Patent Application
20240410378
The invention relates to a compressor, in particular a radial compressor.
In current compressors, in particular radial compressors, stage efficiencies of approximately 90% are achieved, which is considered to be a physical limit. It is possible to increase the degree of efficiency by an injection of water being used. The advantages of the water injection have already been recognized in gas turbines, where the water injection makes a significant contribution to increasing the power and the degree of efficiency. During the water injection, water at high pressure is injected in front of the compressor or between the stages in multi-stage compressors. The water evaporates during the compression and continuously cools the gas, as in the comparison process of isothermal compression. The degree of efficiency can thereby be increased by from 1 to 2%.
In the field of compressor technology, the water injection is used in crude gas compressors, where the water is injected between the compressor stages in order to reduce the discharge temperatures of the medium between the individual stages in order to prevent a polymerization of the medium.
Although the advantages which result from the injection of vaporizable liquid directly into the gas jet of a compressor are known, some disadvantages are also known.
The problem is that the limiting degree of evaporation of the liquid injected into the compressor gas flow is achieved. When the liquid is injected into a region of low speed of the compressor, it may be the case that the break up or atomization of the liquid into very small droplets is not achieved. Very small droplets are necessary in order to achieve a high degree of evaporation since the surface content of such a droplet with respect to the volume of the droplet is large and the droplet can thus easily absorb heat and evaporate.
Large liquid droplets which strike inner compressor components, such as the impeller, lead to the risk of significant erosion.
An object of the invention is to provide an improved compressor, in particular a radial compressor.
This object is achieved by a compressor including a rotor which extends along a rotation axis, a housing, wherein the housing is arranged around the rotor, wherein the housing has an axial inflow and downstream of the axial inflow has a first compressor stage and further downstream of the first compressor stage has a first radial outflow for a process fluid, wherein the first radial outflow leads through the inner housing, furthermore an impeller which is arranged on the rotor, having an injection apparatus for injecting a liquid into the axial inflow, wherein the process fluid which is intended to be compressed is initially drawn in and the quantity of injected liquid is carried out in accordance with the temperature and relative humidity of the medium drawn in.
The dependent claims which are dependent on the main claim contain advantageous further developments of the invention.
In connection with the invention, terms such as axial, radial, tangential or circumferential direction each mean a reference to the axis of the rotor or the rotation axis. A compressor stage means in this instance the compression of a specific mass flow by means of one or more compressor impellers. The decisive aspect with the use according to the invention of the term “compressor stage” or “compression stage” is the compression which takes place in an uninterrupted flow path in the compressor without the mass flow which is intended to be compressed, or a partial flow thereof, being redirected out of the compressor and where applicable being subjected to other process steps. This also means that at the inlet of a compressor stage, the process fluid which is intended to be compressed is introduced by means of an inflow into the housing of the compressor and at the outlet of a compressor stage at least a portion—generally the entire mass flow—of the process fluid is discharged from the housing of the corresponding compressor stage again by means of an outflow.
According to one embodiment, an admixture is used as the liquid.
As a result of the addition of methanol (boiling point 65° C.) or ethanol (boiling point 78° C.), an accurate evaporation in the compression process can be adjusted. Along the compression path, with the temperature increase different proportions of the admixture will evaporate and absorb heat. A lower temperature can thereby be achieved than when only working with a single-phase liquid.
Another improvement involves a higher boiling temperature being produced by means of suitable mixing partners when it is beneficial for the compression process. Furthermore, the mixing could be carried out within the medium which is intended to be compressed when the mixing enthalpy is negative and an additional (mixing) cooling is intended to be achieved.
With the invention, the objective is further sought of approaching an isothermal compression which leads to a high degree of efficiency.
With the evaporation of a liquid according to the invention, such as, for example, water or liquid gas, the volume flow of the flow can be reduced. With a given cross section, the speed and the flow losses are consequently reduced.
Consequently, the evaporation can be used to configure compressors in a more compact manner without the negative consequences of the compactness on the power of the compressor.
In one embodiment, an injection in the helical stage (last stage of a process stage) is particularly effective.
In one embodiment, an injection apparatus is also proposed in inlets and return stages. Depending on the operating location, the quantity of the liquid is intended to be controlled in order to ensure an optimum state close to saturation and to avoid an accumulation of liquid.
In one embodiment, the quantity of water is approximately 2% by weight. In this instance, the overall volume flow including evaporated added water is reduced by approximately 8%, which is intended to reduce the losses of a diffusor and a helix by approximately 15%.
Either a gas can be injected in the liquid aggregation state or another medium, such as, for example, water, methanol or ethanol, or an admixture of a plurality of components can be injected.
The injected medium is selected in such a manner that the evaporation temperature thereof is lower than the temperature at the impeller outlet of the following compression stage without liquid injection with respect to the end pressure at that location.
With an admixture of a plurality of liquids, this condition for the component which boils at the highest level must be complied with. On the other hand, the evaporation temperature (in admixtures: of the component which boils at the lowest level) may be lower than the gas temperature at the injection location.
The injected medium is selected in such a manner that the evaporation temperature is above the temperature of the compressed gas at the injection location and below the temperature after the subsequent compressor stage with respect to the case without liquid injection.
Internal cooling is achieved when the temperature after the compression process which follows the injection is above the evaporation temperature of the liquid with liquid admixtures above the highest evaporation temperature of the individual components. In this instance, the potential of the inner cooling would be used since the high enthalpy of the evaporation process has been used.
As a result of an active metering of the liquid quantity, the liquid injection is improved. The calculation of the liquid quantity is carried out via the temperature and the relative humidity of the medium drawn in. The metering can then be carried out by switching on and off nozzles or via the pump speed or also via a bypass control.
The dwell time with injected liquid for the effective humidification of the process fluid is decisive.
According to one embodiment, a minimum spacing between an injection and an impeller inlet of 3 times the impeller inlet diameter is proposed in order by means of liquid injection to achieve an effective reduction of the compressor drive power.
It has been found that an optimum state can be achieved when the spacing between the injection and the impeller inlet is substantially 10 times the impeller inlet diameter. Generally, the relationship applies that the spacing of the injection from the impeller inlet may be smaller, the finer are the liquid droplets which are introduced.
In one embodiment, a cascading of the injection into a plurality of units at a defined spacing with respect to each other is proposed. Also in this instance, the value should not fall below the minimum spacing of the last cascade. The injection nozzles in the cascade can be arranged when viewed in the flow direction to be offset from one another in order not to disturb each other. In a cascading arrangement, the injected quantity of liquid per position can be reduced.
Embodiments of the invention is explained in greater detail below with reference to specific exemplary embodiments and the drawings.
The properties, features and advantages of embodiments of the invention as described above and the manner in which they are achieved will become clearer and more easily understood in connection with the following description of the exemplary embodiments which are explained in greater detail in connection with the drawings.
Identical components or components with the same function are in this instance given the same reference numerals.
Exemplary embodiments of the invention are described below with reference to the drawings. They are not intended to represent the exemplary embodiments to scale, instead the drawings, where necessary for explanation, are set out in a schematic and/or slightly distorted h regard to additions to the teachings which can be directly identified in the drawings, reference may be made to the relevant prior art.
Terms such as axial, radial, tangential or circumferential direction refer to an X axis of a rotor unless stated otherwise.
The flow machine includes inter alia a radial impeller 2 which is rotatably supported about a rotation axis 3. The impeller 2 has an axial inflow 4 and a radial outflow 5.
Furthermore, the impeller 2 includes a hub 6 and impeller blades 7 which protrude radially from the hub 6. Between the impeller blades 7, there are formed flow channels through which a fluid can flow. Furthermore, the hub 6 is connected to a shaft (which is not illustrated in the Figures) of the compressor.
Furthermore, the impeller 2 has a wheel disk 8 which is formed in one piece with the hub 6 and which connects the impeller blades 7 to each other. In the present exemplary embodiment, the impeller 2 is a so-called open impeller, that is to say, an impeller without any covering plate. In an alternative embodiment (not illustrated in the Figures), the impeller 2 could also be a so-called closed impeller, that is to say, an impeller with a covering plate.
Furthermore, the compressor 1 includes a housing 9 in which the impeller 2 is placed. A portion of the housing 9 is in the form of a helical housing. That is to say, the housing 9 has a helical housing portion 10 having a helical hollow space 11.
Furthermore, the compressor has an annular diffusor 12 which is axially symmetrical with respect to the rotation axis 3 and which is in the form of a hollow chamber or a channel in the housing 9. The diffusor 12 is arranged around a circumference of the impeller 2 and is in the form of a radial diffusor. Furthermore, the diffusor 12 opens in the helical housing portion 10 or in the hollow space 11 thereof.
Furthermore, in
Furthermore, the diffusor 12 has a plurality of diffusor blades 14. That is to say, the diffusor 12 is a bladed diffusor. In the present exemplary embodiment, the diffusor 12 has six diffusor blades 14 of which only two can be seen in
The compressor 1 is used to compress a fluid, such as, for example, 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 caused to rotate by the impeller 2 and leaves the impeller 2 radially in an outward direction through the radial outflow 5.
From there, the fluid discharged from the impeller 2 flows into the diffusor 12. The diffusor 12 converts a portion of the kinetic energy of the fluid into potential energy in the form of pressure and guides the fluid into the hollow space 11 of the helical housing portion 10.
There is arranged at the impeller inlet 17 an inflow housing 18 and they are connected to each other by means of a plurality of flanges 19.
At a spacing 20, a nozzle 21 is arranged in the inflow housing 18. The nozzle 21 is formed to supply liquid. In this instance, a process fluid which flows from the right is moved in the direction of the compressor 1 and by means of the nozzles 21 a liquid reaches the process fluid.
In this instance, the evaporation temperature of the liquid is lower than the temperature of the process fluid which is intended to be compressed after the injection in the compression process.
Furthermore, the injection apparatus 15 has a control device which is not illustrated in greater detail and which is configured in such a manner that the quantity of injected fluid can be controlled.
In this instance, the injection apparatus 5 is configured in such a manner that the process fluid which is intended to be compressed is initially drawn in and the quantity of injected fluid is produced in accordance with the temperature and relative humidity of the process fluid drawn in.
As can be seen in
The injection apparatus 15 may have a plurality of nozzles 21 (not illustrated) which are arranged one behind the other in the flow direction of the process fluid.
It has been found that the effect of the injection is advantageous when the spacing 20 between the last nozzle 21 in front of the impeller 2 and the impeller inlet 17 is 3 times the impeller inlet diameter 16.
Another advantageous effect is evident when the spacing 20 between the last nozzle 21 in front of the impeller 2 and the impeller inlet 17 is from 0.5 to 0.75 times, preferably 0.66 times the impeller inlet diameter 16.
The injection apparatus 15 has a particularly effective action when the spacing 20 between the last nozzle 21 in front of the impeller 2 and the impeller inlet 17 is 10 times the spacing 22 of the impeller inlet diameter 16.
Another possibility of improving the effectiveness of the injection apparatus 5 is achieved in that a plurality of nozzles are arranged are behind the other in the flow direction. An improved mixing is thereby possible. In
Both on the first line 23 and on the second line 24, additional nozzles (not illustrated) are arranged. The spacing between the nozzles 21 and the position which corresponds to 10 times the spacing 22 is the length L. The spacing between the nozzles 21 and the additional nozzles at the position on the first line 23 substantially corresponds to a third of the length L.
The spacing between the additional nozzles at the first position 23 and the additional nozzles at the position on the second line 24 substantially corresponds to a third of the length L.
The spacing between the additional nozzles at the second position 24 and the position which corresponds to 10 times the spacing 22 is substantially a third of the length L.
In
| Number | Date | Country | Kind |
|---|---|---|---|
| 21203945.7 | Oct 2021 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/076327 | 9/22/2022 | WO |
