EP3167195B1 - Return channel of a multistage turbocompressor or turboexpander with rough wall surfaces - Google Patents

Description

In radial turbofluid energy machines, especially in radial turbocompressors process fluid is sucked axially by an impeller or impeller and output radially accelerated. In a multi-stage design, a so-called return stage takes over the supply of the process fluid discharged upstream from the impeller to a further downstream impeller. In this case, this return stage not only has the function of deflecting the process fluid radially outward in the flow direction in an axial flow direction and the other impeller, but also at least partially retard the flow of the process fluid and in this way to increase the pressure according to Bernulli. At the same time, the recirculation stage is regularly designed as a diffuser in a radially outwardly directed flow path and also as a confuser in a radially inwardly directed flow path in the supply of the process fluid to the further impeller. The recirculation stage is stationary relative to the impellers, and vanes provided in the recirculation stage regularly alter the swirl and thus the flow direction of the process fluid in preparation for subsequent entry into the subsequent compression. This demanding aerodynamic task of the recirculation stage requires careful fluidic design to minimize pressure losses and optimize efficiency. Nevertheless, due to the flow of radial diffusers and confusers of the recirculation stage at the surfaces wetted by the flow, friction-induced and basically unavoidable pressure losses occur which reduce the efficiency of the turbomachine. For given operating conditions in terms of gas type, pressure and temperature, the local friction-induced pressure losses are dependent on the local flow velocity and the local roughness or roughness of the surface wetted by flow. In general, large pressure drops occur where the local Flow rates and at the same time the local roughness of the overflow surfaces are large.

From the EP 1 433 960 B1 It is already known to smooth the flow-leading components by means of polishing to the extent that the overall efficiency of the compressor increases. Usually, a uniform maximum roughness (eg RZ12) is required for the wetted surfaces in the radial diffuser or confuser, especially when these surfaces are made from one component or in one production run. This also in the EP 1 433 960 B1 proposed procedure brings additional work and leads to significant additional costs.

From the DE 603 20 519 T2 . US 2 419 669 A . EP 1 953 340 A2 Various surface treatments, in particular smoothing, are already known for surfaces of turbomachine components.

The object of the invention, based on the described prior art, is to design the surface of the flow-guiding regions of the recycling stage in such a way that, compared with the known solutions, a reduced or, if necessary, constant production outlay is achieved while at the same time improving the efficiency of the turbocompressor.

To achieve the object of the invention, a feedback stage of the type defined is proposed with the additional features of the characterizing part of claim 1. The respective dependent claims contain advantageous developments of the invention.

Terms such as axial, tangential, radial or circumferential direction always refer - unless otherwise stated - to an axis of rotation of the radial turbocompressor. The return stage according to the invention is a component which extends annularly around the axis of rotation. This Component may be divided in the circumferential direction or formed undivided. Preferably, a divided in the circumferential direction training is provided so that a parting line of the return stage or the return stages is formed, which allows a separation of the rotor without disassembly of the rotor at split feedback stage. In principle, an embodiment of the feedback stage which is undivided in the direction of contact is also conceivable, in particular in the case of an axially separable rotor.

In the context of this invention roughness always means - unless stated otherwise - the mean roughness Rz in [pm] according to DIN EN ISO 4287: 1998.

The return stage is generally formed axially divided, wherein a blade bottom separates the radially outwardly guided branch of the flow channel of a radially inwardly guided branch downstream of the 180 ° deflection of the flow and this blade bottom is attached to an intermediate floor of the return stage, said Intermediate bottom on the one hand, the flow guide in the return stage is used and on the other hand, the attachment of the return stage to the other components of the turbocompressor, for example on an inner housing or on an inner bundle of the turbo compressor summarizing carrier.

An advantageous development of the invention provides that the flow channel of the feedback stage can mentally be divided into the following sections.

A first portion extends radially and has a radial opening to an upstream impeller at a first end of the first portion.

A second section adjoins a first end of the second section at the second end of the first section upstream of the turbocompressor in the case of the turbocompressor, and the flow is deflected by approximately 180 ° from a radial direction in the opposite radial direction.

A third section, which extends substantially radially, adjoins with a first end on a second end of the second section arranged upstream, in the case of the turbocompressor.

A fourth portion radially adjoins a first end of the fourth portion radially at a second end of the third portion, which is upstream in the case of the turbocompressor. The fourth section diverts the flow by about 90 ° in the axial direction, and with a second end of the fourth section, it has an axial opening to the second downstream impeller.

In these sections, according to the invention, the rough areas are preferably provided at different positions, which are specified in detail below.

Preferably, a first rough region in the first portion is disposed on the axial boundary surface that is axially further from the third portion than the other axial boundary surface.

Preferably, a second rough region on the radially inner boundary surface of the second portion beginning at the second end of the second portion is disposed extending between 30% to 70% of the extent along the flow channel.

Preferably, a third rough region is directly adjacent to the second rough region in the third section and is provided extending between 5% to 40% along the flow channel.

Preferably, a fourth rough region is located in the fourth section on the radially outer boundary surface.

A preferred embodiment of the invention provides that the rough areas each extend over the entire circumference of the flow channel.

When the radial turbofluid energy machine is a turbocompressor, a process fluid flows through the sections in the order of the first section, the second section, the third section, the fourth section.

When the radial turbofan energy machine is a turboexpander, a process fluid flows through the sections in the order fourth section, third section, second section, first section.

Suitably, the first portion of the flow channel may include vanes to direct the flow to downstream conditions.

Expediently, the rough areas have an average roughness of 20 μm <Rz, particularly preferably 30 μm <Rz.

The non-rough regions preferably have an average roughness of 20 μm> Rz, particularly preferably 10 μm> Rz.

In cases where the local flow rate can not be sensibly adapted to a given local surface roughness in order to minimize the pressure losses due to friction, according to the invention, the local surface roughness is to be adapted to the local flow velocity. The area-specific roughness of the surface according to the invention provides that, in the region of high flow velocities, the flow-wetted surface is designed with a smaller roughness than in the region of lower flow velocities.

A preferred application of the invention provides that the recirculation stage a bladed radial diffuser or im Case of the radial turbine having a bladed radial Konfusor.

Another preferred application of the invention provides that the return stage has a blade-less radial diffuser or, in the case of the radial turbine, a blade-less radial confuser.

The speed level in the radial diffuser or in the radial confuser is at the annular space inside diameter - ie at the impeller outer diameter - highest and decreases with increasing radius - ie outward - from. At the same time the wetted surfaces to be machined surface of the annular space walls with the radius becomes larger. Due to the invention according to the invention adjusting the roughness of the local flow rate level of the wetted surfaces in radial diffusers and confusers friction-related pressure losses are reduced without necessarily increasing the manufacturing cost of the components. This is achieved in particular because the increased complexity of a smaller roughness on a small area in the area of high flow velocities is offset by a reduced outlay with a larger permissible roughness on a large area in the region of lower flow velocities.

Figur 1

eine schematische Darstellung eines Längsschnitts durch einen Turboverdichter gemäß der Erfindung.

In the following the invention with reference to a specific embodiment with reference to a drawing is described in more detail. It shows:

FIG. 1

a schematic representation of a longitudinal section through a turbocompressor according to the invention.

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

The two impellers IMP1, IMP2 are components of a rotor R, wherein the impeller IMP1, IMP2 frictionally on a are attached along an axis X extending shaft SH. The rotor R is surrounded by flow-leading stationary components, of which a return stage RS is shown here. As a rule, a multistage turbomachine comprises a plurality of return stages RS which, viewed in the direction of flow, deflects the process fluid PF by 180 ° following a radial diffuser path, by a first impeller IMP1, which in the case of the turbo-compressor TCO axially draws in and radially discharges a process fluid PF back to radially inward and then deflects in the axial direction to supply the process fluid PF to the second downstream impeller IMP2.

As a rule, the return stage comprises a blade bottom SB and an intermediate bottom ZB, which are firmly connected to one another by means of guide vanes V forming a flow channel between them. In general, the return stages RS are formed divided in the circumferential direction, so that a division of the return stage in a parting line allows the removal of the rotor from the structure of the return stages. The rotor is radially inserted during assembly or removed radially during disassembly.

The return stages RS have to the rotor R at different points shaft seals SHS, which should prevent the unused degradation of pressure differences or Beipassströmungen in operation.

For the purposes of the definition of the invention, the flow channel CH extending from the first impeller IMP1 to the second impeller IMP2 is conceptually subdivided into four successive sections S1, S2, S3, S4 arranged in succession in the flow direction in the case of the turbocompressor TCO. In the case of the turboexpander, the numbering of these sections S1-S4 is opposite to the flow direction. The first section S1 extends substantially radially and has a radial opening to the first impeller IMP1 at a first end S1E1 of the first section S1. The second Section S2 abuts with a first end S2E1 of the second section S2 at a second end S1E2 of the first section S1 and deflects the flow through the channel CH by about 180 ° from a radial direction in the opposite radial direction. In the case of the turbocompressor TCO, the flow is deflected from radially outward in a direction radially inward. At the second section S2, the third section S3 connects to a first end S3E1 of the third section S3 adjacent to the second end S2E2 of the second section S2. This section extends essentially radially and, in the case of the turbocompressor TCO, leads the flow from radially further outward to radially further inward. The fourth portion radially adjoins a first end S4E1 of the fourth portion S4 radially at a second end S3E2 of the third portion S3 and diverts the flow by about 90 ° in the direction of the second impeller IMP2. A second end S4E2 of the fourth section S4 adjoins the second impeller IMP2.

A first rough region RZ1 is located in the first section S1 on the axial boundary surface that is axially further away from the third section S3 than the other axial boundary surface.
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. This second rough region RZ2 extends between 30% -70% of the extent along the flow channel of the second section S2.
A third rough region RZ3 directly adjoins the second rough region RZ2 in the third section S3 and extends between 5% -40% along the flow channel CH in the third section S3.
A fourth rough region RZ4 extends in the fourth section S4 on the radially outer boundary surface.

In principle, it is conceivable that not all or only one rough area of the four rough areas RZ1-RZ4 is provided to improve the efficiency of the turbomachine TCO. The highest efficiency gain is achieved by the complete implementation of the rough regions RZ1-RZ4 according to the invention and according to the embodiment FIG. 1 reached. In principle, it is conceivable that the rough areas RZ1-RZ3 are specially roughened by the boundary surfaces SFA of the flow channel CH or the other areas of the boundary surface SFA are provided with a lower surface roughness than the rough areas RZ1-RZ4, for example by means of polishing. In addition, it is also conceivable that both a roughening of the rough areas RZ1-RZ4 and a polishing of the other boundary surfaces SFA is provided in order to achieve the erfindungsmäßen effect.

Claims (15)

1. Return stage (RS) of a radial turbo fluid energy machine, in particular a radial turbocompressor (TCO), having an axis of rotation (X),
   Return stage (RS) comprising an annular flow channel (CH) for feeding a flowing process fluid (PF) from a flow opening of a first impeller (IMP1) to a flow opening of a second impeller (IMP2) arranged downstream,
   characterized in that
   the flow channel (CH) is defined by boundary surface regions (SFA), of which at least one specific rough region extending in the circumferential direction has a surface roughness (RZ) which is increased with respect to the other regions.
2. Return stage (RS) according to Claim 1, wherein the flow channel (CH) has a first portion (S1), which extends radially and has a radial opening to an impeller (IMP) at a first end (S1E1) of the first portion (S1).
3. Return stage (RS) according to Claim 2, wherein the flow channel (CH) has a second portion (S2), which adjoins a second end (S1E2) of the first portion (S1) with a first end (S2E1) of the second portion (S2) and deflects the flow by approximately 180° from one radial direction into the opposing radial direction.
4. Return stage (RS) according to Claim 3, wherein the flow channel (CH) has a third portion (S3), which runs substantially radially and adjoins a second end (S2E2) of the second portion (S2) with a first end (S3E1) of the third portion (S3).
5. Return stage (RS) according to Claim 4, wherein the flow channel (CH) has a fourth portion (S4), which 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° and, with a second end (S4E2) of the fourth portion (S4), has an axial opening to the second impeller (IMP2).
6. Return stage (RS) according to Claim 2, wherein a first rough region (RZ1) in the first portion (S1) is arranged on that axial boundary surface which is at a greater axial distance from the third portion (S3) than the other axial boundary surface.
7. Return stage (RS) according to Claims 2, 3 or 2, 3, 6, wherein a second rough region (RZ2) on the radially inner boundary surface of the second portion (S2), beginning at the second end (S2E2) of the second portion (S2), is located in a manner extending over between 30% and 70% of the extent along the flow channel (CH).
8. Return stage (RS) according to Claims 2, 3, 4 or 2, 3, 4, 6 or 2, 3, 4, 6, 7, wherein a third rough region (RZ3) directly adjoins the second rough region (RZ2) in the third portion (S3) and is located in a manner extending between 5% and 40% along the flow channel (CH).
9. Return stage (RS) according to Claims 2, 3, 4, 5 or 2, 3, 4, 5, 6 or 2, 3, 4, 5, 6, 7 or 2, 3, 4, 5, 6, 7, 8, wherein a fourth rough region (RZ4) is located in the fourth portion (S4) on the radially outer boundary surface.
10. Return stage (RS) according to at least one of the preceding Claims 1 to 9, wherein the rough regions (RZ1-RZ4) each extend over the entire extent of the flow channel (CH).
11. Return stage (RS) according to at least one of the preceding Claims 1 to 10, wherein the fluid energy machine (FEM) is a turbocompressor (TCO) and a process fluid (PF) flows through the portions in the sequence of first portion (S1), second portion (S2), third portion (S3), fourth portion (S4).
12. Return stage (RS) according to at least one of the preceding Claims 1 to 10, wherein the fluid energy machine is a turboexpander and a process fluid (PF) flows through the portions in the sequence of fourth portion (S4), third portion (S3), second portion (S2), first portion (S1).
13. Return stage (RS) according to at least one of the preceding Claims 1 to 12, wherein the first portion (S1) of the flow channel (CH) has guide blades (V).
14. Return stage (RS) according to at least one of the preceding Claims 1 to 13, wherein the rough regions have a mean roughness of 20 µm < Rz.
15. Return stage (RS) according to at least one of the preceding Claims 1 to 13, wherein the non-rough regions have a mean roughness of Rz < 20 µm.

Images