IMPROVED AIRCRAFT ENGINE FUEL PUMP

Abstract

Fuel pump for an aircraft engine, comprising an inducer and a centrifugal impeller fixed together and having an axis of rotation, an annular space spacing axially the inducer and the impeller, and two contact portions between the inducer and the impeller disposed radially outside the annular space, a first plenum chamber and a second plenum chamber, in which the inducer and the impeller are spaced axially from each other, each being disposed between the two contact portions, the plenum chambers being symmetrical to each other with respect to the axis of rotation and in fluid communication with the annular space, the centrifugal impeller comprising a plurality of axial balancing holes distributed about the axis of rotation and opening out into the annular space at one end, and into a downstream space of the impeller at the other end.

Claims

1. A fuel pump for an aircraft engine, comprising: an inducer comprising an axis of rotation, a centrifugal impeller coaxial with the inducer, the inducer being fixed to the centrifugal impeller upstream thereof so as to define an annular interface between the inducer and the impeller about the axis of rotation, the annular interface comprising an annular space spacing axially the inducer and the impeller and two contact portions between the inducer and the impeller disposed radially outside the annular space, a first plenum chamber and a second plenum chamber, in which the inducer and the impeller are spaced axially from each other, each being disposed circumferentially between the two contact portions, the plenum chambers being symmetrical to each other with respect to the axis of rotation and in fluid communication with the annular space, the centrifugal impeller comprising a plurality of axial balancing holes distributed circumferentially about the axis of rotation and opening out into the annular space at one end, and into a downstream space of the impeller at the other end.

2. The fuel pump according to claim 1, wherein the first and second plenum chambers each extend circumferentially over at least a quarter of the circumference of the annular interface.

3. The fuel pump according to claim 1, wherein the inducer comprises a first annular surface comprising two first raised portions protruding axially with respect to the rest of the first annular surface, the first raised portions being symmetrical to each other with respect to the axis of rotation and being in contact with a second annular surface of the impeller, when the impeller and the inducer are fixed together.

4. The fuel pump according to claim 3, wherein the second annular surface of the impeller comprises two second raised portions protruding axially with respect to the rest of the second annular surface, the second raised portions being symmetrical to each other with respect to the axis of rotation and being disposed circumferentially between the first raised portions when the impeller and the inducer are fixed together.

5. The fuel pump according to claim 4, wherein a height of the first raised portions is greater than a height of the second raised portions, such that the first raised portions are in contact with the second annular surface of the impeller, and such that the second raised portions are not in contact with the first annular surface of the inducer.

6. The fuel pump according to claim 1, wherein the balancing holes are distributed circumferentially at regular intervals about the axis of rotation.

7. The fuel pump according to claim 1, wherein the centrifugal impeller comprises sixteen axial balancing holes.

8. The fuel pump according to claim 1, wherein a distance between the balancing holes and the axis of rotation is less than 20%, preferably less than 15%, more preferably less than 10% of the radius of the impeller.

9. The fuel pump according to claim 1, wherein a ratio L/D between a length L and a diameter D of the balancing holes is greater than or equal to 2.

10. An aircraft comprising the pump according to claim 1.

11. The fuel pump according to claim 2, wherein the inducer comprises a first annular surface comprising two first raised portions protruding axially with respect to the rest of the first annular surface, the first raised portions being symmetrical to each other with respect to the axis of rotation and being in contact with a second annular surface of the impeller, when the impeller and the inducer are fixed together.

12. The fuel pump according to claim 2, wherein the balancing holes are distributed circumferentially at regular intervals about the axis of rotation.

13. The fuel pump according to claim 3, wherein the balancing holes-are distributed circumferentially at regular intervals about the axis of rotation.

14. The fuel pump according to claim 4, wherein the balancing holes-are distributed circumferentially at regular intervals about the axis of rotation.

15. The fuel pump according to claim 5, wherein the balancing holes-are distributed circumferentially at regular intervals about the axis of rotation.

16. The fuel pump according to claim 2, wherein the centrifugal impeller comprises sixteen axial balancing holes.

17. The fuel pump according to claim 3, wherein the centrifugal impeller comprises sixteen axial balancing holes.

18. The fuel pump according to claim 4, wherein the centrifugal impeller comprises sixteen axial balancing holes.

19. The fuel pump according to claim 5, wherein the centrifugal impeller comprises sixteen axial balancing holes.

20. The fuel pump according to claim 6, wherein the centrifugal impeller comprises sixteen axial balancing holes.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The invention and its advantages will be better understood upon reading the detailed description given below of various embodiments of the invention given by way of non-limiting examples. This description refers to the pages of appended figures, on which:

[0047] [FIG. 1] FIG. 1 is a perspective view of a fuel pump according to one embodiment of the present disclosure,

[0048] [FIG. 2] FIG. 2 is an exploded view of the fuel pump of FIG. 1,

[0049] [FIG. 3] FIG. 3 represents a sectional view, along a section plane A of the centrifugal pump of FIG. 1,

[0050] [FIG. 4] FIG. 4 represents a top view of the centrifugal impeller of the centrifugal pump of FIG. 3, in the plane B-B,

[0051] [FIG. 5] FIG. 5 represents a perspective bottom view of an inducer of the fuel pump of FIG. 1,

[0052] [FIG. 6] FIG. 6 represents a perspective view of a fuel pump according to one embodiment of the present disclosure in which the upstream flange is hidden and a plenum chamber is visible.

DESCRIPTION OF THE EMBODIMENTS

[0053] A fuel pump according to one embodiment of the invention will be described in the following description with reference to FIGS. 1 to 6.

[0054] FIG. 1 represents a perspective view of an example of a fuel pump 1. More specifically, it represents a low-pressure stage of such a pump, extending about an axis of rotation X and able to rotate about this axis. The environment of this assembly (volute, high-pressure stage, etc.) is not represented.

[0055] This low-pressure stage comprises an inducer 10 and a centrifugal impeller 20 fixed to the inducer 10, downstream thereof.

[0056] The inducer 10 comprises a tubular hub 11, from which a plurality of blades 12 extend radially. An upstream end of the hub 10 comprises an orifice 110, through which a fixing means, for example a threaded screw 60, is inserted.

[0057] The centrifugal impeller 20 comprises a main body 21, from which a plurality of blades 22 extend axially upstream and radially outwards. The impeller 20 comprises in its central part a tubular portion 23 intended to be inserted inside a cavity 13 formed inside the tubular hub 11 of the inducer 10, thus creating a cylindrical contact surface between the inducer 10 and the impeller 20. In addition, the tubular portion 23 of the impeller 20 comprises at its center an orifice 230 disposed coaxially with the orifice 110 of the hub 11 of the inducer 10, the orifices 110 and 230 being themselves coaxial with the axis of rotation X. The orifice 230 is also configured to receive the threaded screw 60. A radially outer face of the downstream end of the impeller 20 can comprise labyrinth seals, making it possible to ensure the sealing between the downstream end of the impeller 20 and a casing of the pump (not illustrated).

[0058] More specifically, the threaded screw 60 comprises a screw head 61 bearing against the upstream end of the hub 11, a bearing washer 50 being interposed between the screw head 61 and said upstream end. A downstream end of the rod of the screw 60 is disposed in the tubular portion 23 of the impeller 20, and comprises a threaded portion 62, configured to be screwed with a tapped portion disposed in the said tubular portion 23. The inducer 10 and the centrifugal impeller 20 are thus fixed axially to each other. The assembly can be driven by a rotation shaft via splines (not visible in the figures).

[0059] An upstream flange 30 is also fixed to the centrifugal impeller 20 upstream thereof, by means of a plurality of screws 40. This upstream flange 30 allows at least partially covering the blades 22 of the impeller 20, thus forming a closed enclosure between said flange 30 and the main body 21 of the impeller 20. By “closed”, it is understood that the blades 22 of the impeller 20 are enclosed axially at least partially between the flange 30 and the main body 21, and thus at least partially isolated from the upstream and the downstream of the impeller 20, by the flange 30 and the main body 21 respectively. A radially outer end of the flange 30 can also comprise labyrinth seals, making it possible to ensure the sealing between the flange 30 and a casing of the pump (not illustrated).

[0060] In addition to the cylindrical interface mentioned above, an annular interface exists between the inducer 10 and the centrifugal impeller 20 when these two parts are fixed together.

[0061] More specifically, the inducer 10 comprises a first annular surface 14 formed at the downstream end of the hub 11 of the inducer 10, and surrounding the end of the cavity 13. Similarly, the centrifugal impeller 20 comprises a second annular surface 24 formed at the upstream end of the main body 21 of the impeller 20 and surrounding the tubular portion 23. When the inducer 10 and the impeller 20 are fixed with each other, the first annular surface 14 and the second annular surface 24 are opposite each other along the axial direction. Some portions of these surfaces 14, 24 are contact with each other, and other portions of these surfaces are spaced from each other, as described below.

[0062] The first annular surface 14 of the inducer 10 comprises two first raised portions 141, 142, extending axially with respect to the rest of the first annular surface 14. These raised portions have the form of arc-shaped crenellations protruding from the rest of the first annular surface 14, and extending circumferentially, and axisymmetrically with respect to the central axis X, but over only part of the circumference of the first annular surface 14. The first raised portions 141, 142 each form an arc of a circle of dimension substantially equal to a quarter of the total circumference of the first annular surface 14. In addition, the first raised portions 141, 142 are disposed symmetrically to each other, with respect to the central axis X. In the example illustrated in FIG. 5, the portions of the first annular surface 14, other than the raised portions 141, 142, are represented on two different levels. This example is however not limiting, this surface can be uniform. It will also be noted that the raised portions 141, 142 do not extend radially over the entire width of the first annular surface 14, but are disposed at an outer radial end thereof, so as to leave a space between these raised portions 141, 142, and the cavity 13. This space allows creating the annular space E described later, when the inducer is fixed to the impeller 20.

[0063] The second annular surface 24 of the centrifugal impeller 20 comprises two second raised portions 241, 242, extending axially with respect to the rest of the second annular surface 24. The second raised portions 241, 242 have substantially the same characteristics as the first raised portions 141, 142, and will not be described again. However, the second raised portions 241, 242 differ from the first raised portions 141, 142 in that their dimension along the axial direction is smaller. In other words, the second raised portions 241, 242 protrude axially upstream over a distance smaller than the distance on which the first raised portions 141, 142 protrude axially downstream.

[0064] Thus, when the inducer 10 and the impeller 20 are fixed with each other, the first raised portions 141, 142, inserted respectively between the two second raised portions 241, 242, come into abutment against the second annular surface 24 of the impeller 20, thus forming a discontinuous annular contact surface about the axis of rotation X. Conversely, a space remains between the second raised portions 241, 242, inserted respectively between the two first raised portions 141, 142, and the first annular surface 14. The two spaces thus created form a first plenum chamber C1 and a second plenum chamber C2, of identical shape and dimensions, and disposed symmetrically to each other with respect to the axis of rotation X.

[0065] This example is however not limiting, the second raised portions 241, 242 can alternatively be axially longer than the first raised portions 141, 142, also making it possible to obtain two plenum chambers C1 and C2.

[0066] Furthermore, the portion of the first annular surface 14 disposed radially inside the first raised portions 141, 142 forms, with the portion of the second annular surface 24 disposed radially inside the second raised portions 241, 242, an annular space E, when the inducer 10 and the impeller 20 are fixed together. This annular space E is disposed radially inside the first raised portions 141, 142, the second raised portions 241, 242 and the plenum chambers C1, C2, and surrounds the tubular portion 23 of the impeller 20, over the entire circumference thereof. The axial thickness of this annular space E is greater than the axial thickness of the plenum chambers C1 and C2.

[0067] The centrifugal impeller 20 further comprises a plurality of balancing holes 16, distributed circumferentially and at regular intervals about the axis of rotation X. These orifices are disposed radially between the second raised portions 241, 242 and the tubular portion 13. They extend axially through the entire thickness of the main body 21 of the impeller 20, over a length L, such that a first end of each of these holes 26 opens out into a downstream space 70, downstream of the impeller 20, and a second end opens out into the annular space E. The balancing holes 16 have a diameter D, determined such that the ratio L/D is greater than or equal to 2. According to this embodiment, the impeller 20 comprises sixteen balancing holes 26. This example is however not limiting, and can be adapted according to the dimensions of the impeller 20.

[0068] FIG. 3 illustrates the path followed by the fluid, for example a liquid, flowing in the centrifugal pump 1 (see black arrows in FIG. 3). The fluid flows first in the inducer 10 and then in the centrifugal impeller 20. The flow along the inducer 10 and the impeller 20 is the main flow. The fluid is then discharged in a volute (not represented). A portion of this fluid, called “recirculating fluid”, can also travel back up to the downstream space 70. This fluid can then be transferred from this downstream space 70 to the annular space E via the balancing holes 26, then ejected radially from this annular space E towards the main flow, at the level of the outlet of the inducer 10, passing through the plenum chambers C1 and C2. The passage of the fluid through these plenum chambers C1 and C2 allows calming this cross flow, thus limiting the shear effect generated on the main flow. It will be noted that a portion of the fluid (not represented) leaving the impeller 20 can also travel back from the impeller 20 to the inducer 10, along the outer wall of the flange 30. This portion is subsequently sucked by the inducer 10 and the impeller 20, in the main flow.

[0069] Although the present invention has been described with reference to specific exemplary embodiments, it is obvious that modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. Particularly, individual characteristics of the different illustrated/mentioned embodiments can be combined in additional embodiments. Accordingly, the description and the drawings should be considered in an illustrative rather than restrictive sense.