• 한국자동차공학회논문집
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• 제9권5호
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• pp.82-88
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• 2001

The EGR is needed fur one of various strategies to reduce NOx emission. But to get the proper EGR rate, the intake and exhaust system become complicated. That is a reason why we consider using the internal EGR system. The internal EGR is a system which reduces NOx by controling the residual gas fraction in cylinder by changing valve timing and valve lift of intake and exhaust. In this paper, characteristics of volumetric efficiency and residual gas fraction in cylinder were investigated for various engine speeds by changing valve timing and valve lift of intake and exhaust in the 4 stroke-cycle diesel engine. Volumetric efficiency and residual gas fraction were calculated by the method of characteristics. As the results, residual gas fraction and volumetric efficiency in cylinder by variable valve timing were visualized.

• Journal of Advanced Marine Engineering and Technology
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• 제23권3호
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• pp.398-404
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• 1999

The EGR is needed for one of various strategies to reduce NOx emission. But to get the proper EGR rate the intake and exhaust system become complicated. That is a reason why we consider using the built0in EGR system. The built-in EGR is a system which reduces Nox by controling the residual gas fraction in cylinder by changing valve timing and valve lift of intake and exhaust. In this paper characteristics of volumetric efficiency and residual gas fraction in cylinder were investigated for various engine speeds by changing valve timing and valve lift of intake and exhaust. In this paper characteristics of volumetric efficiency and residual gas fraction in cylinder were investigated for various engine speeds by changing valve timing and valve lift of intake and exhaust in the 4 stroke-cycle diesel engine. Volumetric efficiency and residual gas fraction were calculated by the method of characteristics. As the results the possibility of suing the built-in EGR system was confirmed.

• 한국자동차공학회논문집
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• 제16권4호
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• pp.151-158
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• 2008

Gasoline Homogeneous Charge Compression Ignition (HCCI) combustion is a new combustion concept. Unlike the conventional internal combustion engine, the premixed fuel mixture with high residual gas rate is auto-ignited and burned without flame propagation. There are several operating factors which affect HCCI combustion such as start of combustion (SOC), residual gas fraction, engine rpm, etc. Among these factors SOC is a critical factor in the combustion because it affects exhaust gas emissions, engine power, fuel economy and combustion characteristics. Therefore SOC of gasoline HCCI should be controlled precisely, and SOC detection should be preceded SOC control. This paper presents a control oriented SOC detection method using 50 percent normalized difference pressure. Normalized difference pressure is defined as the normalized value of difference pressure and difference pressure is difference between the in-cylinder firing pressure and the motoring pressure. These methods were verified through the HCCI combustion experiments. The SOC detection method using difference pressure provides a fast and precise SOC detection.

• 오토저널
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• 제7권1호
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• pp.24-34
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• 1985

The study of unsteady gas exchange processes in the inlet and exhaust systems of the single-cylinder 4-stroke cycle spark ignition engine is presented in this paper. The generalized method of characteristics including friction, heat transfer, change of flow area and entropy gradients was used for solving the equations defining the gas exchange process. The path line calculation was also conducted to allow for calculation of the gas composition and entropy change along the path lines, and of the variable specific heat due to the change of temperature and composition. As the result of the simulation, the properties at each point in the inlet and exhaust pipe, pressure and temperature in the cylinder, and charging efficiency were obtained. Pumping loss and residual gas fraction were also computed. The effect of engine speed, exhaust and inlet pipe length on the pumping loss and charging efficiency were studied showing that the results were in agreement with what has been known from experiments.

• Journal of Advanced Marine Engineering and Technology
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• 제38권7호
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• pp.806-813
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• 2014

가솔린엔진에서 흡기계를 통하여 배기가스의 일부를 재연소시키는 EGR시스템은 NOx를 저감하기 위하여 양호한 배기배출특성을 나타내지만, 엔진으로 유입되는 배기가스량이 적절하지 않을 경우 불안정한 연소를 일으켜 엔진의 출력이 저하된다. 본 연구에서는 흡기관압력을 바탕으로 다양한 엔진운전조건에 따른 EGR율을 예측하는 방법을 검토하고, 이러한 예측자료를 실험적 방법을 통하여 확인하였다. 그리고 이러한 예측자료를 바탕으로 피드백 EGR제어 알고리즘을 구성한 후, 엔진운전조건에 대한 잔류 가스량을 계산한 데이터와 EGR 피드백 제어실험을 통해 얻어진 데이터를 비교한 결과를 통하여 정성적으로 유사한 결과치를 얻었다. 따라서 적용된 피드백 EGR제어 알고리즘 및 시스템은 실제 전자제어식 EGR기술에 응용될 실현 가능성을 보여주었다.