JP7146538B2 - Compressor and LNG tanker - Google Patents

Description

TECHNICAL FIELD The present invention relates to a compressor and an LNG tanker for compressing gas, and more particularly to a compressor that does not require lubrication at each compression stage and does not mix lubricating oil into the gas that has passed through the final compression stage, and an LNG tanker equipped with this compressor. .

Compressors are conventionally used to compress various gases. For example, natural gas is cooled to -162°C or less and transported as liquefied natural gas (LNG). A compressor is used for use as a fuel source to drive the . Patent Literature 1 describes a compressor that compresses boil-off gas.

Japanese Patent Publication No. 2008-528882

The compressor has one or more compression stages each having a cylinder, and each compression stage gradually compresses the gas to a higher pressure. By increasing the number of compression stages, the gas can be pressurized further.

When the number of compression stages is increased, it is necessary to supply lubricating oil to the piston in the latter compression stage in order to further compress the already high pressure gas. Therefore, lubricating oil is mixed in the gas that has passed through the final compression stage. The reason why the latter compression stage cylinder cannot be oil-free is that the life of the resin seal ring is shortened due to high heat.

Accordingly, an object of the present invention is to provide a compressor that does not require lubrication at each compression stage and does not mix lubricating oil into the gas that has passed through the final compression stage, and an LNG tanker equipped with this compressor.

Other objects of the present invention will become clear from the following description.

The above problems are solved by the following inventions.

1.
A compressor that compresses gas supplied from an inlet port in one or more compression stages and delivers it from an outlet port,
the one or more compression stage cylinders do not require lubrication in all compression stages;
A compressor, wherein at least a cylinder in a final compression stage is cooled by circulation of cooling liquid in a flow path provided in a cylinder liner.
2.
A compressor that compresses gas supplied from an inlet port in one or more compression stages and delivers it from an outlet port,
the one or more compression stage cylinders do not require lubrication in all compression stages;
A compressor, wherein at least the cylinder of the final compression stage is cooled by a circulating flow of coolant in a flow path provided in the piston rod.
3.
A compressor that compresses gas supplied from an inlet port in one or more compression stages and delivers it from an outlet port,
the one or more compression stage cylinders do not require lubrication in all compression stages;
A compressor, wherein at least a cylinder in a final compression stage is cooled by circulation of coolant in a flow path provided between a cylinder cylinder and a cylinder liner.
4.
4. The compressor according to 1, 2 or 3 above, wherein the cooling liquid is clean water, oil, or a low-temperature cooling liquid of 0° C. or lower.
5.
5. The compressor according to any one of 1 to 4, wherein the number of compression stages is three or more.
6.
6. The compressor according to any one of 1 to 5, wherein the gas that has passed through the final compression stage is pressurized to 200 bar or more.
7.
7. A compressor according to claim 6, characterized in that said gas passing through a compression stage before said final compression stage is pressurized to between 100 and 120 bar.
8.
8. The compressor according to any one of 1 to 7, wherein the one or more compression stages are driven by a horizontally opposed crank drive mechanism.
9.
9. The compressor according to any one of 1 to 8;
a reliquefaction device provided between the inlet and the outlet for returning the gas to a liquid;
The boil-off gas of liquefied natural gas stored in the LNG storage tank is compressed by the compressor to obtain fuel for a combustion engine for propulsion, and the unused fuel is reliquefied by the reliquefaction device to produce the LNG. An LNG tanker characterized by returning to a storage tank.

According to the present invention, it is possible to provide a compressor that does not require lubrication at each compression stage and does not mix lubricating oil into the gas that has passed through the final compression stage, and an LNG tanker equipped with this compressor.

1 is a schematic block diagram of an embodiment of a compressor of the invention; FIG. Sectional view showing the configuration of the compressor cylinder Longitudinal sectional view showing the shape of the gasket of the cylinder shown in FIG. 2 (cross section AA in FIG. 2) FIG. 2 is a longitudinal cross-sectional view showing the shape of the cylinder liner of the cylinder shown in FIG. FIG. 2 is a longitudinal sectional view showing the shape of the cylinder liner of the cylinder shown in FIG. 2 (CC section in FIG. 2) FIG. 2 is a longitudinal cross-sectional view showing the configuration of the piston and piston rod of the cylinder of the compressor; It is a figure which shows the shape of the support ring of the cylinder shown in FIG. 6, (a) is a longitudinal cross-sectional view, (b) is a front view. Sectional view showing another example of the configuration of the cylinder of the compressor FIG. 9 is a cross-sectional view showing the shape of the flow path of the cooling liquid of the cylinder shown in FIG. 9 is a perspective view showing the shape of the flow path of the cooling liquid of the cylinder shown in FIG. 8. FIG. FIG. 9 is a vertical sectional view showing the structure of the rod packing of the cylinder shown in FIGS. 2, 6 and 8; Appearance perspective view of compressor Compressor cross section

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

The compressor of the present invention, in this embodiment, has one or more (eg, five) compression stages each having a cylinder, and gradually compresses the gas to a higher pressure in each compression stage. In the latter of the compression stages (eg the fourth stage) the gas is already at a high pressure of 100 bar (10 MPa) or more.

In a cylinder that further compresses a high-pressure gas of 100 bar (10 MPa) or more, there is a risk that resin seal rings (piston ring and rod packing ring) will have a short life due to high heat. Under low pressure, the resin seal ring can maintain a practical life even without lubrication. However, under conditions where the suction pressure is 100 bar to 120 bar and the discharge pressure is 200 bar or more, such as in the latter compression stage (for example, the fifth stage), the resin seal ring is not practical for the oil-free type. There is a possibility that a long life cannot be maintained.

The compressor of the present invention eliminates the need to supply oil to the piston in all compression stages by providing a flow path in at least the cylinder at the final compression stage and circulating the coolant in the flow path for cooling.

Therefore, in this compressor, there is no possibility that the compressed gas will be contaminated with lubricating oil. Therefore, not only the gas that has passed through the subsequent compression stage, but also the gas that has passed through any compression stage can be reliquefied and reused at extremely low temperatures and high pressures. This compressor is applicable to all applications, for example when used on ships, it allows compressed natural gas to be returned to the storage tank as cargo.

FIG. 1 is a schematic block diagram of an embodiment of the compressor of the present invention.

The compressor of this embodiment, as shown in FIG. 1, compresses boil-off gas 6 (natural gas 4) produced from liquefied natural gas Ef. This compressor 1 pressurizes the drawn natural gas 4 to 100 bar (10 MPa) to 500 bar (50 MPa), often 150 bar (15 MPa) to 300 bar (30 MPa). The natural gas 4 is used as fuel for combustion engines, for example diesel engines.

The compressor 1 of the present embodiment is for example arranged on a ship, in particular an LNG tanker, making it possible to obtain fuel for the combustion engine for propulsion from the boil-off gas 6 of the liquefied natural gas Ef stored in the LNG storage tank 5. and The boil-off gas 6 is at approximately −162° C. and under a pressure of 1 bar (100 kPa). The compressor 1 pumps the boil-off gas 6 up to a variable feed pressure, preferably in the range from 100 bar (10 MPa) to 500 bar (50 MPa), in particular in the range from 150 bar (15 MPa) to 300 bar (30 MPa). Let it be compressed natural gas 4 . In addition, when the amount of the boil-off gas 6 is insufficient as a fuel source, part of the liquefied natural gas Ef in the LNG storage tank 5 is heated and vaporized.

In this embodiment, the gas that has passed through the final compression stage is pressurized to 200 bar or more, but it may be 150 bar (15 MPa) to 300 bar (30 MPa) depending on the load of the supply destination. Also, depending on the rated pressure, it may be from 150 bar (15 MPa) to 400 bar (40 MPa) or more.

The compressor 1 comprises an inlet 3 for natural gas 4 . The compressor 1 also comprises a discharge port 7 connected to a natural gas supply pipe 8 for a combustion engine located downstream.

The intake port 3 communicates with an LNG storage tank 5 . The LNG storage tank 5 stores liquefied natural gas Ef at a pressure of 1 bar (100 kPa) and a temperature of -162°C. The boil-off gas 6 is generated from the surface of the liquefied natural gas Ef. This boil-off gas 6 is sucked and compressed by the compressor 1 and delivered as natural gas 4 through the outlet 7 under a pressure of preferably 150 bar (15 MPa) to 300 bar (30 MPa).

The compressor 1 comprises first to fifth compression stages 9,10,13,14,15. Although the number of compression stages is five in this embodiment, the number of compression stages is not limited to five in the present invention. If a centrifugal compressor or a screw compressor is applied to the low-pressure stage, the number of stages can be reduced from five to two or three, for example.

The first to fifth compression stages 9, 10, 13, 14, 15 have piston ring seal cylinders 11, 12, 16, 17, 18 connected in series. The piston ring type cylinder 11 is capable of reliably sucking and compressing the natural gas 4 over a wide temperature range of intake gas temperature from -160°C to +45°C.

Stages 1-4 cylinders 11, 12, 16, 17 are double-acting cylinders with compression chambers for natural gas compression on both sides of the piston, and fifth stage cylinder 18 is It has a single-acting cylinder with a compression chamber on one side only. The natural gas 4 passes through these compression stages 9 , 10 , 13 , 14 , 15 and is delivered from the outlet 7 .

Conventionally, since the latter high-pressure compression stage is oil-fed, there is a risk that the natural gas will be contaminated with lubricating oil. When natural gas is reliquefied at cryogenic temperature and high pressure, contamination of lubricating oil in natural gas leads to troubles in the reliquefaction equipment. Lubricating oil mixed with natural gas is removed by an oil separator and an oil filter. However, since complete removal is impossible, problems with the reliquefaction unit are unavoidable. Therefore, considering the case of liquefying the high-pressure gas after the fourth stage, the lubricating oil in the gas after the fifth stage is carried to the previous stage through the bypasses 20e, 20d, 20c, 20b, and 20a provided in each stage. In order to prevent this, in the conventional compressor, a check valve was essential before the subsequent compression stage (between the fourth stage 14 and the fifth stage 15). Since the fifth stage 15, which is the final stage, is a lubrication type, there is a bypass return from after the fifth stage to the previous stage, which is necessary for operation such as capacity adjustment. However, there was a risk of contamination with lubricating oil. If the latter compression stage is oil-free and all stages are oil-free, troubles in the reliquefaction device can be avoided in gas reliquefaction in all compressors, not only those for ships, which is extremely beneficial. Also, a check valve before the subsequent compression stage (between the fourth stage 14 and the fifth stage 15) is not required.

After the fourth or fifth compression stage 14 or 15, a reliquefaction unit 31 is normally provided for liquefying surplus natural gas 4 not needed by the compressed engine.

Any or all of the compression stages 9, 10, 13, 14, 15 pass the natural gas 4 through the respective compression stage 9, 10, 13, 14, 15 to the Bypasses 20a, 20b, 20c, 20d, 20e returning to the front (upstream) are preferably provided. Each bypass 20 a , 20 b , 20 c , 20 d , 20 e is preferably provided with a control valve 24 a , 24 b , 24 c , 24 d , 24 e controlled by the compressor control system 23 . Control valves 24a, 24b, 24c, 24d, and 24e allow adjustment of at least one of the pressure of the natural gas 4 at the discharge port 7 and the amount of supply.

Pressure sensors 21a, 21b, 21c, 21d and 21e are provided after (downstream) each of the compression stages 9, 10, 13, 14 and 15, respectively. The pressure detection values output by these pressure sensors 21 a , 21 b , 21 c , 21 d and 21 e are input to the compressor control system 23 . The compressor control system 23 outputs an opening degree command signal based on the input pressure detection value to control the opening degrees of the control valves 24a, 24b, 24c, 24d, and 24e.

The natural gas 4 is returned via bypasses 20a, 20b, 20c, 20d, 20e to bring the natural gas 4 at the outlet 7 to the desired target pressure Pset. Reverse flow through bypasses 20a, 20b, 20c, 20d, 20e is controlled by control valves 24a, 24b, 24c, 24d, 24e. The feed pressure at outlet 7 is variable from 100 bar (10 MPa) to 500 bar (50 MPa), usually from 150 bar (15 MPa) to 300 bar (30 MPa) depending on the operating conditions. Also, the desired flow rate of natural gas 4 is variable from 0% to 100%. The compressor 2 makes the pressure on the discharge side at the outlet 7 a variable feed pressure specified by the control input value.

In this embodiment, the cylinders 11, 12, 16, 17, 18 of all compression stages 9, 10, 13, 14, 15 do not require piston lubrication, so that these compression stages 9, 10, The compressed natural gas 4 at 13, 14, 15 is not contaminated with impurities. Since the natural gas 4 compressed in each compression stage 9, 10, 13, 14, 15 is not contaminated, unused natural gas 4 can be returned as cargo to the LNG storage tank 5, if desired. .

That is, in the LNG tanker equipped with this compressor 1, the boil-off gas 6 of the liquefied natural gas Ef stored in the LNG storage tank 5 is compressed by the compressor 1 to obtain fuel for the combustion engine for propulsion and use Any fuel that is not liquefied can be reliquefied by the reliquefaction unit 31 and returned to the LNG storage tank 5 as cargo. Therefore, in this LNG tanker, the decrease in the liquefied natural gas Ef in the LNG storage tank 5 can be minimized while effectively using the boil-off gas 6, and the fuel for the combustion engine and the liquefied natural gas Ef can be supplied from the outside. Extremely useful in navigational environments where resupply is not possible.

[First Embodiment of Cylinder]
FIG. 2 is a cross-sectional view showing the configuration of the cylinder of the compressor.

As shown in FIG. 2, the cylinders 9, 10, 16, 17, and 18 are provided with a cylinder tube 34, a cylinder liner 35 arranged in the cylinder tube 34, and a cylinder liner 35 slidably arranged in the cylinder liner 35. It compresses the gas supplied from the suction port 63 via the suction valve 63a and sends it out from the discharge port 64 via the discharge valve 64a.

The inside of the cylinder tube 34 is formed in a tubular shape, and a cylindrical cylinder liner 35 is fitted therein. The piston 33 is formed in a cylindrical shape that can be fitted inside the cylinder liner 35 . The piston 33 is fitted with an annular piston ring 36 and a rider ring 36a. A piston rod 37 is coaxially connected to the piston 33, and when the piston rod 37 is reciprocated by the prime mover, the piston 33 is axially reciprocated. As the piston 33 slides in the cylinder liner 35 in the axial direction of the cylinder tube 34, the gas inside the cylinder tube 34 (inside the cylinder liner 35) is compressed. Since the high-pressure cylinder tube is generally small in diameter, the piston 33 and the piston rod 37 are integrally constructed, but in some cases they may be constructed separately. A rod packing 70 is provided on the outer circumference of the piston rod 37 .

Gas compression heat and sliding frictional heat between the cylinder liner 35 and the piston ring 36 and rider ring 36 a fitted to the piston 33 are generated in the cylinder tube 34 . Gas heat of compression is approximately constant regardless of pressure level. However, the sliding frictional heat between the piston ring 36 and the cylinder liner 35 increases as the pressure increases. This is because the surface pressure between the piston ring 36 and the cylinder liner 35 is the same as in the case of the lubricating type, but the coefficient of friction between the piston ring 36 and the cylinder liner 35 is because it grows. The sliding frictional heat generated by the rider ring 36a is not related to the pressure, but when oil is not supplied, the coefficient of friction between the rider ring 36a and the cylinder liner 35 increases, similar to the piston ring. If the temperature of the piston ring 36 and the rider ring 36a increases due to sliding frictional heat, and the piston ring 36 and the rider ring 36a are melted and worn, the service life of the piston ring 36 and the rider ring 36a will be shortened. By removing sliding frictional heat of the piston ring 36, the service life of the piston ring 36 and the rider ring 36a can be extended even if the piston does not need to be lubricated.

This high-pressure non-lubricating cylinder has a structure to positively remove sliding frictional heat of the piston ring 36 and the rider ring 36a under a high-pressure non-lubricating state, thereby prolonging the life of the piston ring 36 and the rider ring 36a. Equipped with a cooling mechanism, the sliding frictional heat is positively removed, and the temperature rise of the piston ring 36 and the rider ring 36a is suppressed.

This high-pressure oil-free cylinder is provided with a cooling mechanism for removing frictional heat, which eliminates the need to supply oil to the piston. A cooling liquid passage 55 is formed in the cylinder liner 35 inserted with the . The cylinder liner 35 is made of stainless steel or steel and has a thickness of about 15 mm, and is provided with a coolant passage 55 by machining. A rear end portion (left end in FIG. 2) of the coolant passage 55 is closed by welding a rear end portion 56 of the cylinder liner 35 .

A front end portion (right end in FIG. 2) of the cylinder tube 34 is closed by a cylinder cover 57 .

FIG. 3 is a vertical cross-sectional view (cross section along line AA in FIG. 2) showing the shape of the gasket of the cylinder shown in FIG.

Contact surfaces between the cylinder cover 57 and the cylinder liner 35 are sealed with a gasket 58 made of pure iron to prevent leakage of high-pressure gas and coolant. As shown in FIG. 3 (cross-sectional view taken along line AA in FIG. 2), upper and lower cooling liquid passages 60 and 61 each having a semicircular arc shape are formed on the contact surface of the gasket 58 with the cylinder cover 57. ing.

4 is a longitudinal sectional view (sectional view taken along line BB in FIG. 2) showing the shape of the cylinder liner of the cylinder shown in FIG.

In the cylinder liner 35, as shown in FIG. 4 (cross-sectional view along BB in FIG. 2), coolant passages 55 consisting of about 24 round holes are formed in the axial direction of the cylinder liner 35, depending on the diameter of the cylinder. ing. The round holes may be long holes, and the number of round holes need not be 24.

As also shown in FIG. 4, the cylinder tube 34 is provided with an outer peripheral flow path 40 . The outer peripheral flow path 40 communicates from one end side surface 41 to the other end side surface 42 of the cylinder tube 34 . The outer peripheral passage 40 is provided on the outer peripheral side of the cylinder liner 35 and is a normal cylinder coolant passage provided in a high-pressure cylinder in the form of a plurality of through pipes. A cooling liquid is caused to flow in the outer peripheral channel 40 . After flowing through the outer peripheral channel 40 from the side surface 41 , the cooling liquid flows out from the side surface 42 .

By cooling the cylinder liner 35, the coolant flowing through the outer peripheral flow path 40 absorbs the heat of the piston ring 36 and the rider ring 36a, and radiates the heat outside the cylinder cylinder 34, thereby lowering the temperature of the rings. do.

5 is a longitudinal sectional view (CC section in FIG. 2) showing the shape of the cylinder liner of the cylinder shown in FIG.

The sliding surfaces of the cylinder liner 35 with the piston ring 36 and the rider ring 36a are thermally sprayed with nitride or tungsten carbide to prevent the piston ring 36, the rider ring 36a and the cylinder liner 35 from wearing. The cylinder cover 57 is equipped with an O-ring 59 for gas sealing at the insertion portion into the cylinder cylinder 34 . As shown in FIG. 5 (cross-sectional view of CC in FIG. 2), a cooling liquid communication passage 62 is provided in the cylinder liner 35 on the base end side (left side in FIG. 2) of the cylinder liner 35. formed.

The coolant is supplied from the lower coolant passage 61a on the lower side of the cylinder cover 57 in FIG. The cooling liquid enters the lower half of the cylinder liner 35 from the lower cooling liquid passage 61 through a through hole formed in the gasket 58 . The coolant that has entered the cylinder liner 35 flows through the cylinder liner 35 toward the base end side (left side in FIG. 2). After passing through the lower half of the cylinder liner 35 , the coolant changes direction at the base end side of the cylinder liner 35 and moves to the upper half of the cylinder liner 35 through the coolant communication passage 62 . The coolant that has moved to the upper half of the cylinder liner 35 flows to the tip side (right side in FIG. 2) and finally returns to the coolant supply device through the upper coolant passage 60a in the upper half of the cylinder cover 57.

As the coolant, fresh water having a cooling temperature corresponding to the compression pressure is generally used, but if necessary, a low-temperature coolant of 0° C. or less, such as an ethylene glycol aqueous solution, can be used to increase the cooling effect. There is also the possibility of oil cooling, although the cooling effect is somewhat inferior.

The cooling liquid circulating in the cooling liquid passage 55 absorbs heat from the piston 33, the piston ring 36, the rider ring 36a, the cylinder tube 34, and the cylinder liner 35, and dissipates the heat outside the cylinder tube 34. Cool inside. By providing such a cooling mechanism, this high-pressure oil-free cylinder does not require lubrication. In this high-pressure oil-free cylinder, the temperature conditions of the piston ring 36 and the rider ring 36a are approximately the same as in the low-pressure oil-free cylinder, so the life of the piston ring 36 and the rider ring 36a is extended.

The temperature of the piston ring 36 and the rider ring 36a can secure a heat transfer area to the extent that frictional heat can be substantially removed by a cooling mechanism. Therefore, even in the case of the lubrication type, almost the same gas compression heat remains, so that the gas can be pressurized to a high pressure without lubrication.

In a compressor using this high-pressure oil-free cylinder, since it is not necessary to supply oil to the piston at all compression stages, gas is not contaminated with impurities, and unused gas can be returned to the storage tank. . Alternatively, all of the gas that has been circulated within each compression stage can be finally returned to the storage tank.

This cooling mechanism provides a more reliable fit between the cylinder tube 34 and the cylinder liner 35 than the later-described embodiment (FIGS. 8 to 10) that cools the outer peripheral side of the cylinder liner 35 .

[Second Embodiment of Cylinder]
FIG. 6 is a longitudinal sectional view showing the configuration of the piston and piston rod of the cylinder of the compressor.

In the cylinder of this embodiment, instead of or in addition to the cooling mechanism shown in FIGS. 2 to 5, as shown in FIG. Circulate to cool. The flow path 43 is formed along the axial direction of the piston rod 37 from the distal end side to the proximal end side of the piston 33 and the piston rod 37 . The interior of the flow path 43 is partitioned into a central portion 43 a and an outer peripheral portion 43 b by a cylindrical body 44 arranged in the flow path 43 . A support ring 45 is fitted between the tip side portion of the cylindrical body 44 and the inner wall portion of the flow path 43 . Since the cylinder tube for high pressure is generally small in diameter, the piston 33 and the piston rod 37 are integrally constructed, but depending on the situation, they may be constructed separately.

7A and 7B are views showing the shape of the support ring of the cylinder shown in FIG. 6, where FIG. 7A is a longitudinal sectional view and FIG.

As shown in FIGS. 6 and 7, the support ring 45 is axially formed with a plurality of through holes 49 through which the cooling liquid flows.

Coolant flows through a coolant flow path 48 from a coolant inlet 47 provided in the cylinder tube 34 into the flow path 43 in the piston rod 37 . The cooling liquid that has passed through the cooling liquid flow path (flexible tube) 48 flows through the cooling liquid inlet 46 provided on the proximal end side of the piston rod 37 and into the central portion 43 a in the cylindrical body 44 . The cooling liquid in the central portion 43a flows toward the tip side of the piston rod 37, passes through a plurality of through holes 44a provided on the tip side of the cylindrical body 44, and reaches the outer peripheral portion 43b. The coolant in the outer peripheral portion 43 b flows through the insertion hole 49 of the support ring 45 toward the base end side of the piston rod 37 . The coolant on the proximal side of the piston rod 37 flows out of the piston rod 37 through a coolant outlet 50 provided on the proximal side of the piston rod 37 . The coolant that has flowed out from the piston rod 37 passes through a coolant flow path (flexible pipe) 52 provided in the cylinder cylinder 34 and flows out from a coolant outlet 51 .

One end of the cylindrical body 44 is fixed in a guide hole provided in the piston rod 37, and the other end of the cylindrical body 44 is fixed in a guide hole provided in the piston cover 65. I try not to. If the inner diameter dimension of the support ring 45 is adjusted with respect to the outer diameter dimension of the cylindrical body 44, the vibration of the cylindrical body 44 can be prevented.

The cooling liquid circulating in the piston rod 37 absorbs heat from the piston 33, the piston rings 36, the rider ring 36a, the cylinder tube 34, and the cylinder liner 35, and radiates the heat outside the cylinder tube 34, so that the piston rings 36, Cool the rider ring 36a. By providing such a cooling mechanism, this high-pressure oil-free cylinder does not require lubrication.

The temperature of the piston ring 36 and the rider ring 36a can secure a heat transfer area to the extent that frictional heat can be substantially removed by a cooling mechanism. Therefore, even in the case of the lubrication type, almost the same gas compression heat remains, so that the gas can be pressurized to a high pressure without lubrication.

A rod packing 70 is provided on the outer circumference of the piston rod 37 as shown in FIG.

[Third Embodiment of Cylinder]
FIG. 8 is a sectional view showing another example of the configuration of the cylinder of the compressor.

In the cylinder of this embodiment, instead of the cooling mechanism shown in FIGS. 2 to 5 or in addition to the cooling mechanism shown in FIGS. 6 to 7, as shown in FIG. The piston ring 36 and the rider ring 36a may be cooled by circulating a cooling liquid between them. The outer periphery of the cylinder liner 35 has a plurality of annular grooves 38 with a semicircular cross-section in order to circulate the cooling liquid to achieve uniform cooling and to increase the cooling area to increase the cooling effect. O-rings 41a and 41b are inserted in front of and behind the annular groove 38 to prevent leakage of the coolant, and the fitting margin and the O-rings 41a and 41b prevent the high-pressure gas from leaking to the coolant side.

FIG. 9 is a cross-sectional view showing the shape of the cooling liquid flow path of the cylinder shown in FIG.
FIG. 10 is a perspective view showing the shape of the cooling liquid flow path of the cylinder shown in FIG.

As shown in FIG. 9, the cooling liquid is supplied from the outer cooling liquid passage 42a on the side surface 41 of the cylinder cylinder 34, flows through the annular groove 38 on the back surface of the cylinder liner 35 as shown in FIG. Friction sliding heat between the piston ring 36 and the cylinder liner 35 and between the rider ring 36a and the cylinder liner 35 is generated by the cooling circuit discharged from the outer coolant passage 42b of the other side surface 42 of the cylinder cylinder 34 and returned to the coolant recovery line. and the heat of gas compression in the cylinder is effectively removed in the immediate vicinity of its heat source. As shown in FIG. 10, the annular groove 38 is in communication with the communication passage 39 from one end side to the other end side of the cylinder tube 34 .

The cylinder tube 34 is provided with an outer peripheral passage 40 as shown in FIG. The outer peripheral flow path 40 communicates from one end side surface 41 to the other end side surface 42 of the cylinder tube 34 . The outer peripheral passage 40 is a normal cylinder cooling liquid passage provided in the high-pressure cylinder in the shape of a plurality of straight pipes which are provided on the outer peripheral side of the cylinder liner 35 and positioned outside the annular groove 38 . Together with this, the annular groove 38 aims at increasing the cooling effect of the cylinder tube 34 .

Coolant is circulated in the annular groove 38 and in the outer peripheral channel 40 . As shown in FIG. 8, the annular groove 38 communicates with the outer coolant passage 42a of the side surface 41. As shown in FIG. Also, the annular groove 38 is communicated with the outer coolant passage 42b of the side surface 42 . The coolant flows into the annular groove 38 from the side surface 41 , circulates in the annular groove 38 and the outer peripheral channel 40 , and then flows out from the side surface 42 .

The cooling liquid circulating in the annular groove 38 and the outer peripheral passage 40 cools the cylinder liner 35, absorbs the heat of the piston ring 36 and the rider ring 36a, and radiates the heat outside the cylinder tube 34. The ring temperature can be lowered to extend the ring life. By providing such a cooling mechanism, this cylinder does not require lubrication.

The heat transfer area of the inner wall of the annular groove 38 varies depending on the cylinder cylinder diameter and cylinder cylinder length, and also depends on the coolant used, but the temperature of the piston ring 36 and the rider ring 36a is substantially removed by the cooling mechanism. A possible heat transfer area can be secured. Therefore, even in the case of the lubrication type, almost the same gas compression heat remains, so that the gas can be pressurized to a high pressure without lubrication.

[Structure of rod packing]
11 is a longitudinal sectional view showing the structure of the rod packing of the cylinder shown in FIGS. 2, 6 and 8. FIG.

As shown in FIG. 11, the rod packing 70 comprises a plurality of rod packing rings 53 supporting the outer circumference of the piston rod 37 and a plurality of ring cups 54 housing the rod packing rings 53. there is Sliding frictional heat is also generated by sliding between the rod packing ring 53 and the piston rod 37 . This sliding frictional heat is transmitted to the ring cup 54 housing the rod packing ring 53 .

The rod packing 70 distributes and supplies cooling liquid (clean water or oil) to the flow paths in each ring cup 54 from the cooling liquid supply path 66 communicating with the outside at the cooling liquid supply port 68, and the cooling liquid is supplied from these flow paths. may be provided with a cooling mechanism of a direct cooling system that collects and discharges the coolant in the coolant discharge passage 67 communicating with the outside at the coolant discharge port 69 . Furthermore, by increasing the cooling effect, such as using a low-temperature coolant (e.g., low-temperature ethylene glycol aqueous solution), bringing the coolant channel closer to the ring as much as possible, and increasing the coolant channel area, a large amount of sliding friction can be achieved. Heat can be removed.

[Casing and horizontally opposed crank drive mechanism]
FIG. 12 is an external perspective view of the compressor.
FIG. 13 is a cross-sectional view of the compressor.

In this compressor 1 all of the compression stages 9, 10, 13, 14, 15 are mounted in a common casing 29, as shown in FIGS.

12 and 13, the horizontally opposed crank drive mechanism 28 comprises a crankshaft 28a to which bearings are attached. A pair of cylinders are horizontally opposed and connected to both sides of the crankshaft 28a. In the horizontally opposed compressor 1 , cylinders are arranged on the left and right sides of the casing 29 and the crank drive mechanism 28 .

A plurality of joint bars 28b are provided longitudinally spaced along the crankshaft 28a on either side of the crankshaft 28a. Each joint rod 28b is connected to the piston rod 37 by a crosshead pin bearing 28C and a crosshead 28d.

Each piston rod 37 is connected to a piston 11a, 12a, 16a, 17a, 18a of each cylinder 11, 12, 16, 17, 18.

A casing 29 covers the compression stages 9, 10, 13, 14, 15 arranged on both sides of the crankshaft 28a.

A flywheel is mounted on the end of the crankshaft 28a and connected to a drive shaft (not shown) by a shaft coupling. In this embodiment, five (or six) cylinders 11, 12, 16, 17, 18 are attached to the crankshaft 28a. The pistons 11a, 12a, 16a, 17a, 18a of the cylinders 11, 12, 16, 17, 18 are driven by the crankshaft 28a by means of the piston rods 37 within the cylinders.

Note that this compressor is not limited to a configuration using a horizontally opposed crank drive mechanism, and may be configured as a vertical compressor.

The present invention is not limited to the embodiments described above, and various improvements and design changes may be made without departing from the scope of the present invention. For example, the cooling mechanism described above may have each configuration of the first to third embodiments independently, or may have a plurality of configurations.

In addition, it goes without saying that the specific detailed structure, numerical values, etc., and the control content of the control device, etc., can also be changed as appropriate. In addition, the embodiments disclosed this time should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the scope and meaning of equivalents of the scope of the claims.

1 compressor 3 inlet 4 natural gas 7 outlet 8 natural gas supply pipe 9 first compression stage 10 second compression stage 11 cylinder 12 cylinder 13 third compression stage 14 fourth compression stage 15 fifth compression stage 16 Cylinder 17 Cylinder 18 Cylinder 20a, 20b, 20c, 20d, 20e Bypass 21a, 21b, 21c, 21d, 21e Pressure sensor 23 Compressor control system 24a, 24b, 24c, 24d, 24e Control valve 28 Horizontally opposed crank drive mechanism 28a Crankshaft 28b Joint rod 28c Crosshead pin bearing 28d Crosshead 29 Casing 31 Reliquefying device 33 Piston 34 Cylinder tube 35 Cylinder liner 36 Piston ring 36a Rider ring 37 Piston rod 38 Annular groove 39 Communication passage 40 Outer peripheral passage 41 Side surface 41a, 41b O-ring 42 side surface 42a, 42b outer cooling liquid passage 43 flow passage 43a central portion 43b outer peripheral portion 44 cylindrical body 45 support ring 46 cooling liquid inlet 47 cooling liquid inlet 48 cooling liquid flow path 49 insertion hole 50 cooling liquid outlet 52 cooling liquid Flow path 51 Coolant outlet 53 Rod packing ring 54 Ring cup 55 Coolant passage 56 Rear end 57 Cylinder cover 58 Gasket 59 O-ring 60 Upper coolant passage 60a Upper coolant passage 61 Lower coolant passage 61a Lower cooling Liquid passage 62 Coolant communication passage 63 Suction port 63a Suction valve 64 Discharge port 64a Discharge valve 65 Piston cover 66 Coolant supply passage 67 Coolant discharge passage 68 Coolant supply port 69 Coolant discharge port 70 Rod packing

Claims (8)

A compressor that compresses gas supplied from an inlet port in one or more compression stages and delivers it from an outlet port,
the one or more compression stage cylinders do not require lubrication in all compression stages;
The discharge port is provided on one side of the cylinder, and the suction port is provided on the other side of the cylinder opposite to the discharge port,
At least the final compression stage cylinder has a coolant passage provided in a semi-cylindrical portion on one side of the cylinder liner and a coolant passage provided in a semi-cylindrical portion on the other side of the cylinder liner. The cooling liquid is cooled by reciprocating from one end of the cylinder liner to the other end in the liquid passage ,
The cooling liquid is fresh water, an ethylene glycol aqueous solution, or oil, and is supplied to the cooling liquid passage from one end side of the cylinder liner, and is supplied to the one side of the cylinder liner provided with the discharge port . It passes through the coolant passage , changes direction at the other end of the cylinder liner, passes through the coolant passage on the other side of the cylinder liner provided with the suction port , and passes through the other end of the cylinder liner. A compressor, characterized in that it is discharged from said coolant passage on the side thereof. 2. A compressor according to claim 1, wherein at least the cylinder of said final compression stage is cooled by circulation of coolant in a coolant passage provided in the piston rod. 3. The compressor according to claim 1, wherein at least the cylinder in the final compression stage is cooled by circulation of coolant in a coolant passage provided between the cylinder cylinder and the cylinder liner. 4. A compressor according to claim 1 , wherein the number of compression stages is three or more. A compressor according to any one of claims 1 to 4 , characterized in that the gas that has passed through the final compression stage is pressurized to 200 bar or more. 6. Compressor according to claim 5 , characterized in that the gas passing through the compression stages before the final compression stage is pressurized to between 100 and 120 bar. A compressor according to any one of claims 1 to 6 , wherein said one or more compression stages are driven by a horizontally opposed crank drive mechanism. a compressor according to any one of claims 1 to 7 ;
a reliquefaction device provided between the inlet and the outlet for returning the gas to a liquid;
The boil-off gas of liquefied natural gas stored in the LNG storage tank is compressed by the compressor to obtain fuel for a combustion engine for propulsion, and the unused fuel is reliquefied by the reliquefaction device to produce the LNG. An LNG tanker characterized by returning to a storage tank.

Images