This study deals with the thermodynamic design of Stirling engine. Eleven design parameters are optimized. The optimum conditions are determined, first. Most of those are that x∂W_<net>/∂x=ξW_<net>, where W_<net> is the net power and x an optimizing design parameter, under the condition as rotating speed is optimized to make the net power takes the maximum, and ξ is selected 0,±0.1 or 0.9. To optimize porosity and regenerator volume, the efficiency (net output work/heat input) is maximized. It is confirmed that the all eleven parameters can be optimized based on the conditions. The effects of working gas average pressure and the temperature ratio of heat source to heat sink are examined. Because a wrong equation is used to evaluate pressure loss in the regenerator, only qualitative discussion is available on the results.

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A fundamental study on a free-piston Stirling engine with a linear alternator for future space applications has been performed in the National Aerospace Laboratory. Many types of simulation code for a Stirling engine have been developed until now, but there is few analysis model which can be used for the design and development of a free-piston engine with a linear alternator. Therefore, a simulation method, which can calculate performance characteristics of free-piston engines, has been developed. It is a feature that the alternator analytical model is able to estimate alternator loss including the iron loss. The thermodynamic model of the engine is based on the isothermal model. This code is not complicated and easy to apply other engines. The calculated values of engine output power were greater than experimental data. However, the tendency agrees well with the experimental result.

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Stirling engine can be operated by many kinds of heat sources other than fossil fuel. Low temperature hear sources of solar radiation, biogas, geothermal and exhaust heat energies can be utilized. The authors designed and developed a low temperature difference Stirling engine which operates at the temperature difference between the room temperature and ambient temperature with thermal ratio of 0.93. As a result, it is confirmed that the maximum brake power of 1mW/12rpm was obtained on the experimental engine under the condition of higher heat source temperature of about 22℃, heat sink temperature 4℃, buffer pressure of atmospheric pressure. In addition, it was possible to obtain 0.915 mechanism efficiency.

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For driving of multi parallel cylinders, so called barrel type as Daidoji, Aisin and Clucus Engines (1)(2(3) etc, there were many ways. But, we have found that, if Z crank is used, the driving ball's center moves up and dowm along the surface of small circular pillar. So, new Z crank mechanism using this fact is now under developments.

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In this study, a premixed combustor for Stirling engines was developed. To improve the performance of combustor, a premixed combustor was developed. The design method of the premixed combustor was introduced. To prevent backfire in the mixing tube, turbulence burning velocity was calculated. A flame folder was set in the combustor to stabilize the flame. As the result, burner efficiency achieved 65% at 8.3 kW heat input.

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Nowadays the global warming is more and more being severe. Such a situation enables us to utilize soft energy resources more rather than hard energy ones. As the matter of course the engine presented here uses charcoal as its fuel. Less leakage of working gas and easy handling were prior to others in designing the machine. Prior to its performance tests theoretical estimation for engine output were carried out by using Schmidt theory, which informs us that the machine will achieve the predetermined performance. In addition, we can see here general structure of the engine together with its specifications.

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Stirling engines take effect on the environment problem arising on a terrestrial scale. The authors have developed the 1kW class Stirling engines for a home-use co-generation system, and have investigated a machine structure including crank mechanism, an electric generator and heat exchangers in order to improve the performance of Stirling engine generator for practical use. This paper describes the development process of the 1kW class Stirling engine generators. The demonstrator is designed as a γ type machine and two functional prototypes are α type machines. The functional prototype developed later is sealed hermetically because a flywheel is built in a crank case. The performance of functional prototype is the highest engine generator efficiency of 16.3% and the maximum electric power of 502W.

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This paper presents study on a Heat Transfer Characteristics of a hybrid regenerator. Hybrid regenerator as a house hold small size Stirling refrigerator. Authors have continued research about the sterling refrigerator. However, it turns out that machine loss is large compared with an indicated work load. It is the hybrid regenerator which mixes and fills up the thermal storage material of the regenerator of a sterling refrigerator with the copper mesh and nylon mesh which can expect reduction of machine loss was proposed. Thermal conduction loss and an internal temperature distribution of a hybrid regenerator became clear in an experiment and analysis by this research.

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A regenerator wire mesh obtained by knitting, lengthwise and crosswise, whose wires' cross sectional shape are streamline to the flow, is considered to become smaller flow resistance than usual wire mesh of circular cross-sectional shape. Although, Nusselt number may be decrease a little bit than usual mesh, wire mesh having streamline cross-sectional shape is probably superior to that having circular shape cross section because the effect of decrease of flow resistance is larger than that of Nusselt number. In order to confirm this idea, comparison between parallel thin flat plates' flow and cross flow over banks of circular cylinders is carried out. Also simple numerical calculation was carried out.

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In order to develop Stirling cycle machines with high efficiency, suitable regenerator for each machine must be designed. To realize the flexibility of design and to improve the performance of regenerator, a new matrix, mesh sheet was proposed. It is a plate type with electrically etched holes. Three types of the mesh sheet were developed and were respectively stacked to install in a 3-kW Stirling engine. The performance test was carried out and the regenerator losses were compared with conventional stacked wire gauze. In this paper, the relation between the dimensions of the mesh sheet and the regenerator losses were also clarified.

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Oscillatory flow heat transfer is an essential design factor for thermoacoustic refrigerator, especially in a stack of an acoustic refrigerator, regenerator in Stirling refrigerator and related heat exchangers. In the research of the past, the mode of heat transfer of oscillatory flow was mainly classified into laminar and turbulent flow heat transfers. And the space-cycle averaged heat transfer characteristics are well correlated using Nusselt number, Reynolds number, Strouhal number and Prandtl number for the respective heat transfer modes, similarly to forced convective heat transfer. However, the effect of oscillating boundary layer on heat transfer characteristic was not considered. In this study, experimental and analytical investigations were conducted paying attention to the behavior of oscillating boundary layer.

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In Stirling engines and cryocoolers, the regenerator is the indispensable heat exchanger. The regenerator exists between the heater and the cooler in engines, and between the expansion space and the compression space in cryocoolers. So, the flow passage at the regenerator ends is reduced in size. The effects of the small passage on the velocity distribution of working gas in the matrix cause increased flow loss and decreased thermal performance. In this paper, the effects of flow passage with taper between regenerator ends and matrix on flow area in matrix are examined using unidirectional steady flow apparatus and compared with those of flow passage with gap.

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A regenerator is one of the parts which influence performance of the Stirling cycle machine. In generally a metal matrix is used as the material of the regenerator, but a plastic matrix that is represented by Nylon has never been used so far. As for the advantage of the plastic matrix being light, the plastic matrix itself has a small diamter of the matrix wire and it has the possibility to become cheap. The positions of the displacer and the piston for the refrigerator and gas pressure were measured, and the COP of the Stirling refrigerator with the hybrid-regenerator piled up the metal matrix and the plastic matrix was evaluated. The best performance of the Stirling refrigerator is revealed at the volume ratio of the Nylon matrix to the copper matrix 2.3. The COP of the hybrid-regenerator is 80 percent of the COP with the metal matrix regenerator. The COP of the Stirling refrigerator with the hybrid-regenerator was also numericals simulated.

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Stirling coolers using refrigerants, such as helium, take effect on the environment problem arising on a terrestrial scale. The authors developed the Stirling cooler for the ultra-low temperature region used with the equipment for vacuum, biomedical and so on. It has the cooling capacity of 45W at 77K. This paper describes performance test results of the Stirling cooler on operating temperatures and working gas mean pressures, and introduces an ultra-low temperature freezer operating at 93K in which the Stirling cooler is installed.

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This paper presents study on performance of a small stirling refrigerator as a household use. The heat exchanger system for carrying a small stirling refrigerator to a household use was examined. Consequently, it became clear that the heat exchanger system using coolant is suitable in a 100l class. medium size freezer. Moreover, a cooler side heat exchanger was design and development.

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[in Japanese]

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Change in pressure signals in single, open ends and closed ends connected types of thermoacousitc sound wave generators are discussed. Simultaneous measurements of pressure, velocity and temperature are performed. As a result, pressure signals in the open-ends connected one are different from the other's. They oscillate at fundamental frequency of f, which is based on resonance tube length and sound speed in the working fluid, near the closed ends, and oscillate at 2f near the connected region. And its amplitude is larger than those of the others. Simulation of pressure signals are also performed.

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Much effort has recently been devoted to study thermoacousitc machines that have the simple construction and do not use the ozone depleting fluid. A numerical simulation is essential to understand the thermoacoustic characteristics. We are developing a numerical simulation model with a view to analyze the detailed behavior of thermoacoustic machines. Complete differential equations of continuity, momentum and energy of working gas, as well as energy of stack and heat exchanger walls are employed as the governing equations. The experimental results are also discussed to confirm its validity. In this report a thermoacoustic generator of typical standing wave type machine is adopted as the analyzing target.

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This paper describes the results of measurements of work flow in a thermoacoustic engine using helium as the working gas. Based on these results and thermoacoustic theory, the optimum length of the regenerator was predicted, and the efficiency of the thermoacoustic engine was improved. Further, the linear oscillatory alternator was attached to the thermoacoustic engine, and 43W was obtained as the electric power.

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Numerical simulation of viscous compressible flow in basic pulse tube refrigerator was performed to investigate the frequency characteristic. Transient axisymmetric two-dimensional equations of continuity, momentum and energy were solved utilizing the TVD scheme. A physical model combining the pulse tube with wall and regenerator is used for numerical simulation and the dimensions of this model are much the same as one of Gifford's model in which the lowest achieved temperature of 165K was obtained. In this paper, we analyzed the behavior of temporal average gas temperatures during the initial 10 cycles, and the change in gas temperature during a cycle in the first cycle for various frequencies.

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We report results from three pulse tube coolers used at around 60 K. All of them were successfully driven in vacuum conditions and showed similar cooling capabilities with flight Stirling and pulse tube coolers. Vibrations at cold heads and linear compressors have been measured and their displacements were revealed to be less tan 10 μm in x, y and z directions. They imply that vibration form the compressor must be dominant in 'integrated' pulse tube coolers.

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The pulse-tube is no solid piston in the expansion space and the pulse-tube is cooled down by that gas does work in the gas. The pulse-tube cryocooler is doesn't need a moving parts in the expansion space and it is an advantage such as a low vibration and high reliability. On the other hand, a pulse-tube cryocooler is different from the solid piston and the cryocooler operating gas often takes an influence due to the change in the environment. When the low temperature part of the expander is in the top from the normal temperature part, natural convection occurs by the influence of the gravity and a cooling capacity decreases greatly. This report is that an examination was done about the efficiency improvement due to the change in the pulse-tube size and the influence which the inclination of the expander on the cooling performance.

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A Pulse tube cryocooler of simple structure without moving part in the expander has the advantage over a stirling cryocooler of low vibration and long life. So its wide uses for space crafts and high-temperature superconductor devices are extended. Recently Fuji Electric has developed a pulse tube cryocooler with cooling capacity of 2.5W at 70K, based on the technology of the stirling cryocooler for the space crafts. This paper describes the vibration measurement of a miniature pulse tube cryocooler.

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