An annular linear alternator of 100 W class were fabricated. The electrical output of 100 W was obtained for a design operating condition with regular stroke at the highest operating speed. In the alternator testing the magnet plunger was directly connected to a motor-driven moving mechanism. The linear alternator is composed of a plunger with permanent-magnet ring, power coil, inner yoke and outer yoke. We studied on the operating characteristics of three stage magnet rings and two poles linear alternators. An installed force sensor could give mechanical power.

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The NAL, National Aerospace Laboratory of Japan, has been studying Stirling generators as a candidate system for the utilization of solar thermal energy. Several types of semi-free-piston Stirling generator have been fabricated and experimentally evaluated. These prototype engines, called the NALSEM (NAL Stirling Engine Model) series, are semi-free-piston Stirling machines with a moving-magnet linear alternator. The NALSEM500 was designed to achieve thermodynamic efficiency of 30% or more with an indicated power of 500W. The design performance has been achievable to date. Based on this achievement, an improved Stirling engine generator, the NALSEM700, has been designed as part of the present study. This engine has an opposed-piston configuration to minimize mechanical vibration, and is expected to provide higher performance and stability than the NALSEM500. Addressed in this paper are discussions of the NALSEM500 test results, and both the design and design verifications of the NALSEM700.

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The differential pressure (ΔP) should be generated by a pair of rotating disc with partial hollow across the two separated space where temperature is different. When the difference of temperature (ΔT) is very low as several decades, generated ΔP falls below to thousands of Pa. Conversion from low ΔP to the electric power is accomplished by the vibrational voice coil generater (VCG) with high efficiency only when the frequency of the vibration reaches to some level. To obtain a high frequency of ΔP, the rotating discs are driven by an electric motor and the number of hollows should be multiplied by odd. The theoritical analysis is attempted for a simple model. Above mentioned high speed ΔP generator meets to the energy recovery system from the low ΔT heat sources to the electric power.

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In this study, by using a pulsative pressure generator proposed in our previous paper, pressure drop of a circular pipe with sharp egged ends is measured and evaluated as Fanning friction factor F_d. Influence of temperature distribution of the wall on F_d is also confirmed. The values of F_d in both of laminar and turbulent regions are greater than that of steady flow. Critical Reynolds number R_<ec> depends on frequency of the pulsative pressure and decreases with decreasing the frequency. The results with and without a temperature distribution, by using fluid property calculated by firm temperature, agree with together in test conditions.

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Performance of 3kW two-piston Stirling engine, NS03T was examined in this study. The NS03T engine has a unique V-shape cylinder arrangement with an offset crankshaft and a double tube type heat exchanger which has a high indicated efficiency. The engine was reassembled to improve the engine performance. To decrease mechanical losses, a 12L buffer tank and endless one-way-type piston rings were provided. Their effects to the engine performances were evaluated based on experimental data in detail which were taken by a newly developed measuring system.

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In order to develop a low cost and small Stirling engine, a gamma-type Stirling engine which has simple moving-tube-type heat exchangers and a Rhombic mechanism has been developed. Its target shaft power is 50 W at the engine speed, 4000 rpm and the mean pressure, 0.8 MPa using helium as the working gas. In the published reports [1], [2], we measured the engine performance with atmosphere air and the mechanical loss on the motoring test. We also developed a hermetic generator set using the prototype engine. As the results, it was confirmed that the friction loss of a piston drive mechanism is too strong, and the engine has big gas leakage from the power piston. In this paper, we discuss about the Rhombic mechanism. Still more we reform the engine with reorganized parts of the power piston, connecting rods and a heat exchanger, and try to measure the engine performance.

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We have taken much interest in the highly efficient propulsion of fish and attempt to apply the mechanism of fish-like swimming to the underwater robot. The author examined to adopt a semi-free-piston Stirling engine (SFPSE) for the power source of a fish robot. One of characteristics of the SFPSE is that the output power can be obtained directly from the reciprocating motion of a power piston. In the case of a fish robot, it is the best way that the reciprocating piston drives the oscillating tail fin directly. A great deal of mechanical frictional loss can thus be reduced. This mechanism should result in high potential for efficiency. In this paper, the performance of a simple experimental SFPSE - tail fin system was examined experimentally. Also swimming speed of a fish-like mechanism with the engine was discussed.

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The " Steam Rankine Stirling Engine" (SRSE) is a Stirling engine assisted by steam or compressed air injection. So, this engine works in the combination of Rankine cycle and Stirling cycle, so that it is called SRSE. Until today, small size SRSE of double expansion was made first and, experimented by air and steam. Using 0.8Mpa air, about 70 watt output were measured which value is several times higher than usual atmospheric Stirling engine of the same size. New 3kW SRSE was designed and manufactured, which is designed to use wooden pellets and tips as fuel with l.OMpa steam. Now it is under tests and improvements. Already about 1.5kW DC end power was measured using 0.7Mpa steam. This engine would be developed into many ways for utilization of various biomass and other renewable energy sources.

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Recently, the introduction of the co-generation system using gas turbine, diesel engine, gas engine is popular in factories, large-scale office building, general hospital, and so on. Furthermore, the examination of the residential co-generation system is carried out in search of electric power decentralization, energy saving, environment and economical efficiency. In Japan, it views fuel cell and small gas engine as thermoelectric conversion equipment of this system with hope, and the examination of the small Stirling engine has just begun. The merit of the Stirling engine introduction is big, when cold region with much heat demand, diversity of the fuel, operating cost, and the vibration and noise reduction are taken into consideration. In this paper, energy user study results of ordinary homes around Sapporo City are described. The possibility of the introduction of the residential co-generation system using Stirling engine is examined. In energy user study of ordinary homes, energy equipment used, energy source and situation of energy utilization are examined. Based on the survey, the residential co-generation system using Stirling engine for cold area is proposed. The possibility of Stirling engine introduction increases as a result of the evaluation of the initial and running cost.

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This paper propose new equation of indicated power which allow the rapid and accurate calculation of pressure variation, flow friction losses in to the heat exchanger ( heater, regenerator, cooler ) and bend pipe in crank-driven Stirling engine, basis of Schmidt cycle that an isothermal thermodynamic model. These equation can be calculated flow losses given to the only main dimension of engine. These formulate are derived for frictional losses in the three heat exchangers and bend pipe, taking in to account the variation in mass flow rate, fluid resistance, gas flow, shaft torque over the cycle. In the previous report, the analysis on the flow loss work was carried out. Then, the technique which estimated the indicated power from principal particulars of the engine at the good accuracy was proposed. In addition, the analytic solution on flow loss work in bend pipe was deduced.

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The temperature-entropy diagram for α-type Stirling Engines is obtained on the basis of the adiabatic model of Finkelstein(1962). With his model the thermodynamic processes in practical engines can be analyzed, and the relationship between the pressure and volume of the working gas may be obtained. Then, using the pressure thus obtained, both the relationship between the mixing-cup temperature and 'mixing-cup entropy', and the diagram of temperature- entropy are obtained based on the method proposed by Oyama (2000). By comparing it with the cycle for the isothermal model, the characteristics of the cycle for the adiabatic model are clarified. It is found that, when the dead volume and temperature ratios are small, the traces of the cycle of the adiabatic model resembles the Arabic figure 8, which means that the cycle has both the characteristics of a heat engine and a refrigerator. The optimum heat storage of regenerators is also obtained which realizes the Carnot efficiency under given temperature conditions.

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This study deals with the thermodynamic design of Stirling engine. It is selected as the optimum condition that the net output power of the engine takes the maximum with respect to the variation of parameters, such as rotating speed, tube or wire diameter of heat exchangers, the free-flow area of heat exchangers or the volume of heat exchangers. The net output is calculated from indicated power of multi-element simulation in which flow resistance is neglected, subtracting friction power loss calculated from existing correlations. The optimum conditions have been derived as shown in table 1. Existing engines do not meet the condition very well, especially for ratio of free flow areas.

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Cycle simulations were made on SOFC-Stirling engine combined systems fueled with methane and hydrogen to investigate the feasibility of the combined systems. The model system consisted of a SOFC with internal reforming, a combustor burning the exhausted fuel from the SOFC, a conventional Stirling engine and an air-preheater recovering the exhausted heat from the engine. In the system, SOFC served simply as the topper of the engine. The cycle calculation was mainly focused on the influences of temperature efficiency of the preheater and the number of transfer unit of the Stirling engine heat exchanger on the system efficiency and the operation conditions. The methane system revealed that the efficiency attains up to 52% at reasonable temperature efficiency of 0.8, while the operation is restricted in a narrow range of the number of transfer unit by the maximum preheater temperature and the minimum temperature at SOFC inlet. The hydrogen system requiring no reforming showed a higher efficiency and a wider operation range than the methane system.

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KUBOTA has been developing a Stirling heat pump using dual input both shaft power and heat power. This machine is a heat-assisted Stirling heat pump and is constructed as two sets of three-cylinder machines, each a combination of two Stirling sub-systems; one a power producer and one a heat pump. This paper describes performance of the heat pump. The tests were performed at various ratios of heat power to shaft power, heat input temperatures, and output temperature conditions. It was shown that the heat pump was applicable for various driving sources such as a gas engine and a gas turbine, and the heat pump had high performance as a freon-free system at various operating conditions.

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This paper presents a clearance Analysis using 3D-CAD system on a Stirling refrigerator. A prototype Stirling refrigerator employing helium as a working fluid has been investigated to see whether the freon free machine be a viable alternative for the current household refrigerator. It is modify to the most suitable working space by reducing a dead volume. But the working space is a complex form because, the working space composes a displacer and a compression piston. Using 3D-CAD system does the modeling of a Stirling refrigerator. And it is made that a clearance in each part becomes proper. The displacer form and an inside cylinder were modified. These results reveal that the dead volume can reduce about 10.28 m^3 And a theory cooling capacity may improvement about 28.41 W.

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The authors feel that Stirling coolers are much suitable for use at ultra-low temperatures between -200℃ and -50℃ in the field of refrigeration, and have developed a Stirling cooler and a cooling unit using the single Stirling cooler for ultra-low temperature use. In this paper, the new cooling unit with double Stirling coolers is presented to meet a demand in cooling equipment market. The secondary refrigerant circulates in series between the both Stirling coolers. The cooling capacity increases about two times as much as the single cooling unit mentioned above.

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Stirling coolers using refrigerants, such as helium, which have no impact on the depletion of the ozone layer and global warming attract a great deal of attention because they 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. This paper discusses the durability test of the Stirling cooler which achieved the cost decrease and the performance improvement by optimizing a structure and driving condition aiming at practical use was evaluated. It is clear that an increase in the contaminative element of the working gas inside is related as one of causes to with the performance deterioration.

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We have been developing a small-size heat-driven pulse tube cooler to study the possibility of cold production. A thermal compressor unit of the Vuilleumier cooler was utilized for this machine. The charge pressure and speed of displacer piston were selected as major operating parameters. Test results of the heat-driven pulse tube cooler showed that the cooling temperature of 173 K without heat load, and 1 watt was maximum cooling capacity at 200 K.

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The regenerator is the regenerative heat exchanger, which greatly influences the performance of the Stirling cycle machines. A stacked wire screen of which a balance of flow loss and heat transfer characteristics is good, is often utilized for this regenerator matrix. The stacking method of the wire gauze is a method for perpendicularly stacking for the flow of the working gas. Therefore, the basic characteristic of stacked wire gauze reported until now, was only perpendicular stacked wire gauze. However, the method stacking parallel to the flow of the working gas is also considered. In this study, in order to grasp the basic characteristics of parallel stacked wire gauze, the effect of the stacking method on basic characteristic is examined experimentally. The effect on the pressure loss examines experimentally in the previous report. So, the superiority of the parallel stack wire gauze has been confirmed. In this paper, the effect of the stacking method on Nusselt number is examined experimentally. And, the friction factor and Nusselt number of two type stacked wire gauze are compared.

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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 gap distance between regenerator ends and matrix on flow area in matrix, are examined by unidirectional steady flow apparatus.

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This paper presents about pressure loss of the nylon mesh matrix in oscillatory flow. A specific gravity of nylon is lower than that of copper. We anticipate that nylon mesh makes mechanical loss decrease. Nylon mesh regenerator has 80%〜90% of copper mesh regenerator's cooling capacity. Pressure loss of nylon mesh regenerator is more than that of copper.

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Regenerator losses of two 3-kW Stirling engines are analyzed in detail to optimize the regenerators. A fifty-percent indicated efficiency and a lower regenerator loss were obtained by adopting a unique cylinder arrangement and a well-designed heat exchanger system. To clarify the regenerator performance, the losses are adequately evaluated by using reliable experimental data and are analyzed by a mathematical model. Based on these analysis results and optimizing processes during the engine improvements, a design method for regenerators of practical engine was established and was introduced in this report.

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A thermoacoustic refrigerator is remarkable because it uses natural gas as a refrigerant and doesn't need a routine maintenance. Some experimental discussions and analysis have bee done, but there are few effective methods of system design of this refrigerator. In this paper, some results of performance tests of a loudspeaker-driven thermoacoustic refrigerator are discussed. In the investigation on the influence of stack type on the performance, a stack of parallel plate type is the highly efficient stack. From the result, some requirements exist for the stack configuration and some of them are listed. In conclusion, the cross-sectional shape of stack is needed to be the assembly of cells which have almost the same gap between solid walls, and the operating condition has a influential factor as well as the stack configuration does so.

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A small pulse tube refrigerator with a cooling power of 70 W at 165 K was designed, fabricated and tested. It is used for recondensing xenon gas in a liquid xenon photon detector. A type of the pulse tube refrigerator is a co-axial one with an inside regenerator configuration for the space-saving and easy fabrication. The cooling power was tested both with a simple-orifice and a double-inlet phase shift configuration and found that the cooling power at around 165 K was almost the same in this proto-type refrigerator. This refrigerator was then installed in the 100 L large-proto liquid xenon calorimeter and operated for 18 days for recondensing evaporated xenon gas without liquid nitrogen.

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Since environmental problems are getting to be very serious in these days, we have to provide for the protection of the environment as soon as possible. As a result of the Montreal Protocol and the Kyoto Protocol, utilization of CFCs and HFCs are restricted to phase out and to cut down respectively. Therefore, an interest is growing to apply a cryocooler to the non CFCs' and non HFCs' refrigeration system, which will be a candidate for alternatives of the traditional vapor compression refrigeration system. In particular, a helium gas is one of the promising refrigerants for its zero ODP (Ozone Depletion Potential) and zero GWP (Global Warming Potential) characteristics. In this paper, some kinds of heat exchanger have been discussed to compare the characteristics among various kinds of refrigeration system. And in addition, a Stirling cycle refrigeration system, such as pulse tube refrigeration, is focused to concretize the value of it and at the same time a checking up the feature of a pulse tube refrigerator is done. To make further reference to the performance of pulse tube refrigeration, a numerical calculation has been done. As a result of it, a velocity distribution in section varies greatly owing to the operating condition. Especially, near the solid wall, the definition of the thickness of boundary layer is difficult and that thickness acts on the refrigeration performance. Finally to improve or develop the Stirling cycle refrigeration system, some comments are made.

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A new type of pulse tube refrigerator named V-M cycle pulse tube refrigerator is put forward here. By using liquid nitrogen as cold source, we obtain pressure wave through the movement of displacer piston. Then expander and other phase shift mechanisms are used to produce cooling effect at cold end. Preliminary experiments gave lowest temperature of 5.6K at the cold end, with high to low pressure ratio about 1.2.

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In this paper, the heat exchange process between the working gas and the regenerator materials is examined in the second-stage GM refrigerator. The temperature dependence of the cooling power is measured as a function of the phase angle between pressure and displacement oscillations of the working gas. It is found that the optimum phase angle maximizing the cooling power at a given temperature dramatically increases with decreasing temperature particular below 20 K. This behavior represents that the importance of the phase angle in order to increase the cooling power in the low temperature region.

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Numerical simulation of viscous compressible flow in basic pulse tube refrigerator is conducted to clear the working principle of refrigeration. Transient axisymmetric two-dimensional equations of continuity, momentum and energy were solved by means of CIP method. The physical simulation model is a 10mm inner diameter and 50 mm length circular pulse tube containing a 10mm heat exchanger. The two models, adiabatic wall model and non-adiabatic wall model, were used for calculation. Some numerical results were obtained on the transient behaviors of pressure and temperature distributions and the two models were compared. Heat transfer between tube wall and fluid was analyzed in non-adiabatic model.

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We have studied a new conceptive Stirling refrigerator. It is a pulse tube type Stirling refrigerator that has a bigger extra space, called 'pulse tube', between the low temperature heat exchanger and the expansion space. The advantage of the pulse tube type Stirling refrigerator is that the mean gas temperature in the expansion space can be kept around room temperature by the function of pulse tube. We attempt to make clear the working characteristics of the pulse tube type Stirling refrigerator by employing the numerical cycle simulation based on a nodal analysis. The results prove that the pulse tube type Stirling refrigerator can work as the mean gas temperature in the expansion space is kept at room temperature.

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