In the previous paper, the authors presented a simple technique for computing indicated work of piston crank drive machine. In this study, the same way is applied to Ross York Drive machine, and a similar formula is obtained analytically. It allows us usage of an electric calculator instead of personal computer. For results of isothermal analysis, the error of the formula using six pressure data per cycle is within ±0.9%, as compared with numerical integration. Then it can be confirmed that the present method has enough accuracy for practical usage.

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α-type Stirling Engines having a phase-angle of 90° and a stroke-volume ratio equal to 1 are analyzed by using T-S diagram. The results obtained are as follows : The optimum temperature ratio, which makes the diagram work to be maximum, is between 3 and 3.5 and it decreases as the dead volume ratio increases. Absorption of heat by the working gas occurs mostly while the crank angle of the power piston increases from 0 to 90°. The cycle approaches isothermal expansion and isothermal compression processes then the dead volume ratio becomes larger and the temperature ratio smaller. The optimum heat storage of the regenerator, which realizes the Carnot efficiency under given temperature conditions, changes by the temperature ratio and dead volume ratio.

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The authors presented a new and simple technique for computing indicated work, which lies on the fact that pressure and volume change in working space are periodic. Mathematical treatment on the basis of harmonic analysis for pressure and volume change in working space gives us a simple formula. In this study, the technique is applied to realize real-time indicated work meter. Processing programs consist of Basic and assembly language parts, only a part of high speed processing is written by assembly language. Hard wear of the meter and test apparatus also are described.

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The authors have investigated pressure drop in heat exchanger elements, such as regenerator matrix and circular pipes including curved one, and presented several empirical formulas. Those experiments, however, were performed under relatively low Reynolds number due to sinusoidal low pressure change caused by speaker. In this study, a new pulsative pressure generator is developed and applied to evaluate flow characteristics of a circular pipe in the range of Re=250-18000. The experimental results show that similar tendency as compared with previous results is obtained.

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This paper proposes an experimental estimation of heat flow. Five-division model is employed to estimate the heat flow in each element from temperatures measured at the boundaries of the elements, and pressure. As measurement data, the result of multi-element simulation are used. Boundary mass flow, heat flow and gas temperature in the cylinders calculated with the 5-division model are compared with the results of the simulation. Boundary mass flow and heat flow in the heater and cooler were almost the same as those of the simulation. However the results of the heat flow in the cylinders show some discrepancy. But this method may be used in the ordinary situation where heat transfer in the cylinders can be assumed negligible. Heat transfer coefficient estimated experimentally would be used for more realistic design of Stirling engines.

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This paper describes structure and numerical simulation of Stirling engine having pin fins' heat exchangers. The structure of the heater consists of circular disk with pin pins. A shroud is attached on the top of the pin fins. The structure of cooler is similar to the heater. The working gas goes through heater in the radius direction from the cylinder to the heater edge. Then the working gas goes through back of the shroud to the regenerator situated around the displacer cylinder, and then goes to the cooler. First order approximation method was employed. Heat. exchanger's shape is 200mm diameter with 2mm square pin fins of 10mm length, which are shaped out overall the disk surface in 4mm pitch. The numerical result shows the output power of described engine becomes 486 Watts with air at 500kPa, 773K of heater pin fin's disk side and 298K of cooler pin pin's disk side. It is cleared that the fluid and thermal performance of pin finned heat exchanger disk is superior to the heater consisted from 100 pipes with 3mm inner diameter and 100mm length.

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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 first report [1], we measured the engine performance with atmosphere air with no-load condition and the mechanical loss with high-pressurized condition on the motoring test. Therefore, it was confirmed that the friction loss of a rotating rod seal was too strong. In this paper, we develop a hermetic generator set using the prototype engine. It is expected to decrease the mechanical loss, because the rod seal is omitted. Then, the performance is measured with high-pressurized condition using helium or nitrogen as the working gas. As the result, it is confirmed that the helium is suitable working gas for the small Stirling engine. Also, many subjects for getting more high power and efficiency are clarified.

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In this paper, in order to examine the possibility of the practical application of multiple cylinder type Stirling engine, the engine as hundred watts is designed, and friction loss, gas leakage and effect of the buffer pressure of the piston ring are examined. As the result, it is difficult that uses the piston ring for the engine of about 10W. In addition, it is the very ideal combination to adopt the injector as a piston and cylinder, if the durability is not considered.

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The regenerator losses of a 3-kW Stirling engine are analyzed in detail. By adopting a unique cylinder arrangement and a well-designed heat exchanger system for the engine, a fifty-percent indicated efficiency and a lower regenerator loss were obtained. To clarify the regenerator performance, the regenerator losses of the engine are rearranged by using reliable experimental data and analyzed data by a mathematical model. Also, the regenerator losses are analyzed with a proposed method, which is able to derive reasonable regenerator losses from engine operating data.

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Over 98% at the regeneration efficiency of the Regenerator must be made with the goal so that the thermal efficiency of Stirling engine may achieve over 30%. Though the regeneration efficiency is improved, as the volume of Regenerator is increased, and as the area of the heating surface is increased, on the other hand dead space volume and pressure loss increase, and they become the output lowering of the engine. It is a problem that the regeneration efficiency measures the temperature change of operative gas and matrix of the Regenerator inside. However, the accurate thermometry is not possible, when the working fluid is the gas, since the flow velocity of the gas is big for the responsibility of temperature sensor. Then, model test by the water was tried instead of operative gas in this study. Features of the experiment using the water are that the measurement of the temperature behavior is easy, because that it can decrease the flow velocity in the equal Reynold's number region and fact of the matrix in which the model length is done can be increased.

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Heat transfer characteristics of regenerators are studied in order to clarify the effect of entrance and exit areas which are usually smaller than the cross-sectional area of matrix. The change of the air temperature at exit is measured for different entrance areas and stack thicnesses using an abrupt heating method. The result is compared with theoretical one which is calculated based on an axially-symmetric irrotational flow model and a simple convective heat transfer model. This comparison brings two experimental numbers of a representative time and a number of transfer unit under uniform flow. These numbers agree with ones calculated from respective definitions and therefore the experimental results are expained by the models mentioned above. However, some difference is observed when the entrance area and stack thickness are small. This will be mainly due to the effect of heat conduction in matrix neglected in the present model.

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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 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 heat transfer characteristic is examined experimentally. The flow loss and heat transfer characteristics of the two stacked wire gauze are compared.

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A Stirling engine with a single multi-phase working fluid for getting high specific power and high thermal efficiency is thermodynamically studied and proposed. The Stirling engine with supercritical heat recovery process can decrease the high-pressure level of working fluid from common gaseous Stirling engines. The thermal efficiency with three different working fluids of (SF)_6,C_3H_8 and R125 is calculated and the calculated thermodynamic efficiency is found to sufficiently approach the Curzon and Ahlborn efficiency that is drawn from entropy generation minimization of power cycle.

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For accomplishing same demand of power output of 25(kW)_e in tests sites having different intensity and distribution of direct solar radiation, it needs to take matching of collector/receiver and engine/generator systems. In such a case, collector size is sometimes adjusted. In this study, diameter of the collector is decided by using design point solar radiation, which is defined sun of average and 1σ (σ : standard deviation) of distribution of maximum direct solar radiation for a day during a year in test sites. Naha in Japan. seoul, Pusan and Cheju in korea are selected as test sites for simulation. The result show that average power output for system operating time is in the range of 9-13(kW)_e and it is necessary to investigate determining method of design point solar radiation.

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A fundamental study on solar Stirling power generation system has been performed in National Aerospace Laboratory. The research work involves both a solar receiver and a Stirling power generation technologies. The former work is focused on developing a high efficiency solar receiver. It is composed of a cavity receiver, thermal energy storage and sodium heat pipes, and aims at transporting solar heat to a bottoming system with the minimized heat loss. A ground test model of solar receiver system has been fabricated and the performance test has been carried out. As a result, it was found that the receiver system was able to provide enough temperature for enabling engine operations under the simulated in-orbit cycle of solar heat. In parallel, semi-free piston Stirling engine generators have been experimentally studied as one of candidate converters for future space power generation. Through a series of bench tests, the thermodynamic efficiency of 33% and system efficiency of 20% was obtained. Based on these achievements, the design work for an improved linear alternator was carried out.

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Steam Rankin Stirling Cycle Engine (SRSE) has a hybrid cycle of Rankin and Stirling cycle using steam. Steam expands in power cylinders at high temperature after passing regenerators and heaters same as Stirling engines. So, it is a kind of Stirling like regenerated reciprocating steam engine. After many basic experiments on small modified atmospheric Stirling engines using compressed air instead of steam, important technical merits and difficulties of this SRSE engine were studied. Then a small double expanding SRSE was installed on an electric vehicle for generations of electricity. Through these experiments, the following good points were known for this kind of engines. (1) Power increases up to several times of atmospheric Stirling engines. (2) This engine needs no Helium gas, and has nearly no cooling system and pressurized crankcase, resulting be low cost and weight. (3) Theoretical thermal efficiency is expected to be middle of both cycles. Now, three KW double expansion SRSE are being made fit to biomass fuels.

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Performance and combustion characteristics of a hydrogen internal combustion Stirling engine were examined with increasing the injection rates of H_2 and O_2 up to 30% of total thermal input. The hydrogen internal combustion Stiring engine was prototyped by mainly modifying the cooler and the heater in Ecoby-SCM81 Stoichiometric combustion of H_2 and O_2 at a catalytic combustor functions as a heater in the conventional Stirling engine and a finned cooler with a water trap plays both roles of cooling the working gas and removing the water produced by the internal combustion. The P-V diagram of the internal combustion engine showed similar cycles to the external heating. Also, slight pressure rises, which were due to the water vapor and the unburned mixture remaining in the working fluid, appeared during the internal combustion operation. Such pressure rises lowered with the increase of the engine speed, showing that high-speed operation is effective to avoid the explosive combustion in the engine.

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We have constructed a simple loop-type thermoacoustic engine and measured the pressure change at the 13 points along the loop tube with three kinds of the stack shape. The profile of the pressure amplitude along the loop was analyzed assuming the generating wave is piling up a pure progress and standing wave. The results show that the pressure amplitude both a progress and standing wave depend on mesh size of the stack material and the temperature gradient at the stack. The generated progress wave progress wave propagates from both side of the stack to the loop-tube and the ratio of the pressure amplitude depends on the operational conditions and stack shape.

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The characteristics of a coupling thermoacoustic sound wave generator are described. An experiment was carried out using a close-ended connected-type sound wave generator, considering the stack position in which heat transferred by sound waves, Q_<MA>, was the largest when each thermoacoustic sound wave generator was operated independently. Since the sound wave generators interact with each other, the heat transfer characteristics of each sound wave generator of the closed-ended connected type would be different from those of the independently operated one. The lowest temperature of the hot heat exchanger, T_H, is lower than that of the independently operated one. The difference between the lowest T_H values changes from 40℃ to 70℃. Both pressure and velocity waveforms at each point of the resonance tube showed tendencies similar to those of the independently operated one. We propose the development of new thermoacoustic sound wave generator that utilizes and recovers waste heat efficiently.

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The characteristics of a new loop-type thermoacoustic sound wave generator, in which two close-ended, connected-type generators are connected to each other at the open ends by four bent tubes and sealed hermetically, are described. It has been reported that two types of sound wave generators, in which two identically shaped systems are connected to each other at either the open ends or the closed ends, can operate stably. In the new loop-type generator which has the benefits of the above-mentioned two types of sound wave generators, its pressure, velocity amplitude and heat transferred by sound waves are greater than those of the other connected-type ones. And harmonic in pressure signals and no harmonic in velocity signals are observed at the connected part. An optimum theoretical sound wave frequency of 100Hz is also confirmed for this type of sound wave generator.

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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. 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 and zero GWP characleristics. In this paper, an orifice type pulse tube refrigerator (OPTR) is manufactured and some experiments to understand the refrigeration performance have been made. The characteristic of the refrigerator's cooling performance is that there is a proportional relationship between the cooling temperature and the heat load. And the possibility of this refrigerator as an application in terms of cooling temperature is discussed and the guidelines of designing the system are shown.

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Over the past several years, much interest has been devoted to the development of pulse tube refrigerators. But, the applicability of pulse tube refrigerators for the high cooling temperature region has not been studied until now, because basically the expansion work of pulse tube refrigerators can not be recovered. In this paper, we suggest the new type of the pulse tube refrigerator. It is the series type pulse tube refrigerator that has some pulse tubes to be connected in series. We attempt to make clear the characteristics of the series type refrigerator by employing the numerical cycle simulation based on a nodal analysis. The results prove that the series type pulse tube refrigerator has a high potential for the high cooling temperature use of the refrigerators.

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An improved double-compressor pulse tube refrigerator in which one compressor is for power supply and another compressor with buffer is for phase shifter is introduced. The advantage is that the DC gas flow is easily controlled by a second orifice or perfectly cut. A numerical simulation is performed to a double-compressor 4 K pulse tube refrigerator. The numerical calculated results are useful for the experimental. This method is also a good method to confirm the DC gas flow effect at 4 K pulse tube refrigerator.

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Experimental investigation was made on blow-out phenomena of cooled and heated air from a thermoacoustic refrigeration tube. It is well known that the inside air near the cold side of the stack was cooled and the air near the hot side of the stack was heated in a thermoacoustic refrigeration tube. In addition, the cooled air was found to blow out naturally from a small hole near the antinode of the thermoacoustic tube and ambient air was found to be evacuated through a small hole near the pressure node. Mean pressure increased when a hole position approached to the antinode along the tube and with the increase of acoustic power. The phenomena were explained by the acoustic radiation pressure occurred by non-linear effect of acoustic propagation in a tube.

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Acoustic resonance refrigerator is environmentally safe refrigerator and have high reliability. In designing such refrigerator, it is essential to have suitable design criteria for the heat exchanger. Systematic experiment was performed for various types of heat exchanger. This paper describes the effect of heat exchanger on the temperature distribution along stack in the refrigerator model.

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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 the heat-driven thermoacoustic driver and the heat-driven thermoacoustic refrigerator are discussed. In the acoustic driver's test, some kinds of stack are used to find out the optimum condition of stack configuration. From the result, there is an optimum condition of the stack configuration such as the ratio of the hydraulic diameter (D_h) to the thermal penetration depth (δ_K), and heat exchanging area. In conclusion, a large mesh is desirable for the stack, however, since certain amount of heat transfer area is necessary for the stack so the length of stack gets longer as a necessity. In order to enhance the performance, this driver's equipment should be big. In addition, the discussion of enhancement of the system performance and the possibility as an application is done.

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Recently, the development of a thermoacoustic cryocooler is noticed. The cryocooler without moving parts is realized, when the thermoacoustic compressor is combined with a pulse tube. However, the small thermoacoustic compressor is not fund. We have developed a small-size Vuilleumier cryocooler. It has the cooling capacity over 1.5 watts at 80 K. The thermal compressor unit of the Vuilleumier cryocooler was utilized for a heat-driven pulse tube cooler. Since ratio of a volume of pulse tube and a swept volume of thermal compressor is not appropriate, the cooler performance is lower than the Vuilleumier cryocooler. This report describes the result of the initial function test for cryocooler while the structure of produced machine.

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Two different types of thermal compressors instead of the mechanical compressor were introduced for the low frequency pulse tube system. Simplified work flow analysis has been developed to find out the feasibility of the thermal compressor system. Result indicates the cold thermal compressor operating between 300 K and 40 K could be applied to 4 K pulse tube cooler effectively.

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