LIQUID BLADE PUMP

Abstract

A pump for pumping a gas, the pump comprising: a rotor and a stator; the rotor comprising at least one liquid opening configured for fluid communication with a liquid source. The liquid opening is configured such that in response to a driving force a stream of liquid is output from the opening, the stream of liquid forming a liquid blade between the rotor and the stator, gas confined by the stator, the rotor and the liquid blade being driven through the pump along a pumping channel from a gas inlet towards a gas outlet in response to relative rotational motion of the rotor and the stator. A cross sectional area of the pumping channel is configured to increase from the gas inlet to the gas outlet.

Claims

1. A pump for pumping a gas, said pump comprising: a rotor and a stator; at least 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 a cross sectional area of said pumping channel is configured to increase from said gas inlet to said gas outlet.

2. The pump according to claim 1, wherein a distance between said rotor and said stator increases from said gas inlet to said gas outlet.

3. The pump according to claim 1, wherein said pump is configured such that during operation a quantity of liquid output through said liquid opening increases from said gas inlet to said gas outlet.

4. The pump according to claim 3, wherein a cross section of said liquid opening is greater towards said gas outlet than towards said gas inlet.

5. The pump according to claim 1, wherein said liquid opening forms a slit.

6. The pump according to claim 5, wherein said slit extends longitudinally parallel to an axis of rotation of said rotor.

7. The pump according to claim 5, wherein said slit is arranged in the form of a helix extending around an axis of rotation of said rotor.

8. The pump according to claim 7, wherein an angle of said helix changes from said gas inlet towards said gas outlet such that a pitch of said helix increases towards said gas outlet.

9. The pump according to claim 1, wherein one of said rotor and stator comprises a helical protrusion extending towards the other element and defining a helical path of said pumping channel, the other element comprising said liquid opening.

10. The pump according to claim 9, wherein a pitch of said helical protrusion increases from said gas inlet to said has outlet.

11. A 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.

12. The pump according to claim 11, said pump further comprising sealing means between said side walls and said rotor or stator comprising said liquid opening.

13. The pump according to claim 11, 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

14. The pump according to claim 1, wherein a cross sectional area of said pumping channel is defined by a radial length being a distance between said rotor and said stator and an axial width being a dimension of said pumping channel perpendicular to said radial length, said axial width increasing from said gas inlet to said gas outlet.

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

16. The pump according to claim 1, wherein a cross sectional area of said pumping channel is defined by a radial length, said radial length being a distance between said rotor and said stator and an axial width, said axial width being a dimension of said pumping channel perpendicular to said radial length, said pump being configured such that said axial width of said pumping channel decreases with increasing radial distance from said liquid opening.

17. The pump according to claim 1, wherein said pump is configured such that said increase in cross sectional area from said gas inlet to said gas outlet is selected based on an amount of liquid supplied to said pump to form said liquid blade in normal operation, 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.

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

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Embodiments of the present invention will now be described further, with reference to the accompanying drawings, in which:

[0052] FIG. 1 shows a pump with a helical pumping channel according to an embodiment;

[0053] FIG. 2 shows an alternative embodiment of the helical path pump;

[0054] FIG. 3 shows a liquid blade rotary vane type pump according to an embodiment;

[0055] FIG. 4 shows an overview of the path through the pump of FIG. 3; and

[0056] FIG. 5 shows further views of the pump of FIG. 3.

DETAILED DESCRIPTION

[0057] Before discussing the embodiments in any more detail, first an overview will be provided.

[0058] Embodiments of the pump generate rotating sheets of water to separate the pumped gas into discrete volumes and to drive these volumes from an inlet to an outlet. During the passage from inlet to outlet an increasing volume of water is introduced into the mechanism until at the outlet both the water and the gas exit at the exhaust. One of the technical challenges is to maintain sufficient free volume for gas movement through the mechanism. This can be addressed by increasing the cross sectional area of the channel through which the gas is being moved. One approach to address this whilst reducing power consumption is to increase the cross sectional area as a function of distance from the inlet, which in some embodiments is dependent on rotation angle.

[0059] Embodiments of the pump comprise a hollow cylindrical rotor that carries water up from the sump and out through vertical slits to generating rotating sheets of water. These sheets of water separate the pumped gas into discrete volumes and drive these from the inlet to the outlet. In one embodiment these discrete volumes are generated within a screw thread and the gas is driven down a helical channel. In another embodiment these discrete volumes are simply defined by an upper and lower sealing edge and driven radially from the inlet to the outlet in a mechanism analogous to a rotary vane pump. In yet another embodiment, the liquid openings themselves form a screw thread, providing a helical liquid blade for pumping gas from an inlet to an outlet.

[0060] In all of these embodiments, from the inlet to the outlet an increasing volume of liquid, generally water is introduced into the mechanism until at the outlet both the water and the gas exit at the exhaust. One of the technical challenges therefore is to maintain sufficient free volume for gas movement through the mechanism. This can be achieved by increasing the cross-sectional area of the channel through which the gas is being moved by either increasing the height of the channel and/or by increasing the radial distance between the rotor and the stator wall.

[0061] However, simply increasing the cross-sectional area uniformly can be inefficient with regards to energy consumption and provides only limited control over the change in sealed gas volume. In some embodiments, the amount that the cross sectional area increases is set to be dependent upon the amount of liquid added and any desired compression. The liquid blades are continuously replenished and the liquid forming the blades will accumulate in the pumping channel reducing the volume available for the pumped gas. This is predictable and the design can estimate the change in volume due to accumulating liquid, and the desired compression and design the increase in cross sectional area accordingly.

[0062] In one embodiment an energy efficient approach is to increase the cross-sectional area as a function of distance along the pumping channel from the inlet to the outlet, in some embodiments this equates to rotation angle. This allows power consumption to be improved whilst providing the required volumetric compression of the gas. Some example embodiments are shown in the following section.

[0063] FIG. 1 shows the pump having a helical screw stator form where the increase in cross-sectional area of the pumping channel is provided by an increase in radial distance between the stator 20 and rotor 10 from the inlet 52 to the outlet 54. Having a stator form that is tapered as in this embodiment provides the increased cross-sectional area, however there is an increased distance between the rotor and stator and in order to compensate for this the exit velocity of the liquid, in this embodiment water or the thickness of the water sheet must be increased. In this embodiment the thickness of the water sheet is increased by providing an increased width of slit 12 through which water exits towards the outlet 54 side of the pump. This is more energy efficient than an increase in the exit velocity of the water. However, there is still a power consumption penalty associated with the increased water forming the water blade.

[0064] In other embodiments the rotor may be tapered as well as the stator and the increase in rotor diameter towards the outlet leads to an increase in exit velocity of the water exiting the slit 12. The angle of rotor taper may be less than that of the stator taper, leading to an increased distance between them and a corresponding increase in cross-sectional area towards the outlet. Increasing the diameter of the rotor is an energy efficient way of providing the desired increase in exit velocity of the water towards the outlet.

[0065] FIG. 2 shows a second and in some cases preferred embodiment where the radial distance between rotor 10 and stator 20 is constant. The increase in cross-sectional area of the pumping channel is provided by a change in pitch from the inlet 52 to the outlet 54. This allows slit 12 to have a constant width and provides a correspondingly constant width water blade. This may be more energy efficient than the embodiment of FIG. 1.

[0066] Although the embodiments of FIG. 1 and FIG. 2 show a straight water blade, they are also applicable to a helical water blade that can be formed with a helical slit. This can be used with a corresponding helical screw on the stator or indeed with a stator not having a profile. Again the pitch of the slit forming the water blade may vary to provide the increased cross-sectional area of the pumping channel and/or the distance between the rotor 10 and stator 20 may vary to provide this increase in cross-sectional area.

[0067] FIG. 3 shows an alternative embodiment which is analogous to a rotary vane pump. In this embodiment, rotor 10 is mounted within stator 20 and comprises slit 12 through which liquid exits in operation to form the liquid blade. Pumping channel 38 is formed by the walls of stator 20 and on rotation of rotor 10 gas is driven by the blade from inlet 52 to outlet 54. Inlet 52 has a cross-sectional area which is smaller than outlet 54 to accommodate a reduction in volume that will occur due to the liquid from the liquid blade accumulating within the channel as the water blade rotates. The floor of the pumping channel at the inlet is higher than the floor of the pumping channel at the outlet 54 such that during operation any liquid accumulating within the pumping channel will drain and exit with the gas at outlet 54. As can be seen the cross-sectional area 38 of the pumping channel increases from the inlet 52 to outlet 54.

[0068] FIG. 4 shows an overview of the path through the pumping channel from the inlet to the outlet. As can be seen the path follows an almost circular route such that the rotational movement drives the gas in an efficient manner. There is a slight vertical aspect to the circular path due to the requirement for drainage but this is small making this an efficient way of pumping gas. The helical arrangement has a greater vertical component imparted to the gas and this is not in the direction of rotation, and thus, of the blade, so will not be provide as efficient pumping.

[0069] FIG. 5 shows the pump of FIGS. 3 and 4 sideways on. Pumping channel 38 is formed in the stator 20 or of the pump. The rotor 10 is rotatably mounted within the stator 20 and comprises one or more slits 12 that form a liquid blade to push gas along pumping channel 38. The cross sectional area of pumping channel 30 increases from the inlet to the outlet and the lower surface or floor of the pumping channel is in a slightly lower position at the outlet compared to the inlet. Furthermore, sealing members 32 are provided to seal between the stator and the rotor. In this regard, the lengths of slit 12 is longer than the length of the channel for at least some of the circumference of the stator closer to the inlet and thus, to inhibit liquid expelled by slit 12 leaking out of the pump, seals 32 are provided at either edges of the pumping channel.

[0070] 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.

[0071] 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.

[0072] 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.