• 한국추진공학회지
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• 제27권1호
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• pp.49-57
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• 2023

자가증기 가압시스템은 저비용, 고신뢰도의 장점으로 차세대 재사용 발사체들의 추진기관에 널리 채택되고 있다. 자가증기 가압시스템은 구조가 간단하나 탱크 내부에서 일어나는 열과 물질의 전달과정에 대한 이해가 필요하다. 이러한 이유로 자가증기 가압시스템의 모사시험을 구상하였다. 모사시험설비는 해외 가압시험설비 사례와 전문가의 자문을 기반으로 구성하였는데, 실제 자가증기 가압시스템과 달리 추진제 탱크를 단열하여 외부환경에 의한 영향을 배제하고자 하였으며, 열과 물질 전달현상의 연구의 편의를 위하여 가압가스 공급라인과 추진제 배관을 분리하였다. 제작된 자가증기가압 모사시험설비를 이용하여 극저온 추진제에서 가압가스의 응축현상, 헬륨을 이용한 가압과 증발된 추진제를 이용한 자가증기가압의 효율성 비교, 그리고 자가증기의 온도에 따른 가압능력을 평가할 수 있다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1384-1387
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• 2003

Pressurization test is usually required in aircraft full-scale static test. There are several test conditions including pressurization of cockpit, fuselage fuel tank, air inlet duct for T-50 full-scale static test. In this paper, the test conditions, equipment, piping analysis for the pressurization test are introduced. Tank simulation test is performed to verify the validity of piping analysis and to find good tuning parameters for the pressurization channel in the servo controller. Several test setup for pressurization of T-50 test is introduced. Test article volume is filled by form, $60%{\sim}80%$ volume is reduced for the T-50 full-scale static test. Pressurization system is connected to servo controller which also controls hydraulic actuator. Load and pressure control is synchronized by using the same servo controller during T-50 test. Typical control result for pressurization test condition is shown. Pressurization tests of T-50 full-scale static test was completed successfully.

• 문화기술의 융합
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• 제6권1호
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• pp.477-483
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• 2020

콘크리트 박스 구조물이 열화되어 보수보강이 필요할 경우 스프레이 장비로 구조물 단면에 보수재를 분사하여 부착시키는 방법에 의존하고 있는데 천장 또는 벽체부위의 경우 시공 후 보수재 자중 또는 중력에 의해 부착력이 저하될 수 있으며 지하철 구조물의 경우 진동 등에 의해 초기 부착력이 떨어지는 문제점이 발생한다. 또한 작업자의 숙련도와 시공환경에 따라 보수품질이 변동되기에 이에 대한 보완책이 필요한 실정이다. 본 연구에서는 중력에 의한 보수재의 부착력 저하 및 인력시공에 의한 보수품질의 변동과 같은 문제점을 해결하고자 보수재 시공 후 소정의 압력을 가할 수 있는 기계식 가압장비를 개발하였다. 그리고 가압장비의 성능을 알아보고자 현장조건을 모사할 수 있는 챔버를 제작하여 가압 유무, 단면부위 및 환경조건을 달리한 부착강도를 측정한 결과 가압할 경우 그렇지 않은 경우보다 부위별로 차이가 있었으나 최대 70% 부착강도가 증가하는 효과를 얻을 수 있었다.

• KIEAE Journal
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• 제13권3호
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• pp.27-32
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• 2013

Infiltration is air flow that occurs through cracks in buildings. According to level and kind of infiltration, the cooling load and heating load in buildings may increase. In this study I conducted field measurements to evaluate air tightness in 27 new apartment units. Field measurements for new apartments was the focus. For the de-pressurization method, the equipment utilized to gauge airtightness included KNS-5000C and KNS-4000 which were installed on the window in order to measure indoor air leakage. The results are summarized as follows. The average ACH50 of a $59m^2$ APT was 3.98, 3.82 for a $84m^2$ APT, and 2.73 for a $114m^2$ APT. The total average ACH50 of 27units was 3.51.

• 한국철도학회논문집
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• 제5권4호
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• pp.260-266
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• 2002

A numerical simulation has been performed to estimate the transient pressure variation in the tunnel when G7 test train passes through the test tunnel in the Kyoeng-Bu high-speed railway. A modified patched grid scheme is developed to handle the relative motion between a train and a tunnel. Also, a hybrid dimensional approach is proposed to calculate the train-tunnel interaction problem efficiently. An axi-symmetric unsteady Euler solve using the Roe's FDS is used for analyzing a complicated pressure field in tunnel during the test train is passing through the tunnel. Usually, this complex phenomenon depends ell the train speed, train length, tunnel length, blockage ratio between train and tunnel cross-sectional area, relative position between train and tunnel, etc. Therefore, numerical simulation should be done carefully in consideration of these factors. Numerical results in this study would be good guidance to make test plans, test equipments selection and to decide their measuring locations. They will also supply important information to the pressurization equipment for high-speed train.

• 드라이브 ㆍ 컨트롤
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• 제11권4호
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• pp.39-45
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• 2014

With recent oil price increases, the fuel efficiency of hydraulic excavators has become a serious issue. Researchers have considered weight lightening by high pressurization in order to improve the efficiency of the excavator and pump controlled actuation (PCA) and to reduce pressure loss of hybrid and valves using mechanical inertia. However, high pressurization is not very effective because the excavator operates at a low speed; a hybrid is inefficient because little accumulated inertial energy is accumulated; and PCA is ineffective because control precision and responsibility are low. In this study, a method to minimize air and gas in hydraulic oil has been presented as a simple and new way to increase hydraulic efficiency.

• 한국철도학회논문집
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• 제10권6호
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• pp.723-729
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• 2007

환경부는 2006년 12월에 ${\ulcorner}$대중교통수단 실내공기질 관리 가이드라인${\lrcorner}$을 마련하였다. 관리항목으로 이산화탄소$(CO_2)$와 미세먼지(PM10)에 대해 각각 Level 1(평상시)과 Level 2(혼잡시)고 가이드라인을 제시하였다. 이에 따라 현재는 법적 기준이 아니지만, 열차와 전동차에 대해 실내공기질 관리가 필요하게 되었다. KTX는 터널 진입시 발생하는 고압의 압력파로 인한 이명현상을 방지하기 위해 여압장치가 설치되어 있다. 외부 신선공기는 플랩의 작동에 의해 공기 순환이 이루어진다. 본 연구는 2008년까지 진행되고 있는 코레일 기본연구과제로, 2006년 7월에 KTX가 운행하는 경부선(서울-부산)과 호남선(용산-목포)을 대상으로 실내공기청정도를 측정하였다. 터널구간에서 KTX 여압장치 작동에 따른 실내공기질 변화를 측정하고, KTX ATESS 레코더 기록파일과 비교 분석하였다. 측정결과 미세먼지 농도는 환경부 가이드라인에 매우 양호하였고, 이산화탄소 농도는 터널 일부구간으로 옥산-오탄, 고등-휴대, 개착-일직 터널에서 변화가 있지만, KTX 객실 공기청정도는 환경부에서 제시하고 있는 가이드라인에 만족한 수준으로 나타났다.

• 한국초전도ㆍ저온공학회논문지
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• 제23권1호
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• pp.7-11
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• 2021

Cryogenic vessels are special equipment that requires periodic evaluation of their thermal insulation performance. At the current standard, the test is considered as the loss product or heat leakage of cryogenic vessel, which takes over 72 h to evaluate; consequently, a large amount of working medium is discharged to the environment in the process. However, hydrogen is flammable and explosive, and the discharged gas may be dangerous. If liquid hydrogen is replaced with liquid nitrogen before testing, the operation then becomes complicated, and the loss product or heat leakage cannot respond to the thermal insulation performance of cryogenic vessels for liquid hydrogen. Therefore, a novel method is proposed to evaluate the heat leakage of cryogenic vessels for liquid hydrogen in self-pressurization. In contrast to the current testing methods, the method proposed in this study does not require discharge or exchange of working medium in all test processes. The proposed method is based on one-dimensional heat transfer analysis of cryogenic vessels, which is verified by experiment. When this method is used to predict the heat leakage, the comparison with the experimental data of the standard method shows that the maximum error of heat leakage is less than 5.0%.

• 한국산업융합학회 논문집
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• 제19권3호
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• pp.125-132
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• 2016

The swash-type piston pump is a device that discharges as much volume of hydraulic oil generated as it moves the ramp by controlling the angle of the swash. This pump is suitable for high-speed high pressurization, and due to its useful characteristic being the variable capacity-type, it is used as a main pump for heavy equipment in various fields such as defense, shipbuilding, construction, etc. This study intends to obtain optimal design values by conducting a structural analysis in order to verify its reliability during the design process of the newly developed swash-type piston pump.

• 한국정밀공학회지
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• 제32권7호
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• pp.627-631
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• 2015

Conventional etching technology is in the face of problems such as dishing, erosion resulting from non-uniform removal of film. Advanced printed circuit board (PCB) requires accurate wire formation with the aid of planarization by chemical mechanical polishing (CMP). Linear roll CMP is a line contact continuous process which removes the film by pressurization and rotation while slurry is supplied to polishing pad attached to the roll. This paper focuses on the design of floating nozzle on the linear roll CMP equipment which makes the slurry supply uniformly on the roll pad. Experimental results show that removal rate using the floating nozzle increases 3 times higher than that without it and non-uniformity is less than 15%.