• 연구논문집
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• s.34
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• pp.39-46
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• 2004

The compressors in the air conditioner have the role of the pressurization and circulation of the refrigerant. The hermetic reciprocating compressors driven by rotary motor have been used for the air conditioner. The linear compressor has very simple structure and enhancement in the efficiency in comparison to that of conventional reciprocating compressor. The linear compressors are widely used for the small cryogenic refrigerator (below 1 kW), such as the Stirling refrigerator and pulse tube refrigerator. In the cryogenic application, the pressure ratio of the linear compressor is below 1.5, but the linear compressor for the air conditioner should overcome the high pressure ratio and the large pressure difference between the each sides of the piston. The resonance characteristics of the linear compressor has the significant impacts on the power consumption. To minimize the power consumption, the linear compressor should be operated at the resonance point. In the resonance characteristics, the role of the mechanical and gas spring should be considered. In present study, the cycle of the analysis of the vapor compression refrigeration cycle with the different refrigerants (R134a, R4l0a, R600a) and the designs of the linear compressor are performed. The effects of the stiffness of the mechanical spring on the electromagnetic forces would be discussed. Finally, the results show the design specification of the linear compressor for the air conditioner.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.6
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• pp.619-627
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• 2012

This study was experimentally investigated on the effects of spring stiffness applied to linear compressor chambers. The springs prevented piston head from colliding with engine cover, stored the kinetic energy and regenerated the kinetic energy. The linear engine has two combustion chambers and four compressor chamber. The combustion chamber bore size was 30 mm, maximum stroke was 31 mm and effective stroke volume was 25.45 cc respectively. The spring stiffness was varied such as 0, 0.5, 1.00, 2.9 and 14.7 N/mm. The linear engine was fueled with premixed LPG (propane 99%) and air by pre-mixture device. As an experimental result, The stroke, piston velocity and the piston frequency were increased by high spring stiffness. Also, thermal efficiency was grown. because the increased stroke made the higher compression ratio. In conclusion, electric power and efficiency were improved.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.49 no.4
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• pp.61-68
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• 2012

In this paper, a closed-loop sensorless stroke control system for a linear compressor has been designed. In order to estimate the piston position accurately, motor parameters are identified as a function of the piston position and the motor current. These parameters are stored in ROM table and used later for the accurate estimation of piston position. The identified motor parameters are approximated to the several surface functions in order to decrease memory size. They can also be divided into 2 or 4 subsections to decrease identification errors. The effect of the order of surface functions and division of subsections on identification errors and computation time is analyzed.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.67-70
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• 2002

The Stirling cryocooler with helium refrigerant has been widely used for the cooling of the infrared detector, and the alternatives of the helium in the Stirling cryocooler are nitrogen and hydrogen gas. In this study, the performance experiment of the small FPFD(Free Piston and Free Piston) type Stirling cooler and the moving coil type, dual acting linear compressor was performed when the nitrogen and helium is used for the working fluid The results show that the nitrogen refrigerant has small cooling capacity compared with the helium, but the performance characteristics of the linear compressor does not greatly changed.

• Progress in Superconductivity and Cryogenics
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• v.3 no.2
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• pp.55-61
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• 2001

A free piston and free displacer (FPFD) Stirling cryocooler for cooling infrared and cryo-sensor is currently under development at korea Institute of Machinery & Materials. The FPFD Stirling cryocooler consists of two compressor pistons driven by linear motors which make pressure waves and a pneumatically driven displacer piston with regenerator. It is the most suitable design for a mechanical cryocooler utilized in night vision environment In this study, performance test of the Stirling cryocooler with different length of the split tube and operating frequency were performed to get characteristics of the cryocooler.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.172-176
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• 2001

A Stirling cryocooler is relatively compact, reliable, commercially available, and uses helium as a working fluid. The FPFD stirling cryocooler consists of two compressor pistons driven by linear motors which makes pressure waves and a pneumatically driven displacer piston with regenerator. A free piston and free displacer(FPFD) Stirling cryocooler for cooling infrared and cryo-sensors is currently under development at KIMM(Korea Institute of Machinery & Materials). In order to evaluate the feasibility of using a linear motor driving cryocooler, prototype Stirling cryocooler with a nominal cooling capacity of 0.5W at 80K was designed, fabricated and tested. The prototype has achieved no load temperature of 51K and cooling power of 0.33W.

• Progress in Superconductivity and Cryogenics
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• v.4 no.1
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• pp.140-144
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• 2002

A free piston and free displacer (FPFD) Stirling cryocooler has been widely used for the cooling infrared and cryo-sensor. The thermodynamic performance of the free piston and free displacer type (FPFD) Stirling cryocooler is highly dependent on the operating frequency of the linear compressor and the natural frequency of the displacer. In this study, to find optimal relation between operating and natural frequency of the displacer the dynamic characteristics of the displacer in the expansion space of the Stirling cooler was investigated by experiment. The experimental results show that the Stifling cryocooler has maximum cooling capacity at the operating frequency of about 0.8 times of the natural frequency of displacer. Therefore the operating frequency of the Stirring cryocooler should be determined by natural frequency of the linear compressor and displacer.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.766-771
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• 2000

This study is mainly concerned with friction and wear properties for the piston ring of non-lubricating air compressor which made of PTFE-polyimide composites. At the PTFE and polyimide alone mixture specimens, PTFE80%-polyimide20%, which shows the lowest men friction coefficient and specific wear rate at 0.94m/s sliding speed. At each of carbon, copper and oxide lopper mixed with PTFE80%-polyimide20%. In case of copper10%, at 0.94m/s sliding speed, the mean friction coefficient shows 0.087, which is the lowest value in all specimens. In case of the specific wear rate, copper30% specimen shows the lowest value of $2.537E-5(mm^3/Nm)$ in all specimens.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.12
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• pp.1237-1243
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• 2009

A computational procedure to estimate the noise radiated from a discharge valve system in a linear compressor was discussed and established. This procedure was composed of three steps. As the first step, the dynamic behavior of the valve system was estimated taking into consideration of fluid-valve-piston interactions. As the second step, the flow characteristics of refrigerant in the discharge valve system were estimated through computational fluid dynamics applying the behaviors of the valves as moving boundary conditions. The variations of pressures and velocities of fluid were converted to quadrupole noise sources. As the final step, the boundary element method based on Helmholtz equation was applied to predict the radiated acoustic pressure. The computational results by the presented procedure were experimentally validated.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.12
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• pp.56-61
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• 2020

Fuel economy has always been a major issue in the automobile industry, especially owing to the associated environmental concerns. It is widely known that only 5-20% of the energy generated by automobiles running on internal combustion engine engines is used as power, while the rest is consumed because of friction between components. The main components of the reciprocating piston type compressor used in vehicles, such as the shaft, swash plate, piston, and cylinder, cause severe energy loss owing to frictional contact between each other. The wear contact between the main shaft and the other components is particularly severe. Most quality issues arise owing to the sticking phenomenon that occurs between these parts. In this study, a coating solution to reduce friction is prepared by mixing adhesive solid lubricant, organic binder-polyadimide, inorganic binder (Binder), and graphite in four different ratios, and the best combination is determined.