WO2015099538A1

WO2015099538A1 - A multi-step gas compressor system

Info

Publication number: WO2015099538A1
Application number: PCT/NO2013/000052
Authority: WO
Inventors: John Brungot; Ronny JENSSEN; Tom RINGSTAD
Original assignee: Vivid AS
Current assignee: Vivid AS
Priority date: 2013-11-12
Filing date: 2013-11-12
Publication date: 2015-07-02
Anticipated expiration: 2016-05-12

Abstract

A multi-stage gas compressor apparatus in a two-stage version comprises a first, central cylinder, forming a cylindrical chamber (8), and a second cylinder arranged concentrically with the first, central cylinder, forming an annular chamber (9). A first, circular piston (12) is axially movable within the first, cylindrical chamber (8), and a second, annular piston (5) axially movable within the annular chamber (9). A force - exerting member (10) is connected to the first (12) and second (5) pistons. In the apparatus, a first one-way valve (2) is arranged to allow gas transfer from a gas inlet (2) to an end portion of the annular chamber (9). A second one-way valve (11) is arranged to allow gas transfer from the end portion of the annular chamber (9) to an end portion of the cylindrical chamber (8). A third one-way valve (3) is arranged to allow gas transfer from the end portion of the cylindrical chamber (8) to a gas outlet. The force - exerting member (10) may be attached to the sea bottom (15), and the apparatus (1) may be provided with a floating element (6) which causes the apparatus (1) to float on the sea surface (16) while the pistons (11, 5) are anchored to the sea bottom (15). The annular piston (5) may be forced to complete each stroke before the first cylinder (12) starts to move by means of an activating block on the central, anchored rod pulling the central piston (12).

Description

A mult i-step gas compres sor system

Field of the invention

The invention relates to compression of gas, such as air. In particular, the invention relates to a multi-stage gas compressor apparatus. The apparatus may particularly be used for providing pressurized air in an oceanic wave energy installation, but may also be applied in order to store temporary surplus energy from other sources . When the working force is identical in both directions, which is not the case for ocean wave applications based on point absorbers, a boxer version of the compressor may be an alternative. In this case the chambers act alternatingly as air suction and compression chambers. Background

US 1991-5052902 concerns a multi-stage piston compressor containing several cylinders with decreasing diameter connected end after end.

US 1937-2141057 concerns a multistage gas compressor intended to deliver a relatively steady flow of compressed gas. EP2005- 1598553 A2 concerns a two stage reciprocating compressor consisting of a low-pressure part and a two stage high-pressure compression part.

US 1913-1067770 concerns a two stage crank-driven piston compression pump.

US2003-6575712 B l concerns a stationary wave-driven air compressor intended for energy conversion and storage.

Summary

The invention has been set forth in the appended claims. Brief description of the drawings

Figure 1 is a schematic cross-sectional side view illustrating a first embodiment of a multi-stage gas compressor apparatus.

Figure 2 is a schematic cross-sectional top view illustrating a first embodiment of a multi-stage gas compressor apparatus.

Figure 3 is a schematic cross-sectional side view illustrating a second embodiment of a multi-stage gas compressor apparatus. Figure 4 is a schematic cross-sectional top view illustrating a second embodiment of a multi-stage gas compressor apparatus. Figure 5 is a schematic cross-sectional side view illustrating one potential use of the multi-stage gas compressor apparatus.

Figure 6 is a schematic cross-sectional side view illustrating an embodiment where the outer 1^st stage compressor will complete its stroke before the 2^nd inner compressor is engaged by means of an activating block.

Figure 7 is a schematic cross-sectional side view illustrating an embodiment of a boxer system where the compressor works equally in both directions, driven by an alternating outer force.

Figure 8 concerns a schematic cross-sectional side view illustrating an embodiment where the outer cylinder is attached to the driving rod by flexible cords or springs in order to allow the outer cylinder to halt before a full stroke, whereas the central cylinder completes the stroke.

Figure 9 concerns a schematic cross-sectional side view illustrating a three-step embodiment of the compressor system. Figure 10 concerns a schematic cross-sectional side view illustrating an

embodiment with an intermediate tank between the outer and the central cylinder in order to facilitate an easy transfer of gas.

Detailed description

Figure 1 is a schematic cross-sectional diagram illustrating a first, 2-stage embodiment of a general multi-stage gas compressor apparatus 1.

The apparatus 1 comprises a first, central cylinder which forms a cylindrical chamber 8. A second cylinder is arranged concentrically with the first, central cylinder, forming an annular chamber 9 between the second cylinder and the first cylinder. Additional cylinders may be arranged concentrically with the second, the third cylinder etc, forming additional annular chambers outside the second chamber. A 3-stage version is illustrated in Figure 9.

A first, circular piston 12 is arranged within the first, cylindrical chamber 8 in an axially movable fashion. Correspondingly, a second, annular piston 5 is arranged within the annular chamber 9 in an axially movable fashion. Additional pistons may be arranged within the additional annular chambers mentioned above,

A force-exerting member 10 is connected to the first, central piston 12 and the second, annular piston 5. Another arrangement is shown in Figure 8, where the outer force is firmly connected to the piston rod of the first piston 12, but flexibly connected to the outer piston 5 so that the pistons move independently of each other.

A first one-way valve 2 is arranged to allow gas transfer from a gas inlet to an end portion of the annular chamber 9. In the embodiment of figure 1, the end portion of the annular chamber 9 is the annular chamber's upper end, i.e., at the upper end of the apparatus 1.

Further, a second one-way valve 11 is arranged to allow gas transfer from the end portion of the annular chamber 9 to an end portion of the cylindrical chamber 8. In the embodiment of figure 1, the end portion of the cylindrical chamber 8 is the cylindrical chamber's upper end. Hence, in the embodiment of figure 1 the end portions of both the cylindrical chamber 8 and the annular chamber 9 are at the upper end of the apparatus 1.

In an aspect, the cylindrical chamber 8 is closed at its end portion, except for the third one-way valve 3. In the embodiment of figure 1, this means that the upper end of the cylindrical chamber 8 is closed, except for the third one-way valve 3.

In another aspect, the annular chamber 9 is closed at its end portion, except for the first one-way valve 2. In the embodiment of figure 1, this means that the upper end of the annular chamber 9 is closed, except for the first one-way valve 2. In an aspect, a number of spring elements are arranged between the second, annular piston 5 and an upper portion of the annular chamber 9. Figure 1 shows that two such spring elements 4a and 4b are arranged at opposite sides of the cylindrical chamber 8. However, as illustrated in figure 2, although not visible on figure 1, two additional spring elements 4d, 4e may advantageously, for balance, also be arranged between the second, annular piston 5 and the upper portion of the annular chamber 9. At least three spring elements should be arranged at 120 degrees between them and at equal distance from centre.

Further with reference to figure 1, a second spring element 4c may be arranged between the first circular piston 12 and the upper portion of the cylindrical chamber 8.

The spring rate of the outer assembly should be adjusted to the inner spring rate in order to optimize the total efficiency of the compressor unit.

In an aspect, the force-exerting member 10 may be connected to the first 12 and second pistons 5 by means of rigid rods, illustrated at 7a, 7b, 7c. The rod 7c interconnects the first, central piston 12 and the force -exerting member 10, while the rods 7a and 7b interconnects the second, annular piston 5 and the force-exerting member 10. For balance, two additional rods (not illustrated) may also be arranged, interconnecting the second, annular piston 5 and the force -exerting member 10. Other numbers, at least three, of rods are possible.

In another aspect, the said force-exerting member 10 may be connected to the first 12 and second 5 pistons by flexible links, which is illustrated in Figure 8. In this embodiment the driving rod of the central piston 12 and the rod assembly of the outer piston 5 move independently of each other, enabling the outer piston 5 to halt when the counter pressure from the compression chamber of the inner cylinder 8 has reached the maximum level of the outer piston capacity.

As can be seen from figure 1, an upper portion of the annular chamber 9 is arranged at substantially the same vertical level as an upper portion of the cylindrical chamber 8. In an aspect, as shown, the first, central piston 12 may be arranged with an axial displacement with respect to the second piston 5. In particular, the first, central piston 12 may be arranged at a higher level than the second, annular piston, i.e., closer to the level of the upper portion of the cylindrical chamber (which is also the level of the upper portion of the annular chamber) , or vice versa.

The area of the first, central piston is typically substantially less than the areas of the surrounding annular pistons. More specifically, the first, central piston 12 has a first piston area, which is selected in order to gain the intended final pressure, while the area of the second, annular piston 5 will increase the total efficiency of the compressor unit with increasing size. However, this size may not exceed the limits set by the designed buoyancy of the point absorber when applied on ocean waves - or the axial force set by another renewable energy source of whatever kind . The outer body of the compressor will be an integrated part of the buoyancy needed to carry the total weight of the installation included the enveloping floating body 6 and the mooring system below.

Further, in order to enable the outer cylinder to complete its stroke, feeding pre- compressed gas to the inner chamber, the area of its piston 5 should not exceed 3.5 times the area of the inner piston 12. This limitation of size will also limit the friction loss of the piston-to-chamber wall and minimize waste of material. Figure 2 is a schematic cross-sectional top view illustrating the first embodiment of the multi-stage gas compressor apparatus shown in figure 1. The drawn floating body 6 is obviously redundant for applications not related to the buoyancy of waves.

Figure 3 is a schematic cross-sectional diagram illustrating a second embodiment of a multi-stage gas compressor apparatus.

The apparatus 1 corresponds to the first embodiment of the apparatus 1 shown in figures 1 and 2 in most respects. However, in the second embodiment, the end portion of the annular chamber and the end portion of the cylindrical chamber are at a lower end of the apparatus 1. This embodiment enables compression strokes during wave uplift, which in general is an advantage.

Figure 4 is a schematic cross-sectional top view illustrating a second embodiment of the multi-stage gas compressor apparatus shown in figure 3. The gas ducts 13 and 12 inhale and exhale gas at normal and augmented pressure respectively.

Figure 5 is a schematic cross-sectional side view illustrating an exemplary use of the multi-stage gas compressor apparatus, the apparatus being integrated in a point absorber utilizing the wave vertical heave. The force-exerting member 10 is attached to a sea bottom 15 by means of pillars 14 or other mooring systems, which are securely fixed to the sea bottom either directly by a secure anchor or via a fundament. The apparatus is provided with a floating element 6. The floating element 6 may include an annular float, arranged outside the second cylinder which forms the annular chamber 9, causing the apparatus 1 to float on a sea surface 16. Of course, the floating element may be arranged different ways in order to provide buoyancy in such a way that the apparatus 1 floats on the sea surface 16. When the sea surface oscillates, typically due to oceanic waves, the apparatus 1 will move vertically with the waves, while the pistons 11, 5 are held in a fixed vertical position, since they are anchored to the sea bottom 15. In such and other applications and configurations, the gas outlet of the apparatus 1 may be connected to a pressure tank or pressure accumulator 17, resulting in that gas contained in the pressure tank or accumulator will be compressed by the compressor apparatus due to wave movements of the sea surface.

The pressure tank or accumulator 17 may be arranged to be floating on the sea surface 16.

Hence, the multi-stage gas compressor apparatus may advantageously be used for providing pressurized air in a wave energy installation.

Figure 6 is a schematic cross-sectional side view illustrating an embodiment where the outer cylinder may complete its stroke before engaging the central piston by means of an activating block 18 on the driving rod, hence enabling the central piston to complete the compression cycle, due to spring elements 4f, which will also smooth the step change.

Figure 7 is a schematic cross-sectional side view illustrating an embodiment of a boxer version when the driving force works equally in both directions. Then the chambers on each side of the pistons will alternate between a compression and suction function. If advantageous the central piston may be engaged with a lag relatively to the outer piston, by means of activating blocks 18. The transfer of air between the outer cylinder and the central cylinder may be arranged via an intermediate tank as shown in Figure 9.

Figure 8 is a schematic cross-sectional side view of an embodiment where the central rod is not firmly attached to the force-exerting member 10, which is connected to the pulling mooring by flexible lines 19, enabling the outer piston to halt before the completion of the stroke by the central piston.

Figure 9 is a schematic cross-sectional side view showing a three-step embodiment where the two outer cylinders are concentric and annular one outside the other, delivering pressurized gas inwards via one-way valves - alternatively via intermediate tanks - to the central cylinder's compression chamber.

Figure 10 is a schematic cross-sectional side view illustrating an embodiment where the gas between the outer and central cylinder is conducted via an intermediate tank enabling a full exploitation of the compression capacity of the outer cylinder in each stroke. Only one-way valves into and out from the tank is important in order to secure a controlled function. When the counter pressure from the central cylinder equals the maximum pressure affordable by the outer piston during a compression stroke, the remaining gas in the tank will be transferred to the central cylinder when the pressure gets lower during the next, sucking stroke.

Claims

1. A multi-stage gas compressor apparatus (1), comprising a first, central cylinder, forming a cylindrical chamber (8);

at least one outer cylinder arranged concentrically with the first, inner cylinder, forming an annular chamber (9); a first, circular piston (12) axially movable within the first, cylindrical chamber (8); at least one outer, annular piston (5) axially movable within the annular chamber (9); a force-exerting member (10) connected to the first (12) and second or more (5) pistons; a first one-way valve (2) arranged to allow gas transfer from a gas inlet (2) to an end portion of the annular chamber (9); at least one one-way valve (11) arranged to allow gas transfer from the end portion of the annular chamber (9) to an end portion of the closest inner chamber (8); and a third one-way valve (3) arranged to allow gas transfer from the end portion of the cylindrical chamber (8) to a gas outlet.

2. A multi-stage gas compressor apparatus (1) according to claim 1,

wherein the end portion of the annular chamber (9) and the end portion of the cylindrical chamber (8) are at an upper end of the apparatus (1).

3. A multi-stage gas compressor apparatus (1) according to claim 1,

wherein the end portion of the annular chamber (9) and the end portion of the cylindrical chamber (8) are at a lower end of the apparatus (1).

4. A multi-stage gas compressor apparatus (1) according to one of the claims 1-3, wherein the cylindrical chamber (8) is receiving gas from the annular chamber (9) via an intermediate tank, equipped with one-way valves.

5. A multi-stage gas compressor apparatus (1) according to one of the claims 1-3 wherein said annular chamber (9) is connected directly to the accumulator tank 17 via a one-way valve.

6. A multi-stage gas compressor apparatus (1) according to one of the claims 1 -5, wherein at least one first spring element (4a; 4b; 4d; 4e) is arranged between said second, annular piston (5) and an upper portion of the annular chamber (9).

7. A multi-stage gas compressor apparatus (1) according to one of the claims 1 -6, wherein a second spring element (4c) is arranged between said first circular piston (12) and the upper portion of the cylindrical chamber (8).

8. A multi-stage gas compressor apparatus (1) according to one of the claims 1 -7, wherein said force-exerting member (10) is connected to the first (12) and second pistons (5) by rigid rods (7a, 7b, 7c).

9. A multi-stage gas compressor apparatus (1) according to one of the claims 1 -7, wherein said force-exerting member (10) is connected to the first 12) and second pistons (5) by flexible links.

10. A multi-stage gas compressor apparatus (1) according to one of the claims 1 -9, wherein an upper portion of the annular chamber (9) is arranged at substantially the same vertical level as an upper portion of the cylindrical chamber (8).

11. A multi-stage gas compressor apparatus (1) according to claim 10,

wherein the first piston (12) is arranged with a permanent or variable axial displacement with respect to the second piston (5), controlled by different spring rates, pressure level or other means.

12. A multi-stage gas compressor apparatus (1) according to one of the claims 1 - 11, wherein the first, central piston (12) has a first piston area,

the second, annular piston (5) has a second piston area, and

the optimal ratio between the second and the first piston areas is 3,50: 1, which corresponds to a radius ratio of approx. 2, 10: 1, dependent on the wall thickness of the cylinders.

13. A multi-stage gas compressor apparatus (1) according to one of the claims 1 - 12, wherein the force-exerting member (10) is attached to the sea bottom (15); and wherein the apparatus (1) is provided with a floating element (6), causing the apparatus (1) with compressor cylinders to float on the sea surface, following the sea surface movements, while the pistons (11, 5) are firmly anchored to the sea bottom (15), hence causing working cycles of the pistons inside the cylinders to be performed .

14. A multi-stage gas compressor apparatus (1) according to claim 13,

wherein the gas outlet is connected to a pressure tank, resulting in that gas contained in the pressure tank will be compressed by the compressor apparatus due to wave movements of the sea surface or another external force.

15. Use of a multi-stage gas compressor apparatus as set forth in one of the claims 1 - 14 for providing pressurized air in an oceanic wave energy installation

16. Use of a multi-stage gas compressor apparatus as set forth in one of the claims 1 - 12 and 14 for providing pressurized air by conversion of mechanical energy from any relevant source.