• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 춘계학술대회
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• pp.361-365
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• 2005

Since the fuel cell uses the hydrogen for its fuel. it has no emission and higher efficiency than an internal combustion engine. Also fuel cell is much quieter than engine generator and generates heat much less than engine generator. So it has advantage of Army's 'si lent watch' capability and the ability to operate undetected by the enemy. The fuel cell hybrid system combines a fuel cell power system with an ESS. The ESS (e.g., batteries or ultracapacitors) reduces the fuel cell's peak power and transient response requirements. It allows the fuel cell to operate more efficiently and recovery of vehicle energy during deceleration. The battery has high energy density, so it has the advantage regarding driving distance. However, it has a disadvantage considering dynamic characteristic because of low power density. One other hand. the ultracapacitor has higher power density, so it can handle sudden change or discharge of required power. Yet. it has lower energy density. so it will be bigger and heavier than the battery when it has the same energy. This paper proposes the power management strategy for multi-power source fuel cell hybrid system. which is applied with the merits of both battery and ultra capacitor by using both of them simultaneous.

• 동력기계공학회지
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• 제17권6호
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• pp.130-135
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• 2013

It is a research about the change in reduction efficiency and performance resulting from installation of the EGR cooler, which is the core technology reducing NOx in response to standards been tightened of exhaust controls for off-road vehicle. It can reduce NOx by altering combustion temperature and oxygen concentration by recycling high-temperature exhaust gas. The target engine was large diesel engine for construction machine through by which we were able to verify a rate of change in output and capabilities for a heat-exchange within cooler itself depending on the existence of EGR cooler system. We have acquired a emission reduction technology for a construction machine by testing the reduction performance and rate of change in output.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2000년도 춘계학술대회 논문집(Proceeding of the KOSME 2000 Spring Annual Meeting)
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• pp.45-51
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• 2000

Investigators who study on combustion in the cylinders of reciprocating piston type internal combustion engines have been encountered embarrassments due to the difficulties of adjusting specific parameter without interfacing other parameters such as cylinder wall temperature composition of gas in the cylinder existence of cylinder lubricant etc. Rapid compression-expansion machine the position and speed of piston of which are able to be controlled by means of a system controlled electrically and speed of piston of which are able to be controlled by means of a system controlled electrically and actuated hydraulically could be utilized as one of the most preferable countermeasures against those difficulties. Several units of rapid compression-expansion machines were developed but the speed up of frequency of piston movement still is the problem to be improved to cope with actual speed of internal combustion engines. Authors designed and manufactured a new rapid compression-expansion machine electrically controlled hydraulically actuated and computer programed and then examined the performance of one. Results of a set of experiments revealed acquirements of certain improvement of frequency of piston movement preserving the stability of system response and reproducing accurate compression ratio of cylinder those are the key function for the in-cylinder combustion experiments of internal combustion engines.

• International Journal of Aeronautical and Space Sciences
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• 제3권2호
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• pp.59-66
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• 2002

A vertical test stand based on launcher propulsion system was constructed and several tests for the determination of cyclogram were carried out. To make an accurate estimation, static and dynamic pressures were measured and analyzed. Especially, static pressure measurements using fast response sensors without extension tubes were used to determine operation sequence more evidently. The standard operation times of final valves were determined in cold flow tests with an engine head, and fire formation time in combustion chamber was checked in an ignition test with an ignitor only. On the basis of these tests, ignition sequence was established and combustion test cyclogram was finally determined. According to combustion test, test results were well matched with the determined cyclogram within 0.05 sec.

• Journal of Biosystems Engineering
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• 제31권1호
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• pp.16-23
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• 2006

Depth and working load control is one of the most important technique in control system for tractor rotary implement automation. Keeping the depth consistent is critical to bring along crops and to improve the efficiency and quality of the following operations. Keeping the load of engine consistent is an essential factor for the efficiency of operation and engine protection of tractor. In this study we investigated the possibility of application of depth and working load control system for tractor using a proportional valve through field tests. Depth control was implemented by the ascent and descent of 3 point linkage for the change of setting depth. There were 4 mm and 5.2 mm control deviations for setting depths of 50mm and 100mm, respectively. Load control was operated appropriately by the ascent and of descent of 3 point link for the change of setting working load. The standard deviations between setting load and engine load were 171 rpm at 1.3 km/h and 164 rpm at 2.3 km/h tractor travel velocity. The results of experiment showed that the characteristics of response was sufficient to be used as the implement depth and working load control system for tractor using proportional valve.

• 한국자동차공학회논문집
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• 제18권6호
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• pp.138-144
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• 2010

If the vibration is occurred in a large-sized bus roof, it makes people annoying and complaining the quality of a large-sized bus. So in design stage, it must be considered. To assess vibration at the roof which is equipped with air conditioner in design stage, finite element model is constructed. Computer simulation analysis and experimental method are performed. The dynamic characteristics of the large-sized bus are found by using eigenvalue method. It is related with dynamic behavior. The running conditions of a large-sized bus are velocity and road condition which followed experimental conditions. And the frequency response of a large-sized bus is well correlated with analysis result. Modal participation method is used for finding major modes at each peak. Using this method, we found that front and rear suspension system, engine mounting system and roof structure are the major reasons of the roof vibration. To reduce vibration level of roof in a large-sized bus, spring stiffness of front and rear suspension system, spring stiffness of engine mounting system and roof structure are properly combined. From this study, the vibration characteristics of the roof structure of a large-sized bus can be to a satisfactory level.

• 동력기계공학회지
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• 제17권2호
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• pp.29-37
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• 2013

Compared to gasoline engines, diesel engines with a relatively simple ignition system are more advantageous in the application of biodeisel fuel to engine. Then in this study the comparative analysis on the spray characteristics and combustion emissions characteristic between the biodiesel(soybean oil) and diesel, the fuel for commercial diesel engine, was performed with common rail injection system. Injection pressure and ratio of biodiesel blended fuel were selected as main experimental variables. Consequently, it can be found that there is no significant difference in the macro characteristics of the spray behavior(spray penetration and spray angle) in response to change in the blend ratio of soybean oil and diesel at a fixed injection pressure, in particular, soot creation in combustion emissions in the region of low pressure was greatly affected by the blend ratio of soybean oil, however, the creation in the region of high pressure was almost unaffected by the blend ratio because of promoted atomization.

• 한국자동차공학회논문집
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• 제1권3호
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• pp.74-82
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• 1993

Optimal designs of a 3-point and a 4-point engine mount system are presented for reducing the idle shake of a Front Wheel Drive(FWD) vehicle. Design variables used in this study are the locations, the angles and the stiffness of an engine mount system. The goal of the optimization is minimizing the transmitted force without violating the constraints such as static weight sag, resonant frequency and side limits of design variables. The Augmented Lagrange Multiplier(ALM) Method is used for solving the nonlinear constrained optimization. The generalized Jacobi and the impedence method are employed for a free vibration analysis and a forced response analysis. The trend of analysis results well meet that of the experimental results. The optimization results reveal that the 4-point system transmits less torque than the 3-point system. It is also found from the design sensitivity analysis that the vibration characteristics of the 4-point system is less sensitive than those of the 3-point system.

• 방송공학회논문지
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• 제10권2호
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• pp.202-209
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• 2005

본 논문에서는 동영상 저장 시스템에서 검색시간을 단축시킬 수 있는 XML .메타데이터 엔진을 설계한다. 이를 위하여 본 논문에서 제안하는 방법은 XML 메타데이터를 프래그먼트 단위로 저장하면서, 메타데이터에의 접속시간을 최소화시키기 위하여 메타데이터의 내용과 구조적 특성을 고려한 계층적 인덱스 스키마을 구성한다. 계층적 인덱스 스키마는 메타데이터의 내용적 특성을 기반으로 검색에 자주 사용되는 상위 레벨의 메타데이터를 구별하고 그 메타데이터를 기반으로 일반 검색을 위한 노드 인덱스와 구조적 특성을 갖는 그룹 테이블을 기반으로 고급 검색을 위한 그룹 인덱스를 구성한다. 이 접근 방법은 기존 방법에 비해 전체 인덱스 수를 줄이고, 그룹 테이블을 작성함으로써 반환 시간을 향상시킨다. 시뮬레이션 결과 제안하는 메타데이터 엔진이 기존 메타데이터 엔진보다 향상된 검색시간을 보여준다.

• Journal of Magnetics
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• 제18권4호
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• pp.487-493
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• 2013

The automotive industry is showing widespread interest in belt-driven electric motor-assisted (e-Assist) systems. A belt-driven assist system (BAS) starts and assists the combustion engine in place of the conventional generator. In this study, a water-cooled wound rotor synchronous motor (WRSM) for the e-Assist system was designed and analyzed. The performance of the WRSM was compared with that of an interior permanent magnet synchronous motor (IPMSM). The WRSM efficiency can be improved for the BAS by adjusting the field flux at high speeds. The field current map to obtain the maximum efficiency based on the speed and torque was developed. To control the field flux via field current control in the WRSM, a general H-bridge circuit was added to the WRSM inverter to get the rapid current response in the high-speed region; the characteristics were compared with the chopper circuit. A WRSM developed for the belt-driven e-Assist system and a prototype 115 V power electronic converter to drive the WRSM were tested with a 900 cc combustion engine. The test results showed that the WRSM-type e-Assist system had good characteristics and could successfully start and assist the 900 cc combustion engine.