• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.3108-3113
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• 2008

This paper investigated the behaviors of combustion characteristics at part load condition with various intake charge motions induced by the port masking schemes in the CVVT (Continuously Variable valve Timing) engine. Time resolved in-cylinder and exhaust emissions were measured by the fast response HC and NOx analyzers to examine their formation mechanisms and behavior characteristics. As a result, in-cylinder HC decreased with the advanced intake valve timings but HC at the exhaust port increased due to the worse combustion stabilities. However HC reduction could be achieved by the application of the port maskings with a enhancement of the engine stability. NOx also decreased with early intake timings by internal EGR but increased with the charge motion controls which enhance the combustion behavior.

• Journal of Advanced Marine Engineering and Technology
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• 제33권8호
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• pp.1100-1106
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• 2009

최근, 디젤기관의 고효율달성을 위한 방법으로 밀러방식의 고팽창사이클에 대한 연구가 관심이 높다. 본 연구에서는 고팽창 디젤사이클을 구성하여 열역학적으로 해석하고, 몇몇 인자에 의한 사이클 특성을 분석하였다. 이론해석 결과 흡기밸브 닫힘시기가 지각될수록 유효압축비의 감소로 상대적인 팽창비의 효과는 커져 팽창-압축비의 비는 기대할 수 있었으나, 압축압력 및 흡입공기의 역류로 인해 평균유효 압력과 출력의 감고를 수반하였다. 따라서 이에 대한 대책이 있어야 진정한 의미의 고팽창 디젤사이클이 실현되고 열효율향상 가능성이 있음이 확인되었다. 위와 같은 사이클을 실제기관으로부터 구현하기 위해 흡기밸브 닫힘시기를 늦게 하는 제어시스템을 구축하고, 시험을 위해서 S/B가 약 3인 저속 단기통 디젤기관에 가변밸브타이밍(VVT)시스템을 적용하여 성능을 평가하였다. 그 결과 시험기관의 밸브제어에는 큰 문제없는 것으로 평가되었다.

• 한국수소및신에너지학회논문집
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• 제20권6호
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• pp.464-470
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• 2009

In order to analysis the possibility of high expansion and performance without backfire in a hydrogenfueled engine using external mixture injection, combustion characteristics and performance enhancement were analyzed in terms of retarding valve timing and increasing the boosting pressure. As the results, it was found that thermal efficiency increased by retarding intake valve timing with the same level of supplied energy is over 6.6% by the effect of high expansion including effect of combustion enhancement due to supercharging. It was also shown that the achievement of high power (equal to that of a gasoline engine), low brake specific fuel consumption and low emission (NOx of less than 16 ppm) without backfire in a hydrogen-fueled engine is possible around a boosting pressure of 1.5 bar, intake valve opening time of TDC and $\Phi$=0.35 in fuel-air equivalence ratio.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 합동 추계학술대회 논문집 정보 및 제어부문
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• pp.46-49
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• 2001

EMV(electromagnetic valve) 시스템은 자동차에서 기계식 캠을 사용하지 않고 전자기력을 이용하여 흡 배기 밸브를 작동시키고 타이밍을 조절하기 위한 것이다. 본 논문에서는 EMV 시스템을 위한 전자기와 기계적 모델을 사용하여 그에 대한 동역학 모델을 유도하였다. EMV 시스템의 최대 동작주파수가 가솔린엔진의 최대 회전수 6000rpm에 대응한 valve의 주파수가 50Hz 되기 위한 제어기를 설계하였고, 실험을 통하여 문제점들을 파악하고자 한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 D
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• pp.2280-2282
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• 2001

EMV(electromagnetic valve) 시스템은 자동차에서 기계식 캠을 사용하지 않고 전자기력을 이용하여 흡·배기 밸브를 작동시키고 타이밍을 조절하기 위한 것이다. 본 논문에서는 EMV 시스템을 위한 전자기와 기계적 모델을 사용하여 그에 대한 동역학 모델을 유도하였다. EMV 시스템의 최대 동작주파수가 가솔린 엔진의 최대 회전수 6000rpm에 대응한 valve의 주파수가 50Hz 되기 위한 제어기를 설계하였고, 실험을 통하여 문제점들을 파악하고자 한다.

• 한국자동차공학회논문집
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• 제5권3호
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• pp.27-34
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• 1997

The effects of the intake and exhaust valve timing to improve the engine performance in a spark ignition 3-cylinder LPG engine with a closed loop fuel supply system were studied. The engine torque and power have been measured using the 75kW EC-dynamometer while adjusting the optimal fuel consumption ratio with a solen- oid driver. As the results from this experiment, when intake valve opening is $12^{\circ}$ BTDC, intake valve closing is $36^{\circ}$ ABDC, exhaust valve opening is $12^{\circ}$ ATDC, and exhaust valve closing is $36^{\circ}$ BBDC respectively, the best torque characteristics in low and high speeds for a gives engine were obtained. And also we could find that the torque characteristics in low speeds were affected by the timing of exhaust valve open. An increased valve overlap by the EVC delay was ineffectual to the torque characte- ristics improvement in high speeds.

• 한국자동차공학회논문집
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• 제13권4호
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• pp.90-96
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• 2005

The improvement of combustion stability is very important because it is closely related to the exhaust emission concentrations as well as the fuel consumption during the cold start of SI engine. In our previous studies, the spark and exhaust valve timings were retarded individually from the baseline case to increase the exhaust gas temperature far fast warmup of a close-coupled catalyst. In the study, it was found that combustion stability during cold start becomes worse when the valve timing is retarded from the baseline conditions. The spark and valve timings were simultaneously changed from the baseline conditions to find out the variation of combustion stability during cold start of an Sl engine. Through the study. retarded spark timing by $5^{\circ}$ CA helps improvement of $COV_{imep}$ by $2\%$ and $15^{\circ}C$ increase of exhaust temperature. Retarded exhaust valve timing makes the exhaust gas temperature increase by $30^{\circ}C$, but it also deteriorates the $COV_{imep}$ by $1\%$.

• 대한기계학회논문집
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• 제16권7호
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• pp.1408-1418
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• 1992

본 연구에서는 여러가지 흡기관 조건 및 밸브타이밍 변화에 대하여, 현재까지 연구에서 확인된 IVC에서 흡기포트압력 값의 체적효율에 대한 영향을 검토하고, 흡기 밸브가 열리는 동안 흡기 포트압력의 어느 부분 또는 지점이 엔진의 체적효율 변화를 설명해 줄 수가 있는지를 실험적으로 규명하고자 하였다.이 목적을 위해 각 흡입조 건에 대한 흡기포트압력 및 엔진 성능값을 측정.분석하여 서로의 연관성을 비교, 검토 하였다.

• 한국자동차공학회논문집
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• 제7권9호
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• pp.82-88
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• 1999

The object of this study is to find new evaluation index for in-cylinder flow chracteristics istead of current swirl, tumble coefficient using steady flow test rig on intake port system. To this end, port flow system. To this end, port flow rig test was conducted on DOHC head varying intake valve lift respectively. Finally combination angular coefficient and inclination angle were introduced as new evaluation index for in-cylinder angularflow characteristics instead of swirl and tumble coefficient.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3311-3316
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• 2007

To analyze the influence of valve overlap period on a backfire occurrence, the single cylinder research engine with MCVVT(Mechanical Continuous Variable Valve Timing) system is developed and backfire limit equivalence ratio defined as fuel-air ratio equivalence ratio at which backfire occurs is examined according to various valve overlap period. The MCVVT is the system to control valve overlap period by mechanical device. It is estimated that the lower valve overlap period has the higher backfire limit equivalence ratio though the same energy is supplied. When the valve overlap period is changed from 30$^{circ}$ CA to 0$^{circ}$ CA, backfire limit equivalence ratio is increased 74%, approximately. It means that valve overlap period is concern in backfire occurrence, and may be one of the methods for controlling back fire occurred in a $H_2$ engine.