• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.237-243
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• 2002

A centrifugal compressor of 50HP for reverse brayton cryocooler using neon as a coolent has been developed. It has relatively low total-to-total pressure ratio but mass flow rate is very small and the voting gas, neon, has greater specific heat ratio than air. It was essential to have very high rotational speed of 100,000 RPM. The efficiency of compressor has great effects on overall system and the COP of cryocooler. To meet the design requirement of the compressor efficiency and to minimized the required rotational speed, highly efficiency impeller having low specific speed was designed. To maintain the overall system efficient high, gas bearing of bump type and high speed permanent magnet synchronus motor was developed and adopted. In this paper, design and performance prediction results of the compressor impeller is presented.

• Journal of Mechanical Science and Technology
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• v.14 no.6
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• pp.597-604
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• 2000

Low noise of air-conditioners is one of the most important issues because of the users' strong demand. The main source of noise in an air-conditioner is the compressor. Therefore, noise reduction in a compressor is quite significant as an element technology in the air-conditioner field. Recently, scroll compressors are widely used, because they feature low noise, due to less pulsation of gas pressure, than that of rotary compressors. For reduction of noise, the source of noise must be identified. This paper presents a detailed analysis to identify the noise source and shows the dominant factors of noise of the scroll compressor, which will make it possible to design a scroll compressor with low noise.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.1162-1167
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• 2001

Suction valve fluttering is generated by reciprocating motions of the piston inhaling and discharging process of gas in the hermetic compressor. A reactive type suction muffler, which produces high pressure-drop because of its complicated flow path, controls the impulsive noise radiated from the flutter of suction valve. The high-pressure drop in the muffler increases the transmission loss, but reduces the EER(Energy Efficiency Ratio) of the compressor. We consider how to design the high acoustic attenuation and low pressure-drop performance to take account of the acoustic and flow performances of the suction muffler. In this study, we identified the suction noise source of compressor from the measurement of the acoustic pulsation and flutter of suction valve. We analyzed the acoustic characteristics of muffler using the finite element method, and compared the experimental and analytical characteristics of flow path of suction muffler. Theoretical predictions and experimental results are compared from the viewpoint of the acoustic performance and energy efficiency of the compressor.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.362-367
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• 2001

A reciprocating compressor unit with variable rotating speed driven by BLDC motor is mounted inside hermetic chamber on an internal suspension composed of 4 coil springs and a discharge pipe. A method for predicting the dynamic behavior of compressor frame is required to reduce the transmitted vibration level. Mechanical characteristics such as mass, spring and discharge pipe stiffness properties are obtained with experimentation. To confirm the vibration model for compressor frame, free vibration analyses are performed with theoretical and experimental methods. Results for analytical and experimental investigations on dynamic behavior of the compressor frame are presented, and the agreement between measured and predicted results are satisfactory.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.143-147
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• 1998

In this study, nonlinear stiffness characteristics of a discharge valve in a small hermetic compressor was considered. It was approximated, with piecewise-linearity, and cubic or quintic nonlinearity by the static load-displacement experimental results. Based on the fluid-structure interaction effects and mass flow rate, the derived 1-DOF equation of motion for the valve model was analyzed. Finally, the dynamic response of the discharge valve was studied with parameters such as the ratio of the running frequency of the compressor to the linear natural frequency of the valve.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.1206-1212
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• 2003

Shell vibrations of the rotary compressor, which account for considerable portion of the noise from compressor, are caused by various sources. Among them is the vibration of the in nor part or cylinder assembly, which undergoes severe compression process and rotational motion. But little researches have been carried out about the behavior and effect of the inner part because of its structural complexity. Furthermore, the shell of the rotary compressor is hermetic type that experimental approach is very difficult. This research studied the structure-born noise of the Rotary compressor using FE an analysis. The comparison between sound pressure spectrum and natural frequencies of the shell vibration implies that shell vibrations contribute significantly to the noise. It is found that inner part vibrations are responsible for those through the FE analysis. Design modification of the inner part, which shifts the target frequencies, reduced overall noise level of the compressor.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.6 s.123
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• pp.484-490
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• 2007

A reciprocating compressor used in domestic refrigerators can be subjected to many different forms of shock. These shocks are usually experienced during transporting the products from a manufacturer to customers. The hermetic structure of this kind of compressor makes it difficult to conduct drop tests for identifying the failure mechanism and their drop behaviors. The drop/impact simulation for a reciprocating compressor has been carried out with the explicit code LS-DYNA and its validation has been experimentally verified. Simulation results are in good agreement with those of drop test. The present method of drop/impact simulation provides an efficient and powerful solution to improve the design quality and reduce the design period.

• 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 Society of Mechanical Engineers
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• v.17 no.2
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• pp.475-483
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• 1993

A computer simulation model of a hermetic reciprocating type of refrigeration compressor has been developed. The compressor simulation model constitutes 6 control volumes, to each of which conservation laws of mass and energy are applied to yield full description of the refrigerant state along its passage. Instead of ideal gas assumption. real gas equation is employed. Some of valve-related input data required for the simulation are acquired from test bench experiments. The refrigerant states such as pressure and temperature, etc., mass flow rates, and valve motions can be predicted by the simulation. The calculated P-V diagram shows a good agreement with experimental result.

• Tribology and Lubricants
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• v.17 no.6
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• pp.426-434
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• 2001

The hermetic reciprocating compressor driven by the BLDC motor rotating with variable speeds, is modelled and analyzed for dynamic characteristics. The governing equations of piston, connecting rod and crank-shaft of the reciprocating compression mechanism and characteristics of driving torque of the motor are obtained. Dynamic behavior of the crankshaft supported on 2 journal bearings is analyzed considering compression load and eccentric unbalance for the 4 rotating speeds of crankshaft. And. reaction forces generated from oil film in the journal bearings are analyzed under transient condition using Reynolds' equation. To take into account the dynamic characteristics depending on the variable rotating speeds, comparison on the dynamic behavior of crank-shaft is made for the 4 operating modes of the compressor. Results show that the magnitude of crankshaft locioperating on the lower rotating speeds is more larger than the higher ones due to reduction of inertia force of the reciprocating piston.