WO2023066585A1

WO2023066585A1 - Compressor, in particular radial compressor

Info

Publication number: WO2023066585A1
Application number: PCT/EP2022/076327
Authority: WO
Inventors: Bouchaib El-Haissouk; Viktor Hermes; Jörg Rheims; Axel Spanel; Christian Woiczinski; Attilla Yildiz
Original assignee: Siemens Energy Global GmbH & Co. KG
Priority date: 2021-10-21
Filing date: 2022-09-22
Publication date: 2023-04-27
Also published as: EP4170186A1

Abstract

A compressor (1) comprising a rotor which extends along an axis of rotation (3), a housing (9), wherein the housing (9) is arranged around the rotor, wherein the housing (9) has an axial inflow (4) and, downstream of the axial inflow (4), a first compression stage and, further downstream of the first compression stage, a radial outflow (5) for a process fluid, the radial outflow (5) leading through the housing (9), and furthermore comprising an impeller (2) which is arranged on the rotor, with an injection device (15) for injecting a fluid into the axial inflow (4).

Description

Compressors, in particular centrifugal compressors

The invention relates to a compressor, in particular a centrifugal compressor.

In today's compressors, in particular centrifugal compressors, stage efficiencies of around 90% are achieved, which is regarded as the physical limit. It is possible to increase efficiency by using water injection. The advantages of water injection have already been recognized in gas turbines, where water injection makes a significant contribution to increasing performance and efficiency. Water injection involves injecting water at high pressure before the compressor or between stages in multi-stage compressors. The water evaporates during compression and continuously cools the gas, as in the comparative isothermal compression process. As a result, the efficiency can be increased by 1-2%.

In the field of compressor technology, water injection is used in raw gas compressors, where the water is injected between the compressor stages in order to reduce the outlet temperature of the medium between the individual stages in order to prevent the medium from polymerisation.

While the benefits of injecting vaporizable liquid directly into the gas stream of a compressor are well known, some disadvantages are also well known.

The limiting degree of vaporization of the liquid injected into the compressor gas stream is problematic. If the liquid is injected into a low velocity area of the compressor, breaking up or atomizing the liquid into very small droplets may not be achieved. Very small droplets are necessary to achieve a high degree of vaporization len, because the surface area of such a droplet is large in relation to the volume of the droplet and the droplet can so easily absorb heat and evaporate.

Large liquid droplets impacting internal compressor parts, such as the impeller, create the risk of severe erosion.

The object of the invention is to specify an improved compressor, in particular a radial compressor.

This object is achieved according to the invention by a compressor comprising a rotor which extends along an axis of rotation, a housing, the housing being arranged around the rotor, the housing having an axial inflow and downstream of the axial inflow a first compression stage and further downstream of the first Compression stage has a first radial outflow for a process fluid, the first radial outflow leading through the inner housing, furthermore an impeller, which is arranged on the rotor, with an injection device for injecting a liquid into the axial inflow, the process fluid to be compressed is first sucked in and the quantity of injected liquid depends on the temperature and relative humidity of the sucked-in medium.

The subclaims dependent on the main claim contain advantageous developments of the invention.

In connection with the invention, expressions such as axial, radial, tangential or circumferential direction each refer to the axis of the rotor or the axis of rotation. In this case, a compression stage means the compression of a specific mass flow by means of one or more compressor impellers. Crucial to the use of the term "compressor stage" or "compression stage" according to the invention is the compression taking place in an uninterrupted flow path in the compressor, without the compression to be compressed Mass flow or a partial flow thereof is derived from the compressor and possibly. is subjected to other process steps. This also means that at the beginning of a compression stage, the process fluid to be compressed is introduced into the housing of the compressor by means of an inflow, and at the exit of a compression stage at least a part - usually the entire mass flow of the process fluid - is discharged again from the housing of the corresponding compression stage by means of a Outflow is discharged.

According to the invention, a mixture is used as the liquid.

By adding methanol (boiling point 65°C) or ethanol (boiling point 78°C), targeted evaporation can be set in the compression process. As the temperature increases along the compression section, various parts of the mixture will evaporate and absorb heat. This allows a lower temperature to be achieved than when working with only a single-phase liquid.

A further improvement consists in using suitable mixing partners to produce a higher boiling point if this is beneficial to the compression process. Also, mixing could occur within the medium to be compressed if the enthalpy of mixing is negative and additional (mixing) cooling is to be achieved.

The aim of the invention is also to approach isothermal compression, which leads to high efficiency.

With the evaporation of a liquid according to the invention, such as e.g. B. Water or LPG, the volume flow of the flow can be reduced. With a given cross-section, the speed and the flow losses decrease. In this way, evaporation can be used to make compressors more compact, without the negative consequences of compactness on the performance of the compressor.

In an advantageous development, injection in the spiral stage (last stage of a process stage) is particularly effective.

In further advantageous developments, an injection device is also proposed in inlets and return stages. Depending on the operating point, the amount of liquid should be regulated to ensure an optimal condition close to saturation and to avoid liquid accumulation.

In an advantageous development, the amount of water is about 2 wt. -% . This reduces the total volume flow incl. Evaporated added water by about 8% which should reduce losses from a diffuser and coil by about 15%.

Either a gas in the liquid aggregate state can be injected or another medium such as e.g. B. Water, methanol or ethanol, or a mixture of several components.

The injected medium is selected so that its evaporation temperature is lower than the temperature at the impeller outlet of the subsequent compression stage without liquid injection, based on the final pressure there.

In the case of a mixture of several liquids, this condition must be met for the component with the highest boiling point. On the other hand, the evaporation temperature (in the case of mixtures: the lowest-boiling component) can be lower than the gas temperature at the point of injection. The injected medium is selected in such a way that the evaporation temperature is above the temperature of the compressed gas at the point of injection and below the temperature after the subsequent compressor stage, based on the case without liquid injection.

Very good internal cooling is achieved when the temperature after the compression process following the injection is above the evaporation temperature of the liquid, in the case of liquid mixtures it is above the highest evaporation temperature of the individual components. For this case, the potential of internal cooling would be exploited, as the high enthalpy of the evaporation process was exploited.

Active dosing of the amount of liquid improves liquid injection. The amount of liquid is calculated using the temperature and the relative humidity of the sucked-in medium. The dosing can then be done by switching nozzles on and off or via the pump speed or also via a by-pass control.

The dwell time with the injected liquid plays a decisive role in the effective humidification of the process fluid.

According to the invention, a minimum distance between an injection and an impeller inlet of 3 times the impeller inlet diameter is proposed in order to achieve an effective reduction in the compressor drive power by means of liquid injection.

It has been shown that an optimum can be achieved if the distance between the injection and the impeller inlet is essentially 10 times the impeller inlet diameter. In general, the relationship applies that the distance between the injection and the impeller inlet can be smaller, the finer the liquid droplets that are introduced. In a further advantageous development, a cascading of the injection in several units with a defined distance from one another is proposed. Here, too, the minimum distance of the last cascade should not be undershot. The injection nozzles in the cascade can be offset from one another, viewed in the direction of flow, in order not to interfere with one another. In a cascaded arrangement, the quantity of liquid injected per position can be reduced.

The invention is explained in more detail below using specific exemplary embodiments with reference to drawings.

The properties, features and advantages of this invention described above and the manner in which they are achieved will become clearer and more clearly understood in connection with the following description of the exemplary embodiments, which are explained in more detail in connection with the drawings.

Identical components or components with the same function are identified with the same reference symbols.

Exemplary embodiments of the invention are described below with reference to the drawings. These are not intended to represent the exemplary embodiments to scale, rather the drawing, where useful for explanation, is in schematic and/or slightly distorted form. With regard to additions to the teachings that are immediately recognizable in the drawing, reference is made to the relevant state of the art.

Show it :

FIG. 1 shows a sectional illustration of a radial compressor according to the prior art

Figure 2 is a longitudinal section through a schematic Representation of a first compressor according to the invention

Terms such as axial, radial, tangential, or circumferential refer to an axis X of a rotor unless otherwise noted.

1 shows a known radial flow machine in a (simplified) sectional view. The flow machine shown is a compressor 1, in particular a centrifugal compressor.

The turbomachine includes, among other things, a radial impeller 2 which is mounted such that it can rotate about an axis of rotation 3 . The impeller 2 has an axial inflow 4 and a radial outflow 5 .

In addition, the impeller 2 comprises a hub 6 and impeller blades 7 protruding radially from the hub 6 . Flow channels through which a fluid can flow are formed between the impeller blades 7 . Furthermore, the hub 6 is connected to a shaft of the compressor 1 that is not shown in the figure.

In addition, the impeller 2 has a wheel disc 8 which is formed in one piece with the hub 6 and connects the impeller blades 7 to one another. In the present exemplary embodiment, the impeller 2 is a so-called open impeller, ie an impeller without a cover plate. In an alternative embodiment (not shown in the figure), the impeller 2 could be a so-called closed impeller, ie an impeller with a cover disk.

Furthermore, the compressor 1 comprises a housing 9 in which the impeller 2 is placed. A part of the housing 9 is designed as a volute housing. That is, the housing 9 has a NEN spiral housing part 10 with a spiral cavity 11 on.

Furthermore, the compressor has an annular diffuser 12 which is axially symmetrical with respect to the axis of rotation 3 and which is designed as a hollow chamber or as a channel in the housing 9 . The diffuser 12 is arranged around a circumference of the impeller 2 and is designed as a radial diffuser. In addition, the diffuser 12 opens into the spiral housing part 10 or into its cavity 11.

In addition, an outlet diameter 13 of the impeller 2 is shown in FIG. 1 in the form of a double arrow.

Furthermore, the diffuser 12 has a plurality of diffuser vanes 14 . That is, diffuser 12 is a vaned diffuser. In the present exemplary embodiment, the diffuser 12 has six diffuser vanes 14, only two of which can be seen in FIG. In principle, however, the diffuser 12 could also have a different number of diffuser vanes 14 .

The compressor 1 is used to compress a fluid such as air. During operation of the compressor 1, the fluid flows axially through the axial inflow 4 into the impeller 2 or into the flow channels formed by the impeller blades 7. The fluid is set in rotation by the impeller 2 and leaves the impeller 2 radially outwards through the radial outflow 5.

From there, the fluid exiting the impeller 2 flows into the diffuser 12. The diffuser 12 converts part of the kinetic energy of the fluid into potential energy in the form of pressure and guides the fluid into the cavity 11 of the volute casing part 10.

FIG. 2 shows a longitudinal section of a schematic representation of a part of the compressor 1 with an inventive according injection device 15 . Part of the axial inflow 4 can be seen on the left-hand edge of FIG. An impeller inlet diameter 16 is indicated by the double arrow. The impeller inlet 17 is arranged in front of the impeller 2, which is not shown in FIG.

An inflow housing 18 is arranged at the impeller inlet 17 and is connected to one another via a plurality of flanges 19 .

A nozzle 21 is arranged at a distance 20 in the inflow housing 18 . The nozzle 21 is designed to supply liquid. A process fluid flowing from the right is moved in the direction of the compressor 1 and a liquid enters the process fluid by means of the nozzles 21 .

The evaporation temperature of the liquid is lower than the temperature of the process fluid to be compressed after injection in the compression process.

Furthermore, the injection device 15 has a control device, not shown in detail, which is designed in such a way that the quantity of injected liquid can be controlled.

In this case, the injection device 15 is designed in such a way that the process fluid to be compressed is first sucked in and the quantity of injected liquid depends on the temperature and relative humidity of the sucked-in process fluid.

As can be seen in FIG. 2, the injection device 15 is designed in such a way that the liquid is injected within the process fluid to be compressed.

The injection device 15 can have a plurality of nozzles 21 (not shown), which are arranged one behind the other in the direction of flow of the process fluid. It has been shown that the injection effect is advantageous if the distance 20 between the last nozzle 21 in front of the impeller 2 and the impeller inlet 17 is three times the impeller inlet diameter 16 .

A further advantageous effect is seen when the distance 20 between the last nozzle 21 in front of the impeller 2 and the impeller inlet 17 is 0.5 to 0.75 times, preferably 0.66 times, the impeller inlet diameter 16 .

The injection device 15 is particularly effective when the distance 20 between the last nozzle 21 in front of the impeller 2 and the impeller inlet 17 is 10 times the impeller inlet diameter 16 .

A further possibility of improving the effectiveness of the injection device 15 is achieved by arranging a plurality of nozzles one behind the other in the direction of flow. Improved mixing is possible as a result. This improved arrangement is shown schematically in FIG. 2 by a first line 23 and a second line 24 .

Further nozzles (not shown) are arranged both on the first line 23 and on the second line 24 . The distance between the nozzles 21 and the position corresponding to 10 times the distance 22 is the length L. The distance between the nozzle 21 and the further nozzle at the position on the first line 23 corresponds essentially to one third of the length L .

The distance between the further nozzles at the first position 23 and the further nozzles at the position on the second line 24 corresponds essentially to one third of the length L .

The distance between the further nozzles at the second position 24 and the position corresponding to 10 times the distance 22 is essentially one third of the length L . Only two further positions for further nozzles are shown in FIG. Other nozzles that are arranged at a distance from one another are also conceivable.

Claims

patent claims

1. Compressor (1) comprising a rotor, which extends along an axis of rotation (3), a housing (9), the housing (9) being arranged around the rotor, the housing (9) having an axial inflow (4) and downstream of the axial inflow (4) has a first compression stage and further downstream of the first compression stage a radial outflow (5) for a process fluid, the radial outflow (5) leading through the housing (9), furthermore an impeller (2), which is arranged on the rotor, characterized by an injection device (15) for injecting a liquid into the axial inflow (4), wherein the process fluid to be compressed is first sucked in and the amount of liquid injected depends on the temperature and relative humidity of the sucked-in medium .

2. Compressor (1) according to claim 1, wherein the evaporation temperature of the liquid is lower than the temperature of the process fluid to be compressed after injection in the compression process.

3. Compressor (1) according to claim 1 or 2, with a control device which is designed such that the amount of injected liquid can be controlled.

4. Compressor (1) according to any one of the preceding claims, wherein the injection device (15) is formed in such a way is that the liquid is injected inside the medium to be compressed. Compressor (1) according to one of the preceding claims, in which the injection of the liquid takes place in front of the impeller (2). Compressor (1) according to one of the preceding claims, wherein the compressor (1) has a scroll stage and the injection of the liquid takes place in the scroll stage. Compressor (1) according to one of the preceding claims, wherein the compressor (1) has an inlet and the liquid is injected into the inlet. Compressor (1) according to one of the preceding claims, in which the compressor (1) has a recirculation stage and the liquid is injected into the recirculation stage. Compressor (1) according to one of the preceding claims, in which the liquid is injected via a plurality of nozzles (21). Compressor (1) according to one of the preceding claims, wherein the compressor (1) has an impeller inlet (17) with an impeller inlet diameter (16), the distance (20) between the last nozzle (21) before the impeller (2) and the impeller inlet (17) is 3 times the impeller inlet diameter (16). Compressor (1) according to one of claims 1 to 9, wherein the compressor (1) has an impeller inlet (17) with an impeller inlet diameter (16), the distance (20) between the last nozzle (21) before the impeller (2) and the impeller inlet (17) is 10 times the impeller inlet diameter (16).

12. Compressor (1) according to one of the preceding claims, wherein the nozzles (21) are arranged spaced apart from one another in the axial direction and form a cascaded injection.

13. Compressor (1) according to any one of the preceding claims, wherein the nozzles (21) are arranged offset to one another.

14. Compressor (1) according to one of the preceding claims, wherein the quantity of injected liquid can be regulated by switching the nozzles (21) on and off.

15. Compressor (1) according to any one of the preceding claims, wherein the amount of injected liquid can be controlled by the speed.

16. Compressor (1) according to any one of the preceding claims, wherein the amount of injected liquid takes place via a bypass control.

17. Compressor (1) according to one of the preceding claims, wherein the injection device (15) is designed for injection such that a mixture of water and alcohol can be injected.

18. Compressor (1) according to one of the preceding claims, wherein the injection device (15) is designed for injection such that the mixture comprises water and ethanol and/or water and methanol.

19. Compressor (1) according to any one of the preceding claims, designed as a radial compressor.

20. Centrifugal compressor according to claim 19, wherein the centrifugal compressor is designed in one stage. 15 Centrifugal compressor according to claim 19, wherein the centrifugal compressor is designed in multiple stages.