• Progress in Superconductivity and Cryogenics
• /
• v.17 no.3
• /
• pp.51-56
• /
• 2015

Cryogenic cooling system for HTS electric power devices requires a reliable and efficient high-capacity cryocooler. A Striling cryocooler with a linear compressor can be a good candidate. It has advantages of low vibration and long maintenance cycle compared with a kinematic-driven Stirling cryocooler. In this study, we developed dual-opposed linear compressor of 12 kW electric input power with two 6 kW linear motors. Electrical performance of fabricated linear compressor is verified by experimental measurement of thrust constant. The developed Stirling cryocooler has gamma-type configuration. Piston and displacer are supported with flexure spring. A slit-type heat exchanger is adopted for cold and warm-end, and the generated heat is rejected by cooling water. In cooling performance test, waveforms of voltage, current, displacement and pressure are obtained and their amplitude and phase difference are analysed. Moreover, temperatures of cooling water, housing and linear motor are recorded and electric power parameters of driving circuit are also obtained. The developed Stirling cryocooler reaches to 47.8 K within 23.4 min. with no-load. From heat load tests, it shows cooling capacity of 440 W at 78.1 K with 6.45 kW of electric input power and 19.4 of % Carnot COP.

• Journal of KSNVE
• /
• v.10 no.4
• /
• pp.615-622
• /
• 2000

Discharge valve mechanism for an electrodynamic-oscillating compressor is different from that of a conventional reciprocating compressor. It has a larger discharge port area, heavier valve mass and stiffer valve spring comparing with the reciprocating one. Since the motion of piston is not kinematically restricted as in conventional reciprocating compressors, the stroke of the piston can change sensitively with supplied boltage and load. Thus piston can impact with discharge valve occasionally. This work deals on dynamic analysis of discharge valve considering all of those different characteristics. Impact is considered by a spring-mass model, and the pressure fluctuation at the both sides of the valve is also included considering the discharge port area and valve spring preload. It is assumed that piston moves in the region of between top and bottom dead center not by calculating piston motion from an electrodynamic equation but by getting values through experiment. Discharge pressure fluctuation is calculated using Helmholtz modeling. Finally, dynamic model for a discharge valve is constructed. In order to validate the model analysis results, the valve motion is experimentally measured and compared with analysis.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2008.11a
• /
• pp.215-217
• /
• 2008

This paper deals with the structural vibration characteristics for an outdoor units support of an air-conditioner. Even though main noise sources are compressor noise and fluid noise which is caused by the fan, the structural modification of the outdoor units support may affect vibration and noise. In this paper, damping ratios for two kinds of an outdoor units support of an air-conditioner are measured through the modal testing. In order to reduce the structural borne noise due to an outdoor units support of an air-conditioner, four kinds of rubber materials are selected and tested.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2003.05a
• /
• pp.342-352
• /
• 2003

Idle NVH characteristics are one of the most important aspects among the vehicle performances. Vehicle developers are devoted to improve vehicle interior noise and steering wheel and seat vibrations. In order to improve the idle quality, noise and vibration transfer path should be carefully evaluated. Also, effects of various components related to the idle performance should be confirmed. A general procedure for improving the idle qualify is described in detail. The relationship among cylinder pressure characteristics, crankshaft rotational speed variation, and vehicle vibrations is also investigated. Influences of drive shaft, torque converter, air conditioning system, vehicle structure including engine mount system, and idle control parameters on the vehicle idle quality are studied. Weak points of typical vehicles on the idle qualify are identified. Some of improvement measures are proposed and verified.

• Tribology and Lubricants
• /
• v.38 no.2
• /
• pp.33-40
• /
• 2022

In this study, we present rotor dynamic analysis and operation test of a turbo expander for a hydrogen liquefaction plant. The turbo expander consists of a turbine and compressor wheel connected to a shaft supported by two hydrostatic radial and thrust bearings. In rotor dynamic analysis, the shaft is modeled as a rigid body, and the equations of motion for the shaft are solved using the unsteady Reynolds equation. Additionally, the operating test of the turbo expander has been performed in the test rig. Pressurized helium is supplied to the bearings at 8.5 bar. Furthermore, we monitor the shaft vibration and flow rate of the helium supplied to the bearings. The rotor dynamic analysis result shows that there are two critical speeds related with the rigid body mode under 40,000 rpm. At the first critical speed of 36,000 rpm, the vibration at the compressor side is maximum, whereas that of the turbine is maximum at the second critical speed of 40,000 rpm. The predicted maximum shaft vibration is 3 ㎛, whereas sub-synchronous vibration is not presented. The operation test results show that there are two critical speeds under the rated speed, and the measured vibration value agrees well with predicted value. The measured flow rate of the helium supplied to the bearing is 2.0 g/s, which also agrees well with the predicted data.

• The Journal of the Acoustical Society of Korea
• /
• v.15 no.5
• /
• pp.99-106
• /
• 1996

The noise of a compressor is a major contributor to overall noise radiated from the refrigerator. The major source of the noise is radiated by the vibration of the compressor shell. In this study, to identify the dynamic characteristics of compressor shell, a compressor shell is divided into several components and these are analyzed with a commercial FEM(Finite Element Method) package such as MSC/NASTRAN. Using substructure synthesis method, the dynamic characteristics of the total system is identified. The coherence of each component to the total system is computed by using strain and kinetic energy. To increase the frequency of the first resonance mode which is most effective mode to the noise of the compressor shell, the improving strategy of dynamic characteristics is suggested by changing mass and stiffness of the coherence component to the first mode.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1995.10a
• /
• pp.116-122
• /
• 1995

본 논문에서는 컴프레서 쉘의 구조해석을 수행하기 위하여, 범용 구조 해석 패키지인 MSC/NASTRAN을 이용하여 컴프레서 쉘 전체의 동특성 해석을 수행하였으며, MSC/NASTRAN의 Superelement 모듈인 부분구조합성법을 이용하여 구조물 전체의 동특성해석을 수행하였다. 그리고, 각 분계의 변형 및 운동 에너지를 산출하여 전체 구조물의 고유모드에 대한 분계의 기여도를 평가하였으며, 각각의 에너지에 기여가 높은 분계의 형상을 변경하여 구조물 전체가 원하는 동특성을 얻도록 하였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1995.04a
• /
• pp.208-212
• /
• 1995

공기 압축기는 건설 및 토목공사 현장 등의 산업현장을 비롯하여 각종 공장에서 광범위하게 사용되고 있다. 공기 압축기에 공급하는 동력은 전기를 사용한 모터와 연료를 사용한 엔진으로 구분할 수 있으며 전기가 공급되지 않는 사용현장에서는 엔진 구동형 공기 압축기가 선택될 수 밖에 없다. 엔진 구동형 공기 압축기는 발생소음도가 모터 구동형보다 훨씬 높음으로 인하여 주변환경에의 소음으로 인한 피해를 줄이기 위하여 방음형의 개발이 절실하게 요구되고 있다. 따라서 본 연구는 기존의 비방음형 공기 압축기에 대하여 방음형을 개발하여 시제품을 제작하고 평가하는데 그 목적이 있다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2000.06a
• /
• pp.78-83
• /
• 2000

Exterior noise generated by the aircraft induces a serious noise pollution near the airport. For the prediction of an exterior noise radiation of aircraft an empirical formula is employed to model the acoustic sources. It is shown that the fan/compressor noise is the most dominant part of the acoustic sources in all cases.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1993.10a
• /
• pp.107-111
• /
• 1993

본 논문에서는, 특히 고효율에 따른 소음 증가문제를 해결하기 위해 실험계획법을 이용한 머플러를 설계하였고, 설계단계에서부터 시뮬레이션 검증을 통해 효율을 고려한 저소음 머플러 설계가 가능하도록 머플러의 형상을 유한요소법에 의해 모델링한 후에, 소음해석 PACKAGE인 SYSNOISE를 이용하여 전달손실(TRANSMISSON LOSS) 해석을 해석하였고, 유동해석 PACKAGE인 PHONEMICS를 이용하여 압력손실을 최소화함으로써, 효율 및 소음측면에서 기존머플러보다도 더 우수한 머플러를 설계할 수 있는 PROCEDURE를 개발하였다. 이에 따라 차후 머플러내의 냉매유동특성과 소음특성을 동시에 고려한 머플러가 설계가능하리라 생각한다.