METHOD FOR CREATING AN IMPELLER OF A RADIAL TURBO FLUID ENERGY MACHINE, AND STAGE

Abstract

A method for creating an impeller and an impeller of a radial turbo fluid energy machine includes a wheel disc, cover disc, blades, and hub. The hub is mounted on a shaft which extends along an axis, the wheel disc extends substantially radially from the hub, and the cover disc is connected to the wheel disc by the blades such that flow channels separated from one another in the circumferential direction are defined by the blades. The impeller has a first flow passage in a substantially axial direction in the radial proximity of the hub, and the impeller has a second flow passage in a substantially radial direction radially farther away from the hub than the first flow path passage. The cover disc surface facing the wheel disc has a lower degree of roughness at least in some regions than the wheel disc surface facing the cover disc.

Claims

1.-11. (canceled)

12. A method for creating an impeller of a radial turbo fluid energy machine, the method comprising: a. fluidic designing of the component, b. fixing at least one limit value for a first quotient from the surface flow velocity over surface regions of the component at a distance divided by a circumferential velocity in each case related to a design operating point, c. determining surface regions of the component, in which the first quotient is above the limit value, d. creating the component, with the creation of at least two different degrees of roughness for surface regions, a first, lower roughness in at least some surface regions in which the first quotient is above the limit value, and the creation or retention of a higher degree of roughness in at least some surface regions, in which the first quotient is below the limit value.

13. An impeller of a radial turbo fluid energy machine created according to a method as claimed in claim 12, comprising a wheel disk, a cover disk, blades, a hub, wherein the hub is designed to be mounted on a shaft which extends along an axis, wherein the wheel disk extends essentially radially from the hub, wherein the cover disk is connected to the wheel disk by means of the blades such that flow channels which are separated from one another in the circumferential direction are defined by the blades between the wheel disk and the cover disk in the circumferential direction in at least one radial region of the impeller, wherein the impeller has a first flow path passage in an essentially axial direction in the radial proximity of the hub, wherein the impeller has a second flow path passage radially farther away in an essentially radial direction from the hub than the first flow path passage, wherein the cover disk surface facing the wheel disk has a lower degree of roughness at least in some regions than the wheel disk surface facing the cover disk.

14. The impeller as claimed in claim 13, wherein the blades have a lower degree of roughness in a first blade surface region closer and adjacent to the cover disk than a second blade surface region, of the blades, farther away from the cover disk.

15. The impeller as claimed in claim 14, wherein, with increasing distance from the hub, the first blade surface region has a decreasing proportion of the flow channel perpendicular to the main flow direction.

16. The impeller as claimed in claim 15, wherein the blade is designed as a three-dimensionally twisted blade, wherein the first blade surface region extends over more than 40% of the breadth of the flow channel perpendicular to the main flow direction in that section closest to the hub, and reduces continuously until that section farthest away from the hub, to less than 35% of the breadth of the flow channel perpendicular to the main flow direction.

17. The impeller as claimed in claim 15, wherein the blade is designed as an essentially cylindrical blade, wherein the first blade surface region extends over more than 40% of the breadth of the flow channel perpendicular to the main flow direction in that section closest to the hub, and increases continuously until that section farthest away from the hub, to more than 70% of the breadth of the flow channel perpendicular to the main flow direction.

18. The impeller as claimed in claim 13, wherein, in a third surface region, the cover disk has, on the surface oriented away from the blades, a lower degree of roughness than in another, fourth surface region, wherein the third surface region extends radially over an outer portion of up to 50% of the radial extent of the cover disk.

19. The impeller as claimed in claim 18, wherein, in a fifth surface region, the wheel disk has, on the surface oriented away from the blades, a lower degree of roughness than in another, sixth surface region, wherein the fifth surface region extends radially over an outer portion of 10% to 50% of the radial extent of the wheel disk.

20. The impeller as claimed in claim 13, wherein the cover disk and/or the wheel disk each have a radially outer edge surface which extends in the circumferential direction and has a lower degree of roughness than the other regions which do not have a lower degree of roughness.

21. A stage of a radial turbo fluid energy machine, comprising a rotating impeller as claimed in claim 19, and a stator surrounding the impeller, wherein the stator has, adjoining the second flow path passage, a ring chamber which extends essentially radially and in the circumferential direction, wherein a section of the ring chamber adjoining the second flow path passage has, over more than 15% of the radial extent of the ring chamber of a seventh surface region, a reduced degree of roughness in comparison to an eighth surface region of the rest of the radial extent.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The invention is described in greater detail below with reference to a specific exemplary embodiment, with reference to drawings. In the drawings:

[0016] FIG. 1 is a view in longitudinal section along an axis of a rotor of a radial turbo fluid energy machine, through an impeller according to the invention,

[0017] FIG. 2 is a detail view along II in FIG. 1,

[0018] FIG. 3 is a flow chart for a method according to the invention.

DETAILED DESCRIPTION OF INVENTION

[0019] FIG. 1 shows an impeller IMP of a radial turbo fluid energy machine RTF, which is schematically represented here by way of a detail with one stage STA. A process fluid PF flows along a main flow direction MFD through the impeller IMP when the latter is operating as a compressor. If the impeller IMP is used in a radial turbo fluid energy machine designed as a turbine, the process fluid PF flows along a main flow direction MFD′ that is oriented counter to the main flow direction MFD for the compressor. If, in the following, reference is made to a specific main flow direction MFD, MFD′, this is done with reference to a design of the radial turbo fluid energy machine RTF as a compressor, without restricting the invention to a compressor.

[0020] The impeller IMP comprises a wheel disk SW, blades BL and a cover disk CW, wherein the wheel disk SW comprises a hub HB. By means of the hub HB, the impeller IMP is mounted on a shaft SH (not shown) which extends along a rotation axis X. Unless otherwise stated, in the following all of the terms relating to an axis, for example axial, radial, circumferential direction etc., relate to this rotation axis X.

[0021] In the example shown, the blade BL is of three-dimensional twisted design over the breadth direction of the flow channel FC. This design is typical for impellers having a high maximum flow rate. The blades BL extend not only in the essentially radial section of the flow channel FC but also in the axial section.

[0022] Application of the invention to impellers IMP with blades BL located essentially in the radial section is also expedient. These impellers IMP are more frequently used in what are termed high-pressure compressors and generally have essentially cylindrical blades BL.

[0023] The wheel disk SW extends essentially radially from the hub HB. The cover disk CW is connected to the wheel disk SW by the blades BL. This produces, between the wheel disk SW and the cover disk CW, flow channels FC that are separated from one another in the circumferential direction in at least one radial region of the impeller IMP by the blades BL. In those radial regions into which the blade BL does not extend, there is no circumferential separation of the flow channel FC, and furthermore a common flow channel is defined radially and axially by the wheel disk SW and the cover disk CW.

[0024] The main flow direction MFD extends essentially midway between the wheel disk SW and the cover disk CW, from an axial direction in the region of the inflow in the case of the compressor, along a redirection into the radial direction to an outlet from the impeller IMP. For the sake of universality of terminology of the invention, that section of the impeller IMP which is referred to as the inlet in the case of the radial turbocompressor is labeled the first flow path passage O1. Similarly, the outlet is labeled the second flow path passage O2.

[0025] The impeller IMP is surrounded by a stator STO which, with a distance between the impeller IMP and the stator STO, defines what are referred to as wheel side chambers WSC on either side of the impeller IMP.

[0026] It is shown by way of example, to the left of the impeller IMP, how the wheel side chamber WSC is sealed by means of a shaft seal in the form of a labyrinth seal in order to avoid undesired bypass flow through the wheel side chamber WSC past the flow channel FC of the impeller IMP. In practice, a similar seal is also to be found to the right of the impeller IMP, but is not shown here. The flow channel FC of the impeller IMP opens in the radial direction into a ring chamber RC of the stator STO, such that in the case of a compressor the process fluid FD can continue to follow the outflow direction MFD and can leave the impeller IMP, and can possibly be guided into a final recirculation stage (not shown) to another impeller IMP or into a collection space to flow out of the radial turbo fluid energy machine RTF.

[0027] The cover disk CW surface facing the wheel disk SW is formed with a lower degree of roughness at least in some regions—and in the example in its entirety—than the wheel disk SW surface facing the cover disk. In this context, it is provided that the blades BL have a lower degree of roughness in a first blade surface region BLA1 closer and adjacent to the cover disk CW than a second blade surface region BLA2, of the blades, farther away from the cover disk CW. It is also provided that, with increasing distance from the hub HB, the first blade surface region BLA1 has a decreasing proportion of the flow channel FC perpendicular to the main flow direction MFD. Specifically, in the illustrated case of a blade BL of three-dimensionally twisted design over the breadth direction of the flow channel FC, the first blade surface region BLA1 extends over more than 40% of the breadth of the flow channel FC perpendicular to the main flow direction MFD in that section closest to the hub HB, and reduces continuously until that section radially farthest away from the hub HB, to less than 35% of the breadth of the flow channel FC perpendicular to the main flow direction MFD.

[0028] Next to the interior of the impeller IMP, part of the outer surface of the impeller IMP is also adapted in terms of roughness for the purpose of loss reduction. In a third surface region CWA3, the cover disk CW is designed, on the surface oriented away from the blades BL, with a lower degree of roughness than in another, fourth surface region CWA4. The third surface region CWA3 extends radially over a radially outer portion of up to 50% of the radial extent of the cover disk CW. In the drawing, the smallest diameter with reduced roughness is indicated with DRZ, wherein the region extends to the outermost diameter D2 of the impeller IMP. In the specific exemplary embodiment, the smallest diameter with reduced roughness DRZ is identical for the cover disk CW and for the wheel disk SW. In practice, the respective diameters for the cover disk and for the wheel disk can be different. In a fifth surface region SWA5, the wheel disk has, on the surface oriented away from the blades BL, a lower degree of roughness than in another, sixth surface region SWA6. Expediently, the fifth surface region SWA5 extends radially over an outer portion of up to 50% of the radial extent of the wheel disk.

[0029] A radially outer, circumferentially extending annular edge surface ES both of the cover disk CW and of the wheel disk SW is embodied in each case with a lower degree of roughness than the other regions, which do not have a lower degree of roughness. Advantageously and expediently, this lower degree of roughness is also used for the outermost edges of the blades BL.

[0030] FIG. 3 shows, schematically, a flow chart of a method according to the invention for creating a flow-wetted component COM of a fluid energy machine FEM. This can for example be an impeller IMP or part of a stage STA that is wetted by a flow.

[0031] The method is intended to create the wetted component COM from a blank GRN, on the basis of thermodynamic data THD.

[0032] A first step a. involves the fluidic design of the component COM using the thermodynamic data THD. The first design step forms the basis for the second step b. in which a limit value LIM is fixed for a first quotient QO1 from the surface flow velocity VL over surface regions SUA of the component COM at a distance δ divided by a circumferential velocity UV in each case related to a design operating point. This surface flow velocity VL can be found from the appropriate fluid dynamics calculations at a certain distance δ from the actual component surface. The circumferential velocity can be found from the design operating point, directly from the respective diameter and rotational speed (n, ω). While, in the example of FIG. 3, only one limit value LIM for the first quotient QO1 is established, it is also possible, in the context of the invention, to establish quotient value ranges defined by lower and upper limit values to which, in subsequent steps, are assigned surface regions SUA in which, in the context of production, various degrees of roughness are to be provided.

[0033] A third step c. involves using the limit value LIM to determine a surface region SUA which is above the limit value LIM in terms of the first quotient QO1. Accordingly, in the exemplary embodiment of FIG. 3, the surface of the component COM is divided into two groups: one group for which the first quotient QO1 is above the limit value LIM, and one group for which the first quotient QO1 is below the limit value LIM.

[0034] A fourth step d. concerns creating the component COM from a blank and creating at least two different degrees of roughness RZ for the surface regions SUA. The blank GRN can be in the form of a raw workpiece for milling from solid, of a semi-finished product, in pieces or even in the form of a powder for sintering, or in the form of any other raw material for creating the component COM. What is essential to the meaning of the invention is that a surface quality is created in one processing step according to the invention.

[0035] A first, lower degree of roughness RZ is created in at least some surface regions SUA in which the surface flow velocity VL is above the limit value LIM. A higher degree of roughness RZ is created or left in at least some surface regions SUA, in which the surface flow velocity VL is below the limit value LIM.

[0036] The method according to the invention produces the component COM of a fluid energy machine FEM.