JP2010229975A - Stirling engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve a Stirling cycle for exhibiting high efficiency in a comparatively small output usage. <P>SOLUTION: In a Stirling engine, an appropriate amount of a phase change material (air, hydrogen, helium and the like) having a boiling point within an operating temperature difference is added, to eliminate a need of large means directed to improve a thermal exchange performance. That is to say, a high temperature chamber exposed to a high temperature source and a low temperature chamber exposed to a low temperature chamber are communicated with each other, and inside gas is forcedly moved by a displacer. The Stirling engine is filled with additive added to the operating gas, which is adjusted to be atomized on a low temperature side and gasified on a high temperature side. By selecting the additive having a boiling point within the operating temperature difference, optimization can be done when using a heat source of a low temperature difference. Also, an output can be freely set according to an addition amount of a phase change substance. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a Stirling engine, and more particularly to a Stirling engine capable of simplifying the configuration and increasing the output even in a low temperature difference environment.

  A Stirling engine is known as an external combustion engine and can convert heat energy into kinetic energy with the highest efficiency among heat engines. And if there is a temperature difference, kinetic energy can be taken out without choosing a heat source, and it is getting attention again from recent social demands for the environment.

  As an example of increasing the output efficiency, for example, a technique disclosed in Patent Document 1 is known. In this method, a substance that is liquid at normal temperature is used as a working fluid, and a large specific volume change is realized by a phase change at the time of evaporation and condensation of the liquid, thereby realizing an improvement in output. According to this technology, since the output can be increased even when the temperature difference is small, it is possible to use, for example, geothermal energy or ocean temperature difference which is natural energy. A hot spring heat source, a kind of geothermal heat, can also be used.

  However, the conventional technique has the following problems. For example, when using a hot spring heat source, the atmospheric temperature difference between the source spring and the atmosphere is as small as 30 ° C. to 60 ° C. Therefore, in order to obtain an appropriate output, large-scale facilities and complicated heat engine devices are required. There was a problem.

  For example, in the case of utilizing phase change in addition to the displacer as disclosed in Patent Document 1, it is necessary to make the heat exchange amount very large in order to use latent heat due to liquid-gas phase change. is there. In fact, although one substance (such as ethanol) changes phase from liquid to gas and from gas to liquid, in principle it is close to a steam engine and the apparatus is very large, such as forcibly cooling and liquefying the gas. It has become a thing.

  Moreover, in the technique disclosed in Patent Document 1, since the liquid directly touches the heater, there is a principle problem that this acts as a thermal resistance.

Japanese Patent Laid-Open No. 2007-23885 JP 2000-213418 A JP 2002-266699 A Japanese Patent Laid-Open No. 2005-54640 JP 2005-61330 A

  That is, the problem to be solved is to provide a Stirling engine that increases the output without making the apparatus large even if the temperature difference between the high temperature source and the low temperature source is small.

  The Stirling engine according to claim 1 is a Stirling engine in which a high-temperature chamber exposed to a high-temperature source communicates with a low-temperature chamber exposed to a low-temperature source, and the gas inside is forcedly moved by a displacer. The main feature of the additive is that the additive is adjusted so that it is liquefied in the form of a mist on the low temperature side and vaporized on the high temperature side.

  That is, the invention according to claim 1 increases the work amount of one cycle through the additive, and increases the kinetic energy to be extracted. Moreover, since the additive is adjusted to an amount that forms a mist having excellent mobility, efficient heat exchange is realized without the liquid remaining in the low temperature chamber. Furthermore, it is possible to increase the output with a simple configuration while realizing efficient heat reception without causing condensation in the low temperature chamber and acting as a thermal resistance. The working gas can be different from the additive and is not particularly limited, and examples thereof include air and helium. The addition amount of the additive can be appropriately determined depending on the amount of heat received in the high temperature chamber, the amount of heat released in the low temperature chamber, the cycle speed, the heat transfer area, and the like.

  The Stirling engine according to claim 2 is characterized in that, in the Stirling engine according to claim 1, the displacer is a heat exchanging means having a high thermal conductivity and a large specific surface area.

  That is, in the invention according to claim 2, the displacer transfers the mist liquid to the high temperature chamber side. At this time, the displacer may be condensed.

  The Stirling engine according to claim 3 is the Stirling engine according to claim 2, wherein the displacer is made of steel wool.

  That is, the invention according to claim 3 can simplify the apparatus configuration. The steel wool as used herein is not limited to a material mainly composed of iron if the material is a metal, and indicates a cotton-like fine metal wire.

  A Stirling engine according to claim 4 is the Stirling engine according to claim 2, wherein the displacer is made of a porous material.

  That is, the invention according to claim 4 can simplify the apparatus configuration. The porous material referred to here is a material having a large number of pores, and includes a material having a pore space much larger than a substantial space. Moreover, when a hole is bubble-like, the direction which is an open cell is preferable, and the direction where a substantial specific surface area is generally large is more preferable.

  The Stirling engine according to claim 5 is driven in the Stirling engine according to any one of claims 1 to 4 in a range where the high temperature source temperature is 100 ° C. or lower and the low temperature source temperature is 0 ° C. or higher. It is characterized by.

  That is, in the invention according to claim 5, the hot spring source and the low temperature source can be set to room temperature as the high temperature source, and the apparatus configuration can be simplified.

  The Stirling engine according to claim 6 is the Stirling engine according to claim 5, wherein the additive is pentane, isopentane, pentene, diethyl ether, ethyl vinyl ether, or a mixture thereof. And

  That is, the invention according to claim 6 can provide a Stirling engine using an additive having a boiling point in a temperature range slightly higher than room temperature, low latent heat of vaporization and not harmful to the human body.

  A Stirling engine according to a seventh aspect is characterized in that in the Stirling engine according to any one of the first to sixth aspects, the interior of the low temperature room is clouded.

  That is, the invention according to claim 7 makes it difficult for mist to adhere to the inside surface of the low-temperature room and to prevent thermal resistance. The cloudiness is not particularly limited, and a water repellent treatment can be given.

  According to the present invention, even if the temperature difference between the high temperature source and the low temperature source is small, it is possible to provide a Stirling engine that increases the output with a simple configuration without making the apparatus large. In other words, it can be said that the present invention can provide a heat engine that can flexibly cope with a set temperature difference and can improve output while realizing a simple structure.

It is a schematic diagram of the Stirling engine which shows the flow state of the working fluid which added the additive. It is explanatory drawing which showed the state in the high temperature heat source part at the time of throwing in a phase change substance excessively. It is the schematic of an experimental apparatus. Among these, (a) is an overall view, and (b) is a detailed view of a test section. The experimental apparatus represents a PV acupressure diagram at a rotation speed of 10 rpm. It is the figure which showed the relationship between the addition amount of an additive, and work. It is the figure which showed the relationship of the output rotation speed in the case where it is not with the case where an additive is added.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the present embodiment, a Stirling engine will be described in which a hot spring source (temperature: 70 ° C.) is used as a high temperature source, a low temperature source is outside air temperature (about 25 ° C.), and an appropriate amount of additive is added. The Stirling engine of this embodiment is a Stirling engine in which a high-temperature chamber exposed to a spring source communicates with a low-temperature chamber located away from the spring source and not affected by the heat source, and the gas inside is forcedly moved by the displacer. If so, the shape is not particularly limited. FIG. 1 schematically shows the flow state of a working fluid to which an additive has been added. In addition, the figure is conceptual, and the aspect ratio does not mean the actual thing of the high temperature room and the low temperature room as it is.

  Examples of the additive include pentane (boiling point 36 ° C.), isopentane (boiling point 28 ° C.), pentene (boiling point 35 ° C.), diethyl ether (boiling point 35 ° C.), or ethyl vinyl ether (boiling point 36 ° C.).

  The amount of the additive is adjusted so that it is liquefied in a low temperature chamber and vaporized in the high temperature chamber. When adjusting, the heat exchange time for heat reception and heat dissipation decreases as the cycle speed increases, and the amount of heat transfer decreases.If the cycle speed increases, the flow rate of the working fluid increases and the heat transfer rate increases. Considering that the amount of heat transfer increases, the flow loss increases and the output may decrease. Also consider the heat transfer area of the displacer. Preferably, the amount of additive and the amount of heat received from the high temperature source and the latent heat of vaporization and the amount of heat released from the low temperature source and the condensing liquefaction latent heat are added.

  FIG. 2 shows a state in the high-temperature heat source part when the additive is excessively added. When the phase change material is added in excess of the exchange heat amount, a liquid layer of the phase change material is generated in the heat exchange part. This becomes a thermal resistance and greatly reduces the output of the Stirling engine. That is, in the Stirling engine of the present invention, the additive (latent heat substance) is added in an amount that provides a latent heat amount lower than the exchange heat amount.

  If the displacer piston is made of a material having a high thermal conductivity and a large specific surface area, the mist-like additive on the low temperature side can be attached to the surface or moved to the high temperature side together with the working gas. This is preferable because it can be efficiently vaporized in a high temperature chamber. An example of this is a cotton-like fine line made of a copper material.

  Next, examples will be described. FIG. 3 is a schematic diagram of the apparatus. The experimental apparatus is composed of a test unit, a high-temperature source constant temperature device, a low-temperature source constant temperature device, a displacer, and a drive device. The temperature conditions of the high-temperature source and the low-temperature source are set by sending hot water and cold water from the constant temperature device to the upper and lower heat sources, respectively, and circulating them. Here, the experiment was performed under the condition that the high temperature source was fixed at 40 ° C. and the low temperature source was fixed at 15 ° C. The displacer drive rotation speed was measured by detecting the vertical displacement of the link spindle with an ultrasonic displacement sensor installed at the top.

  Inside the test section, a K-type thermocouple having a wire diameter of 0.18 mm and a pressure sensor were installed to collect temperature and pressure data. The experiment was performed by controlling the number of rotations by a motor and moving the displacer up and down, and measuring the pressure increase (air moved to a high temperature source) and the pressure drop (air moved to a low temperature source). The measurement parameters were evaluated as displacer displacement speeds of 10 to 60 rpm and diethyl ether (boiling point 35.0 ° C.) as an additive at 0.005 to 0.035 ml. In addition, the volume of a test part is 260 ml.

  FIG. 4 shows a PV acupressure diagram at a rotation speed of 10 rpm. PCM (Phase Change Material) means an additive. For comparison, the case of air only is also shown. The area enclosed by the PV curve represents the output per cycle. It can be confirmed that when the additive is added, the cycle area increases and the output increases.

  FIG. 5 shows the relationship between the additive amount and work. As is apparent from the figure, it was found that the optimum amount in this experimental system was 0.015 ml. FIG. 6 is a diagram showing the relationship of the output rotation speed when the additive is not added. The increase in the output when the additive is added is remarkable in the low rotational speed region, and it has been confirmed that the increase value tends to decrease as the rotational speed increases. The increase in output when the rotational speed is 50 rpm is considered to be due to the rotational speed at which a high output can be obtained with a good balance between the heat exchange time and the amount of heat transfer.

  From the above, it has been confirmed that the output can be increased by adjusting the type and amount of the additive with a desired output as compared with the case of the displacer alone. In the experimental system, it was confirmed that the output was tripled.

  As described above, according to the present invention, it is possible to obtain an advantageous effect that an output several times that of a conventional single-phase working fluid can be obtained without giving the heat engine a complicated structure. .

Claims (7)

In a Stirling engine in which a high-temperature chamber exposed to a high-temperature source communicates with a low-temperature chamber exposed to a low-temperature source, and the gas inside is forcibly moved by a displacer,
A Stirling engine comprising an additive added to a working gas, which is liquefied in the form of a mist on the low temperature side and vaporized on the high temperature side.   The Stirling engine according to claim 1, wherein the displacer is a heat exchange means having a high thermal conductivity and a large specific surface area.   The Stirling engine according to claim 2, wherein the displacer is made of a porous material.   The Stirling engine according to claim 2, wherein the displacer is made of steel wool.   The Stirling engine according to any one of claims 1 to 4, wherein the Stirling engine is driven in a range where the high temperature source temperature is 100 ° C or lower and the low temperature source temperature is 0 ° C or higher.   The Stirling engine according to claim 5, wherein the additive is pentane, isopentane, pentene, diethyl ether, ethyl vinyl ether, or a mixture thereof. The Stirling engine according to any one of claims 1 to 6, wherein the low temperature indoor surface is clouded.

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