US20220120264A1

US20220120264A1 - Compressor and hydrogen station

Info

Publication number: US20220120264A1
Application number: US17/487,231
Authority: US
Inventors: Tomohiro Otsuka; Naofumi Kanei
Original assignee: Kobe Steel Ltd
Current assignee: Kobe Steel Ltd
Priority date: 2020-10-20
Filing date: 2021-09-28
Publication date: 2022-04-21
Also published as: DE102021126746A1; JP2022067458A

Abstract

A cylinder in a compression stage is provided with a first cooling channel through which a cooling fluid for absorbing heat generated between the cylinder and a first piston ring group flows, a second cooling channel through which a cooling fluid for absorbing heat generated between the cylinder and a second piston ring group flows, and a through hole penetrating a side wall of the cylinder in an intermediate part between the first cooling channel and the second cooling channel A hydrogen gas leaking from a compression chamber to the intermediate part through between the cylinder and a piston and then guided to a leak line. The leak line includes a piping part and a volume expansion unit in which volume in a predetermined distance range is larger than volume of the piping part at the same distance range as the predetermined distance range.

Description

FIELD OF THE INVENTION

The present invention relates to a compressor and a hydrogen station including the compressor.

BACKGROUND ART

Conventionally, a reciprocating compressor configured to reciprocate a piston in a cylinder to compress gas in a compression chamber of the cylinder has been known. In this compressor, a plurality of piston rings is installed on a piston outer peripheral surface such that the piston rings are aligned in an axial direction of the cylinder. This prevents the compressed gas obtained in the compression chamber from leaking through a gap between the piston outer peripheral surface and the cylinder inner peripheral surface.
For example, in a reciprocating compressor disclosed in Japanese Patent No. 5435245, a large number of piston rings divided into two piston ring groups are installed on a piston outer peripheral surface. The compressor disclosed in Japanese Patent No. 5435245 is provided with a gas introduction unit connected to an intermediate part between the two piston ring groups to introduce gas. By this gas introduction unit, a gas having predetermined pressure is introduced into a gap between the piston outer peripheral surface and the cylinder inner peripheral surface.
Japanese Patent No. 5435245 has a structure to allow gas to escape from the intermediate part of the cylinder in order to extend the life of the piston rings. It is considered that damage to the piston rings is cause by an increase in a load applied to the piston rings. That is, every time the gas that has passed through the first piston ring flows downstream and passes through each piston ring, the pressure of the gas decreases. Accordingly, the volume of the gas expands and the flow speed increases. This increases the load applied to the piston rings and causes damage. Therefore, by allowing the gas that has passed through the upper piston ring group to escape through a leak line provided in the cylinder intermediate part, the flow speed through the lower piston ring group is reduced and the lower rings are protected.
In the compressor disclosed in Japanese Patent No. 5435245, the flow speed of the leaked gas fluctuates with the reciprocating sliding of the piston. Along with this fluctuation, the load on the piston ring groups may increase and wear of the piston rings may be accelerated.

SUMMARY OF THE INVENTION

An object of the present invention is to inhibit wear of piston rings in a piston provided with two piston ring groups.
A compressor according to one aspect of the present invention is a compressor for compressing a hydrogen gas, and includes: a plurality of compression stages; and a drive mechanism configured to drive the plurality of compression stages. At least one compression stage out of the plurality of compression stages includes: a cylinder; a piston inserted into the cylinder; a first piston ring group installed on the piston; and a second piston ring group installed on the piston on a side of the drive mechanism of the first piston ring group. The cylinder is provided with: a first cooling channel through which a cooling fluid for absorbing heat generated between the cylinder and the first piston ring group flows; a second cooling channel through which the cooling fluid for absorbing heat generated between the cylinder and the second piston ring group flows; and a through hole penetrating a side wall of the cylinder from an inner surface to an outer surface of the cylinder in an intermediate part between the first cooling channel and the second cooling channel. The compressor further includes a leak line connected to the through hole. The hydrogen gas leaking from a compression chamber in the cylinder into the intermediate part through between the cylinder and the piston and then guided into the leak line through the through hole. The leak line includes a piping part and a volume expansion unit in which volume within a predetermined distance range is larger than volume of the piping part at a distance identical to the predetermined distance.
A hydrogen station according to another aspect of the present invention includes: the compressor; an accumulator for storing the hydrogen gas discharged from the compressor; and a dispenser for receiving supply of the hydrogen gas from the accumulator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram schematically showing a configuration of a hydrogen station according to a first embodiment;

FIG. 2 is a diagram schematically showing appearance of a compressor according to the first embodiment;

FIG. 3 is a diagram schematically showing a configuration of a first block part in the above compressor;

FIG. 4 is a diagram schematically showing a configuration of a fifth compression stage in the above compressor;

FIG. 5 is a diagram schematically showing a configuration of a volume expansion unit in a second embodiment;

FIG. 6 is a diagram schematically showing a configuration of a volume expansion unit in a third embodiment;

FIG. 7 is a diagram schematically showing a configuration of a volume expansion unit in a fourth embodiment;

FIG. 8 is a diagram schematically showing part of a compressor of a fifth embodiment;

FIG. 9 is a diagram schematically showing part of a compressor of a sixth embodiment;

FIG. 10 is a diagram schematically showing part of a compressor of a seventh embodiment; and

FIG. 11 is a diagram schematically showing a compressor of an eighth embodiment.

DESCRIPTION OF EMBODIMENTS

A compressor and a hydrogen station according to embodiments of the present invention will be described in detail below with reference to the drawings.

First Embodiment

To begin with, a configuration of a hydrogen station 100 according to a first embodiment will be described with reference to FIG. 1. The hydrogen station 100 is a facility for replenishing a fuel cell vehicle (FCV) with a hydrogen gas as fuel. As shown in FIG. 1, the hydrogen station 100 includes a compressor 1 for compressing a hydrogen gas, an accumulator 2 for storing the high-pressure hydrogen gas compressed by the compressor 1 and then discharged from the compressor 1, and a dispenser 3 for receiving supply of the high-pressure hydrogen gas from the accumulator 2 and supplies the high-pressure hydrogen gas to a demand destination such as a fuel cell vehicle.
Next, a configuration of the compressor 1 will be described with reference to FIGS. 2 to 4. As shown in FIG. 2, the compressor 1 includes a plurality of compression stages (first to fifth compression stages 11 to 15) and a drive mechanism 5 that drives the plurality of compression stages 11 to 15. Each of the five compression stages 11 to 15 sequentially compresses and delivers a hydrogen gas. Of the five compression stages, the first compression stage 11, the third compression stage 13, and the fifth compression stage 15 constitute a first block part 6. The second compression stage 12 and the fourth compression stage 14 are coupled with each other and constitute a second block part 7 provided separately from the first block part 6.
In the first block part 6, the third compression stage 13 is placed on the first compression stage 11, and the fifth compression stage 15 is placed on the third compression stage 13. Meanwhile, in the second block part 7, the fourth compression stage 14 is placed on the second compression stage 12. The first block part 6 and the second block part 7 are placed on the drive mechanism 5. Rotation of a crankshaft (not shown) of the drive mechanism 5 causes compression of the hydrogen gas in each of the compression stages 11 to 15. In each of the first block part 6 and the second block part 7, a so-called tandem structure compressor is constructed in which a plurality of pistons is connected in series to one piston rod.
The compressor 1 includes a gas introduction pipe 9 a, a first connection pipe 9 b, a second connection pipe 9 c, a third connection pipe 9 d, a fourth connection pipe 9 e, and a gas discharge pipe 9 f. The gas introduction pipe 9 a is connected to a suction port of the first compression stage 11. The first connection pipe 9 b connects the first compression stage 11 to the second compression stage 12. The second connection pipe 9 c connects the second compression stage 12 to the third compression stage 13. The third connection pipe 9 d connects the third compression stage 13 to the fourth compression stage 14. The fourth connection pipe 9 e connects the fourth compression stage 14 to the fifth compression stage 15. The gas discharge pipe 9 f is connected to a discharge port of the fifth compression stage 15. The gas introduction pipe 9 a, the first connection pipe 9 b to the fourth connection pipe 9 e, and the gas discharge pipe 9 f form a channel for flowing a hydrogen gas.
FIG. 3 shows the third compression stage 13 and the fifth compression stage 15 in a simplified manner. The third compression stage 13 includes a third cylinder 23 and a third piston 33 inserted into the third cylinder 23. The fifth compression stage 15 includes a fifth cylinder 25 placed on the third cylinder 23 and a fifth piston 35 inserted in the fifth cylinder 25. The third compression stage 13 is a compression stage preceding to the fifth compression stage 15. The third cylinder 23 is a cylinder on a low pressure side of the fifth cylinder 25. The third piston 33 is a piston on a low pressure side of the fifth piston 35.
Inside the third cylinder 23, a third compression chamber 23S is formed by the third cylinder 23 and the third piston 33. Inside the fifth cylinder 25, a fifth compression chamber 25S is formed by the fifth cylinder 25 and the fifth piston 35. A diameter of the third piston 33 is larger than a diameter of the fifth piston 35. The third piston 33 and the fifth piston 35 are connected to each other by a connecting rod 37.
A plurality of piston rings is installed on the outer peripheral surface of the fifth piston 35. The plurality of piston rings constitutes a first piston ring group 41 and a second piston ring group 42. The second piston ring group 42 is installed on the outer peripheral surface of the fifth piston 35 on the drive mechanism 5 side of the first piston ring group 41. That is, the first piston ring group 41 and the second piston ring group 42 are disposed at a distance larger than the distance between adjacent piston rings. A plurality of piston rings is installed on the outer peripheral surface of the third piston 33. The plurality of piston rings constitutes a third piston ring group 43.
Although not shown, the first compression stage 11 includes a first cylinder and a first piston inserted into the first cylinder. The third cylinder 23 is placed on the first cylinder. The first piston and the third piston 33 are connected to each other by a connecting rod, and a piston rod is connected to the first piston. The piston rod converts rotational motion of the crankshaft of the drive mechanism 5 into reciprocating motion of the first piston via a crosshead. Furthermore, the second compression stage 12 and the fourth compression stage 14 have a configuration in which a piston is disposed inside a cylinder, and the fourth cylinder is placed on the second cylinder.
FIG. 4 is a cross-sectional view schematically showing the fifth compression stage 15. FIG. 4 illustrates the fifth compression stage 15 in more detail than FIG. 3. The fifth cylinder 25 of the fifth compression stage 15 includes a cylinder body 51, a cylinder head 52, a suction side joint member 53, a discharge side joint member 54, an upper jacket member 55, and a lower jacket member 56.
The cylinder body 51 has a long shape in one direction (vertical direction in the illustrated example). A columnar space 51 a extending in the one direction is formed in the center thereof. The columnar space 51 a penetrates the cylinder body 51 in the vertical direction. An opening 51 b is formed on the upper surface of the cylinder body 51.
The cylinder body 51 includes a body head 61, an upper tube part 62, an intermediate part 63, and a lower tube part 64. Note that in the cylinder body 51, these parts 61 to 64 are integrally formed. The body head 61 is located at the upper end of the cylinder body 51 and protrudes laterally (direction orthogonal to the one direction) from the upper tube part 62. On the upper surface of the body head 61, an upper surface recess 61 a, which has a circular shape when viewed from above and shares a center point with the opening 51 b and has an outer diameter larger than the outer diameter of the opening 51 b, is formed to be recessed downward.
A suction hole 61 b and a discharge hole 61 c are formed in the body head 61. The suction hole 61 b is a space communicating with the columnar space 51 a and extending in a direction orthogonal to the one direction, and is open on a side surface of the body head 61. The discharge hole 61 c is a space communicating with the columnar space 51 a and extending from the columnar space 51 a toward the opposite side of the suction hole 61 b. The discharge hole 61 c opens on a side surface of the body head 61 on a side surface opposite to the opening of the suction hole 61 b.
The upper tube part 62 has a tubular shape extending in the vertical direction, and is a portion having a constant outer diameter and disposed under the body head 61. The outer diameter of the upper tube part 62 is smaller than the outer diameter of the body head 61 and the intermediate part 63. The intermediate part 63 is disposed under the upper tube part 62. Therefore, the lower surface of the body head 61, the outer peripheral surface of the upper tube part 62, and the upper surface of the intermediate part 63 form an upper recess 51 c in the cylinder body 51. That is, the upper recess 51 c is formed in a ring shape to surround the outer peripheral surface of the upper tube part 62. The upper recess Mc is covered with the upper jacket member 55.
The lower tube part 64 has a tubular shape extending in the vertical direction, and is a portion having a constant outer diameter and disposed under the intermediate part 63. The outer diameter of the lower tube part 64 is smaller than the outer diameter of the intermediate part 63. Note that the lower end of the cylinder body 51 located under the lower tube part 64 also has the same outer diameter as the intermediate part 63. Therefore, the lower surface of the intermediate part 63, the outer peripheral surface of the lower tube part 64, and the upper surface at the lower end of the cylinder body 51 form a lower recess 51 d in the cylinder body 51. That is, the lower recess 51 d is formed in a ring shape to surround the outer peripheral surface of the lower tube part 64. The lower recess 51 d is covered with the lower jacket member 56.
The cylinder head 52 includes a cylinder head body 52 a and a protrusion 52 b protruding downward from the lower surface of the cylinder head body 52 a. The cylinder head 52 is disposed on the upper surface of the body head 61 with the protrusion 52 b fitted to the upper surface recess 61 a of the cylinder body 51.
The suction side joint member 53 is used to hold a check valve (not shown) provided in the suction hole 61 b of the body head 61. The suction side joint member 53 is attached to the body head 61 to close the opening of the suction hole 61 b.
The discharge side joint member 54 is used to hold a check valve (not shown) provided in the discharge hole 61 c of the body head 61. The discharge side joint member 54 is attached to the body head 61 to close the opening of the discharge hole 61 c.
A through hole that allows the suction hole 61 b to communicate with the outside is formed in the suction side joint member 53. The fourth connection pipe 9 e is inserted into the through hole. The fourth connection pipe 9 e and the suction hole 61 b function as a suction-side channel of the fifth cylinder 25 that leads to the columnar space 51 a in the fifth cylinder 25 and causes the fifth compression chamber 25S, which will be described later, to suction a hydrogen gas.
A through hole that allows the discharge hole 61 c to communicate with the outside is formed in the discharge side joint member 54. The gas discharge pipe 9 f is inserted into the through hole. The gas discharge pipe 9 f and the discharge hole 61 c function as a discharge channel of the fifth cylinder 25 that leads to the columnar space 51 a in the fifth cylinder 25 and discharges a hydrogen gas from the fifth compression chamber 25S described later.
The upper jacket member 55 is disposed to cover the upper recess 51 c. With this configuration, a closed space is formed between the upper jacket member 55 and the outer peripheral surface of the upper tube part 62. This space functions as a first cooling channel 71 for cooling the first piston ring group 41. The first cooling channel 71 has a size that covers the range in which the first piston ring group 41 reciprocates. A cooling fluid for absorbing heat generated between the fifth cylinder 25 (inner surface of the cylinder body 51) and the first piston ring group 41 flows through the first cooling channel 71.
The lower jacket member 56 is disposed to cover the lower recess 51 d. With this configuration, a closed space is formed between the lower jacket member 56 and the outer peripheral surface of the lower tube part 64. This space functions as a second cooling channel 72 for cooling the second piston ring group 42. The second cooling channel 72 has a size that covers the range in which the second piston ring group 42 reciprocates. A cooling fluid for absorbing heat generated between the fifth cylinder 25 (inner surface of the cylinder body 51) and the second piston ring group 42 flows through the second cooling channel 72.
The upper jacket member 55 is provided with an introduction part 57 for introducing the cooling fluid into the first cooling channel 71. The lower jacket member 56 is provided with a discharge part 58 for discharging the cooling fluid from the second cooling channel 72. Note that the introduction part 57 and the discharge part 58 are provided not only at the positions shown in FIG. 4. For example, the introduction part 57 may be provided in the lower jacket member 56, and the discharge part 58 may be provided in the upper jacket member 55.
The fifth piston 35 has a long cylindrical shape in one direction (vertical direction in the illustrated example), and is vertically slidably disposed in the columnar space 51 a of the cylinder body 51. The tip surface (upper surface) of the fifth piston 35, the inner peripheral surface of the cylinder body 51, and the lower surface of the protrusion 52 b of the cylinder head 52 define the fifth compression chamber 25S. A micro gap C1 is formed between the outer peripheral surface of the fifth piston 35 and the inner peripheral surface of the cylinder body 51 (fifth cylinder 25).
The intermediate part 63 is located between the first cooling channel 71 and the second cooling channel 72 in the vertical direction in which the fifth piston 35 reciprocates. A through hole 63 a that allows the columnar space 51 a (micro gap C1) to communicate with the outside is formed in the intermediate part 63. One end of the through hole 63 a opens to the micro gap C1 and the other end opens to the outer peripheral surface of the intermediate part 63. That is, the through hole 63 a penetrates the side wall of the fifth cylinder 25 from the inner surface to the outer surface of the fifth cylinder 25.
The first cooling channel 71 and the second cooling channel 72 communicate with each other through a communication passage 63 b formed to penetrate the intermediate part 63. That is, a channel for flowing the cooling fluid is formed by the introduction part 57, the first cooling channel 71, the communication passage 63 b, the second cooling channel 72, and the discharge part 58. By allowing the first cooling channel 71 to communicate with the second cooling channel 72, the cooling structure in the fifth cylinder 25 can be simplified.
The communication passage 63 b is provided at a different position from the through hole 63 a in the circumferential direction in the intermediate part 63. Specifically, in the present embodiment, the communication passage 63 b is provided on the side opposite to the through hole 63 a in the circumferential direction of the intermediate part 63.
Note that the first cooling channel 71 and the second cooling channel 72 do not have to communicate with each other through the communication passage 63 b. In that case, the first cooling channel 71 and the second cooling channel 72 are each configured as an independent channel. The introduction part 57 for introducing the cooling fluid and the discharge part 58 for discharging the cooling fluid are provided in each of the first cooling channel 71 and the second cooling channel 72.
A leak line 81 is connected to the through hole 63 a provided in the intermediate part 63 of the cylinder body 51. The leak line 81 is a part that guides a hydrogen gas to the outside of the fifth cylinder 25 after leaking into the intermediate part 63 from the fifth compression chamber 25S through the micro gap C1. As shown in FIG. 4, in the present embodiment, one end of the leak line 81 is connected to the through hole 63 a of the intermediate part 63, and the other end is connected to the fourth connection pipe 9 e (channel on the suction side of the fifth compression stage 15). Therefore, the hydrogen gas flowing out from the micro gap C1 to the outside of the fifth cylinder 25 can be returned to the fourth connection pipe 9 e. Note that the other end of the leak line 81 is not always connected to the fourth connection pipe 9 e. For example, the other end of the leak line 81 may be connected to the third connection pipe 9 d or the second connection pipe 9 c. The leak line 81 may be connected to a low pressure tank instead of being connected to a channel through which a hydrogen gas introduced in the fifth compression stage 15 flows.
The leak line 81 includes a piping part 82 and a volume expansion unit 83 with the volume existing in a predetermined distance range larger than the volume of the piping part 82 in the same distance range as the predetermined distance range. In the present embodiment, the cross-sectional area of the channel part where a hydrogen gas flows in the volume expansion unit 83 is larger than the cross-sectional area of the part where a hydrogen gas flows in the piping part 82. Therefore, the volume of the volume expansion unit 83 existing in the predetermined distance range is larger than the volume of the linear piping part 82 in the same distance range. That is, when the volume expansion unit 83 is compared with the piping part 82, the volume expansion unit 83 is larger than the piping part 82 in volume included in the predetermined length range. For example, the volume expansion unit 83 is thicker (wider) than the piping part 82. The volume expansion unit 83 of the present embodiment is configured as a hollow filter connected to the piping part 82, and is configured to remove, from a hydrogen gas, metal powder derived from the cylinder, resin powder derived from the piston ring, and the like. Note that the volume expansion unit 83 may not be formed as a hollow filter, but may be formed as a hollow tank.
The piping part 82 includes a first piping part 82 a and a second piping part 82 b. The volume expansion unit 83 is disposed between the first piping part 82 a and the second piping part 82 b. One end of the first piping part 82 a is connected to the through hole 63 a. One end of the second piping part 82 b is connected to the fourth connection pipe 9 e. The volume expansion unit 83 (filter) is provided with two circulating ports. The other end of the first piping part 82 a and the other end of the second piping part 82 b are connected to the circulating ports. Note that the length of the first piping part 82 a connecting the fifth cylinder 25 to the volume expansion unit 83 is shorter than the length of the second piping part 82 b connecting the fourth connection pipe 9 e to the volume expansion unit 83.
As a material for the piping part 82 in the leak line 81, austenitic stainless steel having excellent corrosion resistance is preferably used. Examples of the material include Japanese Industrial Standards austenitic stainless steel pipes (JIS-G3459) SUS316LTP or SUS316TP, American Society of Mechanical Engineers austenitic stainless steel standard (ASME-Section 2 PART-A 1998 SA-479) XM-19, and the American Society of Mechanical Engineers austenitic stainless steel pipes standard (ASME-Section 2 PART-A 1998 SA-312) TPXM-19. Using the above-described materials for the leak line 81 provides sufficient strength even in an environment where a high-pressure hydrogen gas flows, and hydrogen embrittlement is unlikely to occur.
The volume of the leak line 81 is preferably larger than the volume of the micro gap C1 in the section corresponding to the first piston ring group 41 when the fifth piston 35 is stationary. By giving the leak line 81 predetermined volume in this way, the leak line 81 can easily function as a buffer space for inhibiting pressure fluctuations of a leaked gas.
As described above, the compressor 1 according to the present embodiment cools, by the first cooling channel 71, the leaked gas leaking with expansion of volume and an increase in flow speed in the first piston ring group 41. This makes it possible to inhibit the expansion of the volume and the increase in the flow speed of the leaked gas, and to inhibit the wear of each piston ring of the first piston ring group 41 more than when the leaked gas is not cooled. Then, the gas leaking into the intermediate part 63 from the fifth compression chamber 25S through the micro gap C1 is guided to the leak line 81 through the through hole 63 a. The leak line 81 includes the piping part 82 and the volume expansion unit 83 (filter) in which the volume existing in a predetermined distance range is larger than the volume of the piping part 82 in the same range as the predetermined distance range. For this reason, the fluctuation of the flow speed of the leaked gas in the intermediate part 63 is inhibited during reciprocating sliding of the fifth piston 35. Therefore, the load on the second piston ring group 42 by the leaked gas is reduced, and the wear of the second piston ring group 42 can be inhibited.

Second Embodiment

Next, a compressor according to a second embodiment will be described. The compressor according to the second embodiment is basically similar to the compressor 1 according to the first embodiment, but differs in a configuration of a volume expansion unit. Only differences from the first embodiment will be described below.
FIG. 5 is a diagram schematically showing a configuration of a leak line 81 a in the second embodiment. As shown in FIG. 5, the leak line 81 a includes a volume expansion unit 83 a connected to a piping part 82, and the volume expansion unit 83 a includes a meandering pipe. The volume expansion unit 83 a has a length in a range 84 of a predetermined distance longer than the length of the linear piping part 82 in the same distance range 84. Therefore, the volume in the range 84 is larger than the volume of the piping part 82 in the same range 84. That is, when the volume expansion unit 83 is compared with the piping part 82, the volume expansion unit 83 is larger than the piping part 82 in volume included in the predetermined length range 84. A first piping part 82 a is connected to one end of the volume expansion unit 83 a, and a second piping part 82 b is connected to the other end of the volume expansion unit 83 a.

Third Embodiment

Next, a compressor according to a third embodiment will be described. The compressor according to the third embodiment is basically similar to the compressor 1 according to the first embodiment, but differs in a configuration of a volume expansion unit. Only differences from the first embodiment will be described below.
FIG. 6 is a diagram schematically showing a configuration of a leak line 81 b in the third embodiment. As shown in FIG. 6, the leak line 81 b includes a volume expansion unit 83 b connected to a piping part 82, and the volume expansion unit 83 b includes a pipe formed in a spiral shape. The volume expansion unit 83 b has a length in a range 84 of a predetermined distance longer than the length of the linear piping part 82 in the same distance range 84. Therefore, the volume in the range 84 is larger than the volume of the piping part 82 in the same range 84. A first piping part 82 a is connected to one end of the volume expansion unit 83 b, and a second piping part 82 b is connected to the other end of the volume expansion unit 83 b.

Fourth Embodiment

Next, a compressor according to a fourth embodiment will be described. The compressor according to the fourth embodiment is basically similar to the compressor 1 according to the first embodiment, but differs in a configuration of a volume expansion unit. Only differences from the first embodiment will be described below.
FIG. 7 is a diagram schematically showing a configuration of a leak line 81 c in the fourth embodiment. As shown in FIG. 7, the leak line 81 c includes a volume expansion unit 83 c connected to a piping part 82, and the volume expansion unit 83 c includes a pipe formed in a helical shape. The volume expansion unit 83 c has a length in a range 84 of a predetermined distance longer than the length of the linear piping part 82 in the same distance range 84. Therefore, the volume in the range 84 is larger than the volume of the piping part 82 in the same range 84. A first piping part 82 a is connected to one end of the volume expansion unit 83 c, and a second piping part 82 b is connected to the other end of the volume expansion unit 83 c.

Fifth Embodiment

Next, a compressor according to a fifth embodiment will be described. As shown in FIG. 8, the compressor according to the fifth embodiment differs from the compressor according to the first embodiment in that a fifth compression stage 15 includes a distance piece 8. The distance piece 8 is adjacently disposed under a fifth cylinder 25. In the distance piece 8, a penetrating part 8 a for penetrating a connecting rod 37 connected to a fifth piston 35 is formed. In the distance piece 8, a space 8 b is formed to accommodate a leaked gas leaking through a micro gap C1 corresponding to a first piston ring group 41 and a second piston ring group 42. Note that the distance piece 8 may be coupled with a third cylinder 23, or may be coupled with a drive mechanism 5.
When the compressor 1 is driven, part of the leaked gas leaking from a fifth compression chamber 25S through the micro gap C1 is returned to a fourth connection pipe 9 e through a leak line 81. Therefore, the amount of leaked gas leaking from the fifth cylinder 25 to the distance piece 8 can be reduced.
Note that while descriptions of other configurations, actions, and effects will be omitted, the descriptions of the first to fourth embodiments can be incorporated into the fifth embodiment.

Sixth Embodiment

Next, a compressor according to a sixth embodiment will be described. The compressor according to the sixth embodiment differs from the compressor according to the first embodiment in that a gas cooler 85 is provided on a fourth connection pipe 9 e as shown in FIG. 9.
A high-temperature, high-pressure hydrogen gas discharged from a fourth compression stage 14 is cooled by the gas cooler 85 and then introduced into a fifth compression stage 15. At this time, the gas cooler 85 is disposed downstream of a connection portion of a leak line 81 in the fourth connection pipe 9 e. That is, the leak line 81 is connected to a portion upstream of the gas cooler 85 in the fourth connection pipe 9 e. Therefore, the hydrogen gas returned from the leak line 81 to the fourth connection pipe 9 e joins the hydrogen gas before being cooled by the gas cooler 85. Therefore, the high-temperature leaked gas flowing from the leak line 81 to the fourth connection pipe 9 e can be cooled by the gas cooler 85. This makes it possible to prevent the hydrogen gas cooled by the gas cooler 83 from being heated by the leaked gas.
Note that while the description of other configurations, actions, and effects will be omitted, the description of the first to fifth embodiments can be incorporated into the sixth embodiment.

Seventh Embodiment

Next, a compressor according to a seventh embodiment will be described. The compressor according to the seventh embodiment differs from the compressor according to the first embodiment in that a check valve 86 is provided on a leak line 81 as shown in FIG. 10.
While the check valve 86 allows a hydrogen gas to flow from within an intermediate part 63 to a fourth connection pipe 9 e, the check valve 86 blocks the flow of a hydrogen gas from the fourth connection pipe 9 e to the intermediate part 63. The check valve 86 is disposed downstream of a volume expansion unit 83 (that is, on the side far from a fifth cylinder 25) in the leak line 81.
When a compressor 1 is driven, pressure of a hydrogen gas in the fourth connection pipe 9 e may be higher than pressure of a hydrogen gas in the intermediate part 63. Even in this case, since the check valve 86 is provided in the leak line 81, it is possible to prevent the inflow of a hydrogen gas from the fourth connection pipe 9 e into the intermediate part 63. Moreover, since the volume expansion unit 83 is disposed upstream of the check valve 86, even if the pressure in the fourth connection pipe 9 e is higher than pressure in a micro gap C1 in the fifth cylinder 25, the pressure in the fourth connection pipe 9 e is unlikely to affect the volume expansion unit 83. Therefore, the volume expansion unit 83 is unlikely to be affected by pressure fluctuation in the fourth connection pipe 9 e.
Note that while the description of other configurations, actions, and effects will be omitted, the description of the first to sixth embodiments can be incorporated into the seventh embodiment.

Eighth Embodiment

Next, a compressor according to an eighth embodiment will be described. The compressor according to the eighth embodiment differs from the compressor according to the first embodiment as shown in FIG. 11 in that a pressure reducing valve 87 is provided on a leak line 81, and the leak line 81 is connected to a channel with lower pressure than a fourth connection pipe 9 e (channel on a suction side).
For example, one end of the leak line 81 is connected to an intermediate part 63, and the other end is connected to a gas introduction pipe 9 a. Note that the other end of the leak line 81 may be connected to a third connection pipe 9 d, a second connection pipe 9 c, or a first connection pipe 9 b.
The pressure reducing valve 87 provided on the leak line 81 reduces pressure of a hydrogen gas on the intermediate part 63 side (or on a high pressure side) to predetermined pressure and flow the hydrogen gas to the gas introduction pipe 9 a side that is on a low pressure side. The pressure reducing valve 87 is disposed downstream of a volume expansion unit 83 (that is, on the side far from a fifth cylinder 25) in the leak line 81.
When the compressor 1 is driven, the pressure of a hydrogen gas in the intermediate part 63 may be significantly higher than the pressure of the gas in the gas introduction pipe 9 a. However, since the pressure reducing valve 87 is provided, it is possible to prevent the hydrogen gas from excessively flowing from the intermediate part 63 into the gas introduction pipe 9 a. Moreover, since the volume expansion unit 83 is disposed upstream of the pressure reducing valve 87 in the leak line 81, the pressure change in the volume expansion unit 83 can be inhibited.
Note that the leak line 81 is not always connected to a fifth compression stage 15. For example, one end of the leak line 81 may be connected to the intermediate part 63 of a fourth compression stage 14. In this case, the other end may be connected to the second connection pipe 9 c, the first connection pipe 9 b, or the gas introduction pipe 9 a. Furthermore, one end of the leak line 81 may be connected to the intermediate part 63 of a third compression stage 13. In this case, the other end may be connected to the first connection pipe 9 b or the gas introduction pipe 9 a.
A first compression stage 11, the third compression stage 13, and the fifth compression stage 15 do not have to be configured as a tandem structure. The first compression stage 11, the third compression stage 13, and the fifth compression stage 15 may be configured as separate bodies.
Note that while the description of other configurations, actions, and effects will be omitted, the description of the first to seventh embodiments can be incorporated into the eighth embodiment.
It should be understood that the embodiments disclosed this time are in all respects illustrative and not restrictive. The scope of the present invention is indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and scope of the claims and equivalents are therefore intended to be embraced therein. Therefore, the following embodiments are also included in the scope of the present invention.
For example, the configuration in which the leak line 81 is connected to the through hole 63 a of the intermediate part 63 of the cylinder body 51 may be applied to a second to fourth compression stages 12 to 14.
In the first embodiment, the fifth compression stage 15 may be configured, for example, as a tandem structure with the fourth compression stage that is a compression stage preceding to the fifth compression stage 15.
The first compression stage 11, the third compression stage 13, and the fifth compression stage 15 do not have to be configured as a tandem structure. In this case, the first compression stage 11, the third compression stage 13, and the fifth compression stage 15 may be configured as separate bodies. Similarly, the second compression stage 12 and the fourth compression stage 14 do not have to be configured as a tandem structure. In this case, the second compression stage 12 and the fourth compression stage 14 may be configured as separate bodies.
Here, the above-described embodiments will be outlined.
A compressor according to one aspect of the present invention is a compressor for compressing a hydrogen gas, and includes: a plurality of compression stages; and a drive mechanism configured to drive the plurality of compression stages. At least one compression stage out of the plurality of compression stages includes: a cylinder; a piston inserted into the cylinder; a first piston ring group installed on the piston; and a second piston ring group installed on the piston on a side of the drive mechanism of the first piston ring group. The cylinder is provided with: a first cooling channel through which a cooling fluid for absorbing heat generated between the cylinder and the first piston ring group flows; a second cooling channel through which the cooling fluid for absorbing heat generated between the cylinder and the second piston ring group flows; and a through hole penetrating a side wall of the cylinder from an inner surface to an outer surface of the cylinder in an intermediate part between the first cooling channel and the second cooling channel. The compressor further includes a leak line connected to the through hole. The hydrogen gas leaking from a compression chamber in the cylinder into the intermediate part through between the cylinder and the piston and then guided into the leak line through the through hole. The leak line includes a piping part and a volume expansion unit in which volume within a predetermined distance range is larger than volume of the piping part at a distance range identical to the predetermined distance range.
With this configuration, the leaked gas leaking with expansion of volume and an increase in flow speed in the first piston ring group is cooled by the first cooling channel. This makes it possible to inhibit the expansion of the volume of the leaked gas and the increase in the flow speed, and to inhibit the wear of each piston ring of the first piston ring group more than when the leaked gas is not cooled. Then, the gas leaking into the intermediate part through between the cylinder and the piston is guided to the leak line through the through hole. This leak line includes a piping part and a volume expansion unit in which the volume existing in the predetermined distance range is larger than the volume of the piping part at the same distance range as the predetermined distance range. For this reason, the fluctuation of the flow speed of the leaked gas in the intermediate part is inhibited during reciprocating sliding of the piston. Therefore, the load on the second piston ring group by the leaked gas is reduced, and the wear of the second piston ring group can be inhibited.
(2) In the compressor, the leak line may be connected to a suction side channel of the at least one compression stage, or a channel having pressure lower than the suction side channel.
With this configuration, the leaked gas flowing into the leak line can be recovered.
(3) In the compressor, the volume expansion unit may be a hollow tubular filter connected to the piping part. An inner diameter of a channel part of the hydrogen gas in the filter may be larger than an inner diameter of the piping part.
With this configuration, by using a filter having a large inner diameter as the volume expansion unit, it is possible to reduce the cost more than when the volume expansion unit is separately provided in addition to the filter.
(4) In the compressor, the volume expansion unit may include a pipe formed in a meandering shape, a spiral shape, or a helical shape.
With this configuration, the volume of the leak line can be secured by increasing the pipe length.
(5) A hydrogen station according to the embodiment includes: the compressor; an accumulator for storing the hydrogen gas discharged from the compressor; and a dispenser for receiving supply of the hydrogen gas from the accumulator.
As described above, wear of the piston rings can be inhibited in the piston in which two piston ring groups are provided.
This application is based on Japanese Patent Application No. 2020-176173 filed on Oct. 20, 2020, the contents of which are hereby incorporated by reference.
Although the present invention has been fully described by way of example with reference to the accompanying drawings, it is to be understood that various changes and modifications will be apparent to those skilled in the art. Therefore, unless otherwise such changes and modifications depart from the scope of the present invention hereinafter defined, they should be construed as being included therein.

Claims

1. A compressor for compressing a hydrogen gas, the compressor comprising:

a plurality of compression stages; and

a drive mechanism configured to drive the plurality of compression stages,

wherein at least one compression stage out of the plurality of compression stages includes:

a cylinder;

a piston inserted into the cylinder;

a first piston ring group installed on the piston; and

a second piston ring group installed on the piston closer to the drive mechanism than the first piston ring group,

the cylinder is provided with:

a first cooling channel through which a cooling fluid for absorbing heat generated between the cylinder and the first piston ring group flows;

a second cooling channel through which the cooling fluid for absorbing heat generated between the cylinder and the second piston ring group flows; and

a through hole penetrating a side wall of the cylinder from an inner surface to an outer surface of the cylinder in an intermediate part between the first cooling channel and the second cooling channel,

the compressor further includes a leak line connected to the through hole, the hydrogen gas leaking from a compression chamber in the cylinder into the intermediate part through between the cylinder and the piston and then guided into the leak line through the through hole, and

the leak line includes a piping part and a volume expansion unit in which volume within a predetermined distance range is larger than volume of the piping part at a distance range identical to the predetermined distance range.

2. The compressor according to claim 1, wherein

the leak line is connected to a suction side channel of the at least one compression stage, or a channel having pressure lower than the suction side channel.

3. The compressor according to claim 1, wherein

the volume expansion unit is a hollow tubular filter connected to the piping part, and

an inner diameter of a channel part of the hydrogen gas in the filter is larger than an inner diameter of the piping part.

4. The compressor according to claim 1, wherein

the volume expansion unit includes a pipe formed in a meandering shape, a spiral shape, or a helical shape.

5. A hydrogen station comprising:

the compressor according to claim 1;

an accumulator for storing the hydrogen gas discharged from the compressor; and

a dispenser for receiving supply of the hydrogen gas from the accumulator.