US20120257991A1

US20120257991A1 - Pressure exchanger

Info

Publication number: US20120257991A1
Application number: US13/511,223
Authority: US
Inventors: Mark Owen Woodthorpe
Original assignee: GHD Pty Ltd
Current assignee: BEIJING CHINA WATER GOLDEN WATER DESALINATION TECHNOLOGY APPLICATION AND RESEARCH Co Ltd
Priority date: 2009-11-24
Filing date: 2010-11-23
Publication date: 2012-10-11
Also published as: AU2010324526A1; CA2781473A1; CN102725538A; CN102725538B; EP2504585A1; WO2011063452A1

Abstract

A pressure exchanger for transferring pressure from a high pressure fluid to a low pressure fluid, including a housing and a rotor arranged for rotation within the housing, the rotor having at least one passage extending generally axially through the rotor, the passage having a first opening at one end and a second opening at another end, the openings being mutually spaced along the length of the rotor, the housing having a plurality of ports at one axial portion for communication with the first passage opening and a plurality of ports at another axial portion for communication with the second passage opening, wherein the first passage opening is directed substantially radially such that fluid is directed radially inwardly when entering the first passage opening and radially outwardly when exiting the first passage opening.

Description

FIELD OF THE INVENTION

This invention relates to a pressure exchanger, and more particularly, but not exclusively, to a pressure exchanger having improved efficiency and/or reduced production cost.

BACKGROUND OF THE INVENTION

It is known to provide a pressure exchanger for use in reverse osmosis processes used within the water desalination industry, and in particular the seawater reverse osmosis desalination industry. For example, a rotary positive displacement pressure exchanger is disclosed in U.S. Pat. No. 7,251,557.
However, the applicant has identified that existing rotary positive displacement pressure exchangers are expensive, and are not suitable for use in applications with a relatively high proportion and size of particulate matter in the fluid flowing through the pressure exchanger.
Examples of the present invention seek to provide a pressure exchanger which overcomes or at least alleviates one or more disadvantages of previously proposed pressure exchangers.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, there is provided a pressure exchanger for transferring pressure from a high pressure fluid to a low pressure fluid, including a housing and a rotor arranged for rotation within the housing, the rotor having at least one passage extending generally axially through the rotor, the passage having a first opening at one end and a second opening at another end, the openings being mutually spaced along the length of the rotor, the housing having a plurality of ports at one axial portion for communication with the first passage opening and a plurality of ports at another axial portion for communication with the second passage opening, wherein the first passage opening is directed substantially radially, such that fluid is directed radially inwardly when entering the first passage opening and radially outwardly when exiting the first passage opening.
The first passage opening may be directed to have a tangential component as well as a radial component.
Preferably, the second passage opening is directed substantially radially such that fluid is directed radially inwardly when entering the second passage opening and radially outwardly when exiting the second passage opening.
In accordance with one aspect of the present invention, there is provided a pressure exchanger for transferring pressure from a high pressure fluid to a low pressure fluid, including a housing and a rotor arranged for rotation within the housing, the rotor having at least one passage extending generally axially through the rotor, the passage having a first opening at one end and a second opening at another end, the openings being mutually spaced along the length of the rotor, the housing having a first inlet and a first outlet located axially to correspond with the first passage opening, and a second inlet and second outlet located axially to correspond with the second passage opening, such that in one rotational position of the rotor the passage communicates with the first inlet and the second outlet, in another rotational position of the rotor the passage communicates with the second inlet and the first outlet, wherein the first passage opening is directed substantially radially such that in said one rotational position fluid is directed radially inwardly from the first inlet to the first passage opening, and in said other rotational position fluid is directed radially outwardly from the first passage opening to the first outlet.
Preferably, the second passage opening is directed substantially radially such that in said one rotational position fluid is directed radially outwardly from the second passage opening to the second outlet, and in said other rotational position fluid is directed radially inwardly from the second inlet to the second passage opening.
Preferably, the rotor has a plurality of like passages distributed radially about the axis of rotation. More preferably, the passages are distributed at equal radii and angular intervals about the axis of rotation.
Preferably, the or each passage is offset from a radial direction of the rotor such that the direction of entry and exit of the fluid (ie. a central line of the flow path) is spaced from the axis of rotation of the rotor. More preferably, the passage is curved inward of the openings to induce a change in direction of the fluid entering and exiting the passage, and the net reaction force from the changes in direction acts on a line of action that is offset from (does not intersect and is not parallel to) the axis to result in a torque driving rotation of the rotor. Even more preferably, the net reaction force acts in a plane perpendicular to the axis of rotation of the rotor. In other words, the direction of one or more passage openings includes a component of direction which is tangential relative to the rotor such that the central line of the flow path through each of said openings relative to the rotor is spaced apart from (does not intersect and is not parallel to) the axis of rotation of the rotor.
In one example, the inlets are arranged such that rotation of the rotor is driven by impulse of fluid entering the passage. Accordingly, rotation of the rotor is driven (or assisted) by the direction of flow of fluid entering the passage.
Preferably, the first inlet is opposite the first outlet, the second inlet is opposite the second outlet, and the passages are arranged in opposite pairs, whereby one side of the rotor transfers high pressure as the opposite side of the rotor transfers low pressure, the high pressure side biasing the rotor relative to the housing toward the low pressure side so as to assist in sealing of the openings at the low pressure side.
As an alternative the above may also be achieved with an odd number of passages which may assist to reduce resonance, noise and vibration that may occur with passages arranged in opposite pairs.
In a preferred example, the housing is made of a plurality of separate parts. More preferably, the housing includes two end caps, one end cap having the first inlet and first outlet, the other end cap having the second inlet and second outlet.
As an alternative, the inlets and outlets may be incorporated into the body of the housing with simple end plates closing each end of the housing.
Preferably, the first passage opening is oriented in a direction perpendicular to the axis of rotation of the rotor. Similarly, the second passage opening may also be oriented in a direction perpendicular to the axis of rotation of the rotor.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described, by way of non-limiting example only, with reference to the accompanying drawings in which:

FIG. 1 is a perspective view of a pressure exchanger in accordance with an example of the present invention;

FIG. 2 is a perspective sectional view, with a horizontal section taken through an end cap of the pressure exchanger;

FIG. 3 is a perspective sectional view of the pressure exchanger, with a horizontal section taken midway along the length of the pressure exchanger;

FIG. 4 is a perspective sectional view of the pressure exchanger, with a vertical section taken along an axis of rotation;

FIG. 5 is a sectional view taken along the axis of rotation;

FIG. 6 is a perspective exploded view of the pressure exchanger;

FIG. 7 is a perspective exploded view with a section taken along the axis of rotation;

FIG. 8 is an exploded view of the pressure exchanger, with a section taken along the axis of rotation;

FIG. 9 is a diagrammatic sketch of an alternative housing design having simple end plates closing each end of the housing; and

FIG. 10 is a diagrammatic sketch showing an example internal shape of an inlet and outlet arrangement configured to match more closely the direction of flow into and out of the rotor.

DETAILED DESCRIPTION

FIGS. 1 to 8 show a pressure exchanger 10 for transferring pressure from a high pressure fluid to a low pressure fluid. The pressure exchanger 10 includes a housing 12 and a rotor 14 arranged for rotation in the housing 12. The pressure exchanger 10 is used by connecting ports 16 at one end of the pressure exchanger 10 to a relatively high pressure (prior to the exchange of pressure) fluid, and ports 16 at an opposite end of the pressure exchanger to a relatively low pressure (prior to the exchange of pressure) fluid. By rotation of the rotor 14 within the housing 12, pressure is transferred from the high pressure fluid to the low pressure fluid.
The rotor 14 has a plurality of passages 18 extending generally axially through the rotor 14. Each passage 18 has a first opening 20 (see FIG. 5) at one end of the passage 18 and a second opening 22 at another end of the passage 18. The openings 20, 22 are mutually spaced along the length of the rotor 14, and the housing 12 has a plurality of ports 16 a at one axial portion for communication with the first passage openings 20, and a plurality of ports 16 b at another axial portion for communication with the second passage openings 22. The first passage openings 20 are directed substantially radially such that fluid is directed radially inwardly when entering the first passage openings 20 and radially outwardly when exiting the first passage openings 20. More specifically, the rotor 14 is generally cylindrical, and the first passage openings 20 are directed substantially radially of the rotor 14 such that the first passage openings 20 are formed in an outer circumferential surface 24 of the rotor 14.
In the example shown, the second passage openings 22 are also directed substantially radially such that fluid is directed radially inwardly when entering the second passage openings 22, and radially outwardly when exiting the second passage openings 22. Similarly, as shown in FIG. 6, the second passage openings 22 are formed in the outer circumferential surface 24 of the rotor 14.
Advantageously, by virtue of the first and second passage openings 20, 22 being directed substantially radially, the applicant has determined that it is possible to provide improved sealing between inlets and outlets of the pressure exchanger 10, with potentially greater tolerances and lower manufacturing costs, as well as inducing torque by virtue of the tangential component so as to drive the rotor 14.
With reference to FIG. 1, the housing 12 is formed of an upper cap 26, a lower cap 28, and a housing ring 30 located between the upper cap 26 and the lower cap 28. The upper cap 26 has the ports 16 a formed therein, and the lower cap 28 has the ports 16 b formed therein. One of the ports 16 a forms a first inlet 32 of the pressure exchanger 10, and the other of the ports 16 a forms a first outlet 34 of the pressure exchanger 10. The first inlet 32 and first outlet 34 are located axially to correspond with the first passage openings 20, as shown in FIGS. 2, 4 and 5. The lower cap 28 has the ports 16 b formed therein, one of the ports 16 b forming a second inlet 36 and the other of the ports 16 b forming a second outlet 38. The second outlet 38 is on the same side of the pressure exchanger 10 as the first inlet 32, and the second inlet 36 is on the same side of the pressure exchanger as the first outlet 34. Accordingly, with reference to FIGS. 2 to 8, in one rotational position of the rotor 14 a certain passage 18 communicates with the first inlet 32 and the second outlet 38, and in another rotational position of the rotor 14 the same passage 18 communicates with the second inlet 36 and the first outlet 34. In this way, the first inlet 32 is able to function as the high pressure inlet, the second outlet 38 is able to function as the high pressure outlet, the first outlet 34 is able to function as the low pressure outlet, and the second inlet 36 is able to function as the low pressure inlet.
Accordingly, the rotor 14 rotates slidingly and sealingly within a sleeve 40 of the housing 12. The passages 18 within the rotor 14 connect the high pressure inlet 32 to the high pressure outlet 38 and the low pressure inlet 36 to the low pressure outlet 34. As the rotor rotates, fluid entering the high pressure inlet 32 fills the passages 18 connecting the high pressure inlet 32 and the high pressure outlet 38, pushing fluid that was in these passages 18 out through the high pressure outlet 38. As the rotor 14 rotates, the fluid is firstly sealed in these passages 18 by the close fit between the outer surface of the rotor 14 and the inner surface of the sleeve 40. As the rotor 14 continues to rotate, these passages 18 then connect the low pressure inlet 36 to the low pressure outlet 34. Fluid entering the low pressure inlet 36 fills these passages 18, pushing the fluid that was in these passages 18 out through the low pressure outlet 34. As the rotor 14 continues to rotate, the passages 18 are again sealed by the close fit between the outer circumferential surface 24 of the rotor and the inner surface of the sleeve 40. Finally, as the rotor 14 continues to rotate, having completed one revolution, the passages 18 in question again connect the high pressure inlet 32 to the high pressure outlet 38 and the above described process repeats itself indefinitely. This process occurs continuously for the many passages 18 in the rotor 14. Each passage 18 may be provided with a diaphragm or sliding seal to eliminate contact between the two fluids.
It will be understood by those skilled in the art that various methods may be used for fixing and sealing components of the housing 12 relative to other components of the housing 12 and lie within the scope of the present invention.
The pressure exchanger 10 may include thrust bearings (hydrodynamic or otherwise) to support the weight and/or hydrodynamic thrust of the rotor in axial directions.
If the fluid flow rates into the high pressure inlet 32 and the low pressure inlet 36 are equal (ignoring additional flow associated with leakage), the effect of the pressure exchanger 10 is that fluid flowing into the low pressure inlet 36 flows out the high pressure outlet 38 at increased pressure. Accordingly, there is an exchange of pressure from the high pressure fluid to the low pressure fluid.
With reference to FIGS. 2 and 3, the plurality of like passages 18 in the rotor 14 are distributed with equal radii and angular intervals about the axis 42 of rotation. As shown in FIG. 3, each passage 18 is offset from a radial direction of the rotor 14 such that the direction of entry and exit of the fluid (ie. a central line of the flow path) is spaced from the axis 42 of rotation of the rotor 14. In particular, as shown in FIGS. 4 and 5, each passage 18 is curved inward of the openings 20, 22 to induce a change in direction of the fluid entering and exiting the passage 18, and the net reaction force from the changes in direction acts on a line of action that is offset from (does not intersect and is not parallel to) the axis 42 to result in a torque driving rotation of the rotor 14. The net reaction force from the changes in direction of the fluid at the curved parts of the passage 18 inward of the openings 20, 22 acts in a plane approximately perpendicular to the axis 42 of rotation of the rotor 14. Accordingly, the change of momentum of the fluid entering and exiting the passages 18 in the rotor 14 will provide a force with a line of action that is offset from (does not intersect and is not parallel to) the axis 42 of rotation of the rotor 14, and the corresponding torque is used to drive rotation of the rotor 14. Drive of the rotor 14 may be supplemented or replaced by mechanical and/or electrical means.
The high pressure inlet 32 and low pressure inlet 36 may be configured such that rotation of the rotor 14 is driven (or assisted) by the direction of flow of fluid entering the passages 18, in addition to the torque resulting from the change in direction of fluid in the passages.
As shown in the exploded views in FIGS. 6 to 8, the high pressure inlet 32 is opposite the low pressure, outlet 34, and the low pressure inlet 36 is opposite the high pressure outlet 38. The passages 18 may be arranged in opposite pairs (or alternatively an odd number of passages may be useful in reducing any resonance and/or noise and/or vibration in or produced by the device) whereby one side of the rotor 14 transfers high pressure as the opposite side of the rotor 14 transfers low pressure, the high pressure side of the pressure exchanger 10 biasing the rotor 14 relative to the housing 12 toward the low pressure side of the pressure exchanger so as to assist in sealing of the openings 20, 22 at the low pressure side. The unbalanced pressure forces due to radial entry and exit of the fluid flow to and from the rotor 14 will provide positive sealing pressure and may increase the efficiency of operation of the pressure exchanger 10. An additional benefit of the positive sealing pressure is the possibility that clearances between rotating and stationary parts of the pressure exchanger 10 may be able to be increased without significant reduction or loss of efficiency. This may enable manufacturing tolerances to be relaxed and the possibility of the pressure exchanger 10 being able to accommodate the presence of relatively large particles in the fluid streams. Further, the configuration of the ports 16 at opposite sides directed radially provides the opportunity for greater separation between high pressure and low pressure ports when compared with existing pressure exchangers, with the potential to decrease leakage losses and increase efficiency due to the longer path for leakage between the ports 16.
In one form the unbalanced pressure forces are resisted by hydrodynamic pressure forces in the close fit between the outer surface of the rotor 14 and the inner surface of the sleeve 40 which effectively acts as a hydrodynamic journal bearing.
Although the passage openings 20, 22 are shown in the drawings as being oriented in a direction perpendicular to the axis 42 of rotation of the rotor 14, it will be understood by those skilled in the art that the passage openings 20, 22 may be directed at other angles having a radial component while still falling within the scope of the present invention.
It will also be understood by those skilled in the art that integer multiples of the number of ports described in the preferred embodiments lie within the scope of the present invention and may be used to balance or mitigate unbalanced pressure forces.
Advantageously, examples of the present invention may provide a torque sufficient to drive the rotor 14 using only fluid forces, and may obviate the need for any mechanically or electrically powered rotation of the rotor 14.
It is foreseen that examples of a pressure exchanger in accordance with the present invention may be suitable for use in Dissolved Air Flotation, (and other lower water pressure applications), as well as in higher pressure applications such as seawater reverse osmosis desalination and brackish water reverse osmosis desalination.
FIG. 9 shows a diagrammatic sketch of an alternative housing design in which the inlets and outlets are incorporated into the body of the housing (the housing ring 30) with the end caps 26, 28 being in the form of simple end plates closing each end of the housing. Aside from the changes to the configuration of the housing, the pressure exchanger is similar to the one shown in FIGS. 1 to 8, and like reference numerals are used to indicate like features. In particular, the differences lie in that the ports 16 a and 16 b are formed in the housing ring 30 (rather than in the end caps 26, 28), and in that the end caps 26, 28 are threaded so as to be screwed into corresponding threads formed at either end of the housing ring 30.
Although the end caps 26, 28 (plates) shown in the alternative housing design have a screwed fit within the body of the housing (the housing ring 30), it will be understood that other means may be used for fastening the end caps 26, 28 to the housing ring 30. For example, in alternatives, this could be achieved with a ‘ring’ of bolts (as is the case with a blank flange), or many other possible means of maintaining the required fit.
With reference to FIG. 10, there is shown an alternative inlet/outlet arrangement which is designed to match more closely the direction of flow into and out of the rotor 14. In particular, the port shown on the left-hand side corresponding to the inlet is configured generally tangential to the rotor, whereas the port 16 shown in the right-hand side is configured generally similar to the ports 16 shown in FIGS. 1 to 8.
While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not by way of limitation. It will be apparent to a person skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the present invention should not be limited by any of the above described exemplary embodiments.
Throughout this specification and the claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.
The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge, in the field of endeavour to which this specification relates.

Claims

1. A pressure exchanger for transferring pressure from a high pressure fluid to a low pressure fluid, including a housing and a rotor arranged for rotation within the housing, the rotor having at least one passage extending generally axially through the rotor, the passage having a first opening at one end and a second opening at another end, the openings being mutually spaced along the length of the rotor, the housing having a plurality of ports at one axial portion for communication with the first passage opening and a plurality of ports at another axial portion for communication with the second passage opening, wherein the first passage opening is directed substantially radially such that fluid is directed radially inwardly when entering the first passage opening and radially outwardly when exiting the first passage opening.

2. The pressure exchanger as claimed in claim 1, wherein the second passage opening is directed substantially radially such that fluid is directed radially inwardly when entering the second passage opening and radially outwardly when exiting the second passage opening.

3. A pressure exchanger for transferring pressure from a high pressure fluid to a low pressure fluid, including a housing and a rotor arranged for rotation within the housing, the rotor having at least one passage extending generally axially through the rotor, the passage having a first opening at one end and a second opening at another end, the openings being mutually spaced along the length of the rotor, the housing having a first inlet and a first outlet located axially to correspond with the first passage opening, and a second inlet and second outlet located axially to correspond with the second passage opening, such that in one rotational position of the rotor the passage communicates with the first inlet and the second outlet, in another rotational position of the rotor the passage communicates with the second inlet and the first outlet, wherein the first passage opening is directed substantially radially such that in said one rotational position fluid is directed radially inwardly from the first inlet to the first passage opening, and in said other rotational position fluid is directed radially outwardly from the first passage opening to the first outlet.

4. The pressure exchanger as claimed in claim 3, wherein the second passage opening is directed substantially radially such that in said one rotational position fluid is directed radially outwardly from the second passage opening to the second outlet, and in said other rotational position fluid is directed radially inwardly from the second inlet to the second passage opening.

5. The pressure exchanger as claimed in claim 1, wherein the rotor has a plurality of like passages distributed radially about the axis of rotation.

6. The pressure exchanger as claimed in claim 5, wherein the passages are distributed at equal radii and angular intervals about the axis of rotation.

7. The pressure exchanger as claimed in claim 1, wherein the passage is offset from a radial direction of the rotor such that the direction of entry and exit of the fluid (ie. a central line of the flow path) is spaced from the axis of rotation of the rotor.

8. The pressure exchanger as claimed in claim 1, wherein the passage is curved inward of the openings to induce a change in direction of the fluid entering and exiting the passage, and the net reaction force from the changes in direction acts with a line of action that is offset from (does not intersect and is not parallel to) the axis to result in a torque driving rotation of the rotor.

9. The pressure exchanger as claimed in claim 8, wherein the net reaction force acts in a plane perpendicular to the axis of rotation of the rotor.

10. The pressure exchanger as claimed in claim 1, wherein the inlets are arranged such that rotation of the rotor is driven or at least assisted by the direction of flow of fluid entering the passage.

11. The pressure exchanger as claimed in claim 1, wherein the first inlet is opposite the first outlet, the second inlet is opposite the second outlet, and the passages are arranged whereby one side of the rotor transfers high pressure as the opposite side of the rotor transfers low pressure.

12. The pressure exchanger as claimed in claim 11, wherein the high pressure side biases the rotor relative to the housing toward the low pressure side so as to assist in sealing of the openings at the low pressure side.

13. The pressure exchanger as claimed in claim 1, wherein the housing is made of a plurality of separate parts.

14. The pressure exchanger as claimed in claim 13, wherein the housing includes two end caps, one end cap having the first inlet and first outlet, the other end cap having the second inlet and second outlet.

15. The pressure exchanger as claimed in claim 13, wherein the housing includes two end caps fastened to each end of a central housing body, and wherein the first inlet, first outlet, second inlet and second outlet are formed in said central housing body.

16. The pressure exchanger as claimed in claim 1, wherein the first passage opening is oriented in a direction perpendicular to the axis of rotation of the rotor.

17. The pressure exchanger as claimed in claim 1, wherein the second passage opening is oriented in a direction perpendicular to the axis of rotation of the rotor.

18. The pressure exchanger as claimed in claim 1, wherein the first inlet and/or the second inlet is/are configured generally tangential to the rotor.

19. (canceled)