LIQUID BLADE PUMP

Abstract

A pump includes: a rotor and a stator; the rotor having at least one liquid opening configured for fluid communication with a liquid source. The liquid opening is configured such that a stream of liquid is output to form a liquid blade between the rotor and the stator, and gas confined by the stator, the rotor and the liquid blade is driven through the pump . The pump is configured such that a pumping channel has side walls that slope towards each other from the rotor that comprises the liquid opening towards a further wall of the pumping channel remote from the rotor, such that a distance between the side walls decreases with increasing distance from the liquid opening, a tangent to a midpoint of the side walls having an angle of between 5° and 40° with respect to a line perpendicular to an axis of rotation of the rotor.

Claims

1. A pump for pumping a gas, said pump comprising: a rotor and a stator; one of said rotor or stator comprising at least one liquid opening configured for fluid communication with a liquid source; said liquid opening being configured such that in response to a driving force a stream of liquid is output from said opening, said stream of liquid forming a liquid blade between said rotor and said stator, gas confined by said stator, said rotor and said liquid blade being driven through said pump along a pumping channel from a gas inlet towards a gas outlet in response to relative rotational motion of said rotor and said stator; wherein said pump is configured such that said pumping channel comprises side walls that slope towards each other from said rotor or stator that comprises said liquid opening towards a further wall of said pumping channel remote from said rotor or stator comprising said liquid opening, such that a distance between said side walls decreases with increasing distance from said liquid opening, a tangent to a mid point of said side walls having an angle of between 5° and 40° with respect to a line perpendicular to an axis of rotation of said rotor.

2. The pump according to claim 1, wherein said side walls are sloped such that said angle of a tangent to a mid point of said side wall with respect to a line perpendicular to an axis of rotation of said rotor, is between 8° and 25° preferably, between 10° and 15°.

3. The pump according to claim 1, said pump being configured such that said side walls of said pumping channel flare outwards towards a junction with said rotor or stator comprising said liquid opening.

4. The pump according to claim 1, said pump being configured such that a junction between each of said side walls and said further wall is curved.

5. The pump according to claim 1, said side walls being symmetrical about an axis perpendicular to a mid point of said further wall.

6. The pump according to claim 1, wherein said rotor comprises said liquid opening and is mounted to rotate within said stator.

7. The pump according to claim 1, wherein said liquid opening comprises at least one slit, extending longitudinally parallel to an axis of rotation of said rotor.

8. The pump according to claim 1, wherein said stator and rotor are configured such that said pumping channel runs around a circumference of an inner one of said rotor or stator, said gas inlet being arranged to be vertically higher than said gas outlet in operation.

9. The pump according to claim 8, wherein a lower surface of said pumping channel at said gas outlet is lower than a lower surface of said pumping channel at said gas inlet, and a higher surface of said pumping channel at said gas outlet is higher than a lower surface of said pumping channel at said gas inlet.

10. The pump according to claim 1, wherein a cross sectional area of said pumping channel is configured to increase from said gas inlet to said gas outlet.

11. The pump according to claim 10, wherein said pump is configured such that said increase in cross sectional area from said gas inlet to said gas outlet and an amount of liquid supplied to said pump to form said liquid blade in normal operation are selected such that a cross sectional area of said pumping channel available to gas decreases from said gas inlet to said gas outlet and said gas being pumped is compressed.

12. The pump according to claim 1, further comprising sealing means between said side walls and said rotor or stator comprising said liquid opening.

13. The pump according to claim 1, where said pump comprises a vacuum pump.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Embodiments of the present invention will now be described further, with reference to the accompanying drawings, in which:

[0045] FIG. 1 shows a liquid blade in a pump according to an embodiment;

[0046] FIG. 2 shows a pump according to an embodiment; and

[0047] FIG. 3 shows a cross-section through a pumping channel of a pump according to an embodiment.

DETAILED DESCRIPTION

[0048] Before discussing the embodiments in any more detail, first an overview will be provided.

[0049] Embodiments relate to a pump where the blade of the pump is formed by a liquid such as water that is expelled from one or more apertures in one of the rotor or stator to form a sheet of water that acts as a blade for pushing the fluid to be pumped through the pump. Relative rotation of the stator and rotor cause the fluid to be urged from an inlet to an outlet. When liquid is expelled from the apertures to form a sheet this tapers away from the apertures such that the sheet narrows. This can cause problems of fluid leakage around the edges of the sheet which acts as the blade. Embodiments address this by defining a similarly tapered shaped pumping channel such that the liquid blade adheres to the surface of the pumping channel walls and gaps are avoided or at least inhibited.

[0050] In some embodiments, discrete volumes of gas to be pumped are defined within a stator structure by an upper and lower sealing edge and vertical water sheets. These sealed volumes are then driven radially from the inlet to the outlet in a mechanism analogous to a rotary vane pump. One technical challenge is to maintain an effective gas seal between the water sheet and the sealing faces defined by the stator walls. In one embodiment the pump comprises a hollow cylindrical rotor that carries water up from a sump and out through vertical slits to generating rotating sheets of water. As the water exits the slit the top and bottom edges of the sheet taper inwards towards the centre of the sheet as it travels out from the rotor to stator outer wall. This is compensated for by appropriately sloping the upper and lower sealing edges of the pumping channel walls to match the tapering of the water sheet. In addition, where the sheet first impinges on the sealing edges, the leading edge, it is disturbed and deviates from its original path. This is addressed by introducing a suitable curvature to the slope at the leading edge (inner diameter). It was also observed that at the outer diameter at the corner between the outer stator wall and the sloping edge additional disturbance to the water sheet occurred. This is addressed by introducing a radius at this corner. This combination defines a unique, and novel, geometry for the stator channel .

[0051] FIG. 1 schematically shows the tapering of blade 40 formed of a sheet of liquid expelled through liquid opening 12, which in this embodiment has the form of a slit formed in rotor 10, the edges of the slit defining either edge of the blade 40. In this example, the tapering angle is shown as 20.sup.º It should be understood that this angle may vary depending on both the length and the width of the aperture and the force with which the liquid is expelled through the aperture along with the viscosity and surface tension of the liquid. The liquid is in this embodiment water.

[0052] FIG. 2 schematically shows a pump according to an embodiment. In this embodiment, rotor 10 is mounted to rotate within stator 20. Rotor 10 has a slit 12 through which water is expelled forming blade 40 such as is shown in FIG. 1. As the rotor 10 rotates with respect to stator 20 the blade pushes gas around through the pumping channel 38 within stator 20 from an inlet 52 to an outlet 54.

[0053] The base of inlet 52 is slightly higher than the base of outlet 54 which allows liquid from the liquid blade that collects within the pumping channel 38 during the pumping of the gas, to flow from inlet 52 to outlet 54 where it is exhausted.

[0054] In this embodiment, rotor 10 is a hollow cylinder and the centrifugal force caused by rotation of the rotor causes liquid to rise up from a sump and be expelled through liquid slit 12. In some embodiments, there may be a pump to send water towards and through the slit 12.

[0055] The cross-sectional area of inlet 52 is smaller than the cross-sectional area of outlet 54 in this embodiment and this increase in cross sectional area from inlet to outlet helps compensate for the decrease in available volume for any fluid or gas being pumped that occurs due to the accumulation of the liquid from the liquid blade within the pumping channel 38. The side walls of the pumping channel 38 are sloped such that the cross section of the pumping channel tapers in a corresponding way to the liquid blade of FIG. 1. This avoids or at least inhibits gaps being formed between the side walls and the liquid blade towards the outer edges of the pumping channel, further from the rotor, where the tapering is most pronounced.

[0056] FIG. 3 shows a cross-sectional view of pumping channel 38 where the form of this channel can be seen more clearly. In this embodiment, the side walls 34 are sloped at an angle of 25.sup.º when taken from a tangent at the midpoint 34b of the side walls. The side walls towards the rotor 34a have a more pronounced taper, such that they flare outwards in a curved manner and are further apart than they are towards the middle of the walls. The ends of the side walls 34c towards the further wall 36 are curved so that there are no sharp angles as the side walls curve round to form the further wall and disruptions in the flow are reduced. In this regard the side walls are those that extend substantially radially, while the further wall faces the rotor and runs substantially axially, parallel to the axis of rotation.

[0057] In operation as the liquid exits the slit 12, the top and bottom edges of the blade taper inwards towards the centre of the blade as it travels out from the rotor towards the further wall 36. This tapering is matched and compensated for by appropriately sloping the upper and lower side walls 34 of the stator that along with further wall 36 form the pumping channel 38. This tapering is designed to substantially match the tapering of the water sheet with slightly more taper to avoid or at least reduce any gaps.

[0058] Additionally, where the sheet or blade first impinges on the side walls 34a it is disturbed and deviates from its original path. This is addressed by introducing a suitable curvature to the slope of the side wall adjacent to the leading edge 34a such that the distance between the side walls 34 is greater at this junction between rotor 10 and stator 20 and has a curved shape. It has also been observed that at the end 34c of the side walls at the junction with the further wall 36 additional disturbance to the liquid sheet occurs. This can be reduced by introducing a radius at this corner such that there is curvature here. In this way, the geometry and cross-section of channel 38 is adapted to the properties of the liquid sheet and provides effective sealing for pumping gas.

[0059] As in this embodiment, the slit 12 is longer than the width of channel 38 closer to the inlet, as the channel has a smaller axial dimension here, sealing means 32 are provided between the stator and rotor on either side of the pumping channel, to avoid or at least inhibit liquid leakage from the pumping channel.

[0060] As can be seen from the cross section, the lower side wall slopes vertically downwards from the inlet to the outlet, such that liquid accumulating in the pumping channel 38 drains at the outlet.

[0061] Although illustrative embodiments of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is understood that the invention is not limited to the precise embodiment and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents.

[0062] Although elements have been shown or described as separate embodiments above, portions of each embodiment may be combined with all or part of other embodiments described above.

[0063] Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are described as example forms of implementing the claims.