A fundamental study on solar power generation system using Stirling engine for space application had been performed in the National Aerospace Laboratory of Japan (NAL). The Stirling engine is one of candidates for power converter for future space use. The prototype engines, called the NALSEM (NAL Stirling Engine Model) series, are semi-free-piston Stirling engines with a moving-magnet linear alternator. A basic model of the Stirling engine converter, called NALSEM500, has een experimentally studied since April 1994. The NALSEM 500 was designed to achieve a target thermodynamic efficiency of 30% or more with an indicated power of 500 W. After that, an improved Stirling engine converter, NALSEM700, has been designed and evaluated. This engine has opposed piston configuration in order to minimize mechanical vibrations. Based on these achievements, we designed a basic model of a free-piston Stirling engine converter. The converter is called the NALSEM200, and designed to achieve an overall efficiency of 20 % or more with an electrical output power of 200 W. In order to achieve the design performance, design optimizations are in progress at JAXA (Japan Aerospace Exploration Agency). This paper describes the significant design features and some results of preliminary bench tests on the NALSEM200.

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A cryogenic Stirling engine has been reconstructed from a β-type Stirling cycle refrigerator. This engine is cooled by liquid nitrogen (-196℃) or dry-ice/methanol (-69℃) and heated by warm water (40℃). The working gas is helium of about 1 MPa. Its characteristics, such as net output power, indicated power and thermal efficiency, have been examined at different engine speeds and different cooling temperatures, and they are compared with theoretical ones expected from a simulation code SCM20. The maximum output power of 160W has been obtained at an engine speed of 1030rpm and a mean pressure of 1.24MPa. In this example, the figure of merit (FOM), defined as the ratio of output power to consumed cold, is 0.20 and 1.35 for the net and internal powers, respectively. The experimental results and also the theoretical considerations suggest that the cryogenic Stirling engine may be a promising prime mover for utilization of the cold heat of liquefied gases, such as LNG, liquid oxygen, liquid nitrogen and liquid hydrogen.

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The authors proposed the design technique of a Stirling engine in case the limited heat source like waste heat or the biomass. In order to estimate the design technique and the engine system performance, a Stirling engine for experiments is designed. The engine is multi-stage type engine of three-step composition. When swept volume of a displacer piston and a power piston of each engine can be adjusted according to a heat source suitably, the heat source is changed to engine output efficiently.

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The characteristics of the hydrogen internal combustion engine performances were investigated using two different catalyzers for the internal combustor. One is wavy sheet catalyzer and the other one is wire mesh catalyzer. The comparison of the performances showed that the work in the compression space and the rejected heat of wire mesh were larger than that of wavy sheet catalyzer but the regenerative heat losses are on almost equal level. In addition, the pressure loss of wire mesh was slightly larger and the gas temperatures of the expansion and compression spaces showed drastic decrease and slight increase, respectively. These experimental results suggested that combustion process in the combustor gives a large effect on the temperatures of expansion space and compression space.

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Blow-off limit and unburned gas concentrations were measured for a mult-hole combustor designed for start-up of 4kW class SOFC-Stirling engine combined system. The blow-off limit strongly depended on the preheat temperature and the equivalence ratio and the released heat at the blow-off limit was insufficient for the 4kW system if the operation at higher combustion temperature is avoided to supresss the NOx emission level. The concentrations of CO2 and CH4 at the combustion temperature of 1700K showed the tendency to increase toward the radial direction and with the increase of the flow velocity. Also, the higher preheat temperature showed the lower concentrations of unburned gas. The unburned gas concentrations were still high at 1700K and the higher combustion temperature is needed to improve the combustion efficiency.

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In order to develop Stirling cycle engines with high efficiency, suitable regenerator for each engine 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. Four 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 those of conventional stacked wire gauzes. From the testing results, it was clarified that the indicated efficiency of engine performance was improved about 1 % by the new mesh sheet. In this paper, a newly developed mesh sheet made of nickel is introduced and its experimental results are compared with those of previous three mesh sheets.

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Stirling cycle is one of the machines which can convert power and thermal energy each other. Cogeneration system is a typical example of Stirling cycle as a bilateral application. Stirling system is used as a secondary machine. The system is driven as an engine with an exhaust gas of a primary engine. The same system is also driven as a heat pump. In this study, a bilateral Stirling system is examined both experimentally and analytically. The system performance is then presented. Finally, the expected performance is suggested.

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As to Stirling engine technologies, although R&D work has been done for a long time in all over the world including Japan, technical problems, such as low efficiency and difficulity in raising power output, had hindered its practical use. Under these circumstances, STM Power Inc., U.S., developed a stirling engine which conquered these problems, and it is now beginning to move towards practical use. In this paper, we introduce specification of the 55kWe stirling engine made from STM Power Inc., and evaluate its possibility as systems which will be excellent in energy-saving performance and environmental performance, for example biomass use and a combined system with a fuel cell. Moreover, we also describe the possibility as a distributed power generation.

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Stirling engines take effect on the environment and energy problems arising on a terrestrial scale. The authors have developed 1kW class Stirling engine generators 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 of the 1kW class Stirling engine generator SEG1000-AS, mainly regarding an electric generator, regenerator and piston seal. As a result, the performance achieved the electric power of 895W and the engine generator efficiency of 21.9%.

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This paper presents study on effects of regenerator for miniature Stirling Engine. The generator is set into displacer piston. The effects of pore size and volume of regenerator on Stirling engine performance are discussed. Moreover, effects of the thermal conductivity of regenerator housing materials on the engine output power are discussed.

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This paper describes some performance characteristics shown by the P-V analysis on a stirling refrigerator with a hybrid regenerator made of copper matrixes and nylon ones for the less flow loss by changing the way to mix on hybrid matrixes. In order to perform the efficiency of compact stirling refrigerators with a regenerator in the displacer well, it is effective to lighten the weight of regenerators and reduce motor input. For this reasons, we proposed using the hybrid regenerator. However, the nylon matrixes have larger flow loss than that of copper matrixes. Therefore the ratio of copper matrixes and nylon ones and the way to mix are important to improve the COP.

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This study investigates the design of a new structure of matrix material, called "mesh sheet" for the regenerator of a Stirling engine. Flow and heat transfer characteristics of the matrix materials were analyzed by using a general-purpose finite-element method fluid analysis program, FIDAP. The reliability of the calculation was examined by comparing with the experimental results. Based on the analysis results, the dimensions of the mesh sheet were optimized. According to the results, it is expected that the indicated efficiency of the engine installed new mesh sheets will be about 4% higher than the using mesh sheets developed last year.

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The sudden expansion and contraction flow in the regenerator ends greatly influences the performance of the Stirling engines. The regenerator is installed between the heater and the cooler. The cross-sectional flow areas of regenerator ends of typical Stirling engines are smaller than the cross-sectional area of the regenerator matrix. So, the gas flow in the matrix becomes a flow field with non-uniform flow at end of the regenerator. The non-uniform flow causes increased pressure loss and decreased thermal performance. In this paper, the effects of gap in the regenerator ends on the engine performance have been examined experimentally and confirmed.

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In Stirling engines and cryocoolers, the regenerator is the indispensable heat exchanger. The regenerator is installed 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 effect of the small passage on the velocity distribution of working gas in the matrix causes increased flow loss and decreased thermal performance. In this paper, the effect of tapered flow passage between regenerator ends and matrix on flow area in matrix are examined using unidirectional steady flow apparatus and CFD.

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Oscillatory flow heat transfer is an essential design factor of the regenerator and heat exchangers of Stirling cycle refrigerator. In the previous study, the effect of oscillating boundary layer on heat transfer characteristic was discussed. The separation is observed every half cycle of the oscillation since velocity direction changed and velocity accelerated and the local heat transfer coefficient was increased at the point where the separation occurred. In this study, experimental investigations were conducted covering wide Ra and Re ranges. Consequently, the flow pattern was classified by use of Ra and Re numbers.

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Based on the γ type YA-1 and α type YA-2 Low Temperature Difference Stirling Engine, we have designed high speed compact engine using new concept in the engine configuration. This technology enabled the Stirling engine operation for higher engine speed than existing type of Stirling engines. This article shows compact Low Temperature Difference Stirling engine will be realized from the above new technology and a concept.

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In order to demonstrate the effectiveness of Stirling engine with heat exchangers consisting of the pin-fin arrays, small atmospheric β and γ-type pin-fin Stirling engine have been manufactured and simple experiments were carried out as the graduation research work. In the present paper, the structure of pin fin heater, pin fin cooler, regenerator, crank mechanism, motion of the power piston and displacer piston of engines are reported. Both engines' bore diameter and strokes are same 70 mm and 30mm, respectively. In the concluding remark, effectiveness of pin fin Stirling engine is confirmed because its structure is simple and number of engine part are smaller than the conventional Stirling engine.

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Performance characteristics of a 1kW-class Stirling engine generator in hydrogen working fluid were investigated and compared to those with helium working fluid. While almost the similar characteristics were observed, slight differences were found out in thermal input and in engine speed dependence of efficiencies and thermal loss. In low engine speed region, the performance of hydrogen working gas was worse than that of helium working gas and vice versa in high engine speed region. These experimental results suggest that internal leak through the piston ring gives influences on these characteristics and more improvement than 1% intermal efficiency is expected at high engine speed region by reducing the internal leak of hydrogen through the piston ring.

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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. And one made with stainless steel, and the other made with nickel. The performance test of cooling mode was carried out with a 3-kW Stirling engine in order to measure its cooling performance. Two types of mesh sheet were respectively and alternate stacking to install in the machine. From the results, it was clarified that the performance of the cooling mode was improved about 3 to 7% by the mesh sheet. In this paper, the relation between the performance and the operating conditions by using conventional wire gauze and mesh sheets was also clarified.

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The green house effect by carbon dioxide issue would make better recognizing the importance of efficient use of energy in terms of high energy conservation measures. The Stirling cycle has the highest theoretical cycle efficiency corresponding to the value of the Carnot cycle among the proposed thermodynamic cycles. Moreover, the Stirling refrigerator is a perfect a freon free refrigerator. The authors have designed and developed a 100 W class Stirling refrigerator for household use. Moreover, the prototype machine has been integrated with a 100 litter class refrigerator. The operating characteristics of this Stirling unit or the prototype machine have been evaluated and are presented in this paper. As a result, the operational characteristics of the Stirling refrigerator have been clarified with respect to design factors such as pull down characteristics.

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A two-stage Stirling cooler has been developed and tested for the infrared astronomical satellite ASTRO-F that is planned to be launched by Japanese M-V rocket in 2005. ASTRO-F has a hybrid cryogenic system that is a combination of superfluid liquid helium and two-stage Stirling coolers. The cooler has a new linear-ball-bearing system for the piston-supporting structure in a compressor. The linear-ball-bearing supporting system achieves the piston clearance seal, the long piston-stroke operation and the low frequency operation. The typical cooling power is 0.2W at 20 K and the total input power to the compressor and the cold head is below 90 W. The engineering, the prototype and the flight models of the cooler have been fabricated and evaluated to verify the capability for ASTRO-F. This paper describes the design of the cooler and the results from verification tests including cooler performance test, thermal vacuum test, vibration test and lifetime test.

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ASTER is an advanced multi-spectral imager for EOS spacecraft Terra which was launched with other four instruments on December 18, 1999. The development of ASTER instruments was carried out with Japan Resources Observation System Organization (JAROS) under the control of Ministry of Economy, Trade and Industry (METI). The ASTER instrument covers a wide spectral region, from visible to thermal infrared with 14 spectral bands which are consist of visible and near-infrared (VNIR) subsystem, short-wave infrared (SWIR) subsystem and thermal infrared (TIR) subsystem. Two cryocoolers has been adopted the coolers of the detectors of the SWIR and the TIR subsystems. The performances of these coolers has been very stable and will be maintained until 5 years design life period of this December.

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In these days, against the background of global environment problems including deletion of ozone depletion, it tends to multiuse the refrigerator along with the upgrade of the earth observation sensor and the use of the superconducting devices such as communications equipment. Therefore, it is necessary to establish a basic technology of the refrigerator development of long-lived, small, high performance, and high trust. As a cooling system that answers such a request, the pulse tube cooler and the thermoacoustic prime mover that can be ordinarily driven in a simple structure attract attention. In general, to use the resonance phenomena of the working fluid, the thermoacoustic prime mover needs a long resonance tube. Therefore, the method to use the solid displacer instead of the resonance tube was proposed. This paper reports on the test result when the stack mesh size is took as an experimental parameter by using the solid displacer and performance was examined.

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The Stifling engine is the composition of 2 pistons in 2 cylinders or 2 pistons in 1 cylinder. Heater, regenerator and cooler are installed between 2 pistons. The pulse tube engine is constituted by output mechanism with 1 piston in 1 cylinder, pulse tube, heater, regenerator and cooler. Therefore, the composition resembles the Stirling engine well. So, the engine composition is more simplified, and then, the miniaturization becomes possible. In this paper, in order to understand the basic characteristic of the pulse tube engine, the engine of the simple composition which used atmospheric pressure air for the working gas has been manufactured Then, the relationship between regenerator length and shaft power is examined experimentally. As one of the performance improvement, the bypass using capillary tube is established during pulse tube and cooler division, and the effect of the bypass geometries on the engine performance is examined experimentally. As the result, the excellent effect of the bypass has been confirmed.

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Heat transfer during compression and expansion occurs in almost every reciprocating energy conversion machine and can have large effects on its Performance. It is particularly important in closed-cycle machines such as Stirling engines and pulse-tube refrigerators. Heat flow adding to the gas is the increasing rate of internal energy plus the power done to the gas and calculated from measured pressure changing with time. Apparatus have a 39mm diameter, 28mm stroke piston and 336cm3 reserver. The compression ratio is 1.1. The piston is driven by D.C. motor to allow speed adjustment. Surface area is changed with inserting stacks of stainless steal plates. Measurement was carried out for a range of pressure, frequency, surface area, and for several gases. Experimental data were correlated with non-dimensional parameters for the design of Stirling engines or pulse tube refrigerators.

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A mathematical model of regenerative refrigerators has been developed, and an active buffer pulse tube refrigerator was numerically analyzed. The model is based on one space dimensional approximations of time dependent conservation laws in gasdynamics; different from the previous models it does not require to assume the temperature of cold head heat exchanger apriori, but can analyze the dynamic properties of refrigerators, such as cooling rates, time dependent temperature distributions, and gas displacements. Analytical results on the dynamic properties of the active buffer pulse tube refrigerator as well as the energy fluxes in the refrigerator are reported.

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Numerical simulation of viscous compressible flow in a basic pulse-tube refrigerator was performed to investigate the effect of thickness of wall on refrigeration in basic pulse-tube refrigerators. 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. In this paper, we analyzed the lowest achieved temperatures, wall temperature profiles and heat flowing in the wall for various thickness of the wall.

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In this experiment we have studied the characteristic of the Stirling type pulse tube cryocooler. A linear piston drive compressor commercially manufactured by CFIC was adopted for making pressure vibration of Helium gas. The cooling power of 146W and Carnot % of 12% at a temperature of 80K have been obtained for electric input power of 3.3kW. A simple simulation analysis used in this study has shown that it quantitatively agrees with the experimental results.

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Thermoacoustic prime movers and coolers constitutes a new class of heat engines, which use acoustic waves instead of moving parts such as pistons and valves. Their simple structure, and absence of moving parts offer a new way to understand heat engines. Thermoacoustic point of view, in which heat flow and work flow are used instead of heat and work, is introduced based on the experimental results on energy flows.

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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 HTS devices are extended. Recently Fuji Electric has developed a pulse tube cryocooler with cooling capacity of 2.5W at 70K class, based on the technologies of the stirling cryocooler for the space crafts. This paper describes the main performance including inclination and the structure of an expander relaxed thermal stress, of the commercial miniature pulse tube cryocooler.

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Performances of six kinds of thermoacoustic sound wave generators, which are made of both in different sizes and in different construction, are described. Those sound wave generators are almost classified into two types. First, a single, simplified and heater built-in type ones in which only one generator is used. Second, open-ends connected, closed-ends connected, loop-type ones in which either two or four sound wave generators are employed. Instantaneous measurement of pressure, velocity and temperature are performed. Also, work of oscillatory flow in the resonance tube which is based on both pressure and velocity is employed for evaluating those performances. As a result, some effects of size and construction of thermoacoustic sound wave generators on those performances are ascertained.

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