to move over a distance of between 0.024% and 0.06% of the diameter of the centrifugal wheel. The second balancing portion is configured to move over a distance of between 0.06 mm and 0.15 mm, for example for a diameter of the centrifugal wheel of 250 mm, a rotational speed of the centrifugal wheel of 40000 tr / min and for a temperature of about 40 K.

With these provisions, the fluid inlet in the restrictive passage of flow is better restricted, axial balancing of the pump or the compressor is better ensured while implementing a method of mounting the system. simple axial balancing.

According to one aspect of the present disclosure, the second balancing portion is configured to be received in a balancing groove formed by the first balancing portion and a portion of the housing adjacent to the first balancing portion.

It is understood that the first and second balancing portions are configured to form the inlet of the flow restricting passage by the cooperation between the second balancing portion and the balancing groove, in the operating position.

It is understood that in the rest position, conversely, the first and second balancing portions are remote from one another. In other words, in the rest position, the second balancing portion does not fit into the balancing groove. In the rest position, the first and second balancing portions do not overlap axially.

It is understood that the entrance of the flow restricting passage is for example generally labyrinth shape or baffle.

With these provisions, in addition to the above advantages, the recirculation flow is calibrated easily, and a better axial balance of the pump or compressor is ensured.

In some embodiments, the centrifugal wheel includes an expansion portion configured to move the second balancing portion from the home position to the operating position.

It is understood that the mounting portion, the expansion portion and the second balancing portion are arranged in this order in the radial direction, starting from the main axis.

With these provisions, the expansion portion of the centrifugal wheel allows a displacement of the second balancing portion with the centrifugal force, which allows even more simplifying the mounting of the balancing system while ensuring a better axial balancing of the pump or compressor.

According to one aspect of this disclosure, the expansion portion is annular.

In some embodiments, the expansion portion is configured to expand further than other portions of the centrifugal wheel due to centrifugal force.

With these provisions, the expansion portion allows the second balancing portion to move more easily from the rest position to the operating position when the centrifugal wheel is in operation and also to return to the rest position when the centrifugal wheel stops working. These provisions still allow more simplify the assembly of the balancing system while ensuring better axial balancing of the pump or compressor.

In some embodiments, the expansion portion comprises at least a portion of reduced thickness in the axial direction relative to adjacent portions of the centrifugal wheel.

It is understood that the thickness of the centrifugal wheel is reduced at the level of the expansion portion, which allows the expansion portion to expand more than the other parts of the centrifugal wheel.

According to one aspect of the present disclosure, the expansion portion comprises an expansion member, which may be disposed along the flow restricting passage.

It is understood that the expansion element is adjacent restrictive passage of flow.

It is understood that the expansion element is disposed on the back of the centrifugal wheel, that is to say on the side of the rear portion of the centrifugal wheel.

These provisions even further simplify the mounting of the balancing system while ensuring a better axial balance of the pump or compressor. These provisions also make it possible not to disturb the main flow of the fluid.

According to one aspect of the present disclosure, the expansion element comprises a groove.

It is understood that the groove opens on the restrictive passage of flow.

It is understood that the groove is configured to thin at least a portion of the expansion portion in the axial direction.

With these provisions, the expansion portion is simple to achieve. These arrangements make it even easier to of the balancing system while ensuring better axial balancing of the pump or compressor.

According to one aspect of this disclosure, the expansion element may comprise a plurality of grooves.

According to one aspect of the present disclosure, the expansion element comprises a lattice structure, that is to say a mesh structure or a reticular structure.

We understand lattice structure, a structure

"Lattice" in the English language.

With these provisions, the lattice structure having an anisotropic behavior and / or flexible, it allows more easily the expansion portion of the centrifugal wheel to expand radially under the centrifugal effect to pass the second portion of balancing from the rest position to the operating position.

According to one aspect of the present disclosure, the expansion element comprises an anisotropic material.

With these provisions, in addition to the aforementioned advantages, the anisotropic material makes it easier for the expansion portion of the centrifugal wheel to expand radially under the centrifugal effect to pass the second balancing portion of the position. rest at the operating position.

In one aspect, the anisotropic material is solid.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention and its advantages will be better understood on reading the following detailed description of embodiments of the invention given by way of non-limiting examples. This description refers to the accompanying drawings, in which: FIG. 1 represents an axial section of a part of the pump comprising the axial balancing system, in which the second axial balancing portion is in the rest position,

FIG. 2 represents an axial section of a portion of the pump comprising an axial balancing system, in which the second axial balancing portion is in the operating position,

FIG. 3 shows the displacement of the second axial balancing portion between the rest position and the operating position, in axial section,

FIG. 4 represents an axial section of a part of the pump comprising the axial balancing system of the pump according to a second embodiment,

- Figure 5 shows an axial section of a portion of the pump comprising the axial balancing system of the pump according to a third embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 shows a portion of a pump 11 of an aerospace turbomachine, configured to allow the flow of a fluid.

For example, the pump may comprise one or more axial compression stage (s) and one or more centrifugal compression stage (s).

The pump 11 comprises a casing 13 and a centrifugal wheel 15.

The casing 13 surrounds externally blades of the centrifugal wheel 15. The blades of the centrifugal wheel 15 are disposed on the front side of the centrifugal wheel 15. A diffuser 12 is located downstream of the centrifugal wheel 15. The turbomachine has a fluid inlet (not shown), the fluid passing through this inlet to reach the pump IL The rotation of the centrifugal wheel 15 about its axis of rotation, called the main axis, draws the fluid through the before the centrifugal wheel and the axial speed of the fluid passing through the centrifugal wheel 15 is progressively transformed into a radial velocity, the fluid exiting at the outer periphery of the centrifugal wheel 15. The fluid enters the centrifugal wheel 15 substantially in a direction axial DA, defined by the main axis, and out of the centrifugal wheel 15 substantially in a radial direction DR, substantially perpendicular to the main axis.

The fluid leaving the centrifugal wheel 15 passes through the diffuser 12 before reaching the combustion chamber (not shown).

The centrifugal wheel 15 can be mounted on a shaft driven in rotation by the turbine.

The centrifugal wheel 15 is configured to be rotated relative to the housing 13 around the main axis.

The pump 11 comprises a main fluid flow passage 17, defined between the casing 13 and the front of the centrifugal wheel 15, and a restrictive fluid flow passage 19 defining an axial balancing system, here provided between the rear of the centrifugal wheel 15, or the back of the centrifugal wheel 15, and the housing 13. The restricting flow passage 19 is a secondary fluid passage, configured to receive a flow rate, or a leakage flow which exerts an axial counter-pressure on the centrifugal wheel 15 with a view to the axial equilibration of the pump 11.

The casing 13 comprises a body 21 and a first balancing portion 23. In this embodiment, the first balancing portion 23 is integral with the body 21. The centrifugal wheel 15 comprises a mounting portion 25, an expansion portion 27 and a second balancing portion 29, arranged radially in this order. The mounting portion 25 is mounted on the shaft. The mounting portion 25, the expansion portion 27, and the second balancing portion 29 are integral.

The first and second balancing portions 23, 29 define the inlet of the flow restricting passage 19.

The first balancing portion 23 includes an inwardly projecting portion and the second balancing portion 29 includes an outwardly protruding portion. As shown in FIG. 3, in the operating position, the first and second balancing portions 23, 29 are offset with respect to one another in the axial direction DA, and therefore have an axial clearance JA. The axial clearance JA between the first and second balancing portions is between 0.02% and 0.4% of the radius of the centrifugal wheel, preferably between 0.08% and 0.2% of the radius of the centrifugal wheel. and more preferably, the axial clearance JA between the first and second balancing portions 23, 29 is 0.12% of the radius of the centrifugal wheel 15. For example, the axial clearance JA between the first and second balancing portions 23, 29 is between 30 μm and 500 μm, preferably between 100 μm and 250 μm. For example, for a centrifugal wheel having a diameter of 250 mm, having a rotational speed of about 40,000 rpm and a temperature of about 40 K, the axial clearance JA between the first and second balancing portions is 150 pm. The axial play JA in the rest position is dimensioned so as to obtain a satisfactory clearance in the operating position. The axial clearance JA thus makes it possible to calibrate the flow rate of the fluid in the restrictive flow passage 19.

The second balancing portion 29 is disposed facing a balancing groove 31 formed by the first axial balancing portion 23 and an adjacent portion 32 of the housing 13. The expansion portion TJ is configured to undergo an expansion greater than the mounting portion 25 and the second balancing portion 29 of the centrifugal wheel 15 under the effect of the centrifugal force. The expansion portion 27 includes, along the flow restrictive passage 19, an expansion member 35. In this embodiment, the expansion member 35 includes a groove 33. Here, the expansion member 35 comprises only Throat 33. The reduced thickness of the centrifugal wheel 15 at this point allows it to expand more strongly at this expansion portion 27. Here, the expansion element 35 is annular.

For example, the groove 33 extends over a length of about 40% of the diameter of the centrifugal wheel in the radial direction. In this example, the groove 33 has a depth of about 20% of the thickness of the centrifugal wheel, in the axial direction, considered at mid-height of the centrifugal wheel 15 in the radial direction, that is to say say at about 50% of the outside radius of the centrifugal wheel 15.

In an exemplary embodiment where the diameter of the centrifugal wheel is 250 mm and the thickness of the centrifugal wheel in the axial direction, halfway up the centrifugal wheel 15 in the radial direction, is about 300 mm, the groove 33 extends over a length of about 50 mm in the radial direction. In this example, the groove 33 has a depth of about 5 mm in the axial direction.

In this embodiment, the centrifugal wheel 15 may consist of a material conventionally used for cryotechnical turbomachines. For example, such a material has a dYoung modulus of 200,000 MPa, a fish coefficient of 0.3 and a density of 8.26 × 10 ⁶ kg / mm ³ . For example, the centrifugal wheel 15 is made of titanium, aluminum or a nickel-based material, such as a nickel-based superalloy, for example Inconel (trademark). Thanks to the expansion of the expansion portion 27, the second balancing portion 29 of the centrifugal wheel 15 is configured to move from a rest position visible in Figure 1, to an operating position, visible in Figure 2.

As shown in Figure 3, in the rest position, the first and second balancing portions 23, 29 are at a distance from one another and the centrifugal wheel 15 is not rotated.

In the rest position, an inner edge 23a of the first balancing portion 23 and an outer edge of the second balancing portion 29 are spaced from a radial play of rest in a radial direction DR. For example, the radial resting clearance J RR is between 0.03 mm and 0.08 mm, preferably between 0.04 mm and 0.07 mm, and more preferably, the clearance is 0.05 mm. In the rest position, the second balancing portion 29 does not fit into the balancing groove 31. Thus, the mounting of the centrifugal wheel 15 on the housing 13 is easily achieved.

When the pump is put into operation, the centrifugal wheel 15 begins to rotate and is subjected to centrifugal force. Under this force, the centrifugal wheel 15 expands outwardly, due to the expansion of the expansion portion 27, in particular.

Thus, in the operating position, the first and second balancing portions 23, 29 overlap in the axial direction DA under the effect of the centrifugal force exerted on the centrifugal wheel 15 when the centrifugal wheel 15 is driven. in rotation. For example, the nominal speed of the pump is between 1000 rpm and 120000 rpm, preferably between 10000 rpm and 100000 rpm and more preferably 40 000 rpm.

In the operating position, the second balancing portion 29 fits into the balancing groove 31, which forms a labyrinth passage at the entrance of the restricting flow passage 19. Thus, the calibration of the flow rate is easy.

The first and second balancing portions 23, 29 overlap over an overlap distance DC between 0.03 mm and 0.08 mm, preferably between 0.04 mm and 0.07 mm, and more preferably over a distance of 0.05 mm in the radial direction DR.

Between the rest position and the operating position, the second balancing portion 23 moves over a displacement distance DD, in the radial direction DR, between 0.06 mm and 0.15 mm, preferably between 0.08 mm and 0.13 mm, more preferably, over a displacement distance DD of 0.1 mm.

FIG. 4 represents a second embodiment of the expansion portion 27. This second example differs from the first embodiment in that the expansion element 135 comprises a trellis structure 137, that is to say say a mesh or reticular structure.

For example, the lattice structure 137 is attached to the centrifugal wheel 15, after having been manufactured by an additive manufacturing process, for example by laser melting on a bed of powder.

The lattice structure 137 is disposed in place of the groove 33 of the first embodiment. Here, the expansion element 135 comprises only the lattice structure 137.

FIG. 5 represents a third exemplary embodiment of the expansion portion 27. This third embodiment differs from the first and second exemplary embodiments in that the expansion element 235 comprises an anisotropic material 237. For example, the anisotropic material 237 is full. In this embodiment, the anisotropic material 237 is disposed in place of the groove 33 of the first embodiment. Here, the dilation element 235 only includes the anisotropic material 237. The anisotropic material 237 is configured to undergo preferential expansion in the radial direction DR. For example, the anisotropic material 237 is a composite material comprising oriented fibers. For example, the fibers may be generally oriented in the radial direction DR, which allows to give more flexibility to the expansion element 235 in the radial direction DR.

According to other embodiments, the expansion portion 27 consists entirely of the anisotropic material 237.

According to other embodiments, the centrifugal wheel 15 consists entirely of the anisotropic material 237.

Although the present invention has been described with reference to specific embodiments, modifications can be made to these examples without departing from the general scope of the invention as defined by the claims. For example, some or all of the detailed features about the groove 33 may apply, mutatis mutandis, to the expansion element 135 or 235 of the second or third embodiment. More generally, individual features of the various embodiments illustrated / mentioned can be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

Claims

A pump (11) or compressor for the flow of a fluid, comprising:

a housing (13), and

a centrifugal wheel (15), configured to be rotated with respect to the housing (13) about a main axis defining an axial direction (DA),

a restrictive passage of fluid flow provided between the casing (13) and the centrifugal wheel (15) defining an axial balancing system (19),

the casing (13) comprising a first balancing portion (23) and the centrifugal wheel (15) comprising a second balancing portion (29), the first and second balancing portions (23, 29) defining the inlet the restrictive flow passage,

the second balancing portion (29) of the centrifugal wheel (15) being configured to move from a rest position, wherein the outer diameter of the second balancing portion (29) is smaller than the inner diameter of the first balancing portion (23) at an operating position in which the first and second balancing portions (23, 29) overlap in the axial direction (DA) under the effect of the centrifugal force exerted on the wheel Centrifugal (15) in rotation.

The pump or compressor according to claim 1, wherein the second balancing portion (29) is configured to move a displacement distance (DD) between 0.024% and 0.06% of the diameter of the centrifugal wheel ( 15).

3. Pump or compressor according to one of claims 1 or 2, wherein the second balancing portion (29) is configured to be received in a balancing groove (31) formed by the first balancing portion (23). ) and a portion of the housing (13) adjacent to the first balancing portion

(23).

4. Pump or compressor according to one of the preceding claims, wherein, the centrifugal wheel (15) comprises an expansion portion (27) configured to pass the second balancing portion (29) from the rest position to the operating position.

The pump or compressor of claim 4, wherein the expansion portion (27) is configured to expand further than the other portions of the centrifugal wheel (15) by centrifugal force.

6. Pump or compressor according to one of claims 4 or 5, wherein the expansion portion (27) comprises an expansion element (35, 135, 235) disposed along the restricting flow passage (19).

7. Pump or compressor according to one of claims 4 to 6, wherein the expansion portion (27) comprises at least a portion of a reduced thickness in the axial direction (DA) relative to the adjacent portions of the centrifugal wheel (15).

8. Pump or compressor according to one of claims 4 to 7, wherein the expansion element (35) comprises a groove (33). 9. Pump or compressor according to one of claims 4 or 5, wherein the expansion element (135) comprises a lattice structure (137).

10. Pump or compressor according to one of claims 4 or 5, wherein the expansion element (235) comprises an anisotropic material (237).