RETURN STAGE OF A MULTI-STAGE TURBOCOMPRESSOR OR TURBOEXPANDER HAVING ROUGH WALL SURFACES

Abstract

A return stage of a radial turbo fluid energy machine, in particular of a radial turbo compressor, having an axis of rotation, the return stage has an annular flow channel for feeding a flowing process fluid from a flow opening of a first impeller to a flow opening of a second impeller arranged downstream. In order to increase efficiency, the flow channel is defined by bounding surface areas, of which at least one certain rough area extending in the circumferential direction has a surface roughness that is increased in relation to the her areas.

Claims

1. A return stage of a radial turbo fluid energy machine having an axis of rotation, the return stage comprising: an annular flow channel for feeding a flowing process fluid from a flow opening of a first impeller to a flow opening of a second impeller arranged downstream, wherein the flow channel is defined by boundary surface regions, of which at least one specific rough region extending in the circumferential direction has a surface roughness Rz which is increased with respect to other regions.

2. The return stage as claimed in claim 1, wherein the flow channel has a first portion, which extends radially and has a radial opening to an impeller at a first end of the first portion.

3. The return stage as claimed in claim 2, wherein the flow channel has a second portion, which adjoins a second end of the first portion with a first end of the second portion and deflects the flow by approximately 180° from one radial direction into the opposing radial direction.

4. The return stage as claimed in claim 3, wherein the flow channel has a third portion, which runs substantially radially and adjoins a second end of the second portion with a first end of the third portion.

5. The return stage as claimed in claim 4, wherein the flow channel has a fourth portion, which radially adjoins a second end of the third portion radially with a first end of the fourth portion and deflects the flow by approximately 90° and, with a second end of the fourth portion, has an axial opening to the second impeller.

6. The return stage as claimed in claim 4, wherein a first rough region in the first portion is arranged on that axial boundary surface which is at a greater axial distance from the third portion than the other axial boundary surface.

7. The return stage as claimed in claim 6, wherein a second rough region on the radially inner boundary surface of the second portion, beginning at the second end of the second portion, is located in a manner extending over between 30% and 70% of the extent along the flow channel.

8. The return stage as claimed in claim 7, wherein a third rough region directly adjoins the second rough region in the third portion and is located in a manner extending between 5% and 40% along the flow channel.

9. The return stage as claimed in claim 8, wherein a fourth rough region is located in the fourth portion on the radially outer boundary surface.

10. The return stage as claimed in claim 8, wherein the rough regions each extend over the entire extent of the flow channel.

11. The return stage as claimed in claim 5, wherein the fluid energy machine is a turbocompressor and a process fluid flows through the portions in the sequence of first portion, second portion, third portion, fourth portion.

12. The return stage as claimed in claim 5, wherein the fluid energy machine is a turboexpander and a process fluid flows through the portions in the sequence of fourth portion, third portion, second portion, first portion.

13. The return stage as claimed claim 2, wherein the first portion of the flow channel has guide blades.

14. The return stage as claimed in claim 8, wherein the rough regions have a mean roughness of 20 μm<Rz.

15. The return stage as claimed in claim 1, wherein non-rough regions have a mean roughness of Rz<20 μm.

16. The return stage as claimed in claim 1, wherein the radial turbo fluid energy machine is a radial turbocompressor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Hereinbelow, the invention is described in more detail on the basis of a specific exemplary embodiment and with reference to a drawing, in which:

[0032] FIG. 1 shows a schematic illustration of a longitudinal section through a turbocompressor according to the invention.

DETAILED DESCRIPTION OF INVENTION

[0033] FIG. 1 shows a schematic longitudinal section through a return stage RS from a first impeller IMP1 to a second impeller IMP2 of a turbocompressor TCO.

[0034] The two impellers IMP1, IMP2 are component parts of a rotor R, the impellers IMP1, IMP2 being mounted in a force-fitting manner on a shaft SH extending along an axis X. The rotor R is surrounded by flow-guiding stationary components, of which here a return stage RS is shown. A multi-stage turbomachine generally comprises a plurality of return stages RS, which, as considered in the direction of flow from a first impeller IMP1, which, in the case of the turbocompressor TCO, axially sucks a process fluid PF and discharges it radially, deflect the process fluid PF by 180° following a radial diffuser section and guide it back radially inward and then deflect it in an axial direction, in order to feed the process fluid PF to the second impeller IMP2 located downstream.

[0035] The return stage generally comprises a blade base SB and an intermediate base ZB, which are fixedly connected to one another by means of guide blades V so as to form a flow channel between them. The return stages RS are generally configured in a manner split in the circumferential direction, such that a split of the return stage at a split joint makes it possible to remove the rotor from the structure of the return stages. The rotor is inserted radially during assembly or removed radially during disassembly.

[0036] The return stages RS have shaft seals SHS in relation to the rotor R at various locations, these shaft seals being intended to prevent the unused reduction of pressure differences or bypass flows during operation.

[0037] For the purposes of defining the invention, the flow channel CH extending from the first impeller IMP1 to the second impeller IMP2 is divided conceptually into four successive portions S1, S2, S3, S4, arranged in succession in the direction of flow in the case of the turbocompressor TCO. In the case of the turboexpander, the numbering of said portions S1-S4 is counter to the direction of flow. The first portion S1 extends substantially radially and has a radial opening to the first impeller IMP1 at a first end S1E1 of the first portion S1. The second portion S2 adjoins a second end S1E2 of the first portion S1 with a first end S2E1 of the second portion S2 and deflects the flow through the channel CH by approximately 180° from one radial direction into the opposing radial direction. In the case of the turbocompressor TCO, the flow is deflected from a direction in which it is directed radially outward into a direction radially inward. The third portion S3 adjoins the second portion S2 with a first end S3E1 of the third portion S3 adjoining the second end S2E2 of the second portion S2. Said portion runs substantially radially and, in the case of the turbocompressor TCO, guides the flow from radially further outward to radially further inward. The fourth portion radially adjoins a second end S3E2 of the third portion S3 radially with a first end S4E1 of the fourth portion S4 and deflects the flow by approximately 90° in the direction of the second impeller IMP2. A second end S4E2 of the fourth portion S4 adjoins the second impeller IMP2.

[0038] A first rough region RZ1 is located in the first portion S1 on that axial boundary surface which is at a greater axial distance from the third portion S3 than the other axial boundary surface.

[0039] A second rough region RZ2 is located on the radially inner boundary surface of the second portion S2, beginning at the second end S2E2 of the second portion S2. Said second rough region RZ2 extends over between 30%-70% of the extent along the flow channel of the second portion S2.

[0040] A third rough region RZ3 directly adjoins the second rough region RZ2 in the third portion S3 and extends over between 5%-40% along the flow channel CH in the third portion S3. A fourth rough region RZ4 extends in the fourth portion S4 on the radially outer boundary surface.

[0041] In principle, it is conceivable that not all of the four rough regions RZ1-RZ4 or only a single rough region are or is provided for improving the efficiency of the turbomachine TCO. The highest gain in efficiency is achieved by the complete implementation of the rough regions RZ1-RZ4 according to the invention and as per the exemplary embodiment shown in FIG. 1. In principle, it is conceivable that, of the boundary surfaces SFA of the flow channel CH, the rough regions RZ1-RZ3 are configured with extra roughness, or the other regions of the boundary surface SFA are provided with a lower surface roughness than the rough regions RZ1-RZ4, for example by means of polishing. In addition, it is also conceivable for provision to be made both of roughening of the rough regions RZ1-RZ4 and polishing of the other boundary surfaces SFA in order to achieve the effect according to the invention.