• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.475-481
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• 2001

Foil bearings have been successfully used for small high speed rotors, such as ACM(Air Cycle Machine), turbo charger, turbo compressor, high speed motor, etc. Recently advanced researches are concentrated on the high load capacity and the extreme temperature foil bearings to extend the application boundary. Some bearings are already adopted into cryogenic machines and micro gas turbines. In this paper, a foil journal bearing designed for high load capacity, which is under development, is introduced. The bearing is for the turbo refrigerator which has a rotor of 18${\~}$25 kgf rotating at 23,000${\~}$38,000 rpm. This application is well beyond conventional spectrum of foil bearings because the rotor is relatively heavy and the rotational speed is low. Therefore, the development is challenging. The foil bearing is a bump type, the size is 60mm in diameter and 50mm in length, the operating fluid is air and rotational speed is 26,000 rpm. In-house software was developed and used for bearing design. Tested maximum load capacity is 80kgf, 0.62 in terms of load capacity coefficient, and testing is being continued.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.93-93
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• 2011

고진공 펌프 국산화의 일환으로 터보분자 펌프와 크라이오 펌프 개발이 진행 중이다. 크라이오 펌프 개발은 기계연구원, 우성진공(주), 국민대학교가 연합해서 수행하고 있다. 올해 9월말에 끝나는 1단계 마지막 3차 년도에는 두 고진공 펌프 모두 시제품을 완성하고 성능을 입증해야 한다. 이를 위해 고진공 펌프 개발과 별도로 진공 펌프 종합특성평가 시스템 개발도 표준과학연구원 주도로 진행되고 있는데 크라이오 펌프 평가 시스템은 원자력연구원이 담당하고 있다. 완성된 크라이오 펌프 성능평가 장치는 상온 기준 5${\times}$10-11 mbar의 기저압력을 보이고 있어서 초고진공 영역에서 크라이오 펌프 운전성능을 평가할 수 있는 준비를 마쳤다. 현재 크라이오 펌프 냉동기는 전반적으로 목표 설계치에 근접한 냉각성능을 나타내고 있는데 예를 들면 2차 냉각단 냉각능력이 10 K, 10 W로 대형 크라이오 펌프를 제작하기에도 충분하다. 활성탄 어레이도 여러 모델들을 자작하여 배기성능을 시험해 보았으므로, 최종적으로 3,600 L/s 급에 적합한 어레이를 만들고 이를 개발된 냉동기에 얹고 열차폐와 몸통을 씌워 펌프로서의 운전성능을 평가하는 일이 남아있다. 시제품은 상용품과 달리 기기가 차지하는 공간이 크고 부대설비가 복잡해서 운전성능 평가 장치에 부착해서 실험하기 어려울 수도 있으므로 기계연구원 현장에서 진공 게이지와 기체도입구만 부착한 마구리 플랜지를 펌프 흡기구 위에 달고 간이로 배기속도를 측정하는 것도 고려하고 있다. 이 경우는 표준용기를 사용할 때보다 배기속도가 과대평가되므로 이를 보정해 주는 방안을 마련해 놓아야 한다.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.30-35
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• 2008

This paper describes a fault detection and diagnosis (FDD) system developed for the heat source apparatus in building air-conditioning system. As HVAC&R systems in building become complex and instrumented with highly automated controllers, the processes and systems get more difficult for the operator to understand and detect the mal-functions. Poorly maintained, degraded, and improperly controlled equipment wastes an estimated 15% to 30% of energy used in commercial building. When operating a complex facility, FDD system is beneficial in equipment management to provide the operator with tools which can help in decision making for recovery from a failure of the system. Automated FDD for HVAC&R system has the potential to reduce energy and maintenance costs and improves comfort and reliability. Over the last decade there has been considerable research for developing FDD system for HVAC&R equipment. However, they are being made too much of a theoretical study, so only a small of FDD methods are deployed in the field. This study deduced an actual defect source for the heat source apparatus and suggested a low price FDD method which is ready to be deployed in the field.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.109-109
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• 2013

고주파 가속기의 전자선원의 설계 및 제작검증을 위한 hot-firing station을 설계하였다. 본 장치는 전자총의 빔 사이즈, 빔 전류 등을 측정할 수 있는 기기로 전원장치부, 고진공 챔버, 측정장치부 등 크게 세 부분으로 이루어져 있다. 특히 전원장치는 이중에너지 모드를 구현할 수 있도록 에너지의 크기가 다른 두개의 전자총 펄스를 생산해 낼 수 있도록 설계되었다. 고진공 챔버는 고전압 절연체를 이용하여 제작되었으며, 스크롤(건식) 펌프 와 터보 분자펌프를 이용하여 $10^{-7}$ torr 저/고진공 배기를 수행한 뒤, 이온 펌프를 이용하여 $10^{-8}$ torr까지 초고진공 배기를 수행할 수 있도록 설계하였다. 전자총으로 부터 나오는 전자들의 특성을 분석하기 위하여 패러데이 컵과 YAG 스크린을 설치하였다. 패러데이 컵은 전자빔의 인출 파형및 빔 전류를 측정하고, YAG 스크린은 CCD 카메라와 컴퓨터를 이용하여 전자빔의 균일도를 측정하여 정보를 얻도록 한다. 진공 쳄버의 최대 진공배기는 $10^{-9}$ torr이다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.7
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• pp.4659-4664
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• 2014

The noise produced in a factory is a cause of the noise complaint of the surrounding residential areas. In addition, it affects the work efficiency and health of workers. This paper presents the results of a basic study to reduce the noise generated from the blower, which is often used in the factory of a small and medium scale, using an active noise controller (ANC) in three-dimensional space. For this purpose, the simulator program, which can compare various parameters of the original noise and controlled noise, such as sound pressure levels, power spectra, and equivalent noise levels, was developed. The noise data was recorded at 17 points around a turbo fan blower currently being operated in a small-medium size factory. The simulation results showed that the power spectrum was reduced by a maximum of 40dB in the low frequency band and the average equivalent noise level attenuation was 12.6dB.

• Aerospace Engineering and Technology
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• v.7 no.2
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• pp.46-52
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• 2008

The instrumentation was studied in order to measure aerodynamic performance and efficiency of a compressor as a component of a 5MW-class gas turbine for power generation. In case of an axial compressor, the distributions of static pressure on a casing can be obtained by averaging at each stage and those of total pressure and temperature in the flow field of the compressor can be measured with a Kiel temperature probe. In case of a centrifugal compressor, the static pressures at the hub and the tip, respectively, of an impeller exit are considerably different, so the pressures need to be measured at both positions and thereafter averaged. The distributions of static pressures in a diffuser and a deswirler are measured at ten positions along five streamlines in one pitch. In addition the flow field can be measured in detail by 5-hole Pitot tube in order to analyze the flow characteristics of the core flow region and wake region and the rotor-stator interaction of the compressor.

• Journal of Hydrogen and New Energy
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• v.31 no.5
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• pp.429-435
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• 2020

This paper describes the experimental study of reverse-Brayton refrigeration system for application to high temperature superconductivity electric devices and LNG re-liquefaction. The reverse-Brayton refrigeration cycle is designed with operating pressure of 0.5 and 1.0 MPa, cooling capacity of 2 kW at 77 K, and neon as a working fluid. The refrigeration system is developed with multi scroll compressor, turbo expander and plate heat exchanger. From experiments, the performance characteristics of used components is measured and discussed for 77-120 K of operating temperature. The developed refrigeration system shows the cooling capacity of 1.23 kW at 77 K and 1.64 kW at 110 K.