GB2568277A

GB2568277A - Improved pump

Info

Publication number: GB2568277A
Application number: GB1718608.1A
Authority: GB
Inventors: Martin Allport John
Original assignee: Longcroft Engineering Ltd
Current assignee: Longcroft Engineering Ltd
Priority date: 2017-11-10
Filing date: 2017-11-10
Publication date: 2019-05-15
Also published as: GB201718608D0

Abstract

A pump 10 is fluidly connected to a liquid piston Stirling engine 12, having fluidly connectable first 20 and second 22 columns to contain a working liquid to a variable liquid level. The second column 22 comprises first and second legs 26, 28 that partly delimit a sealed volume 36 containing a working fluid. Fluid pressure in a pump chamber 14 is variable in response to a variation of the variable liquid level. The pump chamber 14 has a weir 54 over which a liquid to be pumped is spillable by the variation of the fluid pressure to inhibit backflow, through the pump chamber, of the liquid to be pumped. The pump may be useable for pumping water in an irrigation system. The pump outlet 52 may comprise a U-bend fillable with liquid to fluidly seal the pump chamber 14.

Description

(57) A pump 10 is fluidly connected to a liquid piston Stirling engine 12, having fluidly connectable first 20 and second 22 columns to contain a working liquid to a variable liquid level. The second column 22 comprises first and second legs 26, 28 that partly delimit a sealed volume 36 containing a working fluid. Fluid pressure in a pump chamber 14 is variable in response to a variation of the variable liquid level. The pump chamber 14 has a weir 54 over which a liquid to be pumped is spillable by the variation of the fluid pressure to inhibit backflow, through the pump chamber, of the liquid to be pumped. The pump may be useable for pumping water in an irrigation system. The pump outlet 52 may comprise a U-bend fillable with liquid to fluidly seal the pump chamber 14.

1/1

Figure 1

Improved pump

TECHNICAL FIELD

The invention relates to a fluid pump particularly, though not exclusively, for the purpose of pumping water in an irrigation system.

BACKGROUND

There is a desire to develop simple, low-cost fluid pumps that enable irrigation of cropland. Such pumps may particularly benefit farmers in regions where conventional irrigation systems are prohibitively expensive to implement and/or maintain, e.g. subSaharan Africa. Known arrangements include pumps based on a liquid piston Stirling engine. As the skilled reader will appreciate, the liquid piston Stirling engine is a heat engine operable by cyclic compression and expansion of a working fluid at varying temperatures to convert thermal energy into mechanical work. Liquid piston Stirling engines differ from conventional Stirling engines in that mechanical pistons are replaced with liquid filled columns. However, known fluid pumps based on the liquid piston Stirling engine typically require fluidic valves to enable pumping, e.g. one-way valves may be inserted into an output column of a liquid piston Stirling engine to convert motion of a liquid contained in the output column into a pumping action. Known arrangements may also exhibit undesirably low pumping rates and/or low increases in total head. The aforementioned problems are understood to be restricting the potential use of such pumps.

Embodiments of the invention may at least mitigate one or more problems associated with known arrangements.

SUMMARY OF THE INVENTION

According to the invention, there is provided a pump comprising: a liquid piston Stirling engine having fluidly connectable first and second columns to contain a working liquid to a variable liquid level, the second column comprising first and second legs at least in part delimiting a variable volume to contain a working fluid; and a pump chamber fluidly connectable to the liquid piston Stirling engine such that a fluid pressure within the pump chamber is variable in response to a variation of the variable liquid level, the pump chamber comprising a weir over which a liquid to be pumped is spillable by the variation of the fluid pressure to inhibit back-flow, through the pump chamber, of the liquid to be pumped. The pump may move the liquid to be pumped in the absence mechanical fluidic valves, e.g. one way valves. In certain embodiments, the pump chamber may be fluidly connectable to the first column and the variable liquid level may be a liquid level of the first column. The first column may be an output column of the liquid piston Stirling engine.

Optionally, the second column may comprise one or more first portions to allow, or at least facilitate, transfer of heat energy out of the variable volume. Either one or each of the first and second legs may comprise at least one of the one or more first portions of the second column. Additionally, or alternatively, the second column may comprise one or more second portions to allow, or at least facilitate, transfer of heat energy into the variable volume. Either one or each of the first and second legs may comprise at least one of the one or more second portions of the second column.

The one or more first portions of the second column may be submergible in a coolant e.g. a liquid coolant to allow, or at least facilitate, transfer of heat energy out of the variable volume. In certain embodiments, the second column may be at least partially submerged in the coolant such that the one or more first portions of the second column are substantially submerged in the coolant, at least prior to operation of the pump. Additionally, or alternatively, the second column may be at least partially submerged in the coolant such that the one or more second portions of the second column are substantially non-submerged in the coolant, at least prior to operation of the pump. The coolant may comprise the liquid to be pumped.

Optionally, the pump may comprise a heat collector to allow, or at least facilitate, transfer of heat energy from a heat source into the variable volume. The heat collector may comprise a solar collector and/or a heat exchanger. The heat collector may in part delimit the variable volume, i.e. the heat collector may be fluidly connectable to the second column. In certain embodiments, the pump may comprise a riser fluidly connectable to the pump chamber to fluidly connect the pump chamber to a quantity of the liquid to be pumped. The riser may extend into the pump chamber to at least in part provide the weir. The riser may be tapered or bell-mouthed. In certain embodiments, the pump chamber has a pump outlet comprising a U-bend, which, in use, may fluidly seal the pump chamber. The first and second legs may be different in length to one another. A junction between the first and second columns may be closer to a liquid level, e.g. an initial liquid level, of the one of the first and second legs than a liquid level of the other of the first and second legs.

In certain embodiments, a third column may be fluidly connectable in series to the second column, the third column having features as described above in relation to the second column. According to a further aspect of the invention, there is provided a pump assembly having two or more pumps as described above, wherein the respective pumping chambers are fluidly connectable to one another in series.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURE

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying figure, Figure 1, which shows a schematic of a pump according to an embodiment of the invention.

DETAILED DESCRIPTION

A pump 10 comprises an engine 12, a pump chamber 14 and a riser 16. The engine 12 is a liquid piston Stirling engine, which the skilled reader will understand to be a heat engine that utilises motion of a liquid to convert thermal energy into mechanical work. The pump 10 has particular application in an irrigation system. However, other applications are contemplated, e.g. moving waste water or other liquids. The engine 12 has a heat collector 18, an output (“first”) column 20 and a displacer (“second”) column 22. As shown in Figure 1, the displacer column 22 may be a generally Ushaped vessel or tube. The displacer column 22 has a first leg 26 and a second leg

28. The first and second legs 26, 28 may be substantially parallel to one another. As shown in the illustrated embodiment, the first and second legs 26, 28 may be of equal length. However, in certain embodiments, the first leg 26 may be longer than the second leg 28, or vice versa, as this may facilitate starting and/or continued operation of the engine 12. The output column 20 and the displacer column 22 are fluidly connectable to one another. As such, the output column 20 and the displacer column 22 are configured to contain a volume of a working liquid 40 that is moveable, i.e. flowable, between the output column 20 and the displacer column 22. The working liquid 40 may be water, although any suitable liquid may be used, e.g. engine oil. In use, the working liquid 40 fills the output column 20 and the displacer column 22 to respective liquid levels 30, 32, 34. In the illustrated embodiment, a first liquid level 30 may be provided in the output column 20, a second liquid level 32 may be provided in the first leg 26 and a third liquid 34 level may be provided in the second leg 28. A junction 24 is necessarily formed between the output column 20 and the displacer column 22, such that the working liquid 40 is moveable therebetween. The junction 24 may be provided closer to liquid level 30 of the first leg 26 than to the liquid level 32 of the second leg 28, as this may facilitate starting and/or continued operation of the engine 12.

Each of the liquid levels 30, 32, 34 may be variable, i.e. changeable between respective maximum and minimum values. As the skilled reader will appreciate, each of the liquid levels 30, 32, 34 may be variable by gravity and/or a fluid pressure, e.g. a gas pressure acting on the working liquid 40. In use, the liquid levels 30, 32, 34 correspond to respective liquid surfaces of the working liquid 40 contained in the output column 20 and the displacer column 22. As such, the liquid levels 30, 32, 34 may be determined in the absence of the working liquid 40, e.g. for design purposes.

The displacer column 22 in part delimits a variable volume 36. More specifically, upper portions of the first and second legs 26, 28 may in part delimit the variable volume 36. The heat collector 18 may also in part delimit the variable volume 36. Thus, the heat collector 18 may be fluidly connected to the displacer column 22. The variable volume 36 is further delimited by the respective liquid levels 32, 34 of the first and second legs 26,28. In other words, in use, the variable volume 36 is in part delimited by the working liquid 40 contained in the first and second legs 26, 28. The variable volume 36 is variable by movement of the liquid levels 32, 34 of the displacer column 22. In certain embodiments, the variable volume 36 may be fluidly isolated from the heat collector

18. To this end, the variable volume 36 may extend between the first leg 26 and the second leg 28 by way of a duct (not shown) extending through and/or adjacent the heat collector 18. The variable volume 36 is configured to contain a first working fluid 42, e.g. air. However, the first working fluid 42 may comprise and/or contain any suitable fluid. The variable volume 36 may be fluidly sealable from atmosphere, at least in use, to contain the first working fluid 42. The variable volume 36 may be fluidly, e.g. gaseously, sealable by the working liquid 40, i.e. the working liquid 40 may prevent the first working fluid 42 from escaping from the variable volume 36. The variable volume 36 may provide one or more hot spaces configured to heat the first working fluid 42. To this end, the heat collector 18 may be configured to allow, or at least facilitate, transfer of heat energy from a heat source, e.g. solar radiation from the Sun or waste heat from an industrial process, into the variable volume 36 to heat the first working fluid 42. As such, the heat collector 18 may provide the one or more hot spaces in which, in use, the working fluid 42 may be heated. The heat collector 18 may comprise or be provided by a solar collector of any suitable type, e.g. tube and plate, parabolic focused or simple volume solar collector. In certain embodiments, the heat collector 18 may comprise or be provided by a heat exchanger.

The variable volume 36 may provide one or more cold spaces configured to cool the first working fluid 42. To this end, a portion of the displacer column 22 may be configured to allow, or at least facilitate, transfer of heat energy out of the variable volume 36 to cool the first working fluid 42. More specifically, a portion of the displacer column 22 may be configured to allow, or at least facilitate, transfer of heat energy out of the variable volume 36 and into a coolant 70 external to the displacer column 22. As such, the displacer column 22 may provide the one or more cold spaces in which, in use, the working fluid 42 may be cooled. To this end, a portion of the displacer column 22 may be submersible in the coolant 70, e.g. water. The coolant 70 may provide a heat sink to receive heat energy from the engine 12. In certain embodiments, respective lower portions of either or both of the first and second legs 26, 28 may provide the one or more cold spaces. To this end, in certain embodiments, a portion of the first leg 26 may be submersible in the coolant 70. Additionally, or alternatively, a portion of the second leg 28 may be submersible in the coolant 70.

The pump chamber 14 is configured to move, i.e. pump, a useful liquid (“liquid to be pumped”) 44. To this end, the pump chamber 14 has a pump inlet 50 to receive the useful liquid 44 into the pump chamber 14 and a pump outlet 52 to discharge the useful liquid 44 from the pump chamber 14. In certain embodiments, the useful liquid 44 may drain from the pump chamber 14 via the pump outlet 52 under gravity. Each of the pump inlet and outlet 50, 52 may be provided in a bottom or a side of the pump chamber 14. In certain embodiments, the pump inlet 50 may be provided in a top of the pump chamber 14. As shown in the illustrated embodiment, the riser 16 may extend from the pump chamber 14. In use, the useful liquid 44 is moved through the pump chamber 14 from the pump inlet 50 to the pump outlet 52. In certain embodiments, the riser 16 may be fluidly connectable to the pump inlet 50 or may provide the pump inlet 50. In use, the riser 16 fluidly connects the pump chamber 14 to a quantity of the useful liquid 44 at a first total head. As shown in the illustrated embodiment, the riser 16 may be a generally straight pipe or duct. However, the riser 16 may be any suitable shape and/or may comprise one or more elbows and/or bends. The riser 16 has an inlet end 56 and outlet end 58, through which the useful liquid 44 may flow into and out of the riser 16 during operation of the engine 12, respectively. In use, the inlet end 56 is at least partially immersed in a quantity of the useful liquid 44 at the first total head. In certain embodiments, the riser 16 may be absent. In such embodiments, the pump chamber 14 may be at least partially immersed in the useful liquid 44, such that the pump inlet 50 is submerged. As shown in the accompanying figure, the riser 16 may have a uniform cross sectional area along its length. However, in certain embodiments, the riser 16 may be tapered or bell-mouthed, as such nonuniform configurations may increase the efficiency of the pump 10.

The pump chamber 14 comprises a weir 54. The riser 16 may extend into the pump chamber 14 to provide the weir 54. However, in certain embodiments, the weir 54 may be alternatively provided. The weir 54 may be a wall or barrier extending from an inner surface of the pump chamber 14 and/or the weir 54 may extend across the pump chamber 14. In use, the useful liquid 44 is spillable over the weir to inhibit back-flow,

i.e. movement of the useful liquid 44 through the pump chamber 14 from the pump outlet 52 to the pump inlet 50.

The engine 12 is fluidly connected to the pump chamber 14. In the illustrated embodiment, the output column 20 is fluidly connected to the pump chamber 14 above the liquid level 30 of the output column 22. A duct 38 may fluidly connect the output column 20 to the pump chamber 14. Fluid connection of the engine 12 to the pump chamber 14 is such that, in use, movement of the working liquid 40 may vary a fluid pressure, e.g. a gas pressure, within the pump chamber 14 and/or generate a partial vacuum within the pump chamber 14. As such, the pump chamber 14 may be fluidly sealable from atmosphere, at least in use, to contain a second working fluid 46. The pump chamber 14 may be fluidly, e.g. gaseously, sealable by the useful liquid 44, i.e. the useful liquid 44 may prevent the second working fluid 46 from escaping from the pump chamber 14. To this end, the pump outlet 52 may comprise a U-bend (not shown).

In use, the output and displacer columns 20, 22 contain a quantity of the working liquid 40 and the variable volume 36 contains a quantity of the first working fluid 42. With the engine 12 in a state of equilibrium, i.e. prior to operation of the engine 12, the liquid levels 30, 32, 34 of the output column 20 and the displacer column 22 may by substantially equal, as shown in Figure 1. Heat energy is transferred into the first working fluid 42 by the heat collector 18 such that, as a temperature of the first working fluid 42 rises, a fluid pressure of the first working fluid 42 rises, due to expansion of the first working fluid 42. Consequently, the fluid pressure of the first working fluid 42 will act on the working liquid 40, to lower the liquid levels 32, 34 of the first and second legs 26, 28, which, in turn, will raise the liquid level 30 in the output column 20. However, the respective liquid levels 32, 34 of the first and second legs 26, 28 may be lowered by different amounts, due to imbalances in the engine 12. The skilled reader will appreciate that the engine 12 will likely be inherently unbalanced, e.g. due to tolerances. Though, in certain embodiments, the engine 12 may be unbalanced by design, e.g. the first leg 26 may be longer than the second leg 28.

With the liquid levels 32, 34 in the first and second legs 26, 28 lowered by different amounts, each of the liquid levels 32, 34 in the first and second legs 26, 28 will begin to oscillate, i.e. rise and fall cyclically, as the working liquid 40 moves back and forth between the first and second legs 26, 28. This is caused by gravity acting on the working liquid 40 to return the liquid levels 30, 32, 34 to a state of equilibrium. As the working liquid 40 oscillates a quantity of the first working fluid 42 to be cyclically displaced from the respective legs 26, 28, thus moving at least a quantity of the first working fluid 42 between the one or more hot spaces and the one or more cold spaces. The temperature of the first working fluid 42 will oscillate as the working fluid 42 moves between the one or more hot spaces and the one or more cold spaces. Thus, the temperature variations in the first working fluid 42 cause a cyclic variation of the fluid pressure of the first working fluid 42. Consequently, the first working fluid 42 may act cyclically on the working liquid 40 in the displacer column 22 to lower and raise the liquid levels 32, 34 of the first and second legs 26, 28. Specifically, the first working fluid 42 may act cyclically on working liquid 40 in the displacer column 22 to lower and raise the liquid levels 32, 34 of the first and second legs 26, 28. Movement of the working liquid 40 may continue so long as the heat energy transferred into the first working fluid 42 is greater than losses experienced by the engine 12. The cyclic variation of the liquid levels 32, 34 in the first and second legs 26, 28 causes corresponding cyclic variation of the liquid level 30 in the output column 20. Thus, heat energy transferred to the heat collector 18 may be converted into work in the form of the oscillating motion of the working liquid 42 in the output column 20.

The oscillating motion of the working liquid 40 in the output column 20 causes an oscillation, i.e. variation, of the fluid pressure within the pump chamber 14. In other words, the oscillating motion of the working liquid 40 in the output column 20 causes an oscillation of a fluid pressure of the second working fluid 46. Consequently, the useful liquid 44 may be drawn though/from the pump inlet 50 to spill over the weir 54, such that the useful liquid 44 can no longer flow back through the pump chamber 14,

i.e. out of the pump inlet 50. The pump chamber 14 and/or the riser 16 may contain a volume of the useful liquid 44 prior to operation of the pump 10, to contain the second working fluid 46 in the pump chamber 14, i.e. to fluidly/gaseously seal the pump chamber 14. In certain embodiments, upon discharge from the pump chamber 14, the useful liquid 44 may be at a second total head, the second total head being greater than the first total head.

Figure 1 shows, the displacer column 22 at least partially submerged in the coolant 70. In use, the displacer column 22 may be submerged in the coolant 70 such that a surface 72 of the coolant 70 is substantially equal to the liquid levels 30, 32, 34 of the output column 20 and the displacer column 22 when the engine 12 is in a state of equilibrium. Thus, the portions of the displacer column 22 configured to allow, or at least facilitate, transfer of heat energy out of the variable volume 36 and into to coolant 70 may be submerged portions of the displacer column 22. As the liquid levels 32, 34 in the displacer column 22 fall, a quantity of the working fluid 42 may fill the submerged portions to transfer heat energy out of the variable volume 36 and into to coolant 70. In certain embodiments, substantially all of the variable volume 36 that extends below the surface 72 of the coolant 70 may provide the one or more cold spaces. Substantially all of the variable volume 36 that extends above the surface 72 of the coolant 70 may provide the one or more hot spaces. In certain embodiments, the useful liquid 44 and the coolant 70 may be one and the same. Thus, in use, the displacer column 22 may be at least partially submerged in the useful liquid 44.

Certain embodiments may comprise multiple displacer columns 22 connected to one another in series. Such embodiments may allow for higher operating pressures and higher pumping rates. Additionally, or alternately, multiple pumps 10, each having one or more of the features described above may be connected to one another in series or in parallel. Such embodiments may allow for higher pumping rates and/or increased total head, when compared to a single pump 10. Certain embodiments may be constructed from simple and/or low-cost components, i.e. components that are widely available, e.g. oil drums, plastic containers/tanks, hose pipe, steel pipe. Certain embodiments may enable the pumping of liquid while having no moving parts, i.e. mechanical valves, other than fluids.

The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including the accompanying claims and drawings) or to any novel one, or any novel combination, of the steps of any method or process so disclosed. The claims should not be construed to cover merely the foregoing embodiments, but also any embodiments which fall within the scope of the claims.

All of the features disclosed in this specification (including the accompanying claims and drawings) and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including the accompanying claims and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

Claims

1. A pump comprising:

a liquid piston Stirling engine having fluidly connectable first and second columns to contain a working liquid to a variable liquid level, the second column comprising first and second legs at least in part delimiting a variable volume to contain a working fluid; and a pump chamber fluidly connectable to the liquid piston Stirling engine such that a fluid pressure within the pump chamber is variable in response to a variation of the variable liquid level, the pump chamber comprising a weir over which a liquid to be pumped is spillable by the variation of the fluid pressure to inhibit back-flow, through the pump chamber, of the liquid to be pumped.

2. A pump according to claim 1, wherein the pump chamber is fluidly connectable to the first column and the variable liquid level is a liquid level of the first column.

3. A pump according to claim 1 or 2, wherein the first column is an output column of the liquid piston Stirling engine.

4. A pump according to any preceding claim, wherein the second column comprises one or more first portions to allow, or at least facilitate, transfer of heat energy out of the variable volume.

5. A pump according to claim 4, wherein either one or each of the first and second legs comprise at least one of the one or more first portions of the second column.

6. A pump according to any preceding claim, wherein the second column comprises one or more second portions to allow, or at least facilitate, transfer of heat energy into the variable volume.

7. A pump according to claim 6, wherein either one or each of the first and second legs comprise at least one of the one or more second portions of the second column.

8. A pump according to any of claims 4 to 7, wherein the one or more first portions of the second column are submergible in a coolant to allow, or at least facilitate, transfer of heat energy out of the variable volume.

9. A pump according to claim 8, wherein the second column is at least partially submerged in the coolant such that the one or more first portions of the second column are substantially submerged in the coolant.

10. A pump according to claim 8 or 9, wherein the second column is at least partially submerged in the coolant such that the one or more second portions of the second column are substantially non-submerged in the coolant.

11. A pump according to any of claims 8 to 10, wherein the coolant comprises the liquid to be pumped.

12. A pump according to any preceding claim, wherein the pump comprises a heat collector to allow, or at least facilitate, transfer of heat energy from a heat source into the variable volume.

13. A pump according to claim 12, wherein the heat collector comprises a solar collector and/or a heat exchanger.

14. A pump according to claim 12 or 13, wherein the heat collector in part delimits the variable volume.

15. A pump according to any preceding claim, wherein the pump comprises a riser fluidly connectable to the pump chamber to fluidly connect the pump chamber to a quantity of the liquid to be pumped.

16. A pump according to claim 15, wherein the riser extends into the pump chamber to at least in part provide the weir.

17. A pump according to claim 15 or 16, wherein the riser is tapered or bellmouthed.

18. A pump according to any preceding claim, wherein the pump chamber has a pump outlet comprising a U-bend tillable with a liquid to fluidly seal the pump chamber.

19. A pump according to any preceding claim, wherein the first and second legs 5 are different in length to one another.

20. A pump according to any preceding claim, wherein a junction between the first and second columns is closer to a liquid level of one of the first and second legs than a liquid level of the other of the first and second legs.

21. A pump according to any preceding claim, wherein a third column is fluidly connectable in series to the second column, the third column having features of the second column according to any preceding claim.

15 22. A pump assembly having two or more pumps according to any preceding claim, wherein the respective pumping chambers are fluidly connectable to one another in series or in parallel.

Amendments to the claims have been filed as follows:

03 07 18

1. A pump comprising:

a liquid piston Stirling engine having fluidly connectable first and second columns to contain a working liquid to a variable liquid level, the second column 5 comprising first and second legs in part delimiting a variable volume to contain a working fluid; and a pump chamber fluidly connectable to the liquid piston Stirling engine such that a fluid pressure within the pump chamber is variable in response to a variation of the variable liquid level, the pump chamber comprising a weir over which a liquid to be 10 pumped is spillable by the variation of the fluid pressure to inhibit back-flow, through the pump chamber, of the liquid to be pumped.

2. A pump according to claim 1, wherein the pump chamber is fluidly connectable to the first column and the variable liquid level is a liquid level of the first

15 column.

20 4. A pump according to any preceding claim, wherein the second column comprises one or more first portions to allow, or at least facilitate, transfer of heat energy out of the variable volume.

5. A pump according to claim 4, wherein either one or each of the first and 25 second legs comprise at least one of the one or more first portions of the second column.

6. A pump according to any preceding claim, wherein the second column comprises one or more second portions to allow, or at least facilitate, transfer of heat

30 energy into the variable volume.

03 07 18

5 9. A pump according to claim 8, wherein the second column is at least partially submerged in the coolant such that the one or more first portions of the second column are substantially submerged in the coolant.

10. A pump according to claim 8 or 9, wherein the second column is at least 10 partially submerged in the coolant such that the one or more second portions of the second column are substantially non-submerged in the coolant.