JPH08313083A - Regenerative heat exchanger for stirling engine - Google Patents

Abstract

PURPOSE: To improve the heat exchange performance in the regenerative heat exchanger of a Stirling engine having heat exchange cool storage medium capable of passing operating gas in a cylinder opened at both end faces. CONSTITUTION: In a displacer containing cool storage medium 24 made of sintered metal in a cylinder 22, threaded surfaces extending at the entire periphery engaging the inner periphery of the cylinder 22 with the outer periphery of the medium 24 or the outer periphery of the medium is covered with a sealing material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Stirling engine such as a Stirling engine used for generating power and a Stirling refrigerator used for generating low temperature, and more particularly to improvement of heat exchange performance of a regenerative heat exchanger thereof. is there.

[0002]

2. Description of the Related Art Stirling engines are theoretically extremely high in thermal efficiency, can use all kinds of heat sources other than petroleum, and are quiet and have low pollution. It is being advanced.
Further, also for the Stirling refrigerator, which is the reverse cycle of the Stirling engine, for the same reason as above, particularly in recent years, because harmful refrigerants such as CFC are unnecessary,
It's getting a lot of attention.

For example, FIG. 5 shows a displacer type Stirling refrigerator. The expansion cylinder (2) and the compression cylinder (3) are attached to the main body housing (1) at an angle difference of 90 degrees, and the expansion cylinder (2) has a built-in displacer (6) and a compression cylinder (3). The built-in compression piston (7) is connected to a common crank mechanism (5) and is reciprocally driven in a state in which the phases are shifted from each other.

As shown in FIG. 6, the displacer (6) is filled with a regenerator material (14) made of, for example, a sintered metal inside a cylindrical body (17) having openings (18) and (19) at both ends. The working gas G that has flowed in from one opening (18) of the tubular body (17) passes through the inside of the cold storage material (14) and then flows out from the other opening (19) to the cold storage material (14). Heat exchange is performed. The displacer (6) also has a function as a regenerative heat exchanger, and its heat exchange performance greatly influences the coefficient of performance of the Stirling refrigerator.

Further, as shown in FIG. 5, the expansion cylinder (2) and the compression cylinder (3) are separated from the crank chamber (12) by oil seals (8) and (9), respectively.
The base end of the cylinder and the tip of the compression cylinder (3) are connected
They are communicated with each other by (4). Oil (10) is injected into the crank chamber (12).

FIG. 7 shows the operation of the above Stirling refrigerator with the horizontal axis representing time T and the vertical axis representing stroke S. In the Stirling refrigerator, the displacer (6) reciprocates as shown by curves B and C in FIG. 7, and at the same time the compression piston (7) reciprocates as shown by curve D in FIG. ) Expansion space (11)
Shows a change in volume in the width region between the straight line A and the curve B in FIG. 7, and the compression space (13) of the compression cylinder (3) has a volume in the width region between the curves C and D in FIG. Change.

As a result, in the process of FIG.
The gas in (13) is compressed and flows into the expansion cylinder (2) through the connecting pipe (4) (isothermal compression). This gas passes through the cool storage material (14) in the displacer (6) in the process of FIG. 7 and exchanges heat with the cool storage material (14) to lower the temperature (constant volume cooling). The gas that has passed through the regenerator material (14) flows into the expansion space (11) of the expansion cylinder (2) in the process of FIG. 7, and then expands as the displacer (6) descends (isothermal expansion). Next, in the process of FIG. 7, the displacer is
As the temperature of (6) rises, the gas in the expansion space (11)
After passing through 4), exchanging heat with the regenerator material (14) and raising the temperature, it again flows into the compression space (13) via the connecting pipe (4).
(Heating with constant volume). As a result, the cold head (15) provided on the head of the expansion cylinder (2) is cooled.

By the way, the displacer (6) has a cylindrical body (17) filled with a cool storage material (14) as shown in FIG. 6, but the cool storage material (14) made of a sintered metal is The heat exchange with the working gas G is performed as described above, and the temperature difference generated at that time is generated.
(For example, about 200 ° C.) causes thermal deformation. The displacer (6) is required to maintain airtightness with the inner peripheral surface of the expansion cylinder (2) and to smoothly reciprocate, so that the tubular body (17) is deformed due to the thermal deformation of the regenerator material (14). Changes in the outer diameter of the must be avoided. Therefore, cool storage material (14)
For the free thermal deformation of the regenerator material (14) and cylinder
A certain amount of gap (for example, about 0.5 mm) is provided between (17).

Further, there is a limit to the processing accuracy when the cold storage material (14) is formed from sintered metal, and in order to load the cold storage material (14) into the cylindrical body (17) at the time of assembly. , There is no choice but to fit them with a clearance fit.

[0010]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
If there is a gap between the (14) and the cylinder (17), the working gas flowing from the opening (18) of the cylinder (17) into the regenerator material (14), the regenerator material (14) It leaks out from the outer peripheral surface to the clearance space, goes straight through the clearance space with small flow resistance, and flows out from the opening (19) of the tubular body (17) with almost no heat exchange with the regenerator material (14). Become. As a result, there is a problem that the heat exchange performance of the reheat exchanger constituted by the displacer (6) deteriorates, and the coefficient of performance of the Stirling refrigerator greatly decreases. This problem also occurs not only in the Stirling refrigerator but also in other Stirling engines equipped with a regenerative heat exchanger.

It is an object of the present invention to improve the heat exchange performance of a regenerative heat exchanger, thereby increasing the thermal efficiency of a Stirling engine.

[0012]

A regenerative heat exchanger for a Stirling engine according to the present invention has a tubular body having open ends.
A filler for heat exchange that allows passage of working gas is arranged, and an uneven surface is formed on the inner peripheral surface of the cylindrical body and the outer peripheral surface of the filler that mesh with each other and extend all around. Is characterized by. In a specific configuration, the uneven surface is a threaded surface that meshes with each other.

Further, in another regenerative heat exchanger of the Stirling engine according to the present invention, the outer peripheral surface of the filling material is covered with a sealing material which prevents leakage of the working gas. In a specific configuration, the seal material is made of a material having a thermal expansion coefficient that is substantially the same as that of the filler.

In any structure, a gap corresponding to the coefficient of thermal expansion of the filler is provided between the inner peripheral surface of the cylinder and the outer peripheral surface of the filler.

[0015]

With the structure in which the inner and outer peripheral surfaces of the cylindrical body and the outer peripheral surface of the filling material are formed with irregularities, even if the working gas flowing into the filling material leaks into the space between the cylindrical body and the gap, Space is
The meshing of the concave and convex surfaces forms a flow path having a large flow resistance that is bent along the cylinder axis direction, so that the working gas in the gap space becomes a turbulent flow and collides with the surface of the filler. Further, as the flow resistance increases, the gas pressure in the gap space becomes higher than that in the conventional straight gap space, and the flow rate of the working gas leaking from the filling material decreases.
As a result, most of the working gas that has flowed into the filling material from the opening of the tubular body does not leak out, passes through the inside of the filling material, and sufficiently exchanges heat with the filling material.

Further, in a concrete structure in which the uneven surface is a threaded surface, a spiral flow path is formed by the engagement of the threaded surfaces, and the working gas flows along the flow path. The gas flow path becomes long according to the thread pitch, and the flow resistance of the working gas increases. As a result, most of the working gas that has flowed into the filler through the opening of the cylinder does not leak,
It passes through the inside of the filling material and sufficiently exchanges heat with the filling material.

In the structure in which the outer peripheral surface of the filling material is covered with the sealing material, the working gas that has flowed into the inside of the filling material is sealed by the sealing material and does not flow out into the space between the tubular body. Therefore, all the working gas flowing into the filling material from the opening of the tubular body does not leak, and passes through the inside of the filling material,
Sufficient heat exchange with the filler.

Further, in a specific structure in which the seal material is made of a material having substantially the same coefficient of thermal expansion as the filler, even if the filler expands or contracts due to temperature change, the seal material also expands or contracts. Therefore, a gap is not created between the seal material and the filler, and the seal material is not damaged by thermal stress.

In any of the structures, a gap space is provided between the inner peripheral surface of the cylindrical body and the outer peripheral surface of the filling material according to the coefficient of thermal expansion of the filling material. The space absorbs the thermal deformation of the filler. Therefore, there is no possibility that the cylinder will be deformed.

[0020]

According to the regenerative heat exchanger of the Stirling engine according to the present invention, the working gas and the filling material are sufficiently brought into contact with each other to perform the heat exchange, so that the heat exchange performance is excellent. As a result, the Stirling engine The thermal efficiency of is high.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Two examples in which the present invention is applied to the displacer of the Stirling refrigerator shown in FIG. 5 will be described in detail with reference to the drawings. Since the operation of the Stirling refrigerator is the same as the conventional one, the description is omitted.

First Embodiment A displacer (21) shown in FIG. 1 has an inner thread (23) formed on the inner peripheral surface of a resin cylinder (22) and is made of stainless steel,
An outer screw (25) is formed on the outer peripheral surface of a regenerator material (24) made of a sintered metal such as lead or copper, and the inner screw (23) and the outer screw (25) are meshed with each other. However, the inner screw (23) and the outer screw
Specifications of (25) such as a pitch circle diameter are determined in order to provide a proper gap between them in accordance with the thermal expansion of the regenerator material (24). Therefore, the displacer (21) can be assembled by screwing the regenerator material (24) into the tubular body (22).

The working gas such as helium sent from the compression space of the compression cylinder to the expansion cylinder is stored in the cylinder (2
2) It flows into the inside of the cold storage material (24) through one of the openings, most of it passes through the inside of the cold storage material (24), and after sufficient heat exchange with the cold storage material (24), the tubular body It flows into the expansion space of the expansion cylinder from the other opening of (22).

Here, only a part of the working gas is the cylindrical body (22).
It will leak into the gap space between the inner peripheral surface of and the outer peripheral surface of the cool storage material (24). However, as shown in FIG. 2, a zigzag bent flow path is formed between the inner screw (23) of the tubular body (22) and the outer screw (25) of the regenerator material (24). The working gas flowing in the flow path in the cylinder axis direction swirls every time the direction of the flow changes, resulting in a large pressure loss.

Further, a part of the leaked gas flows spirally along the screw thread as shown by the arrow. In this case, the total length L of the spiral gas flow path is defined by the diameter D of the cold storage material (24),
If the height of (24) is H and the screw pitch is p, L ≒ πDH
/ P. On the other hand, in the conventional displacer, since the leaked gas traveled straight through the gap between the cylinder and the regenerator material in the cylinder axis direction, the length of the gas flow path was equal to the height H of the regenerator material (24). Become. Therefore, in the case of the present embodiment of FIG.
The flow path becomes longer by a factor of / p, and the flow resistance increases accordingly.

As a result, the flow rate of the gas leaking from the inside of the cool storage material (24) to the clearance space becomes extremely small, and most of the working gas flowing into the cool storage material (24) flows in the cool storage material (24). , Sufficient heat exchange with the cold storage material (24).

Second Embodiment In the displacer (27) shown in FIG. 3, the sealing material (30) is provided so as to cover the outer peripheral surface of the regenerator material (29) made of sintered metal. The seal material (30) is made of the same metal as the sintered metal that constitutes the cold storage material (29) or a material having a thermal expansion coefficient of approximately the same, and as shown in FIG. 4, it adheres closely to the outer peripheral surface of the cold storage material (29). Are arranged.

For example, when the sealing material (30) is made of stainless steel, a thin-walled pipe made of stainless steel is prepared in advance, the thin-walled pipe is filled with sintered metal, and heat is applied to the sintered metal in this state. A method of performing molding can be adopted. According to this method, the outer peripheral surface of the regenerator material (29) and the inner peripheral surface of the seal material (30) are fused to each other.

When the sealing material (30) is made of resin, the regenerator material (29) is prepared by sintering and then the regenerator material (2) is used.
A method of applying resin to the outer peripheral surface of 9) can be adopted.

According to the displacer (27), the regenerator material (2
The working gas that has flowed into the inside of 9) is sealed by the sealing material (30) and does not flow out into the space between the tubular body (28). Therefore, all the working gas flowing into the cool storage material (29) from the opening of the tubular body (28) does not leak out, and the cool storage material (29)
It passes through the inside and sufficiently exchanges heat with the regenerator material (29).

Since the seal material (30) is made of a material having substantially the same coefficient of thermal expansion as the regenerator material (29), when the regenerator material (29) expands or contracts due to a temperature change, it seals. Since the material (30) also expands or contracts in the same manner, the sealing material (3
No gap is created between the cold storage material (0) and the cold storage material (29), and the seal material (30) is not damaged by thermal stress.

The description of the above embodiments is for the purpose of illustrating the present invention, and should not be construed as limiting the invention described in the claims or reducing the scope thereof. Further, the configuration of each part of the present invention is not limited to the above embodiment, but various modifications can be made within the technical scope described in the claims. For example, the uneven surface to be formed on the inner peripheral surface of the tubular body (22) and the outer peripheral surface of the cool storage material (24) is not limited to the screw surface, but various flow resistances such as a bellows surface and a repeating pattern of square grooves are generated. The shape of can be adopted. Further, the present invention is not limited to the Stirling refrigerator in which the cold storage material is incorporated in the displacer as shown in FIG. 5, but can be applied to all types of Stirling engines such as a regenerator arranged separately from the displacer. Needless to say.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view of a displacer according to a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a main part of the displacer.

FIG. 3 is a partially cutaway perspective view of a displacer according to a second embodiment of the present invention.

FIG. 4 is an enlarged sectional view of a main part of the displacer.

FIG. 5 is a sectional view of a Stirling refrigerator in which the present invention is implemented.

FIG. 6 is a cross-sectional view of a conventional displacer.

FIG. 7 is a diagram illustrating a process of a Stirling refrigeration cycle.

[Explanation of symbols]

 (21) Displacer (22) Cylindrical body (23) Inner thread (24) Regenerator material (25) Outer thread

Claims (5)

[Claims] 1. A regenerative heat exchanger for a Stirling engine, wherein a heat exchange filler capable of passing a working gas is arranged inside a cylindrical body having open both ends. A regenerative heat exchanger for a Stirling engine, characterized in that an uneven surface that meshes with each other and extends over the entire circumference is formed on the outer peripheral surface of the filling material. 2. The regenerative heat exchanger according to claim 1, wherein the uneven surface is a threaded surface that meshes with each other. 3. In a regenerative heat exchanger of a Stirling engine, wherein a filler capable of passing a working gas is arranged inside a cylindrical body having both ends opened, and an outer peripheral surface of the filler is filled with a working gas. A regenerative heat exchanger for a Stirling engine, which is covered with a sealing material that prevents leakage. 4. The regenerative heat exchanger according to claim 3, wherein the sealing material is made of a material having substantially the same coefficient of thermal expansion as the filling material. 5. The gap according to claim 1, wherein a gap corresponding to the coefficient of thermal expansion of the filler is provided between the inner peripheral surface of the cylindrical body and the outer peripheral surface of the filler. Regenerative heat exchanger.