Stirling cryocoolers have been used in space since 1970's. Recently, it is an indispensable comportment for spacecraft such as earth observation satellites and space telescopes. On the other hand, Stirling engine has not been used yet. However, it has been studied as heat-to-electricity power converter for space applications, especially for deep space missions, because it can be expected to achieve high conversion efficiency. In JAXA (Japan Aerospace Exploration Agency), both the Stirling engine and cryocooler technologies are being studied for space applications. This paper reviews recent advances in Stirling cycle technology and their application for space development.

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This paper refers to the operating characteristics of a compact Stirling engine capable of recycling waste heat and operating at low temperature differences. Recently, from the perspective of global environmental protection and energy saving, waste heat recovery and its reuse are matters of increasing public concern. However, the required temperature level of recyclable waste heat is rather high, and reuse of waste heat of relatively low temperature of about 200℃ emitted from general plants, etc., is teclmically difficult. For the purpose of recovering and recycling such energy that is wasted unused, a compact Stirling engine capable of operating at low temperature differences has been designed and manufactured on an experimental basis. The basic performance of the prototype has been experimentally verified and evaluated with good results, which are reported in this paper.

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This micro stirling engine has been developed as light for hot spring heat using a source of heat of the biomass incinerator to supply the hot spring heat with warm water installed in a hiking course in village-vicinity mountain. This report is compared and examined with the engine performance and a simulation for the purpose of durability increase of an micro stirling engine. As the result, The brake power by this engine is about 0.6 W/2800 rpm. And The biggest engine speed improves this airpot engine compared with an old engine. And This airpot engine improves the durability big compared with an old engine. Brake power was calculated using a simulation, the high price was obtained about 60 %.

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Indicated diagrams of low temperature differential Stirling engine (LTDSE) were measured experimentally. The temperatures of the heat exchangers and working fluid were also measured at the hot side and the cold side, simultaneously. The LTDSE of which indicated diagrams were measured had the cylindrical displacer chamber which had the height of 45mm and the bore of 128mm. The stroke volume of the power piston is 3.9cc. The Compression ratio was 1.009. The heat source of the LTDSE was steam. Cooling of the cold side heat exchanger was done by air cooled or air cooled with the water spray. The atmospheric temperature was controlled at 20 degree Celsius. The experimental data make clarify the things mentioned bellow. Although the experimental temperature difference in displacer chamber was about 20 to 30 degree Celsius, the temperature difference which is calculated from the data of indicated diagrams based on the assumption that the temperature of working fluid is uniform is about 3 to 6 degree Celsius. The compression and expansion by the power piston caused temperature difference of working fluid even in LTDSE. The indicated work has relation with the temperature difference between the heat exchangers of cold side and hot side. Temperature distribution on the surface of the cold side heat exchanger was not uniform.

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Recently, a power converter from waste heat to electricity is expected from the viewpoint of environment protection. The free piston Stirling engine (FPSE) has a feature that the output power of the working gas is directly used as the linear alternator input and then converted into electrical power. Therefore, it can be expected to achieve a high effectiveness as heat-to-electricity power converter for space applications. Test models of FPSE converter have been developed for a demonstration of solar heat energy utilization at the Japan Aerospace Exploration Agency (JAXA), for future aerospace applications. On the other hand, FPSEs using an empty can have also been developed, and they are being used for educational events held by JAXA. Based on JAXA's FPSE technology mentioned above, two types of FPSEs have been designed and developed to realize efficient use of low temperature heat energy. In this paper the design specifications and test results of these engines are described.

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Resonance tube is essential component in thermoacoustic system. And its dimensions are determined based on resonance wavelength. This is an obstacle to realize compact apparatus. Replacing resonance tube with lumped mass system, that matter can be eliminated. And also use of solid body, which has much higher density than air or other gases, as wave medium enables getting large power in small size equipment. In this report outline of Lumped Mass Circular Traveling Wave Stirling System based on that concept and numerical simulation results are shown.

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Woody biomass such as the thinned wood is widely distributed in the mountain-ringed region and the field, and it is difficult economically to collect and to transport it. Therefore, small-scale power generation is suitable in many cases. Development of small-scale power system based on the biomass gasification is under going. But because of so complicated system and high cost, the commercialization is not progressing as expected. Small-scale system which has high thermal efficiency and low cost is requested. So, in this study we develop small-scale power system, in which stirling engine power system is combined with biomass combustion furnace. We aim at high thermal efficiency and low cost of the biomass power system through this development. In this paper, the demonstration plant of 30kW-class stirling engine system using biomass is evaluated about the durability. Especially, secular change of the plant performance and condition of heater tubes are reported.

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We had designed and prototyped original gamma-type circulating flow stirling engine (CFSE) with pulse converter branch and confluent connection in operating gas flow for application of waist heat recovering, low temperature differential Stirling engine. Though the pulse converters are incomplete preventing reverse flow compared with lead valve, they are simpler, low pressure loss and wide section area, it could change the heater and cooler flow into counter flow heat exchanger. One-dimensional numerical method is developed for simulating the operation gas transient flow through the pulse converter using a method of characteristics that had been adopted to pulse flow driven turbochargers.

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In response to today's environmental and energy issues, the civilian sector desires a reduction of CO_2 emissions as well as energy saving. In order to deal with such issues, power generation systems which have better performance are desired. This paper suggests a combined power generation system using Stirling engine and closed Brayton cycle machine (Brayton engine). Brayton engine is suitable for effective application of existing waste energy such as cogeneration systems and boilers. Performance of the combined system is improved in comparison with the Stirling engine generator. In addition, characteristics of an expander installed in the proto-type system are inspected.

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Pulse tube cryocoolers are more attractive than other small cryocoolers because they have no moving parts in the expander and thus have higher reliability. Especially, Stirling type pulse tube cryocooler needs further improvement on regenerator. The working gas flow in the regenerator has non-uniform velocity distribution with the expansion and contraction flow. They cause the excessive pressure loss and reheat loss. The effect of the regenerator entrance shape on the performance of U shape pulse tube cryocooler was examined experimentally. So, the effect of cold-head end was bigger than that of after-cooler end.

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A refrigerator using a double tube was proposed to miniaturize the pulse tube refrigerator. To design a double tube refrigerator, experiments changing parameters such as pulse tube volume, tube length, tank volume were carried out by a pulse tube refrigerator. On the basis of experimental results refrigerator using a double tube for the flow area composed of regenerator and tank was constructed. Experiment by double tube type refrigerator was carried out. However, cooling performance was not obtained. Then structure of double tube type refrigerator was reconsidered and its improvement was proposed.

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We introduce a forced oscillation method for analyzing a thermoacoustic engine unit. In this method, the internal gas is forced to oscillate by an acoustic driver at the arbitral operating condition regarding the oscillating frequency and the temperature difference. In the experiment, we found the thermal efficiency of the multistage thermoacoustic engine unit reached 6.1 % of Carnot efficiency when the operating frequency was 40 Hz and the temperature difference was 130 K.

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This paper refers to experimental and analytical evaluation of the flow field in the workspace of a Stirling refrigerator. Recently, from the perspective of global environmental protection, Stirling cycle equipment that is high in efficiency and alleviates the burden on the global environment is increasingly gaining attention. To improve the efficiency of an actual Stirling refrigerator, it is necessary to understand fluid behavior under the oscillating flow condition in the regenerator and the heat exchanger. In particular, understanding the flow in the regenerator is required for the design of an active-type regenerator accompanied by change in the bulk density of heat storage material. The 3D-CFD approach is used to conduct a trial analysis of gas behavior in the workspace of a household Stirling refrigerator, and we have successfully ascertained the relevant basic gas flow characteristics, which are reported in this paper.

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In this study, performance and characteristics of four types of new matrixes for Stirling engine regenerator, called 'Mesh sheet", were examined by a numerical analysis. Also, performance differences by Mesh sheet stacking method were analyzed. As the results, it was clear that a Mesh sheet, M3, has the largest performance among the Mesh sheets. And, it was considered that the performance improvement is possible by changing the stacking method in a case of a double-acting type Stirling engine what is under developing.

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Numerical simulation of heat and fluid flow has been performed to estimate the value of time-averaged heat transfer coefficient between the working gas and the wail in oscillatory flows. Transient two-dimensional equations of continuity, momentum and energy were solved utilizing a TVD scheme. A physical model of a simple circular tube was used for the numerical simulation. In this study, the value of heat transfer coefficient in a heat exchanger was clarified by analyzing the numerical results of the two-dimensional simulation.

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Through measurements of acoustic power, we studied two types of regenerators experimentally; one is made of ceramic honeycomb catalyst and the other is comprised of stacked wire meshes. It is found that the thermoacoustic theory can explain acoustic power decrease and increase by the positive temperature difference for the ceramic honeycomb but not for the stacked wire meshes. We proposed an empirical equation of wire mesh resistance by using two dimensionless meters; acoustic Reynolds number and ωτ_v. The observed acoustic power increase is found to be the sum of square term and cubic term of velocity amplitude.

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We have tried to develop a heat recovery system with Stirling engine generator from a marine Diesel engine since 2005. In this paper, we report results of our research project related the waste heat recovery Stirling engine for an electric propulsion ship. Also we discuss about technical subjects for practical design.

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We have tried to develop a marine heat recovery system with a Stirling engine generator since 2005. The Stirling engine operates with exhaust gas from a marine Diesel engine as the heat source. From 2010, in order to set a waste heat recovery system to an electric propulsion ship, a 3 kW class waste heat recovery Stirling engine has been developed. In this paper, we report the experimental results of the Stirling engine on bench tests.

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We have tried to develop a marine heat recovery system with a Stirling engine generator since 2005. The Stirling engine operates with exhaust gas from a marine Diesel engine as the heat source. In this paper, we report the development of a control system for the heat recovery system, and the performance of the system after installation to the electric propulsion ship "Kakuyo Maru".

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From a viewpoint of energy saving and environmental problem, a LNG fueled ship is noticed in the marine field. The LNG (Liquid Natural Gas) is needed to vaporize in the ship. In order to develop of the energy omission equipment for the LNG fueled ship, we have discussed to apply a Stirling engine generator system using exhaust gas of the Diesel engine and cold energy of LNG. In this paper, we discuss about the basic structure of the system, and report the previous test for the application with two Stirling engine generators.

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This paper deals with an engine added a relatively large dead volume between the high temperature heat exchanger and the expansion cylinder, after a pulse tube refrigerator. This would improve seal performance at the expansion cylinder. P-V diagram derived from the measurement is almost the same as that obtained from multi-element simulation. The phase angle and the amount of regenerator matrix of the engine are near the optimum. The length of pulse tube can be shortened to improve output with little effect of efficiency.

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α^+ type low temperature difference Stirling Engine achieved 800W of shaft power for 1kW class by using heat source of 300degC, and their thermal efficiency are about 12%. Now, we made some improvement on this engine. We have achieved 1500W of shaft power and 14% of thermal efficiency.In this paper, the contents of improvement and test results of 1kw class engine are described.

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This paper reports a new type of Stirling engine based on a quite different principle from any ordinary engine, which releases from the problem of dead volume and makes the pressure difference between the heater and the cooler by thermodynamic process (patent obtained). In this study, the new type engine developed was carried out, whose the validity of operating prmciple was proven, and was obtained the knowledge for design of 5 kW engine to be developed in next stage.

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Because energy consumption by demand for electricity, air-conditioning and hot water supply is so large in the small-scale stores such as a restaurant and a convenience store, it is very effective in saving energy and environmental preservation to introduce a power generation and heat supply system. In this paper, examination in effect of introducing the system with various heat sources is conducted in these small-scale stores. The system consists of a Stirling engine generator, a combustor, an exhaust gas heat exchanger or air pre-heater, and a low temperature regenerative desiccant air-conditioner. From the results of examination using the biomass fuel (wood pellet, wood chip and firewood), it makes clear that reduction in CO_2 emissions is vastly realized, but nmning cost down is difficult because of current biomass fuel cost.

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This paper proposes a new type stirling engine released from the constraint of dead volume originating in the structure of engine itsell in which is placed all components of heater cooler displacer piston and power piston in a wntainei respectively. In this study, there was described the method removing the constraint of dead volume, by which each component of stirling engine is divided by valve. The thermodynamic performance of this cycle was estimated by the engine theory originating for the present engine. Accordingto this theory obtained, the performance of engine cycle is strongly effocted by each volume of components, therefore, the present analysis was carried out taking volume ratio of component based on the stroke volume of power piston as a parameter. The results were displayed as the characteristic diagram which were summarized by the most important volume ratio of heater and piston siroke.

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The Tohoku earthquake occurred on March 11th, 2011, and the large tsunami brought with it great suffering in the coast of Tohoku district. In this region, the recovery activity is still executing. Then, rubbish of the wood- base is stacked up in everywhere. In the meantime, we have examined an effective utilization of the woody biomass until now. In this report, the challenge in a disaster area using Stirling cooler and Stirling engine is introduced.

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The system which combined a wooden biomass boiler and a Stirling engine has been already run at the test site in The Expo'70 Commemorative Park for over 1,000 hours. To make it easy to treat this system more, automatic control of thermal oil temperature, and the improvement of the starting method were given to this system. In this paper, the experimental results of this improved system operated in the test site are reported

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The acoustic power gain of differentially-heated regenerators was measured as a function of frequency. When the ceramic honeycomb was used as a regenerator, it was found that the acoustic power gain can be numerically calculated by using the capillary-tube-based theory in which the regenerator was modeled as an array of cylindrical tubes. However, when stacked-screen meshes were used as a regenerator, the calculated gain did not agree with the experiment one.

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Onset temperatures of a spontaneous gas oscillation occurring in a looped tube thermoacoustic engine were numerically calculated. The looped tube engine had two regenerators inside a looped tube. In the calculation, the relative position between the regenerators was changed. As a result, it was found that there is the optimum relative position and the onset temperature with the optimum one is 108℃. This value is lower than the onset temperature of the looped tube with one regenerator by 170℃.

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We have constructed and tested a travelling wave thermoacoustic refrigerator using a coaxial configuration with the regenerator positioned in the annulus. We have tested the device using three operating frequencies: 100 Hz, 140 Hz and 200 Hz. The rise and the descent from an initial temperature were recorded at both ends of the regenerator for 60 minutes. This is due to the fact that the change in frequency has caused a change in the direction of the dominant travelling wave at one end of regenerator. This will change the heat pumping direction within the regenerator as it is dependent on the direction of the dominant travelling wave at that end.

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A looped tube type thermoacoustic prime mover with multiple regenerators driven by pressurized steam is being constructed. The pressurized steam is produced within a container filled by water which is boiled by an immersion electric heater. The steam is then let to flow t the hot heat exchangers of the thermoacoustic prime mover. The maximum pressure and temperature of the steam can be increased by adding extra water into the container when most of initial amount of water has changed to steam. The thermoacoustic prime mover with one to four regenerators will be tested. After laboratory test, we plan to realize a thermoacoustic prime mover driven by natural heat, by replacing the immersion electric heater with concentrated sunlight, and by utilizing steam from geothermal well.

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A thermoacoustic engine has attracted attention because it can work without moving parts and use variety of heat sources. When the thermoacoustic engine receives heat from a hot heat source,, the gas inside it spontaneously oscillates and outputs acoustical energy. In general, this acoustical energy is converted into electrical energy or cold energy by the thermoacoustic coolers or linear alternators. The performance of the engine depends on the acoustic-to-heat or -electric converter. In this study, we characterized the converter consists of a tank and a valve, and constructed the traveling-wave thermoacoustic engine with the characterized converter. The measurements of the performance were shown.

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The single-phase forced-oscillating-flow heat pipe is called a "dream pipe". In this study, the performance of the dream pipe was measured as a function of the oscillation amplitude and frequency. The measured results were compared with the analytically obtained results that were calculated by using thermoacoustic theory. As a result, it was found that the dependence of the experimental results on the dimensionless parameter related to the amplitude and frequency was similar to that of analytical ones.

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