IMPELLER AND TURBOCOMPRESSOR EQUIPPED WITH SUCH IMPELLER AND METHOD FOR MANUFACTURING SUCH AN IMPELLER

Abstract

An impeller includes a central shaft or a tube for mounting on a shaft; around the shaft or tube a hollow hub, which in the direction from one end to the other end increases in diameter. The hub possesses an outside and an inside oriented towards the shaft or tube; a back wall which is provided at the end of the hub with the largest diameter perpendicular to the shaft or tube which at least partially closes the hollow space of the hub; a series of blades that are attached to the outside of the hub by their base; wherein a number of flat, straight reinforcing ribs are provided which extend on the shaft or tube in an essentially radial direction and form a radial connection between the shaft or tube and the inside of the hub.

Claims

1.-21. (canceled)

22. An impeller containing: a central shaft or a tube for mounting on a shaft; around the shaft or tube a hollow hub which in the direction from one end to the other end increases in diameter, said hub possessing an outside and an inside oriented towards the shaft or tube; a back wall which is provided at the end of the hub with the largest diameter perpendicular to the shaft or tube which at least partially closes the hollow space of the hub; a series of blades that are attached to the outside of the hub by their base; wherein a number of flat, straight reinforcing ribs are provided which extend on the shaft or tube in an essentially radial direction and form a radial connection between the shaft or tube and the inside of the hub, wherein the impeller is provided with at least one polygon or ring connecting all reinforcing ribs with each other and which is concentric with the central shaft or tube, wherein said ring or polygon is provided with passages, wherein at least one passage is always provided in the section of the ring or polygon located between two reinforcing ribs.

23. The impeller according to claim 22, wherein the geometric plane of the reinforcing ribs intersects with the tip of the blades at the end of the hub with the largest diameter.

24. The impeller according to claim 22, wherein the geometric centreline of the central shaft or tube coincides with the plane of the reinforcing ribs.

25. The impeller according to claim 22, wherein the number of reinforcing ribs is in proportion to the number of blades.

26. The impeller according to claim 22, wherein the tube or central shaft is provided with holes which extend in the axial direction, and which form a connection bet ween the hollow space of the hub and the environment.

27. The impeller according to claim 22, wherein the impeller shows a local thickening of the central shaft or tube on the level of the end of the tube located at the end of the hub with the smallest diameter.

28. The impeller according to claim 22, wherein the impeller shows a local thickening of the back wall on the level of the outer edge.

29. The impeller according to claim 22, wherein the reinforcing ribs are directly connected with the back wall.

30. The impeller according to claim 22, wherein the attachments between the reinforcing ribs and the at least one concentric polygon or ring with the rest of the impeller are rounded.

31. A turbocompressor, wherein it is provided with an impeller according to claim 22.

32. A method for manufacturing an impeller, said method comprising the following steps: providing a central shaft or a tube for mounting on a shaft; providing a hollow hub around the shaft or tube which in the direction from one end to the other end increases in diameter, said hub possessing an outside and an inside oriented towards the shaft or tube; providing a back wall which is provided at the end of the hub with the largest diameter perpendicular to the shaft or tube which at least partially closes the hollow space of the hub; providing a series of blades that are attached to the outside of the hub by their base, wherein the method further comprises the step of providing a number of flat, straight reinforcing ribs which extend on the shaft or tube in an essentially radial direction and forma radial connection between the shaft or tube and the inside of the hub, wherein it further comprises the step of providing the impeller with a t least one polygon or ring connecting all reinforcing ribs with each other, and which is concentric with the central shaft or tube, wherein the method further comprises the step of providing one or more passages during the additive production process, wherein at least one passage is always provided in the section of the polygon or ring located between two reinforcing ribs.

33. The method according to claim 32, wherein said steps are executed by means of an additive production method.

34. The method according to claim 33, wherein for the additive production method a powder bed fusion method is applied to selectively fuse together certain regions in a powder bed.

35. The method according to claim 34, wherein the fusion step comprises the step of at least partially melting or sintering the powder material by means of an electron beam or by means of a laser.

36. The method according to claim 33, wherein for the additive production method a direct energy deposition method is applied, wherein beamed thermal energy is used to allow materials to melt while they are deposited.

37. The method according to claim 36, wherein for the direct energy deposition method, laser cladding technology is applied.

38. The method according to claim 32, wherein the method further comprises the step of providing one or more holes in the central tube during the additive production process which form a connection between the hollow space of the hub and the environment.

39. The method according to the claim 38, wherein after the additive production process the method further comprises the step of shaking the impeller to remove excess powder material from the hollow space of the hub via the aforementioned one or more holes.

40. The method according to claim 39, wherein the method after removing the remaining powder, further comprises the step of balancing the impeller by removing or adding material in certain locations until the impeller is balanced.

41. The method according to claim 40, wherein it comprises the step of adding additional material during the additive production process for balancing purposes, which after the removal of the excessive powder, can be removed locally to balance the impeller.

42. The method according to 33, wherein it comprises the step of ensuring during the production process that all internal edges, sides and corners of the impeller are rounded.

Description

[0056] With the intention of better showing the characteristics of the invention, a few preferred embodiments of an impeller according to the invention and a turbocompressor equipped with it are described by way of an example without any limiting nature, with reference to the accompanying drawings, wherein:

[0057] FIG. 1 schematically shows a perspective view of an impeller according to the invention;

[0058] FIG. 2 shows a cross-section according to the plane II-II in FIG. 1;

[0059] FIG. 3 shows a cross-section according to the plane III-III in FIG. 1;

[0060] FIG. 4 shows the view according to the arrow F4 from FIG. 1.

[0061] The impeller 1 shown in the FIGS. 1 to 4 is an impeller of a turbocompressor by way of example.

[0062] The impeller 1 according to the invention, as shown in FIG. 1, is very similar in terms of external design to a traditionally known impeller.

[0063] The impeller 1 contains a central tube 2 with which the impeller 1 can be mounted on a drive shaft (not shown in the figures) in order to be driven around the geometric centreline X-X′ of the tube 2 in the housing of, for example, a compressor element.

[0064] Instead of a central tube 2, the impeller 1 can also be provided with a solid shaft which can be coupled to said drive shaft.

[0065] The impeller 1 further comprises a trumpet-shaped hub 3 extending around the tube 2, which in the direction from one end 4 to the other end 5 increases in diameter.

[0066] According to the invention the hub 3 is a hollow hub 3 with an outside 6 and an inside 7 oriented toward the tube 2. This is visible in FIGS. 2 and 3.

[0067] The hub 3 connects to on one end 8a of the central tube 2 with the end 4 with the smallest diameter. This end 4 is also called the axial end of the hub 3.

[0068] The hub 3 connects to a back wall 9 with the end 5 with the largest diameter, which is visible in FIGS. 3 and 4. This end 5 is also called the radial end of the hub 3.

[0069] This essentially disk-shaped back wall 9, on the level of the other end 8b of the central tube 2, extends perpendicularly to the tube 2 and will close or enclose the hollow space 10 between the hub 3, the tube 2 and the back wall 9.

[0070] The outside 6 or the outer surface of the hub 3 changes in a sloping way from an essentially axial direction X-X′ at the end 4 with the smallest diameter to an essentially radial direction at the end 5 with the largest diameter. This slope is visible in FIG. 3.

[0071] On the hub 3 a series of curved blades 11 is attached, which are affixed with their base 12 on said outside 6 of the hub 3.

[0072] In the example shown, two series of blades are provided, i.e. main blades 11a, on the one hand, which extend over a certain length from the axially oriented end 4 of the hub 3 to the radially oriented end 5 of the hub 3, and splitter blades 11b on the other hand, which extend between the main blades 11a over a shorter length, starting at an axial distance from the end 4 of the hub 3 to the end 5 of the hub 3.

[0073] However, the invention is not limited to two series of blades 11, but is also applicable to any number of series of blades 11, whereby for example no splitter blades 11b are present or on the contrary a number of series of splitter blades 11b can be provided.

[0074] According to the invention, in the hollow space 10 of the hub 3, flat, straight reinforcing ribs 13 are provided, which extend on the tube 2 in radial direction and form a radial connection between the tube 2 and the inside 7 of the hub 3.

[0075] The reinforcing ribs 13 are connected with their base 14 to the tube 2 and with their head 15 to the inside 7 of the hub 3.

[0076] In this case, the reinforcing ribs 13 extend from the back wall 9 to the end 4 of the hub 3 with the smallest diameter, as shown in FIG. 3. In other words, the reinforcing ribs 13 are connected directly to the back wall 9 along an edge 16 over their height.

[0077] The reinforcing ribs 13 will divide the hollow space 10 into a number of chambers 17.

[0078] In this case the geometric plane of the reinforcing ribs 13 will intersect with the tip 18 of the blades 11 on the end 5 of the hub 3 with the largest diameter.

[0079] The geometric plane also refers to the geometric or imaginary extension of the reinforcing ribs 13.

[0080] In this way the reinforcing ribs 13 are located in the direction of the largest centrifugal force, such that they can absorb the centrifugal force optimally.

[0081] Moreover, the geometric centreline X-X′ of the central tube 2 coincides with the geometric plane of the reinforcing ribs 13. This means that the angle between the reinforcing ribs 13 and the geometric centreline X-X′ of the central shaft 2 is zero degrees. This is not necessary for the invention, but this angle is maximum ten degrees according to the invention and preferably maximum seven degrees and even more preferable maximum five degrees.

[0082] The number of reinforcing ribs 13 is not restrictive for the invention and will depend, among others, on the dimensions of the impeller 1. Typically, a larger impeller 1 will require more reinforcing ribs 13, as it will be subject to greater centrifugal forces due to its dimensions.

[0083] However, preferably the number of reinforcing ribs 13 is always in proportion to the number of blades 11.

[0084] This means, when there are eight main blades 11a and eight splitter blades 11b, for example, there are sixteen reinforcing ribs 13. This is also the case in the example shown.

[0085] For example, it is also possible that thirty-two reinforcing ribs 13 are provided. Moreover, it is also not excluded that the number of reinforcing ribs 13 is in proportion to the number of main blades 11a, such that it is also possible only eight reinforcing ribs 13 are provided.

[0086] The foregoing will ensure that a cyclical-symmetrical structure is obtained, whereby the impeller 1 comprises a number of sections 19, in the example of the figures eight sections, which are repeated every time.

[0087] The reinforcing ribs 13 are primarily under a tensile load, whereby the entire mass of the reinforcing ribs 13 is used to divert a part of the stresses from the hub 3 to the tube 2 and also to the back wall 9 if necessary, and there is thus no, or practically no, dead mass, in other words unloaded mass, in the hollow space 10 of the hub 3 which does not contribute to the strength of the impeller 1 in the radial direction.

[0088] In this case, but not necessarily in, for example, smaller impellers 1, the impeller 1 is provided with one ring 20 connecting all reinforcing ribs 13 with each other.

[0089] It could also be more than one ring 20.

[0090] Moreover, instead of a ring 20 one or several polygons or a combination of polygon and circle 20 could be applied.

[0091] In order to preserve the cyclical symmetry, said ring 20 is concentric with the central tube 2.

[0092] The ring 20 will subdivide each chamber 17 into two subchambers 17a, 17b.

[0093] The ring 20 will provide sturdiness or mechanical strength and counter deformation.

[0094] It is indeed important that the impeller 1 does not deform too much. Indeed, the inward deformation may not be too big, in order to counter air and air pressure losses. The outward deformation is also crucial, as there is a housing around the impeller 1, whereby the rotating impeller 1 must never touch this housing and other stationary components of the compressor element.

[0095] As shown in the figures, the attachments between the reinforcing ribs 13 and the at least one concentric polygon or ring 20 with the rest of the impeller 1 are rounded.

[0096] This means that all internal edges, sides and corners are rounded. This is important to avoid stress concentrations.

[0097] This will also be necessary when the impeller 1 is manufactured by means of an additive production method.

[0098] Additive production refers to a category of production methods, for example powder bed fusion whereby thermal energy is utilised to selectively fuse together certain regions in a powder bed, or direct energy deposition whereby beamed thermal energy is used to melt materials while they are deposited.

[0099] Within the category of powder bed fusion there are a number of technologies such as electron beam melting, whereby powder material is melted using an electron beam; selective laser melting whereby powder material is melted by means of a laser; selective laser sintering whereby powder material is sintered using a laser. The category of direct energy deposition includes the technology of laser cladding.

[0100] In such production methods based on powder bed fusion it is important there are no structures with too big a slope, such that in some cases, corners must be rounded in order to avoid such slopes.

[0101] Another consequence of such production method is that the hollow internal space and (sub)chambers 17, 17a, 17b must be connected with the environment, in order to be able to remove the remaining powder.

[0102] In this case, powder will remain in the chambers 17 and subchambers 17a, 17b during the manufacture of the screw rotor 1 by means of powder bed fusion.

[0103] That is why in the example shown the central tube 2 is provided with holes 21 which extend in the axial direction and which form a connection between the hollow space 10 of the hub 3 and the environment.

[0104] Said ring 20 is also provided with passages 22, whereby at least one passage 22 is always provided in the section of the ring 20 located between two reinforcing ribs 13.

[0105] Preferably these holes 21 and passages 22 are already provided during the production process.

[0106] Via said holes 21 and passages 22 the powder will be able to leave the (sub)chambers.

[0107] Due to the straight and flat form of the reinforcing ribs 13 and the straight form of the ring 20 the powder can be simply removed by shaking the impeller 1.

[0108] After the impeller 1 has been manufactured and the remaining powder is removed, every impeller 1 is balanced. This means that the impeller 1 is measured or weighed and that material is removed or added in certain locations until the impeller 1 is balanced, this means: the weight is distributed (cyclically-)symmetrically. This is very important for the functioning of the impeller 1, as the smallest imbalance can result in adverse effects due to unwanted stresses and vibrations.

[0109] When cyclical-symmetric is referred to in this context, it must be noted that perfect cyclical-symmetry is very difficult to achieve in practice. That is why in the current text this needs to be interpreted as “practically cyclical-symmetric”, which in this context corresponds with a maximum distance between the geometric centreline of the central shaft on the one hand and the intersection of the reinforcing ribs with the back wall on the other hand, which is 10% of the height of the impeller.

[0110] To allow the impeller 1 to approximate cyclical-symmetry as much as is practically realisable, additional material can be provided in a number of locations in the impeller 1, which can be used later to balance the impeller 1 by removing material locally.

[0111] As shown in FIGS. 3 and 4, the impeller 1 shows a local thickening 23 of the central tube 2 on the level of the end 8a of the tube 2.

[0112] This local thickening 23 can be executed as a solid ring at the end 8a of the tube 2, whereby material can be removed from this ring, for example by drilling holes.

[0113] The impeller 1 shows a local thickening 24 of the back wall 9 on the level of the outer edge 25.

[0114] In other words, this thickening 24 is located at the location where the end 4 of the hub 3 with the largest diameter makes contact with the back wall 9.

[0115] Material can also be removed at this location for balancing, for example by milling or grinding.

[0116] As already mentioned, instead of on a tube 2 this can also be applied on a solid haft, in which holes 21 may or may not be provided to remove powder from the space.

[0117] The present invention is by no means limited to the embodiments described as an example and shown in the drawings, but an impeller according to the invention and a turbocompressor equipped therewith can be realised in all kinds of forms and dimensions, without departing from the scope of the invention.