JP5327464B2 - Cryogenic Stirling Engine and Method for Manufacturing Chilled Stirling Engine - Google Patents

Description

  The present invention particularly relates to a cold Stirling engine that uses cold energy when vaporizing liquefied gas, and a method for manufacturing a cold Stirling engine.

Natural gas, which is a typical example of liquefied gas, is a mixture of hydrocarbons such as methane, ethane, and propane, and is an energy source that naturally exists in underground storage tanks. Although natural gas is said to be less economical than oil, it has attracted a great deal of attention from the global interest in recent energy problems and global warming issues.
Liquefied natural gas (LNG) is transported by a LNG tanker to a large LNG receiving terminal. In major cities, they are led to factories and households by pipelines. At this time, the liquid LNG is vaporized at the LNG receiving terminal and sent out as so-called city gas. On the other hand, in rural areas where it is difficult to install pipelines, LNG is transported to the satellite bases in each area by tank trucks. At the satellite base, the amount of LNG used is vaporized and natural gas is supplied to factories and homes.
Conventionally, large-scale power generation using a direct expansion turbine or Rankine cycle has been performed at some LNG receiving terminals. The output level is about 1 to 10 MW, and in these large-scale power generation facilities, the coefficient of performance (COP) based on LNG latent heat is estimated to be 20 to 40%.
On the other hand, at the satellite base, cold recovery is not possible due to the fact that nighttime LNG shipments are small and continuous operation of power generation facilities is difficult, and that steam turbines that require time and effort to warm up are not suitable for intermittent operation. It is not carried out, and cold heat when vaporizing LNG is released to the atmosphere.
Therefore, it is necessary to make effective use of LNG cold heat, and those using a Stirling engine in a cycle using the cold heat of LNG have already been proposed (for example, Patent Document 1 to Patent Document 3).
Patent Document 4 proposes using a bayonet type heat exchanger as a heat exchanger of a Stirling engine.
Moreover, as a bayonet-type heat exchanger, the structure as shown in patent document 5 to patent document 7 is proposed.

JP 2008-175151 A JP 2006-329059 A JP 2006-275018 A JP 58-25556 A JP-A-7-187603 Japanese Patent Laid-Open No. 10-103882 Japanese Patent Laid-Open No. 11-264677

In Patent Document 1 to Patent Document 3, it is proposed to use cold heat, but these are all related to the cycle and are not related to the configuration of the Stirling engine.
In order to effectively use the cold energy at the time of vaporizing LNG, the heat exchanger for cold heat becomes an operating environment in the temperature range near -200 ° C, so there are performance characteristics and problems in the configuration of the existing Stirling engine. It is not clear.
Therefore, the present inventors investigated performance characteristics using liquid nitrogen as a low-temperature heat source in order to investigate basic characteristics of a cold-powered Stirling engine.
As a result of the experiment, the following points were clarified in a low-temperature heat exchanger using liquid nitrogen as a low-temperature heat source.
Since the heat transfer outside the tube of the low-temperature heat exchanger used for the cold Stirling engine is a heat exchange using a liquid as a heat source, high heat transfer performance is not required as compared with a heat exchanger using a combustion exhaust gas as a heat source. Therefore, it is not necessary to increase the heat transfer area outside the tube, and a simple shape may be used.
When the cold Stirling engine tries to obtain the same output performance as the high temperature heated Stirling engine, the heat exchange in the low temperature heat exchanger of the cold Stirling engine may be small, so that the heat transfer in the pipe can be reduced and an appropriate transmission can be achieved. What is necessary is just to set a heat area.
The heat conduction in the heat exchanger wall varies greatly depending on the type of heat exchanger, but due to the problem of sealing performance in a temperature range close to -200 ° C, workability is high and the ease of supplying a cooling heat source is important. It is a difficult task.
In Patent Document 4, a bayonet type heat exchanger is proposed from the viewpoint that the number of parts is small and the workability is high, but since a Stirling engine using liquid nitrogen as a low-temperature heat source is not assumed, the heat outside the tube While fins for enhancing transmission are provided, workability with an emphasis on sealing performance is not high, and it is not suitable as a low-temperature heat exchanger for a cold Stirling engine.
Also, Patent Documents 5 to 7 do not assume a low-temperature heat exchanger used for a cold Stirling engine, and are not suitable for a cold Stirling engine.

  Accordingly, an object of the present invention is to provide a cold Stirling engine that is excellent in workability especially considering the sealing performance and also excellent in the supply of a cooling heat source, and a method for manufacturing the cold Stirling engine.

  The cold Stirling engine according to claim 1 uses a liquefied gas in a liquefied state as cold energy, a low-temperature heat exchanger, an integrated block body in which a working gas passage space is formed, and a working gas passage space. And a reciprocating flow path of the working gas by a first passage formed in the core tube and a second passage formed between the core and the working gas passage space. It is formed. According to the first aspect of the present invention, it is not necessary to increase the heat transfer area outside the tube by using the liquefied gas in the liquefied state as the cold energy, so that the low-temperature heat exchanger is an integral block body. Since the working gas passage space is formed inside the integrated block body and the core is disposed in the working gas passage space to form the reciprocating flow path, the workability considering the sealing performance is excellent. Yes. Moreover, it can be set as the structure excellent also in the supply of a cooling heat source by making a low-temperature heat exchanger into an integrated block main body.

  According to a second aspect of the present invention, in the cold Stirling engine according to the first aspect, a support portion that contacts the inner peripheral surface of the working gas passage space is formed on the outer peripheral portion of the core, A plurality of grooves that allow the working gas to pass therethrough are formed. According to the second aspect of the present invention, since the core and the inner peripheral surface of the working gas passage space come into contact with each other by the support portion, the cold heat of the block main body can be transmitted to the core and is formed in the core tube. The cold heat can be effectively transmitted to the working gas flowing through the first passage.

  According to a third aspect of the present invention, in the cold Stirling engine according to the first or second aspect, the block body is made of a material having a larger linear expansion coefficient than the core, and the inner diameter dimension of the working gas passage space is The outer diameter dimension of the core is set to a dimension that can maintain an interference fit during cold operation. According to the third aspect of the present invention, the heat conduction loss from the block main body to the core can be reduced, and the cold heat of the block main body can be effectively transmitted to the core.

  According to a fourth aspect of the present invention, in the cold Stirling engine according to any one of the first to third aspects, the block body is made of an aluminum-based material and the core is made of a copper-based material. . According to the fourth aspect of the present invention, high output characteristics can be obtained.

  According to a fifth aspect of the present invention, in the method for manufacturing a cold Stirling engine according to any one of the first to fourth aspects, if the insertion fitting of the core into the working gas passage space is performed by cooling or heating, It is characterized by being performed by According to this invention of Claim 5, while being able to transmit the cold heat of a block main body to a core effectively, damage to members, such as a core, can be prevented compared with press injection.

  According to a sixth aspect of the present invention, in the cold Stirling engine according to the first aspect, a liquid heat medium is used as the heat medium of the high-temperature heat exchanger. According to the sixth aspect of the present invention, the downsizing of the apparatus can be realized by using the liquid heat medium for the high temperature heat exchanger as well as the low temperature heat exchanger.

  According to a seventh aspect of the present invention, in the cold Stirling engine according to the sixth aspect, the present invention is characterized in that it includes a fluidity reduction preventing means for preventing a fluidity degradation of a heat medium used in a high-temperature heat exchanger. According to this invention of Claim 7, the fluidity | liquidity fall of the heat medium by the influence of the low temperature heat exchanger used as an extremely low temperature can be prevented, and the heat transfer performance of a high temperature heat exchanger can be maintained.

According to the present invention, the working gas passage space is formed inside the integrated block body, and the core is disposed in the working gas passage space to form the reciprocating flow passage. Excellent in properties.
In the present invention, the working gas passage space is formed by the integrated block main body, so that dimensional accuracy can be obtained by machining so that the workability is excellent and the sealing property is good. Further, by forming the working gas passage space by the integrated block body, the second passage can be manufactured at an equal interval and can be maintained, so that there is no drift of the working gas and the heat exchange property is improved.
In addition, when the support part which contact | abuts with an internal peripheral surface is formed, the effective cold heat transmission by contact can be performed and a working gas can be equally distributed by the correct positioning of a core.
In addition, when a plurality of grooves are formed in the support portion, heat transfer can be promoted by increasing the heat transfer area to the working gas, promoting turbulent flow accompanying contraction / expansion, and further uniformizing the working gas by applying resistance. In addition, it is possible to secure the working gas passage and facilitate the insertion fitting. In addition, since it is an interference fit during cold operation, the heat transfer is good and the sealing portion can prevent leakage of the working gas.
Further, when the block main body is made of an aluminum material and the core is made of a copper material, heat transfer is good and a high output can be obtained, and the effect of the interference fit can be promoted by the difference in coefficient of linear expansion. Moreover, weight reduction can be achieved by using an aluminum-based material for the outer block body. In particular, the block body is made of an aluminum-based material, so that the outside can be cooled quickly with little cold, and the core is made of a copper-based material. Good temperature drop.
In addition, when an interference fit is achieved by cooling or heating, for example, no eccentricity is generated compared to press-fitting, damage to the block main body and the core can be prevented, a close contact effect is high, and the second passage can be equally spaced. Therefore, there is no drift of the working gas, and the heat exchange is good.
In addition, when a liquid heat medium is used as the heat medium of the high-temperature heat exchanger, the apparatus can be downsized, and the high-temperature side can also quickly start up the apparatus because of heat transfer due to the liquid.
In addition, when equipped with fluidity reduction prevention means, it is possible to prevent the flow rate from decreasing due to freezing or increase in viscosity, maintain heat transfer characteristics, and prevent engine operation troubles such as shutdown due to no high-temperature heat supply. It can be prevented.

The whole block diagram of the cooling Stirling engine which shows the example in one embodiment of the present invention. 1 is an enlarged cross-sectional view of the main part of FIG. Partial cutaway perspective view of a low-temperature heat exchanger used in the cold Stirling engine Bottom view of the low-temperature heat exchanger Perspective view of the core used in the cold Stirling engine Cross section of the core Output characteristic diagram showing experimental results of indicated output Wi and power generation output Wg with respect to engine speed when working gas average gas pressure Pm is 2.5 MPa Temperature characteristic diagram showing experimental results of compressed space gas temperature Tcomp and low temperature heat exchanger wall temperature Tw2 with respect to engine speed Temperature characteristic diagram showing experimental results of expansion space gas temperature Texp and normal temperature water outlet temperature Tout with respect to engine speed Calorific value characteristic graph showing experimental results of total engine heat input amount Qtotal and cooling heat amount Qrej with respect to engine speed Characteristic diagram of main thermal efficiency and COP Power generation end efficiency ηg (= Wg / Qtotal), internal conversion efficiency ηint (ratio of indicated output Wi and expansion space indicated output WE) and COP (coefficient of performance = Wg / Qrej) Characteristic diagram showing energy balance of experimental Stirling engine with respect to engine speed when working gas average gas pressure Pm is 3.5 MPa

Hereinafter, examples of one embodiment of the cold Stirling engine of the present invention will be described.
FIG. 1 is an overall configuration diagram of a cooling Stirling engine according to the present embodiment, FIG. 2 is an enlarged cross-sectional view of the main part of FIG. 1, FIG. 3 is a partially cutaway perspective view of a low-temperature heat exchanger used in the cooling Stirling engine, FIG. Is a bottom view of the low temperature heat exchanger, FIG. 5 is a perspective view of a core used in the cold Stirling engine, and FIG. 6 is a sectional view of the core.

As shown in FIG. 1, the Stirling engine according to this embodiment is a cold Stirling engine that cools a low-temperature heat exchanger 10 using cold energy, and the low-temperature heat exchanger 10 is directly connected to a low-temperature heat source 1 such as liquid nitrogen. It installs so that it may touch and uses liquefied gas in a liquefied state as cold energy. The low-temperature heat source 1 is stored in a space covered by a container 2 made of a heat insulating material. Instead of the container 2, a pipe through which the low-temperature heat source 1 is circulated may be used. Basically, it is preferable that the low-temperature heat exchanger 10 is in contact with the liquefied gas in a liquid state. When piping is provided, the vaporization means (not shown) located downstream of the low-temperature heat source 1 is finally vaporized. It is preferable to make it.
The cold heat Stirling engine has a displacer piston 21 and a power piston 22. The displacer piston 21 and the power piston 22 are connected to a crankshaft 24 via a scotch / yoke mechanism 23, respectively. The displacer piston 21 and the power piston 22 are provided with phases shifted by a predetermined angle. One end side of the crankshaft 24 is connected to the generator 25. A flywheel 26 is connected between the crankshaft 24 and the generator 25 and the other end of the crankshaft 24.

The low-temperature heat exchanger 10 includes an integrated block body 12 having a working gas passage space 11 formed therein, and a core 13 inserted and fitted into the working gas passage space 11.
The regenerator 31 and the high temperature heat exchanger 32 are disposed on the outer peripheral portion of the cylinder 27. A displacer piston 21 is disposed in the cylinder 27. One of the cylinders 27 is covered by the head portion 14 formed by the low-temperature heat exchanger 10, a compression space is formed between the head portion 14 and the displacer piston 21, and between the displacer piston 21 and the power piston 22. An expansion space is formed.
The regenerator 31 has circular tubes arranged concentrically with respect to the cylinder 27, and a gap between each circular tube is filled with a wire mesh matrix material such as austenitic stainless steel or brass. The working gas passes through the matrix material and flows to the low temperature heat exchanger 10 or the high temperature heat exchanger 32. When the working gas passes through the regenerator 31, the working gas absorbs heat from the matrix material or dissipates heat to the matrix material.
The high temperature heat exchanger 32 is divided into a passage through which a heat medium flows and a passage through which a working gas flows, and the working gas is heated by the heat medium.
The high temperature heat exchanger 32 is supplied with a liquid heat medium such as room temperature water. In the present embodiment, a constant temperature water tank 33 is provided, and normal temperature water in the constant temperature water tank 33 is supplied to the high temperature heat exchanger 32 by a pump 34. By using a liquid heat medium such as room temperature water for the high-temperature heat exchanger 32, the high-temperature heat exchanger 32 can be downsized and quickly started up because of its high heat transfer coefficient and large heat capacity. Along with the fact that the side heat exchanger 10 operates with liquid, the cold Stirling engine is small and highly responsive. The room temperature water supplied to the high temperature heat exchanger 32 is returned to the constant temperature water tank 33 after radiating heat to the working gas. The high temperature heat exchanger 32 is provided with a detecting means 35 for detecting the fluidity of room temperature water (heat medium). When the detecting means 35 detects a decrease in the fluidity of the ordinary temperature water, it is heated by the control unit 36. The means 37 is operated. As the detection means 35, for example, a temperature detector can be used, and the temperature of the heat medium outlet side flow path of the high temperature heat exchanger 32 is detected. This detecting means 35 may be provided anywhere in the path of room temperature water including the constant temperature water tank 33, but in particular, by providing it in the flow path on the outlet side of the heat medium, room temperature water due to the influence of the low temperature heat exchanger 10 is provided. It can respond quickly to freezing. Moreover, the flow rate detector which detects the flow volume of a heat medium can be used for the other means as the detection means 35. FIG.

  In this embodiment, by operating the heating means 37, the room temperature water in the constant temperature water tank 33 is maintained at a predetermined temperature or the temperature of the room temperature water is increased to prevent freezing and to prevent a decrease in fluidity. . In the present embodiment, the fluidity reduction prevention means is configured by the detection means 35, the control unit 36, and the heating means 37. However, the fluidity reduction prevention means does not include the detection means 35 or the control unit 36, and includes atmospheric heat, The temperature of the heat medium may be maintained at a predetermined temperature or higher by using sunlight or industrial waste heat. In addition to the electric heater, the heating means 37 may use natural gas combustion heat vaporized by the cold Stirling engine of this embodiment. As the power source of the electric heater, the electric power generated by the cold Stirling engine of this embodiment can be used, and it is also effective to use the heat loss of the generator and the mechanical loss of the drive unit. Further, as the fluidity reduction preventing means, when the liquid heat medium is water, chemical means using an additive such as an antifreeze solution may be used.

Next, the low temperature heat exchanger 10 according to the present embodiment will be described with reference to FIGS.
The low-temperature heat exchanger 10 includes an integrated block body 12. The block main body 12 includes a cylindrical portion 12A that forms a heat source side concave portion therein, and a flange portion 12B that is disposed at one end of the cylindrical portion 12A and forms a head portion 14 in the center portion. Heat transfer performance is enhanced by forming a plurality of axial slits 12C at predetermined intervals on the outer periphery of the cylindrical portion 12A. A plurality of holes 16 for inserting fastening bolts 15 are provided in the flange portion 12B. The flange portion 12 </ b> B abuts on a cylinder side flange 27 </ b> A formed at the end of the cylinder 27 and is connected to the cylinder side flange 27 </ b> A by the fastening bolt 15. At this time, the sealing material 27B composed of a carbon sheet or the like mounted in a groove provided in the cylinder side flange 27A is deformed, and sealing is performed between the flange portion 12B on the low temperature heat exchanger 10 side and the cylinder side flange 27A. ing. The sealing material composed of the carbon sheet or the like is formed in a flat packing shape without providing a groove, and is sandwiched between the flange portion 12B and the cylinder side flange 27A, and is tightened by the fastening bolt 15 to be sealed. May be performed. The cylindrical portion 12A, the flange portion 12B, and the cylinder side flange 27A of the block main body 12 are configured to be easily machined. The flatness and surface roughness of the flange portion 12B and the cylinder side flange 27A, and the groove of the sealing material 27B. Since the dimensional accuracy and surface roughness can be processed moderately, the compression of the sealing material 27B can be ensured properly, and the sealing performance is good.
A plurality of working gas passage spaces 11 are formed in the block body 12. The working gas passage space 11 is a columnar concave portion, and is formed inside the cylindrical portion 12A with the end face of the flange portion 12B as an opening. In this embodiment, a plurality of working gas passage spaces 11 are concentrically arranged, but are not necessarily arranged concentrically, so that the working gas in the head portion 14 can flow uniformly. The working gas passage spaces 11 are evenly arranged.

The cylindrical recess inner peripheral surface of the working gas passage space 11 communicates with the head portion 14 through a working gas communication passage 11A. The working gas communication passages 11 </ b> A are formed for each working gas passage space 11, and each working gas communication passage 11 </ b> A is formed radially from the center of the head portion 14. Further, an imaginary point X where the axes of the working gas communication passages 11A intersect is set on the displacer piston 21 side outside the space of the head portion 14, so that the working gas communication passage 11A is a surface perpendicular to the axis of the cylinder 27. It is inclined with respect to. In this manner, the working gas communication passage 11A is formed radially from the center of the head portion 14 for each working gas passage space 11, and further provided with an inclination, so that the working gas in the head portion 14 can flow uniformly. At the same time, workability can be improved.
A communication passage 11B that connects the working gas passage space 11 and the regenerator 31 is formed on the end face of the cylinder side flange 27A. Since the block main body 12 has a block configuration and is not configured by a combination of piping, fins, and the like, machining is possible, dimensional accuracy of each part is easily obtained, and workability is high. In addition, since a plurality of working gas passage spaces 11 do not have a welding structure and do not have a seal portion that causes external leakage, the device has high sealing performance.

A core 13 is inserted and fitted into the working gas passage space 11. The core 13 is a cylindrical tube that is open at both ends, and a support portion 13 </ b> A that contacts the inner peripheral surface of the working gas passage space 11 is formed on the outer peripheral portion of the core 13. By bringing the core 13 and the inner peripheral surface of the working gas passage space 11 into contact with each other by the support portion 13A, the cold heat of the block body 12 can be directly transmitted to the core 13 and the first formed in the tube of the core 13 is formed. The cold heat can be effectively transmitted also to the working gas flowing through the passage. A plurality of grooves 13B that allow the working gas to pass therethrough are formed in the support portion 13A. In this embodiment, the grooves 13B are provided in the axial direction of the core 13, but heat transfer performance can be improved by providing the grooves 13B in a spiral shape. The support portion 13A is preferably formed by being divided into a plurality of portions. By dividing the support portion 13A into a plurality of parts, the insertion fitting of the core 13 into the working gas passage space 11 can be facilitated, and the flow resistance of the working gas flowing through the outer peripheral portion of the core 13 can be reduced. In addition, nonuniformity between the grooves of the working gas flow divided by the grooves 13B can be eliminated. A sealing portion 13C is formed at the end of the core 13 on the flange portion 12B side. The sealing portion 13 </ b> C prevents leakage between the first passage formed in the tube of the core 13 and the second passage formed in the outer peripheral portion of the core 13. Further, the support 13A is not formed at the other end of the core 13 so that the first passage formed in the tube of the core 13 and the second passage formed in the outer peripheral portion of the core 13 are provided. The flow resistance at the edge is reduced. Further, since the outer peripheral portion of the support portion 13A of the core 13 and the sealing portion 13C can be machined, dimensional accuracy can be easily obtained and the height of the groove 13B can be made uniform. For this reason, the difference in resistance between the grooves is small, and in combination with the effect of eliminating the non-uniformity of the working gas flow between the grooves by providing the groove portions at a plurality of positions as in this embodiment, the second passage is formed. The flow of working gas can be made uniform. Further, the heat transfer coefficient can be expected to be improved by the action of the working gas contracting and expanding after the groove and the groove.
Furthermore, since the size of the core inserted into the plurality of working gas passage spaces 11 is small, the block main body 12 can be machined, and the working gas passage space 11 itself can be manufactured with high precision. It is possible to reduce variation in resistance between a plurality of working gas passages. As a result, in addition to the effect of imparting resistance to the working gas flow by the groove 13B, the working gas flow between the plurality of working gas passages can be evenly distributed, and there is no drift.

The second passage formed in the outer peripheral portion of the core 13 communicates with the compression space between the displacer piston 21 and the head portion 14 through the working gas communication passage 11 </ b> A, and is formed in the tube of the core 13. The first passage communicates with the regenerator 31 through the communication passage 11B.
Therefore, the working gas flowing out from the compression space is led to the regenerator 31 through the working gas communication passage 11A, the second passage, the first passage, and the communication passage 11B in order, and then the high temperature heat exchanger 32 is passed through the high temperature heat exchanger 32. Via, it is guided into the expansion space between the displacer piston 21 and the power piston 22. The working gas in the expansion space is led to the compression space through the high-temperature heat exchanger 32, the regenerator 31, the communication passage 11B, the first passage, the second passage, and the working gas communication passage 11A in this order.
In the above configuration, when the starter is started, the displacer piston 21 is operated using the generator 25 as a power source, so that the working gas moves between the expansion space that is one space of the displacer piston 21 and the compression space that is the other space. . The working gas is heated by the high temperature heat exchanger 32 and introduced into the expansion space, and cooled by the low temperature heat exchanger 10 and introduced into the compression space, so that the working gas is interposed between the compression space and the space behind the power piston 22. A pressure fluctuation occurs, and an output can be obtained by operating the power piston 22 due to the pressure fluctuation in the working space.

The block body 12 is made of a material having a larger linear expansion coefficient than the core 13. The block body 12 is manufactured by integral cutting. The core 13 is also preferably manufactured by integral cutting. For the block main body 12, for example, an aluminum alloy (A7075) having high strength and high thermal conductivity or stainless steel (SUS316) that has excellent corrosion resistance and has a track record as a cryogenic structural material is suitable. For example, a copper alloy (C1100) having a high thermal conductivity is suitable. In particular, high output characteristics can be obtained by using the block body 12 as an aluminum material and the core 13 as a copper material. An aluminum alloy has a characteristic that it has high strength in a low temperature range. Among them, A7075 is a high-strength material having a tensile strength of 600 MPa or more at a level of −100 to −200 ° C. Further, by using the block main body 12 as an aluminum material and the core 13 as a copper material, it is possible to promote interference fit and reduce the weight from the difference in linear expansion coefficient between them. Furthermore, since the outer block body 12 is made of aluminum, it can be cooled quickly with a small amount of cold heat, has a high temperature drop, and the core 13 has a high thermal conductivity, so that the working gas can be cooled effectively.
Insertion fitting of the core 13 into the working gas passage space 11 is performed by interference fit by cooling or heating. At the time of assembly, the core 13 is cooled with liquid nitrogen, and the core 13 having a diameter of 15 mm is contracted by about 20 to 30 μm and inserted into the block main body 12 kept warm by a ribbon heater. In this way, it is confirmed that the core 13 after the interference fit is fitted with a firm fit. Note that the interference fit by cooling or heating can be performed only by cooling or only by heating depending on dimensions, materials, use conditions, and the like.
Since the block main body 12 and the core 13 are assembled by an interference fit by cooling or heating, a dimensional tolerance is given so that the components become an interference fit during the cold operation. Heat conduction from the block body 12 to the core 13 by setting the inner diameter dimension of the working gas passage space 11 and the outer diameter dimension of the support portion 13A of the core 13 so as to maintain an interference fit during the cooling operation. Loss can be reduced and the cold heat of the block body 12 can be effectively transmitted to the core. Further, it is possible to reliably prevent the working gas from leaking from between the working gas passage space 11 and the sealing portion 13C of the core 13, and for example, by using a combination of an aluminum alloy and a copper alloy, the operation gas can be more reliably operated. Leakage can be eliminated. Therefore, the sealing performance is high from the viewpoint of preventing internal leakage of the working gas.

Hereinafter, experimental examples of the cold Stirling engine according to the embodiment of the present invention will be described.
The basic specifications are the configuration of the cold Stirling engine already described, but the main specifications are the beta type, the piston diameter is 100 mm, the displacer piston 21 stroke is 32 mm, and the power piston 22 stroke is 28 mm. Helium was used, the average pressure was 3-4 MPa, and the target output was 500 W / 1000 rpm. A PM generator was used as the generator 25. This engine is based on an exhaust heat utilization engine that can generate a power output of about 500 W by operating a diesel engine exhaust gas at about 400 ° C. as a high-temperature heat source.
As shown in FIG. 1, as a container 2 around the low-temperature heat exchanger 10, an insulating container made of polystyrene foam was attached, and a low-temperature heat source such as liquid nitrogen was supplied into the inside thereof to exchange heat.
In this experiment, the working gas temperature and pressure were measured at three locations, the compression space, the expansion space, and the buffer space (the space around the flywheel 26), and the wall temperature of the low-temperature heat exchanger 10 was 2 in the vertical direction. Measurements were made at several locations. In addition, the temperature at the inlet and outlet of room temperature water was measured at two locations. In addition, a constant temperature water tank 33 is installed in order to stabilize the performance of the high temperature heat exchanger 32, and an electric heater with a rated capacity of 4 kW is installed as a heating means 37 in the constant temperature water tank 33 so that room temperature water is heated to about 40 ° C. It was kept warm and circulated. Liquid nitrogen was supplied intermittently from the storage container according to the measured value of the wall temperature of the low-temperature heat exchanger 10 and the temperature in the insulated container 2 made of polystyrene foam.

FIG. 7 is an output characteristic diagram, and FIGS. 8 and 9 are temperature characteristic diagrams.
FIG. 7 shows the experimental results of the indicated output Wi and the power generation output Wg with respect to the engine speed when the working gas average gas pressure Pm is 2.5 MPa. From this, it can be seen that when an A7075 heat exchanger is used, a power output of about 100 W higher than that of a SUS316 heat exchanger is obtained. In addition, the output performance at the time of using the heat exchanger made from SUS316 is comparable as the heat exchanger made from a copper pipe used for the preliminary test.
FIG. 8 shows the experimental results of the compressed space gas temperature Tcomp and the low-temperature heat exchanger wall temperature Tw2 with respect to the engine speed. This shows that the compressed space gas temperature when using the A7075 heat exchanger is about 15 ° C. lower than that of the SUS316 heat exchanger. This is considered to be due to the difference in the thermal conductivity of the heat exchanger block main body, and it is considered that the output of the A7075 heat exchanger was higher due to this difference.
FIG. 9 shows the experimental results of the expansion space gas temperature Texp and the normal temperature water outlet temperature Tout with respect to the engine speed. The normal temperature water inlet temperature is maintained at about 40 ° C. by the electric heater in the constant temperature water tank 33, and the normal temperature water outlet temperature is lowered to about 18 to 24 ° C. In the preliminary test conducted without a constant temperature water tank, the temperature of the room temperature water dropped to 0 ° C or below and it was frozen in the heat exchanger. It has been confirmed that the temperature is generally stable at about 15 to 18 ° C.

FIG. 10 shows a calorific value characteristic chart, and FIG. 11 shows a thermal efficiency and COP characteristic chart.
FIG. 10 shows the experimental results of the total engine heat input amount Qtotal and the cooling heat amount Qrej with respect to the engine speed. Here, the total engine heat input is calculated from the room temperature water flow rate and the inlet / outlet temperature, and the total cooling heat is calculated as the difference between the total engine heat input and the indicated output (see FIG. 12). It can be seen from this that the total engine heat input when using the A7075 heat exchanger is slightly larger than that of the SUS316 heat exchanger.
FIG. 11 shows the power generation end efficiency ηg (= Wg / Qtotal), the internal conversion efficiency ηint (ratio of the indicated output Wi and the expansion space indicated output WE), and COP (coefficient of performance = Wg / Qrej). This shows that the power generation end efficiency of the experimental Stirling engine is about 20%, the internal conversion efficiency is about 40-50%, and the COP is about 25-30%. In order to evaluate the net COP, it is necessary to examine the consumption amount of liquid nitrogen.
From this experiment, as a result of operation using liquid nitrogen as a low-temperature heat source using the same shape stainless steel heat exchanger and aluminum alloy heat exchanger, the heat exchanger made of aluminum alloy with high thermal conductivity High output performance was obtained.

FIG. 12 shows the energy balance of the experimental Stirling engine under the conditions (maximum working gas pressure: 3.5 MPa, engine speed: 1200 rpm) where the maximum output was obtained in the above operation.
In general, performance evaluation is often performed on a cooling / heating device on the basis of the amount of heat of cooling, but this figure shows the transfer of heat from a high-temperature heat source (room temperature water). The engine heat input is 4953 W, the cooling heat is 3841 W, the power generation efficiency is 18%, and the COP is 23%. Moreover, the miscellaneous heat loss (total of heat conduction loss and reheat loss) in this experiment is 2219W. This is considerably large in the high-temperature heating engine using a heat source of about 400 ° C., while the miscellaneous heat loss is about 700 to 800 W. Although it is difficult to make a detailed evaluation from the current measurement data, it is thought that there is no significant difference in the heat conduction loss due to the temperature difference between the upper and lower cylinders, so it is assumed that the cold engine has a large reheat loss . That is, the thermal efficiency and COP can be increased by reducing this loss.
From this experiment, it was confirmed that stable long-time operation was possible by keeping the room temperature water warm using the constant temperature water bath 33. In practical use, it is important to optimize the heat transfer performance of the high-temperature heat exchanger 32 and supply room temperature water at a stable temperature.

  The present invention can be used particularly for cold recovery at a local LNG satellite station, but the low-temperature heat exchanger according to the present invention is suitable for a heat exchanger using liquefied gas as a cold heat source.

DESCRIPTION OF SYMBOLS 1 Low temperature heat source 2 Container 10 Low temperature heat exchanger 11 Working gas passage space 12 Block main body 13 Core 13A Support part 13B Groove 32 High temperature heat exchanger 35 Detection means (fluidity fall prevention means)
36 control unit (fluidity lowering prevention means)
37 Heating means (fluidity reduction preventing means)

Claims (7)

  In a cold Stirling engine that cools a low-temperature heat exchanger using cold energy, a liquefied gas is used in the liquefied state as the cold energy, and the low-temperature heat exchanger is an integrated block in which a working gas passage space is formed. A main body and a core inserted and fitted in the working gas passage space, and a first passage formed in a pipe of the core and a first passage formed between the core and the working gas passage space. A refrigerating Stirling engine characterized in that a reciprocating flow path for the working gas is formed in two passages.   A support portion that contacts the inner peripheral surface of the working gas passage space is formed on the outer peripheral portion of the core, and a plurality of grooves that allow the working gas to pass therethrough are formed on the support portion. The cold Stirling engine according to claim 1.   The block body is made of a material having a linear expansion coefficient larger than that of the core, and the inner diameter dimension of the working gas passage space and the outer diameter dimension of the core are set to dimensions that can maintain an interference fit during cold operation. The cold Stirling engine of Claim 1 or Claim 2 characterized by the above-mentioned.   4. The cold Stirling engine according to claim 1, wherein the block main body is made of an aluminum-based material and the core is made of a copper-based material. 5.   The method for manufacturing a cold Stirling engine according to any one of claims 1 to 4, wherein the fitting of the core into the working gas passage space is performed by the interference fit by cooling or heating. A method of manufacturing a cold Stirling engine.   The cold heat Stirling engine according to claim 1, wherein a liquid heat medium is used as a heat medium of the high temperature heat exchanger.   The cold Stirling engine according to claim 6, further comprising fluidity reduction preventing means for preventing fluidity reduction of the heat medium used in the high temperature heat exchanger.