• 한국수소및신에너지학회논문집
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• 제24권5호
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• pp.461-466
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• 2013

In this research, the diesel cycle was thermodynamically interpreted to evaluate the possibility of high efficiency by converting diesel engine to the atkinson cycle, and general cycle features were analyzed after comparing these two cycles. That an experimental single cylinder and a long stroke diesel-atkinson engine, of which S/B ratio was more than 3, were manufactured. After evaluating the engine through basic experiments, a diesel engine was converted into the atkinson cycle by constituent VCR (variable compression ratio) device and VVT (variable valve timing) system. The experimental method was to observe compression work reduction effects due to low compression effects from delayed intake valve closing of the early stage atkinson engine. The result, the possibility of increasing compression ratio about each engine load was confirmation by constructing compensate expansion-compression ratio in accordance with the delayed intake valve close.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
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• pp.319-321
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• 1999

To solve the problems in the present ree1-to-reel deposition method, we have developed a new deposition system for a 12m long YBCO coated conductor. The system comprises two chambers, a reaction chamber and a evaporation chamber which are connected through window. A tan long fi tape textured by RABiTS was wound around a cylinderical sample holder of 20cm diameter. The cylinder was rotated in the reaction chamber during deposition of YBCO film by coevaporation. We'll describe the details of the performance of this system as well as the RABiTS process for a 12m long Ni tape.

• 한국소음진동공학회논문집
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• 제23권9호
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• pp.806-813
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• 2013

For the past years, higher power rating 2 stroke super long stroke diesel engines having more than 8 cylinders and larger cylinder bore are installed mainly on very large containerships to save on fuel consumption. However, these engines are prone to X-mode vibration due to 2nd node torsional vibration or the X-type moment, particularly because of the increase in total length and height. Recently, cases of excessive X-mode vibration often occurred on engine's major components. This vibration is manifested also as secondary vibration causing failure in engine-mount large structures. This study investigated the excitations caused by the 2nd node propulsion shafting torsional vibration that influence X-mode vibration of the main engine and practical countermeasures are proposed. An 8RT-flex82T 8 cylinder engine and 11S90ME-C 11 cylinder engine for a container ship was used as research model.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 추계 학술대회논문집
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• pp.219-222
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• 2005

Recently, the interest of the engine capacity and environment of the atmosphere is increasing, so the researches for the engine capacity have been conducted for a long time. But the internal environment of an automotive engine is very severe. A piston is exposed to combustion gas of over $2000^{\circ}C$ and strong friction is occurred by high speed motion in the cylinder. The fraction between piston and wall of the cylinder causes the increase of temperature in the engine. The temperature of the engine has an effect on the engine capacity. If the temperature is high, the capacity of the engine is low. So we have to maintain the optimum temperature. To maintain the optimum temperature, the enough flow rate of the engine oil is needed. The oil jet is used to control the flow rate of the engine oil and supply the engine oil to the piston and cylinder. The purpose of this study is to check the mass flow rate of the engine oil and the characteristics of internal flow of the oil jet. Flow pattern of the engine oil is very important because it concludes the loss in the oil jet. This study is the previous research about the oil jet and we will consider the movement of the ball check valve to get more accuracy result.

• 한국자기학회지
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• 제17권2호
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• pp.103-107
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• 2007

본 연구에서는 고체 안에 둘러쌓인 감마선 원천핵 $^{133}Cs$를 금판(gold plate)으로 된 실린더 안에 놓았을 때 첫 여기상태인 81 keV 에너지 준위폭이 더 좁아짐을 볼 수 있었다. 이러한 결과는 에너지 준위의 수명이 연장된 것을 의미한다. 두께 0.5 mm, 길이 5 cm, 반경 1 mm의 실린더를 사용했을 때 4.2 K에서 에너지 준위폭은 6.1 %정도 좁아지는 결과를 얻었다.

• 한국자동차공학회논문집
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• 제18권2호
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• pp.97-103
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• 2010

The four combustion stages in a diesel engine have close correlation among them. Especially, the ignition delay period has significant effect on the following combustion stage. And the period is also one of inevitable combustion processes in the diesel engine. For example, the diesel knocking is a well-known phenomenon due to the long ignition delay period. The interval of the ignition delay period is affected by the mixture formation process in the cylinder. However, in the case of the D.I. diesel engine, the available duration to make the mixture formation of air-fuel is very short. In addition, the means of the mixture formation mainly depends on the injection characteristics and properties of the fuel. It is difficult to make complete mixture. Therefore, an early stage of combustion is violent, which leads to the weakness of noise and vibration. In this study, using the visible engine, we measured the ignition delay period by photo sensor which detect occurrence of flame and presented the factors of the injection characteristics such as kinds of injection system, the injection pressure and the injection timing. The relation between the ignition delay period and cylinder pressure diagram which was concurrently obtained was also estimated.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 춘계학술대회 논문집
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• pp.549-554
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• 2013

For the past years, higher power rating 2 stroke super long stroke diesel engines having more than 8 cylinders and larger cylinder bore are installed mainly on very large containerships to save on fuel consumption. However, these engines are prone to X-mode vibration due to $2^{nd}$ node torsional vibration or the X-type moment, particularly because of the increase in total length and height. Recently, cases of excessive X-mode vibration often occurred on engine's major components. This vibration is manifested also as secondary vibration causing failure in engine-mount large structures. This study investigated the excitations caused by the $2^{nd}$ node propulsion shafting torsional vibration that influence X-mode vibration of the main engine and practical countermeasures are proposed. An 8RT-82RT-flex 8 cylinder engine and 11S90S-ME 11 cylinder engine for a container ship was used as research model.

• 유공압시스템학회논문집
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• 제7권4호
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• pp.9-14
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• 2010

Most power steering systems work by using a hydraulic system to turn the vehicle's wheels. The pressure is usually provided by a hydraulic pump driven by the vehicle's engine. A double-acting hydraulic cylinder applies a force to the steering gear, which in turn applies a torque to the steering axis of the road wheels. The flow to the cylinder is controlled by valves operated by the steering wheel ; the more torque the driver applies to the steering wheel and the shaft it is attached to, the more fluid the valves allow through to the cylinder, and so the more force is applied to steer the wheels in the appropriate direction. Since the pumps employed are of the positive displacement type, the flow rate they deliver is directly proportional to the speed of the engine. And for a long time, the type of hydraulic pump pulley was boss welding type. But recently, monolith type driving pulley is widely used. Therefore in this paper we studied the safety of monolith type driving pulley to the extracting force and endurance by FEM analysis and experiments.

• 설비공학논문집
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• 제8권3호
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• pp.338-350
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• 1996

A numerical analysis is carried out to study the two-dimensional steady state natural convection from vertical wires immersed in cold pure water. The surface of the wire is $0^{\circ}C$ unifrom temperature. Results of the analysis are presented for free stream temperature from $0^{\circ}C$ to $25^{\circ}C$ and the aspect ratio N from $5.26{\times}10^{-3}$ to $1.0{\times}10^{-3}$. The effects of the density extremum and aspect ratio on the flow pattern and the heat transfer characteristics are discussed As the aspect ratio N becomes larger, in the range of $1.0^{\circ}C{\leq}T_{\infty}{\leq}4.4^{\circ}C$ and $6{^{\circ}C}{\leq}T_{\infty}{\leq}17^{\circ}C$, the effect of Pr number on the heat transfer is shown to be more significant than the aspect ratio. Investigating into the effect of the density extremum on the heat transfer from wires, the new heat transfer correlations are suggested with the relation of average Nu mumber vs. modified Ra number. Here, the coefficient values C of correlations are presented as the function of density extremum parameter $R^*$. The effects of the density extremum parameter are also discussed.

• 드라이브 ㆍ 컨트롤
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• 제20권4호
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• pp.35-44
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• 2023

This study aimed to analyze the performance of hydraulic systems for dental chair when long working hours makes the temperature of hydraulic fluid rise. The study was carried out in the following manner. First, 'cylinder's clearance' was reflected in the three kinds of hydraulic circuits, which were developed through the preceding study, in order to analyze oil leak. Second, 12 cases of simulations comprised of the up and down of cylinders were carried out. Third, it was determined whether the cylinder velocity of dental chair surpasses 1cm/s required in the development even in the hydraulic fluid temperature of 60℃. In conclusion, this study used SimulationX to verify the performance stability at high temperatures using three types of hydraulic circuits designed to develop a Korean unit chair.