• 한국생산제조학회지
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• 제18권6호
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• pp.642-651
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• 2009

The history of excavator design is not long enough which still causes most of the design considerations to be focused on static analysis or simple functional improvement based on static analysis. However, the real forces experiencing on each component of excavator are highly transient and impulsive. Therefore, the prediction and the evaluation of the movement of the excavator by dynamic load in the early design stage through the dynamic transient analysis of the excavator and ensuring of design technique plays an importance role to reduce development-cost, shorten product-deliver, decrease vehicle-weight and optimize the system design. In this paper, Commercial software DADS and ANSYS help to develop the track model of the crawler type excavator, and to evaluate the performance and the dynamic characteristics of excavator with various simulations. For that reason, the track of crawler type excavator is modelled with DADS Track Vehicle Superelement, and the reaction forces on the track rollers were predicted through the driving simulation. Also, the upper frame and cabin vibration characteristics, at the low RPM idle state, were evaluated with engine rigid body modelling. And flexibility body effects were considered to determine the more accurate joint reaction forces and accelerations under the upper frame swing motion.

• 설비공학논문집
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• 제22권2호
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• pp.78-85
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• 2010

A dynamic model has been developed to investigate the operability of a single and double-effect solar energy assisted parallel type absorption chiller. In the study, main components and fluid transport mechanism were modeled. And solar radiation and the solar collector were also modeled along with its control design. The model was run for the single mode with solar energy supply only and the solar/gas driving double effect mode. From the simulation results, it was found that the present configuration of the chiller is not capable of regulating solution flow rates according to variable solar energy input. And the issues of the excessive circulation flow rate and the mismatch between available solar power and cooling load discourages the use of the single mode, but the dual use of gas and solar power is recommendable in view of controllability and enhanced COP.

• 한국자동차공학회논문집
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• 제19권2호
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• pp.26-34
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• 2011

Hybrid powertrain systems have been developed to improve the fuel efficiency of internal combustion engines. In the case of a parallel hybrid powertrain system, an engine and a motor are directly coupled. Because of the hardware configuration of the parallel hybrid system, friction and the pumping losses of internal combustion engines always exists. Such losses are the primary factors that result in the deterioration of fuel efficiency in the parallel-type hybrid powertrain system. In particular, the engine operates as a power consumption device during the fuel-cut condition. In order to improve the fuel efficiency for the parallel-type hybrid system, cylinder deactivation (CDA) technology was developed. Cylinder deactivation technology can improve fuel efficiency by reducing pumping losses during the fuel-cut driving condition. In a CDA engine, there are two operating modes: a CDA mode and an SI mode according to the vehicle operating condition. However, during the mode change from CDA to SI, a serious fluctuation of the air-fuel ratio can occur without adequate control. In this study, an air-fuel ratio control algorithm during the mode transition from CDA to SI was proposed. The control algorithm was developed based on the mean value CDA engine model. Finally, the performance of the control algorithm was validated by various engine experiments.

• 수산해양기술연구
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• 제36권3호
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• pp.157-165
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• 2000

연안 소형 어선의 조업 효율을 향상시키기 위한 연구의 일환으로 소형 유압식 어로윈치시스템을 설계하고, auto tension 기능을 내장시켜 이 시스템의 개루프 상태에 대한 동적 응답 특성을 분석, 고찰한 결과를 요약하면 다음과 같다. 1. 본 연구에서 설계, 제작한 소형 윈치시스템은 갑판상 어느 장소에서도 조작이 가능하도록 원격조작방식을 채용하고 있기 때문에 어로 작업시의 인력 감소와 작업의 효율성을 높일수 있다고 생각된다. 2. 솔레노이드 밸브를 ou/off 조작하여 윈치를 구동할 때, 정전 및 역전 구동 조작에 대한 윈치 드럼의 회전 지연시간(dead time)은 각각 0.09 sec, 0.04 sec이었다. 또한 on/off 레버의 조작을 행한 직후 응답 특성은 약간 불안정하였지만, 짧은 경과 시간을 거쳐 안정되는 추종성능을 나타내었다. 3. 윈치를 auto tension mode로서 구동하는 경우, 윈치의 회전축에 55.9 kgf$.$m 이상의 토오크가 작용하면 윈치는 5.1 rpm의 회전속도로서 줄을 풀어내고, 그 이하의 토오크가 작용하면 11.1 rpm의 회전속도로서 줄을 감아들이는 자동 권양 윈치의 기능을 발휘한다. 4. 윈치의 auto tension mode에 대한 과도 응답에서 부하가 급격히 증가할 때와 감소할 때의 정정 시간은 0.12 sec, 0.2sec이었고, 그 때의 회전속도는 각각 11 rpm, 5.3 rpm이었다. 5. 원격제어조작에 따른 윈치의 토오크 및 회전속도에 대한 추종성능은 정전 구동에 있어서는 0.23 sec, 역전 구동의 경우에 있어서는 0.37 sec 이내로서 비교적 안정된 응답 특성을 나타내었다. 이상의 결과로부터 본 연구에서 설계한 소형 어선용 자동 권양 윈치 시스템은 인력을 절감하고, 부하의 급속한 변화에 대한 추종 성능이 현용 어로시스템에 비하여 매우 우수하기 때문에 해상에서 어로작업시 과부하에 대한 어구의 손상 방지 및 조업 효율의 향상에 크게 기여할 것으로 판단된다.

• 한국자동차공학회논문집
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• 제17권5호
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• pp.97-106
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• 2009

An objective of this study is to give practical information that could be used for calculating pollutant emission factors and fuel economy from Korean Inspection & Maintenance program, which has been using steady state acceleration simulation mode. Concentration results from I/M test is adequately converted to mass emission factors and fuel efficiency data, which have unit of g/km and km/L, respectively. Exhaust volume flow(EVF), which is for converting emission result from concentration to mass, is measured by tracer method in various vehicle speed - power condition. It is found that there is an apparent second order relationship between EVF and vehicle inertia weight. EVF is expressed in function of vehicle inertia weight in order to estimate EVF in I/M site without measuring device. Converted mass emission results from measured EVF and raw emission analyzer show a satisfactory agreement with those from conventional CVS-bag type measurement system. Mass emission factors and fuel efficiency from measured EVF and estimated EVF also show good agreement to each other. Considering that an I/M program has great advantages to recruit-based emission test in terms of the number of test vehicle, the information in this study can be used for developing an alternative procedure to collect more various data to establish national database of mobile emission factors and fuel economy, even though the driving cycle in I/M program is steady state cycle rather than transient cycle.

• 에너지공학
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• 제8권2호
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• pp.298-308
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• 1999

과냉각수조로 분사되는 증기의 직접접촉 응축특성을 알아보기 위하여 다섯 개의 수평 노즐에 대해 증기 질량유량과 수조 온도를 여러 가지로 변화시키면서 실험적 연구를 수행하였다. 증기응축현상을 육안관찰과 고속 비디오 카메라를 사용한 방법으로 분석한 결과, 안정된 증기제트인 경우 증기 질량속과 수조온도가 변화함에 따라 타원형 및 원추형 증기제트 형상이 나타나는 것을 관찰하였다. 증기제트 팽창비, 증기제트 길이 및 응축연전달계수를 구하였고, 증기 질량속, 수조온도 및 노즐 내경이 미치는 영향을 분석하였다. 증기제트 길이와 응축열전달계수를 증기 질량속 및 응축추진 포텐셜의 함수로 나타낸 상관식을 구하였다. 증기제트 내부와 주위 수조온도 분포를 구했으며 증기 질량속, 수조온도 및 노즐 내경이 미치는 영향을 분석하였다. 처깅, 천이처깅, 응축진동, 안정응축, 방울응축진동 및 간헐진동응축 등 여섯 가지 영역으로 구분된 응축 영역도를 작성하였다. 그 외, 수조 벽면에서의 동압을 측정하였고, 증기 질량속과 수조온도에 따라 변화하는 증기 응축모드와 동압과는 밀접한 연관성이 있음을 확인하였다.