WO2009124339A1

WO2009124339A1 - Fluid pump

Info

Publication number: WO2009124339A1
Application number: PCT/AU2009/000421
Authority: WO
Inventors: Terence Robert Day
Original assignee: New Fluid Technology Pty Ltd
Priority date: 2008-04-11
Filing date: 2009-04-07
Publication date: 2009-10-15
Also published as: EP2294321A4; EP2294321A1; CN102037248B; CN102037248A

Abstract

An apparatus for pumping or compressing a fluid, the apparatus comprising: a housing having a front wall, a rear wall and one or more side walls interconnecting the front and rear walls to define a fluid rotation chamber; at least one inlet located substantially centrally in the front wall; an impeller located at least partially within the at least one inlet such that at least a portion of the impeller extends outwardly beyond at least a portion of the front wall; and at least one outlet, wherein rotation of the impeller causes fluid entering the apparatus through the at least one inlet to rotate within the fluid rotation chamber prior to exiting the apparatus through the at least one outlet.

Description

New Fluid Pump

Field of the Invention.

The present invention relates to a pump. In particular, the present invention relates to a fluid pump, especially a fluid pump that utilizes the principle of solid-body rotation.

Background Art.

Pumps are commonly used for a wide variety of different applications. Common conventional varieties of pump include positive displacement pumps (such as those comprising a reciprocating piston in a cylinder) and non-positive displacement pumps (such as those comprising centrifugal impellers which fling fluid into a diffusing passageway).

Conventional centrifugal fluid pumps employ a rotating impeller that draws in fluid (for instance, water or air) before ejecting the fluid at high speed from the tips of the impeller blades into one or more diffusing passageways. The purpose of the diffusing passageways is to reduce the high kinetic energy imparted to the fluid by the impeller.

This is achieved through providing the diffusing passageways with a progressively increasing cross sectional area that causes the fluid to decelerate in a controlled manner. As fluid speed decreases, an increase in static pressure takes place.

This increase in static pressure is required in many pump applications in order to overcome downstream resistance to the flow of fluid caused by fluid drag against pump walls, surfaces, bends, cross-sectional area changes or introduced elements such as filters.

These conventional pumps suffer from a number of significant disadvantages. Firstly, the impeller flings fluid (such as water) off the tips of the blades into the diffusing passageways but not does force it into the diffusing passageways. This means that the diffuser inlets must be placed close to the blade tips so that the fluid velocity is as high as practical as the fluid enters the passageways. This arrangement results in wake collisions which generate a significant amount of noise. Another disadvantage of conventional pumps is that, due to a large number of cross- sectional area changes through the passageways within the impeller, casing and pump body, the velocity of the fluid changes repeatedly as the fluid moves through the pump. These velocity changes generally result in a decrease in fluid momentum, meaning that additional power input is required to compensate for the loss in fluid momentum, resulting in a reduction in the efficiency of the pump.

A further disadvantage of conventional pumps is the significant cost of manufacturing the one or more diffusing passageways that are integral to conventional centrifugal pumps.

Thus, there would be an advantage if it were possible to provide a fluid pump that reduced or eliminated at least some of the inefficient design features of conventional centrifugal fluid pumps, thereby providing a pump having improved efficiency and reduced noise.

It will be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country.

Throughout this specification, the term "comprising" and its grammatical equivalents shall be taken to have an inclusive meaning unless the context of use indicates otherwise.

Object of the Invention.

It is an object of the present invention to provide a fluid pump which may overcome at least some of the abovementioned disadvantages, or provide a useful or commercial choice.

In a first aspect, the invention resides broadly in an apparatus for pumping or compressing a fluid, the apparatus comprising: a housing having a front wall, a rear wall and one or more side walls interconnecting the front and rear walls to define a fluid rotation chamber; at least one inlet; an impeller located at least partially within the at least one inlet such that at least a portion of the impeller extends outwardly beyond at least a portion of the housing; and at least one outlet, wherein rotation of the impeller causes fluid entering the apparatus through the at least one inlet to rotate within the fluid rotation chamber prior to exiting the apparatus through the at least one outlet.

The housing of the apparatus may be a unitary housing, a two-part housing or a multiple part housing in which the parts are attached together. Typically, the housing comprises a two-part housing consisting of an upper part and a lower part which are fastened together typically via separate fasteners such as screws, bolts and the like. Each housing part may be of any suitable size, shape or configuration. In some embodiments of the invention, a first housing part may contain the at least one inlet while a second housing part may contain the at least one outlet. Alternatively, each housing part may contain both the at least one inlet and the at least one outlet.

The front and rear walls of the housing may be of any suitable size, shape or configuration. However, in a preferred embodiment of the invention, the front and rear walls of the housing are substantially the same size and shape as one another. In some embodiments of the invention, the front and rear walls of the housing are substantially circular in plan view. Thus, in this embodiment of the invention, the housing is substantially cylindrical.

The one or more inlets may be located at any suitable point on the housing. For instance, the one or more inlets may be located in the side wall or the front wall of the housing. The one or more inlets may be located such that fluid enters the apparatus tangentially to the side wall of the apparatus.

Alternatively, the one or more inlets may be located substantially centrally in the front wall of the apparatus. In this embodiment of the invention, the impeller may be located such that at least a portion of the impeller extends outwardly beyond at least a portion of the housing.

In another embodiment of the invention, the apparatus may comprise one or more tangential inlets and one or more substantially centrally located inlets.

As previously mentioned, the front wall of the housing includes one or more inlets located substantially centrally therein. In some embodiments of the invention, the one or more inlets may be associated with one or more inlet passageways, such that fluid entering the apparatus passes through the one or more inlet passageways prior to entering the apparatus through the one or more inlets.

The one or more inlet passageways may be of any suitable size, shape or configuration. In some embodiments of the invention, the one or more inlet passageways may be adapted to connect to the front wall of the housing. Alternatively, in some embodiments of the invention, the front wall of the housing may consist of a raised portion at or adjacent the one or more inlets that projects outwardly from the surface of the front wall. In these embodiments of the invention, the raised portion may be adapted for connection to the one or more inlet passageways.

In some embodiments, the one or more inlet passageways may be formed integrally with the housing. In other embodiments of the invention, the one or more inlet passageways may be formed separately from the housing and may be adapted for temporary or permanent engagement therewith, using any suitable technique.

The impeller may be of any suitable form. However, in a preferred embodiment of the present invention, the impeller is provided with one or more blades and, more preferably, a plurality of blades. In a most preferred embodiment of the invention, the impeller is provided with a plurality of curved blades. It has surprisingly been found that by providing the impeller with a plurality of curved blades, the efficiency of the apparatus may be improved. As has been stated previously, the impeller may be located at least partially within the at least one inlet such that at least a portion of the impeller extends outwardly beyond at least a portion of the front wall. In embodiments of the invention in which the one or more inlets are provided with a raised portion, the impeller may be located at least partly within the raised portion. Alternatively, the impeller may be located at least partly within the inlet passageway, if one is present.

As previously mentioned, the walls of the housing serve to define a fluid rotation chamber. In some embodiments of the invention, fluid is introduced into the apparatus through the one or more inlets, is ejected from the impeller into the fluid rotation chamber. In a preferred embodiment of the invention, the rotation of fluid within the fluid rotation chamber is in the form of solid-body rotation, in which the rotating fluid acts as a solid body rather than a fluid. Preferably, the impeller and the body of rotating fluid in the fluid rotation chamber are substantially co-axial with one another.

There are a number of benefits to achieving solid-body rotation of the fluid. Firstly, the rotating fluid effectively stores momentum, and considerable force is required to slow or arrest the rotation of the fluid. Secondly, as the fluid is rotating as a solid body, substantially no shear forces exist within the body of fluid, meaning that there is substantially no turbulence in the fluid. This lack of turbulence assists in maintaining the efficiency of the apparatus.

The one or more outlets may be of any suitable size, shape or configuration. In a preferred embodiment of the present invention, the one or more outlets may be located tangentially to the direction of rotation of fluid within the fluid rotation chamber. Preferably, the one or more outlets are located in the side walls of the housing. More preferably, the one or more outlets are located at a point in the side walls remote from the one or more inlets in order to reduce the degree of turbulence in the fluid. In a most preferred embodiment of the invention, the apparatus comprises one outlet.

As the fluid rotates in the fluid rotation chamber, the pressure of the fluid is at its greatest adjacent the inner surface of the housing. Thus, by locating the outlet tangentially in a side wall of the housing, the rotating fluid exiting the apparatus through the outlet has the highest pressure required to overcome downstream resistance.

The outlet may be in fluid communication with an outlet passageway (such as a pipe or conduit). While the passageway outlet may be of any suitable shape or configuration, in a preferred embodiment of the invention the outlet passageway is substantially square or rectangular in cross-section along at least a portion of its length. In some embodiments of the invention, the outlet passageway may be substantially square or rectangular in cross-section along the entirety of its length.

In a second aspect, the invention resides broadly in an apparatus for pumping or compressing a fluid, the apparatus comprising: a housing having a front wall, a rear wall and one or more side walls interconnecting the front and rear walls to define a fluid rotation chamber; at least one inlet; rotation means adapted to impart rotation to fluid entering the apparatus; and at least one outlet, wherein rotation of the rotation means causes fluid entering the apparatus through the at least one inlet to rotate within the fluid rotation chamber prior to exiting the apparatus through the at least one outlet.

The rotation means may be of any suitable form provided that the rotation means imparts sufficient rotation to the fluid entering the apparatus. For instance, the rotation means may comprise one or more impellers, one or more magnetic (or magnetizable) rotating members within the housing actuable by exerting a magnetic or electromagnetic attraction or repulsion from outside the housing, one or more water jets directed tangentially within the housing, or the like, or any combination thereof.

Alternatively, the one or more inlets may be located substantially centrally in the front wall of the apparatus.

In a third aspect, the invention resides broadly in an apparatus for pumping or compressing a fluid, the apparatus comprising: a housing having a front wall, a rear wall and one or more side walls interconnecting the front and rear walls to define a fluid rotation chamber; at least one inlet; an impeller located at least partially within the at least one inlet; and at least one outlet, wherein rotation of the impeller causes fluid entering the apparatus through the at least one inlet to rotate within the fluid rotation chamber prior to exiting the apparatus through the at least one outlet, and wherein the angle at which the front and rear walls join the one or more side walls is a tightly-radiused curve.

As mentioned above, the angle at which the front and rear walls join the one or more side walls is a tightly-radiused curve. In a preferred embodiment of the invention, the radius of the tightly-radiused curve is less than 10mm. More preferably, the radius of the tighly-radiused curve is less than 5mm. Still more preferably, the radius of the tightly-radiused curve is between lmm and 2mm. The radius of the tightly-radiused curve between the front wall and the side wall may be the same or different to that between the rear wall and the side wall. In a preferred embodiment of the invention, however, the radius of the tightly-radiused curve between the front wall and the side wall may be substantially identical to that between the rear wall and the side wall.

By providing these tightly-radiused curves at the points at which the front and rear walls join the side walls, a fluid rotation chamber having an almost square or rectangular cross-sectional shape may be achieved. It has surprisingly been found that providing a fluid rotation chamber having this substantially cylindrical geometry results in improvements to the efficiency of the apparatus.

In a fourth aspect of the invention, the invention resides broadly in an apparatus for pumping or compressing a fluid, the apparatus comprising: a housing having a front wall, a rear wall and one or more side walls interconnecting the front and rear walls to define a fluid rotation chamber; at least one inlet; an impeller located at least partially within the at least one inlet; and at least one outlet, wherein rotation of the impeller causes fluid entering the apparatus through the at least one inlet to rotate within the fluid rotation chamber prior to exiting the apparatus through the at least one outlet, and wherein the angle at which the front and rear walls join the one or more side walls is substantially a right angle.

Alternatively, the one or more inlets may be located substantially centrally in the front wall of the apparatus. In this embodiment of the invention, the impeller may be located such that at least a poition of the impeller extends outwardly beyond at least a portion of the housing

In this embodiment of the invention, it is preferred that the cross-sectional shape of the fluid rotation chamber is substantially square or rectangular. It has surprisingly been found that providing a fluid rotation chamber having this geometry results in improvements to the efficiency of the apparatus.

In some embodiments of the invention (and equally applicable to all aspects of the present invention), the apparatus may be provided with one or more outlet tubes. The one or more outlet tubes may be of any suitable size, shape or configuration. In a preferred embodiment of the invention, a first end of the one or more outlet tubes may extend at least partially into the fluid rotation chamber. The second end of the one or more outlet tubes may extend to the one or more outlets. Alternatively, the second end of the one or more outlet tubes may extend beyond the one or more outlets, such as, for instance, at least partially into the one or more outlet pipes.

The cross-sectional area of the one or more outlet tubes may be of any suitable type. In some embodiments of the invention, the cross-sectional area of the one or more outlet tubes varies across the length of the outlet tubes, while in other embodiments of the invention, the cross-sectional area of the one or more outlet tubes is substantially constant over the length of the one or more outlet tubes. In embodiments of the invention in which a plurality of outlet tubes are present, all of the plurality of outlet tubes may have cross-sectional areas that are substantially constant over the length of the outlet tubes, or all of the outlet tubes may have cross-sectional areas that vary across the length of the outlet tubes, or the outlet tubes may be a combination of the two.

Preferably, the one or more outlet tubes are sized so that the amount of fluid leaving the fluid rotation chamber through the one or more outlet tubes is not so great that the remaining fluid in the fluid rotation chamber can no longer rotate under the principle of solid-body rotation. In some embodiments of the present invention, the one or more outlet tubes have a foil-like cross-sectional shape.

In embodiments of the invention in which a plurality of outlets are present, each outlet may be provided with one or more outlet tubes.

In some embodiments of the invention, the one or more outlet tubes may be the one or more outlets.

By locating the first end of the one or more outlet tubes within the fluid rotation chamber, it can be ensured that fluid rotating at a higher velocity within the chamber than the fluid rotating close to the wall of the housing will be discharged through the one or more outlets. In some embodiments of the invention, the fluid that flows through the one or more outlets is a combination of the higher velocity fluid that discharges through the outlet through the one or more outlet tubes, and the lower velocity fluid rotating close to the wall of the housing. In this embodiment of the invention, the average velocity of the fluid exiting the apparatus through the one or more outlets may be increased through the addition of higher velocity fluid exiting the outlet through the one or more outlet tubes.

In some embodiments of the invention (and equally applicable to all aspects of the present invention), the impeller may have a discharge portion from which the fluid is discharged into the fluid rotation chamber. While the discharge portion of the impeller may be located at any suitable point, in a preferred embodiment of the invention, the discharge portion of the impeller may be located within the fluid rotation chamber. The discharge portion of the impeller may be located at any suitable point within the fluid rotation chamber, such that fluid may be discharged into substantially any point of the fluid rotation chamber.

The present invention provides a number of advantages over the prior art. Firstly, the simplicity of the design of the present invention ensures low manufacturing costs. In addition, the present invention has significantly lower operational costs associated with it.

Further, by eliminating the need to provide one or more diffusing passageways, the present invention produces significantly less noise than prior art devices. This was not previously thought possible, as conventional understanding is that, without diffusing passageways, the pressure development in a pump is inadequate and the pump would operate at sub-optimal efficiency.

Brief Description of the Drawings. An embodiment of the invention will be described with reference to the following drawings in which: Figure 1 illustrates a plan view of an apparatus according to an embodiment of the present invention;

Figure 2 illustrates a plan cross-sectional view of an apparatus according to an embodiment of the present invention;

Figure 3 illustrates a side view of an apparatus according to an embodiment of the present invention;

Figure 4 illustrates a side cross-sectional view of an apparatus according to an embodiment of the present invention; Figure 5 illustrates a perspective view of an apparatus according to an embodiment of the present invention; Figure 6 illustrates a plan cross-sectional view of an apparatus according to an embodiment of the present invention; and Figure 7 illustrates a view of an outlet tube according to an embodiment of the present invention.

Detailed Description of the Drawings.

It will be appreciated that the drawings have been provided for the purposes of illustrating preferred embodiments of the present invention and that the invention should not be considered to be limited solely to the features as shown in the drawings.

In Figure 1 there is illustrated a plan view of an apparatus 10 according to an embodiment of the present invention. The apparatus 10 comprises a housing having circular front wall 11 with an inlet 12 located centrally therein. An impeller 13 comprising a plurality of curved blades 14 is located within the inlet 12.

The apparatus 10 further comprises an outlet pipe 15 located tangentially to the circular front wall 11, the outlet pipe 15 being rectangular along a portion of its length.

Figure 2 illustrates a cross-sectional view of the apparatus 10 in which the upper part of the housing (including the front wall) has been removed. It may be seen in this Figure that the rear wall 16 of the housing comprising an aperture 17 through which the drive shaft (not shown) for the impeller (not shown) extends.

It may be seen in this Figure that a fluid rotation chamber 18 is defined inside the apparatus 10 by the rear wall 16, the side walls 19 and the front wall (not shown). When in use, fluid rotates inside the fluid rotation chamber 18 according to the principles of solid-body rotation, such that the fluid with the greatest momentum (i.e. that rotating within the chamber 18 adjacent the side wall 19 is ejected from the apparatus 10 through the outlet 20. Fluid exiting the apparatus 10 through the outlet 20 then travels through the outlet pipe 15.

In Figure 3, a side view of the apparatus 10 is illustrated. In this Figure it is shown that the front wall 11 comprises a raised portion 21 that surrounds the inlet (obscured) and extends outwardly from the front wall 11.

In this Figure, an inlet passageway 22 is also shown. The inlet passageway 22 is in fluid communication with the inlet (obscured). In this embodiment of the invention, the inlet passageway 22 is formed integrally with the front wall 11 of the apparatus 10. In Figure 4 a cross-sectional side view of the apparatus 10 is shown. In this Figure it may be seen that the impeller 13 is located in the inlet 12 in such a manner that a portion of the impeller 13 extends outwardly beyond at least a portion of the front wall 11 of the housing. In this way, fluid entering the apparatus 10 through the inlet 12 immediately has rotation imparted to it by the impeller 13 prior to entering the fluid rotation chamber 18.

The corner 23 at which the front wall 11 joins the side wall 19 and the corner 24 at which the rear wall 16 joins the side wall 19 are provided with tightly-radiused curves. In the embodiment of the invention illustrated in Figure 4, the radius of the tightly- radiused curves is approximately 1.5mm.

The radius of the tightly-radiused curves is maintained as low as possible in order to provide the fluid rotation chamber 18 with a suitable geometry for encouraging solid- body rotation of the fluid therein. It has surprisingly been found that providing the fluid rotation chamber 18 with such tightly-radiused curves at the corners where the front 11 and rear 16 walls join the side walls 19 increases the efficiency with which the apparatus 10 operates by promoting solid-body rotation of the fluid.

In some embodiments of the invention, the corners 23, 24 may be at substantially 90° angles. While this would provide a geometry that would improve the efficiency of the pump, it is also possible that this would lead to the accumulation of mechanical stresses at the corners 23, 24. Thus, providing a tightly-radiused curve at the corners 23, 24 may overcome the accumulation of mechanical stresses without any significant loss of pump efficiency.

It may be further seen in Figure 4 that impeller 13 has a discharge portion 29 from which fluid is discharged into the fluid rotation chamber 18. The discharge portion 29 of the impeller 13 is located entirely within the fluid rotation chamber 18 and, in the embodiment of the invention shown in Figure 4, is adapted to discharge fluid into the fluid rotation chamber in a direction substantially parallel to the front wall 11.

In Figure 5, a perspective view of the apparatus 10 according to an embodiment of the present invention is shown. In this Figure, the raised portion 21 of the front wall 11 surrounding the inlet 12 may be clearly seen. Further, the tangential location in the side wall 19 of the outlet (obscured) and the outlet pipe 15 may be seen.

It may also be seen more clearly in this Figure that the front wall 11, side wall 19 and rear wall (obscured) serve to define an essentially cylindrical housing for the apparatus 10.

In Figure 6 there is shown an apparatus 10 according to an alternative embodiment of the present invention. In this Figure, the apparatus 10 is provided with an outlet tube 25. The outlet tube 25 has a first end 26 which extends into the fluid rotation chamber 18 to capture higher velocity fluid which passes through the outlet tube 25 and exits the apparatus 10 through the outlet pipe 15.

In the embodiment of the invention shown in Figure 6, the outlet tube 25 has a second end 27 which extends beyond the outlet 20 and into the outlet pipe 15. The location of the outlet tube 25 creates a passageway 28 between the outlet tube 25 and the side wall 19 of the housing through which lower velocity fluid rotating close to the side wall 19 can exit through the outlet 20. In this way the fluid exiting the apparatus 10 through the outlet pipe 15 is combination of higher and lower velocity fluid. Thus, the presence of the outlet tube 25 serve to increase the average velocity (and therefore momentum) of the fluid leaving the apparatus 10.

In Figure 7, a detailed view of an outlet tube 25 is shown, in which it may be seen that the outlet tube 25 is foil-like in shape.

Those skilled in the art will appreciate that the present invention may be susceptible to variations and modifications other than those specifically described. It will be understood that the present invention encompasses all such variations and modifications that fall within its spirit and scope.

Claims

Claims.

1. An apparatus for pumping or compressing a fluid, the apparatus comprising: a housing having a front wall, a rear wall and one or more side walls interconnecting the front and rear walls to define a fluid rotation chamber; at least one inlet; an impeller located at least partially within the at least one inlet such that at least a portion of the impeller extends outwardly beyond at least a portion of the housing; and at least one outlet, wherein rotation of the impeller causes fluid entering the apparatus through the at least one inlet to rotate within the fluid rotation chamber prior to exiting the apparatus through the at least one outlet.

2. An apparatus according to claim 1 wherein the housing is substantially cylindrical.

3. An apparatus according to claim 1 or claim 2 wherein the at least one inlet is located substantially centrally in the front wall.

4. An apparatus according to any one of the preceding claims wherein the front wall comprises a raised portion at or adjacent the at least one inlet that projects outwardly from a surface of the front wall.

5. An apparatus according to claim 4 wherein the impeller is located at least partially within the raised portion.

6. An apparatus according to any one of the preceding claims wherein the at least one outlet is located tangentially to the direction of rotation of fluid within the fluid rotation chamber.

7. An apparatus according to any one of the preceding claims wherein the at least one outlet is located at a point in the housing remote from the at least one inlet.

8. An apparatus according to any one of the preceding claims wherein the at least one outlet is in fluid communication with an outlet passageway, the outlet passageway being substantially square or rectangular in cross-section along at least a portion of its length.

9. An apparatus according to any one of the preceding claims wherein the impeller comprises a discharge portion located within the fluid rotation chamber.

10. An apparatus for pumping or compressing a fluid, the apparatus comprising: a housing having a front wall, a rear wall and one or more side walls interconnecting the front and rear walls to define a fluid rotation chamber; at least one inlet; rotation means adapted to impart rotation to fluid entering the apparatus; and at least one outlet, wherein rotation of the rotation means causes fluid entering the apparatus through the at least one inlet to rotate within the fluid rotation chamber prior to exiting the apparatus through the at least one outlet.

11. An apparatus according to claim 10 wherein the rotation means comprises one or more impellers, magnetic or magnetizable members, water jets, or any combination thereof.

12. An apparatus according to claim 10 or claim 11 wherein the at least one inlet is located substantially centrally in the front wall.

13. An apparatus for pumping or compressing a fluid, the apparatus comprising: a housing having a front wall, a rear wall and one or more side walls interconnecting the front and rear walls to define a fluid rotation chamber; at least one inlet; an impeller located at least partially within the at least one inlet; and at least one outlet, wherein rotation of the impeller causes fluid entering the apparatus through the at least one inlet to rotate within the fluid rotation chamber prior to exiting the apparatus through the at least one outlet, and wherein the angle at which the front and rear walls join the one or more side walls is a tightly-radiused curve.

14. An apparatus according to claim 13 wherein the tightly-radiused curve has a radius of less than 10mm.

15. An apparatus according to claim 13 or claim 14 wherein the tightly-radiused curve has a radius of less than 5mm.

16. An apparatus according to any one of claims 13 to 15 wherein the tightly- radiused curve has a radius of between lmm and 2mm.

17. An apparatus according to any one of claims 13 to 16 wherein the radius of the tightly-radiused curve between the front wall and the one or more side walls is substantially identical to the radius of the tightly-radiused curve between the rear wall and the one or more side walls.

18. An apparatus according to any one of claims 13 to 17 wherein the at least one inlet is located substantially centrally in the front wall.

19. An apparatus for pumping or compressing a fluid, the apparatus comprising: a housing having a front wall, a rear wall and one or more side walls interconnecting the front and rear walls to define a fluid rotation chamber; at least one inlet; an impeller located at least partially within the at least one inlet; and at least one outlet, wherein rotation of the impeller causes fluid entering the apparatus through the at least one inlet to rotate within the fluid rotation chamber prior to exiting the apparatus through the at least one outlet, and wherein the angle at which the front and rear walls join the one or more side walls is substantially a right angle.

20. An apparatus according to claim 19 wherein the cross-sectional shape of the fluid rotation chamber is square or rectangular.

21. An apparatus according to claim 19 or claim 20 wherein the at least one inlet is located substantially centrally in the front wall.

22. An apparatus according to any one of the preceding claims wherein the apparatus further comprises one or more outlet tubes having a first end located within the fluid rotation chamber and a second end located at or beyond the at least one outlet.

23. An apparatus according to claim 22 wherein each of the at least one outlets is provided with one or more outlet tubes.