• 전자공학회논문지T
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• 제35T권1호
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• pp.67-74
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• 1998

자동차 배기가스의 증가요인인 실화발생을 감지하고 실화가 발생하는 기통까지 판별하기 위하여 종래에는 크랭크각속도를 측정하는 방법을 이용하였으나 이 방법은 고속의 회전시 감지가 어려운 문제를 가지고 있다. 이러한 문제를 해결하기 위해서 본 논문은 이산 월쉬-푸리에(Walsh Discrete Fourier Transform; WDFT)를 이용하여 고속의 엔진회전수에서도 실화발생여부를 판단 가능하게 하였고, 월쉬함수의 Moving window방식을 이용하여 다기통 실화발생에 대한 기통판별까지 가능하게 하였다. 이상의 내용을 시스템으로 구현하여 무부하 Idle상태와 운전상태(Drive)에서 시험한 결과도 실화발생여부를 감지하는데 기존의 방법보다 더 효과적임을 알 수 있었다.

• 비파괴검사학회지
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• 제14권1호
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• pp.16-22
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• 1994

일반적으로 구름 베어링 시스템에 비해 발전용 터어빈이나 내연기관 엔진과 같은 저어널 베어링을 가진 시스템은 상대적으로 대형 설비이거나 더 가혹한 운전조건에서 가동되는 경우가 많다. 이런 회전기계류에서의 베어링의 파손은 설비의 운전 중단 및 관련 설비의 파손까지도 초래할 수 있게 된다. 따라서 이로 인한 보수에 소비되는 시간 및 경제적인 손실등을 피하기 위해서는 저어널 베어링의 조기파손 감지의,역할은 매우 중요하게 된다. 본 연구에서는 음향방출 기술을 이용하여 베어링에서 발생할 수 있는 파손의 조기검출을 위해 실험실용으로 직접 제작한 저어널 베어링 시스템을 이용하여 여러 형태의 비정상 조건을 만들어 가며 실험을 행하였다. 베어링 손상 및 피로의 주 요인으로서는 윤활유 부족, 윤활층에의 이물질의 혼입, 조립 불량 등이 대표적인 원인으로서 알려져 있으며 이에 근거하여 실험 조건을 윤활유에의 이물질 혼입, 윤활유 부족, 그리고 축과 베어링간의 금속간 접촉등의 인위적인 형태로 구성하여 실험하였다. 그 결과로서 음향방출 기술이 저어널 베어링의 조기파손 감지에 매우 효과적인 도구라는 것을 입증하였다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2012년도 춘계학술대회
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• pp.391-394
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• 2012

최근 국 내외의 강화된 배출가스 규제 기준을 만족시킬 수 있는 CRDI 디젤엔진을 산업용 엔진에 적용하기 위해, 제작사에서만 제어할 수 있는 ECU를 사용자의 요구대로 분사시기와 분사량을 조절할 수 있는 엔진 제어 알고리즘을 개발하여, 엔진 성능 향상과 배출가스 저감 등을 위한 테스트 및 검증에 사용하고자 한다. 이러한 CRDI 디젤엔진 전용 Emulator를 개발하기 위해 CRDI 엔진 제어 ECU의 입력 요소 중 CKP와 CMP 센서의 작동원리를 이용하여 디젤 노킹을 판별하고 엔진 밸런스 보정 알고리즘의 설계 방안을 제안함으로써 연비 향상 및 유해 배출가스의 저감을 위한 효율적인 개선 방안을 제안한다.

• 한국자동차공학회논문집
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• 제17권5호
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• pp.16-25
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• 2009

Testing engine performance using an engine dynamometer requires high technical researchers and many facilities. Nowadays, different variables of CAE program are used for identifying the engine performance instead of engine dynamometer test. This is more convenience, as it does not necessitate an abundance of engine dynamometer experiments and, in addition, produces better results. However, CAE programs also contain various variables which can affect engine performance. Those are coupled with each other, thus making it difficult to determine the effectiveness of different variables on engines. DoE (Design of Experiments) methodology is an efficient way to verify the magnitude of effectiveness on engine performance as well as making responses to be optimized at once without trial & error. This study used data from WAVE simulations, which modeled the DOHC SI engine with in-line 4 cylinders at 1500, 3000 and 4500rpm. DoE methodology is designed properly to determine the effectiveness of five variables on power, BSFC, and volumetric efficiency, as well as to find the optimal response conditions at each rpm through a minimized number of experiments. After finishing DoE process, all the results are examined concerning the reliability of test through a verification experiment.

• 소성∙가공
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• 제20권3호
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• pp.236-242
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• 2011

The two objectives of this study were, first, to determine the optimal friction welding process parameters using finite element simulations and, second, to evaluate the mechanical properties of the friction welded zone for large piston rods in marine diesel engines. Since the diameters of the rod and its connecting part are very different, the manufacturing costs using friction welding are reduced compared to those using the forging process of a single piece. Modeling is a generally accepted method to significantly reduce the number of experimental trials needed when determining the optimal parameters. Therefore, because friction welding depends on many process parameters such as axial force, initial rotational speed and energy, amount of upset and working time, finite element simulations were performed. Then, friction welding experiments were carried out with the optimal process parameter conditions resulting from the simulations. The base material used in this investigation was AISI 4140 with a rod outer diameter of 280 mm and an inner diameter of 160 mm. In this study, various investigation methods, including microstructure characterization, hardness measurements and tensile and fatigue testing, were conducted in order to evaluate the mechanical properties of the friction welded zone.

• 한국항공우주학회지
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• 제31권5호
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• pp.93-99
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• 2003

극초음속 추진기관의 설계 및 평가에 있어 추력의 측정은 매우 중요하다. 일반적인 추력 측정방법으로는 추력 측정기를 사용하고 있지만 이러한 방법으론 엔진의 자유제트 실험이나 모델 연소기 같은 실험에는 적용이 부적절하다. 이 때문에 피토압력을 이용한 새로운 추력 계산 방법을 고려하였고 검증하였다. 피토 압력을 통해 계산된 추력의 검증은 추력측정기를 통해 측정된 실제 추력값과의 비료를 통해 이루어질 수 있으며 이를 위해 추력측정기 위에 소형 초음속 풍동을 장착하였다. 추력이 측정되는 동안 충동 후방의 피토압력을 동시에 측정하였다. 측정된 피토 압력을 이용하여 구한 추력값을 검증하기 위해서, 추력측정기로 측정한 추력을 완정팽창 노즐이론 및 추력계수를 이용한 이론적인 계산에 의해 구해진 추력값과 비료, 분석하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 춘계학술대회 논문집
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• pp.275-278
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• 2005

INCONEL 718, nickel based superalloy, has good formability, high strength, excellent corrosion resistance and mechanical properties at high temperature. Owing to theses attractive properties, it finds use in applications such as combustion system, turbine engines and nuclear reactors. In such applications, components are typically required to be tolerant of high stress impact loading. This may cause material degradation and lead to catastrophic failure during service operation. In order to design optimal structural parts made of INCONEL 718, accurate understanding of material's mechanical properties, dynamic behavior and fracture characteristic as a function of strain rates are required. This paper concerned with the dynamic material properties of the INCONEL 718 for the various strain rates. The dynamic response of the INCONEL 718 at intermediate strain rate is obtained from the high speed tensile test machine test and at the high strain rate is from the split Hopkinson pressure bar test. Based on the experimental results, the effects of strain rate on dynamic flow stress, work hardening characteristics, strain rate sensitivity and elongation to the failure are evaluated. Experimental results from both quasi-static and high strain rate up to the 5000/sec are interpolated in order to construct the Johnson-Cook model as the constitutive relation that should be applied to simulate and design the structural parts made of INCONEL 718.

• 소성∙가공
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• 제14권6호
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• pp.559-564
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• 2005

INCONEL 718, nickel based superalloy, has good formability, high strength, excellent corrosion resistance and mechanical properties at high temperature. Owing to theses attractive properties, it is utilized in applications such as combustion system, turbine engines and nuclear reactors. In such applications, components are typically required to be tolerant of high stress impact loading. This may cause material degradation and lead to catastrophic failure during service operation. Accurate understanding of material's mechanical properties with various strain rates is required in order to guarantee the reliability of structural parts made of INCONEL 718. This paper is concerned with the dynamic material properties of the INCONEL 718 at various strain rates. The dynamic response of the INCONEL 718 at the intermediate strain rate is obtained from the high speed tensile test and at the high strain rate is from the split Hopkinson pressure bar test. The effect of the strain rate on dynamic flow stress, work hardening characteristics, strain rate sensitivity and elongation to the failure is evaluated with the experimental results. Experimental results from both the quasi-static and the high strain rate up to 5000/sec are interpolated in order to construct the Johnson-Cook model as the constitutive relation that should be applied to simulate and design the structural parts made of rNCONEL 718.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.173-181
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• 2008

Gas turbine engine for aircraft are usually operated at the altitude condition which is quite different from the ground condition. In order to measure the precise performance data at the altitude condition, the engine should be tested at the altitude condition by a real flight test or an altitude simulation test with an altitude test facility. In this paper describes the design of altitude test facility for turbo shaft engine. This facility will be located in test cell #2 at the Korea Aerospace Research Institute. Test Cell #2 will be used for altitude testing engines with mass flow rate up to 40kg/s and inlet temperatures in the range from $-65^{\circ}C$ to $200^{\circ}C$. The existing compressor/exhauster station with heater & cooler system will be used to simulate altitude conditions in Test Cell #2.

• 한국태양에너지학회 논문집
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• 제35권1호
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• pp.21-28
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• 2015

A small washer powered directly and solely by thermal radiation was constructed and tested to explore the feasibility of using solar energy or other types of thermal radiation for washing and cleaning. In principle, TA (ThermoAcoustic) washers have the benefits of simpler design and operation and fewer energy conversion processes, thus should be more energy efficient and cost less than electric washing/cleaning systems. The prototype TA converter we constructed could sustain itself with consistent fluid oscillations for more than 20 minutes when powered by either concentrated solar radiation or an IR (infrared) heater. The frequencies of water oscillations in the wash chamber ranged from 2.6 to 3.6 Hz. The overall conversion efficiency was lower than the typical efficiencies of TA engines. Change in water temperature had little effect on the oscillatory flow in the TA washer due to its low efficiency. On the other hand higher water temperatures enhanced grease removal considerably in our tests. Methods for measuring the overall conversion efficiency, frictional loss, and grease removal of the TA washing system we designed were developed and discussed.