[in Japanese]

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In the case of the free piston Stirling engine (FPSE), 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 free piston Stirling engine (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, PFSEs using an empty can have also been developed, and they are being used for educational events held by JAXA. Recently, a power converter from waste heat to electricity is expected from the viewpoint of environment protection. Based on JAXA's FPSE technology, two types of FPSEs have been designed and developed to realize efficient use of low temperature heat energy. In this paper, the design specifications of these engines are described.

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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 has 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. A One-cylinder, 1.0kw experimental CFSE model is manufactured. In addition, DP and PP are connected by oval-gear drive for enhancement of indicated power. For cancel the side thrust of DP and PP, contra-rotating drive system is adopted.

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Apart from the double acting type engine, Stirling engines have either 2 pistons in 2 cylinders or 2 pistons in a single cylinder, with the heater, regenerator and cooler installed between the pistons. The single piston type Stirling engine, on the other hand, consists of a single piston in a single cylinder, a cooler, a generator, a heater and a gas damper. The gas damper has a role equivalent to the expansion piston. For this paper, a simple prototype engine, using air at normal atmospheric pressure as the working gas, was fabricated. The basic characteristics of this engine were examined experimentally. In addition, a simple cycle simulation was carried out and compared with the experimental result.

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α^+type low temperature difference Stirling Engine have achieved 800W of shaft power for 1kW class and 10.4kW for 10kW class by using heat source of 300degC, and their thermal efficienct are about 12%. Now, we made some improvement on this engine. In this paper, the contents of improvement and test results of 1kw class engine are described.

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The use of Stirling engine has been restrictive in view of the actual conversion efficiency, the maintenance, the product cost and the reliability. However the potential of Stirling engine comes to be focused in the sense of the global environment protection, because the recovery of manifold exhaust heats is definitely contributed to reduce CO_2 emissions. We have developed the prototype of Stirling engine with high efficiency and the simple mechanism and constitution that can realize the low cost. This recovery system of exhaust heats with prototype of Stirling engine is so compact that could be simply installed to exhaust pipe, while a general steam turbine system composed with plural complex machinery such as waste-heat boilers and steam turbines and high pressure pipes. The recovery system with Stirling engine has not only simplicity but higher efficiency than general steam turbine systems. So, this system is suited to small and middle facilities. In this paper we illustrate how to develop the 5kW Class engine and report the result of the proven test, and then discuss the durability and the reliability.

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Based on the developed 5kW Stirling engine generator, 10kW〜30kW class engine generators and application systems are examined. The 10kW class Stirling engine generator is built by composing two 5kW engines with a phase angle of 180 degree in operation. The 20kW class Stirling engine generator is built by the four 5kW engines constituted as 4 cylinder double-acting type engine, and also its generation output becomes 40kW by raising a working gas mean pressure. On commercialization of the Stirling engine generator, correspondence to many kinds heat sources is a matter of course, but setting of the generation output which matches market needs and examination of effective utilization of heat output are indispensable. One of them is air-conditioning by using a low temperature regenerative desiccant air-conditioner.

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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 generator 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 developement. In this paper, the demonstration plant of 30kW-class stirling engine system using biomass is introduced and typical results of the field test of the plant are reported. Moreover, the possibility of the optimization of the system is reported.

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For the prevention of environment against global warming and at the same time for the preservation of energy, we are focused on the utilization of unused or waste energy. In this research, we have tested the new type of energy conversion system with thermoacoustic prime mover. The advantages of this prime mover are the simplicity and the flexibility for various heat sources such as an external engine. To enhance the performance of the system, we introduce membrane of natural rubber into the system to cut the DC heat flow inside the resonant tube. In this paper, some discussions on the basic of membrane insertion and effect of it on the performance have been done.

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Stirling engines have the composition of 2 pistons in 2 cylinders or 2 pistons in 1 cylinder except for a double acting type engine. Heater, regenerator and cooler are installed between 2 pistons. The pulse tube engine consists of 1 piston in 1 cylinder, cooler, pulse tube, regenerator, heater, and gas damper. The pulse tube engine can be driven by the heat source with the low temperature. For the recovery of the low temperature heat, the flat shape is good in the external heating section. In this paper, in order to investigate the effects of pulse tube shape on pulse tube engine performance, a cylindrical type pulse engine and a flat type pulse tube engine of simple composition, which used atmospheric pressure air as the working gas, has been manufactured. Effects of pulse tube shape on pulse tube engine performance on shaft power and indicated power are examined experimentally. The effect of flat shape pulse tube has been confirmed.

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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. Stirling type pulse tube cryocooler need further improvement, on especially, regenerator. The working gas flow in the regenerator becomes a flow field with non-uniform velocity distribution accompanying the expansion and contraction flow. They cause the excessice pressure loss and reheat loss. We examined the effect of the regenerator entrance shape on the performance of pulse tube cryocooler experimentally. The effect of after-cooler end was bigger than that of cold-head end.

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A looped tube type heat-driven thermoacoustic cooler has no moving parts, only a pair of regenerators sandwiched between heat exchanger. One regenerator amplifies the acoustic power and the amplified wave is supplied to the other regenerator as the diving energy to pump heat. Because it uses extremely simple hardware consisting of a few parts, the cooling device is potentially a powerful tool for application such as conventional cooling system. A looped tube type heat-driven thermoacoustic cooler having feedback path tube would achieve higher efficiency than the cooler no having feedback path tube. In this study, by using thermoacoustic theory, we design the looped tube type heat-driven thermoacoustic cooler having diverged tube that can be driven with highly efficiency.

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A standing wave thermoacoustic engine is composed of a stack introduced inside a tube. The tube used for general thermoacoustic engines has high aspect ratio which is the ratio of its length to its diameter. When the length of a thermoacoustic engine is set to 10 mm with keeping the same aspect ratio, the diameter of the engine becomes excessively small and little output power can be delivered from it. Therefore, it is necessary to reduce the aspect ratio in order to develop a miniature thermoacoustic engine. In this paper, we investigate the onset temperature ratio T_h/T_c of a thermoacoustic engine with the low aspect ratio.

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A gas-filled looped pipe having a regenerator can operate as an efficient thermoacoustic cooler, when it is driven by an acoustic driver via a branch resonator. This is because the loop provides a feed-back pass of the acoustic work flow supplied from the driver. In this work, we test capability of a coaxial tube as a different configuration from the loop. The acoustic field in the coaxial tube having the regenerator between the inner and the output pipes is measured using a laser Doppler vecocimeter and a small pressure transducers. The work flow is observed to circulate through regenerator, meaning the feed back of the work flow.

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We designed and built a multistage thermoacoustic Stirling engine electric generator prototype, where three regenerators aligned in series, not in parallel, enables the power gain of 5.1 with the temperature ratio of 1.95. In this study, we increased the acoustic power level to 17 W from 20 mW in the previous experiment. Additionally, we studied the thermal efficiency of thermoacoustic energy conversion by controlling specific acoustic impedance, in order to verify the multistage thermoacoustic Stirlung engine as a useful energy conversion device.

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Thermoacoustic engines generally need the large temperature difference of several hundred degrees. On the other hand, KIBITUNOKAMA that is one of generators of thermoacoustic spontaneous gas oscillation in Japan generates sound wave below the temperature difference of one hundred degrees by boiling water. Since the difference of conventional thermoacoustic engines and KIBITUNOKAMA is the working gas, we think that the evaporation and condensation of water is important factor to reduce the onset temperature difference of thermoacoustic devices. In this study, we made thermoacoustic engine having water as aworking gas and measured the onset temperature of a spontaneous gas oscillation.

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A prototype of cogeneration system (or CHP) with 3.2W electric output and 271W heat supply has been constructed for educational purposes by using our previously-made small Stirling engine to drive a DC generator which serves as a starter motor as well. Although only about 45% of the total energy supplied to this system has been utilized as electric power output or heat supply in the form of warm water, it still shows the potentials of developing such small CHPs for practical uses.

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Because not only electricity consumption per unit area but also hot water supply demand is large in the small-scale stores such as a restaurant, a fast food 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, present conditions of energy consumption and electricity/heat demand in these small-scale stores are investigated, and the new system using a Stirling engine is suggested, which can supply electricity, hot water and air-conditioning output. The system consists of a Stirling engine generator, a combustor, an exhaust gas heat exchanger or air pre-heater, and a low temeperature regenerative desiccant air-conditioner. It is expected an efficiency of 80% or more at cooling and 90% or more at heating.

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We have tried to develop a heat recovery system with a Stirling engine generator. The engine operates with exhaust gas from a Diesel engine as the heat source. Because the exhaust gas has low temperature, the working gas temperature strongly affects to the engine performance. So it is important to predict the gas temperature accurately in the engine design stage. In this paper, we report the comparisons between the calculated results by an isothermal simulation model with heat transfer of heat exchangers and the experimental results of the Stirling engine.

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In this study, we compared performance for a multistage Stirling engine and a steam engine for a wast heat recovery system. The multistage Stirling cycle and the simple Rankine cycle were analyzed at ideal cycles. It was shown that Stirling engine was able to improve the waste heat recovery efficienciy to make it to the multistage by two steps or more. We discussed waste heat application using the diesel engine of 750kW. It was shown to obtain the waste heat recovery efficienciy of about 7% at the multistage Stirling engine and the steam engine. When all of the wast heat were not able to be collected because the installation space was small, it was clarified that the Stirling engine was higher efficiency compared with the Rankine cycle.

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Heat transfer has been investigated on the end surface of cylinder enhanced by an annular jet from a channel installed in the displacer. The heat flux was estimated from heat generation in the foil heaters each temperature of which was controlled with CTA circuit individually. The heat flux histories for higher reciprocating speeds showed slow-changing waveform. So, the response of the temperature controlling system has been investigated in the present study. The frequency response of CTA circuits was measured, and transfer function from heat generation in the foil heater to its temperature was derived assuming one-dimensional heat conduction in the base plate of the foil heater. The sensitivity from actual heat flux to the working gas to its estimation was calculated, which showed cut-off frequency about 52 Hz. This is not sufficient for the measurement but it can be improved by dumping high frequency as to suppress undesirable oscillation and making high gain and small integration time of the controller to make the gain higher around several hundreds hertz.

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In this study, we examined performance and characteristics of regenerator composed of three types of mesh sheet matrix. The mesh sheets were installed in a 3 kW double-acting stirling engine SERENUM05, and each matrix performance were examined from the engine operating results. Also, characteristics differences between two-piston and double-acting type engines are examined. As the results, it was clear that the mesh sheet, M3, has the largest indicated efficiency among the manufactured mesh sheets, and the required characteristics of regenerator matrix for the double-acting stirling engine are different from those of the two-piston type.

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Double acting type (DA type) six cylinder engine is developed in this laboratory, and to raise the engine performance, it keeps researching. Then, it was going to raise the engine performance by developing a new piston ring, and decreasing the number of the gas leakage and frictional force at current year. The development of the testing set to be able to measure the gas leakage and the frictional force at the same time in having reproduced the usage condition of an actual piston ring to need the gas leakage and the friction power examination device in the piston ring unit to evaluate the effect of the piston ring quantitatively is advanced. In this report, the outline and the content of the design of the testing set under development are described.

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We have developed double acting type (DA type) six cylinder Stirling engine. In the engine our developing, it is thought that the increase and decrease of the frictional force and the working mixture leakage greatly influences at the temperature around the piston ring because of the difference of Coefficient of thermal expansion of both with the endless type piston ring made of polytetrafluoethylene though the cylinder of a stainless steel-made is used. The piston ring that can correspond to the thermal expansion by putting the multistep type step cutting in the endless type piston ring used to improve this problem so far is developed. On the other hand, it reports on output data that the performance of the endless type piston ring and the piston ring by the multistep type step cutting was able to be measured.

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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. Accordingly, attention is drawn to the Stirling cycle machine, which is a perfect freon free and efficient machine. Most Stirling engines operate in temperature ranges in which the temperature difference between the heat source and heat sink is between 100 K and 700 K, with the room temperature being at the lower end of the operating temperature range. However, information available on engines that utilize the room temperature as the heat source and the ultra-low temperature of liquid nitrogen as the heat sink is scarce. Engines that operate within such temperature ranges are called cryogenic heat engines. If their practical applications are realized, energy that has hitherto been wasted during the use of ultra-low-temperature media can be recovered in the form of electrical energy. We have designed and developed a 500 W class Stirling machine as a cryogenic engine. This paper presents results of some PV analysis or torque tests.

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In a small-scale LNG (Liquefied Natural Gas) satellite station, a lot of cold energy is released to atmosphere when the LNG is vaporized. In order to use the cold energy effectively, we have discussed to apply a cold energy used Stirling engine generator. As the first step for the application, we have operated a Stirling engine with liquid nitrogen in our laboratory. In this paper, we show new-type heat exchangers for the experimental Stirling engine, and report detailed experimental results of the engine.

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We made a pulse tube refrigerator as well as 2 types Stirling refrigerator which applied 2 pistons. Refrigerator performance was investigated for several kinds of regenerator. Experimental result obtained a -20℃ of refrigerator achieving temperature for pulse tube refrigerator.

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[in Japanese]

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