• 한국자동차공학회논문집
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• 제12권5호
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• pp.1-11
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• 2004

In order to recognize thermal efficiency and power improvement in case that diesel cycle is turned into diesel-atkinson cycle, the fuel-air diesel-atkinson cycle considered gas exchange process is analyzed non-dimensionally and thermodynamically. As a result, in case of diesel-atkinson cycle, as expansion ratio is increased, thermal efficiency and mean effective pressure is increased and it has maximum value at Rec=1. When diesel cycle is turned into diesel-atkinson cycle by late intake valve closing timing, thermal efficiency and power is decreased because of the decline of effective compression ratio and intake airflow, but it could be compensated by increase of compression ratio or super-charged. In case compression ratio is compensated, Rec appears 1 around 100$^{\circ}$ ABDC, and it is expected that thermal efficiency is enhanced by 14.3% compared with conventional diesel cycle. In case compression ratio and intake airflow are compensated simultaneously, super-charged pressure is demanded 2.06bar at Rec=1 and it is more efficient when only compression ratio is compensated in the view point of thermal efficiency.

• 한국항공우주학회지
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• 제35권5호
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• pp.426-437
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• 2007

초음속 흡입구는 설계점에서 안정된 작동을 보이지만 탈설계점에서는 흔히 버즈라고 불리는 공력 불안정성에 직면하게 되고, 결과적으로 현저한 엔진 성능의 저하를 초래하게 된다. 버즈의 일반적인 특성을 파악하기 위해 1단 꺽임각을 갖는 외부 압축식 축대칭 흡입구를 이용하여 실험적, 수치적 연구를 수행하였다. 본 연구를 통해, 흡입구 목에서 박리에 의한 흡입구 질식이 버즈의 주요 원인임을 밝힘으로써 버즈 현상의 메커니즘을 파악하였다. 여러 면적비율에 따라 간헐적 버즈와 연속적 버즈가 관찰되었고 그 천이과정이 파악되었다. 면적비율이 감소할수록 버즈 주파수가 증가하였으나, 각 면적비율에서 흡입구 내 모든 위치의 압력 진동 주파수는 동일한 특성을 갖는다.

• 한국분무공학회지
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• 제14권1호
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• pp.34-38
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• 2009

This paper presents the pulsation of carburetor inlet and outlet pressure of a small SI gasoline engine. The engine used in this paper is a 23cc, single cylinder, diaphragm carburetor, two-stroke, air-cooled for brush cutter. The rpm and pressure wave pulsation at the inlet and the outlet of carburetor were measured and analysed for the understand of the internal air flow into the barrel on the diaphragm carburetor. These data should be used for the development of the duel fuel injection system for gasoline and LPG. The results showed that the carburetor inlet pressure variations were very steady, but the pressure variations at carburetor outlet were very sensitive to the pressure variation into the crank case and were to similar independently to the engine speed on partial opened throttle conditions. According to increasing engine speed, the pressure waves started to come out and be developed after closing the intake port of the engine at carburetor outlet. Reverse flow occurred on the WOT (wide open throttle) condition.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2003년도 하계학술대회 논문집
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• pp.13-13
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• 2003

• 한국자동차공학회논문집
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• 제11권2호
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• pp.48-55
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• 2003

The effects of pressure charge on combustion stability and emissions have been analyzed using a GDI single cylinder engine. A late injection mode of stratified condition at the air-fuel ratio of 40:1 for 1200∼2400 rpm was tested while the boosted pressure ratio was increased up to 1.5:1. In-cylinder CFD analysis was also performed for better understanding of in-cylinder flow and fuel spray behavior. With a higher boosted pressure ratio the IMEP was increased greatly due to the increased engine load, and the ISFC was improved by more than 10% at all engine speeds. The regime of stable stratified combustion was extended to a higher engine speed, but the spark ignition angle had to be more advanced for stable combustion. The emissions of ISHC and ISNOx did not show a particular trend for the increased engine speed but a general trend of lower ISHC and higher ISNOx for a gasoline engine.

• Journal of Advanced Marine Engineering and Technology
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• 제35권8호
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• pp.1009-1015
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• 2011

본 연구에서는 고팽창사이클의 경우 가변밸브시스템을 구성하여 흡기밸브 닫힘시기를 늦추는 방식으로 실현하였고, 저압축에 따른 흡입공기의 감소는 과급압력으로 해결하였다. 이와 같이 디젤기관에 아트킨슨사이클을 실현하여 엔진의 열효율향상 가능성을 알아보았다. 그 결과 흡기밸브 닫힘시기 ABDC $40^{\circ}$ 부터 ABDC $80^{\circ}$ 까지 전 영역에 걸쳐 열효율 및 출력의 향상이 있었다. 다만, 흡기밸브 닫힘시기가 ABDC $70^{\circ}$이후로는 열효율 증가 폭이 둔화되는 경향을 보였다. 위와 같은 연구결과 저속 디젤-아트킨슨사이클화의 최적 연소조건은 흡기밸브 닫힘시기가 ABDC $70^{\circ}$전후로 보이며, 고부하영역이 저부하영역보다 더 효과적으로 나타났고, 중부하영역에서 기관운전은 안정적이었다. 이때 정미열효율은 통상의 디젤기관보다 평균 약 12.5% 높게 나타났다.

• Journal of Advanced Marine Engineering and Technology
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• 제33권6호
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• pp.835-842
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• 2009

The present thesis carried out a research on a compression pressure's reduction phenomenon and its countermeasure according to the thermal efficiency improvement method by a Miller method in 4-cycle low speed diesel engine. In case of retardation of intake valve closing time in a engine, the theoretical heat efficiency shows a remarkably reducing trend when a compression ratio is not compensated. Accordingly, the thermal efficiency showed an increasing trend in case of compensating the compression ratio. Especially, it could be understood that the theoretical heat efficiency at near ABDC $100^{\circ}$ of intake valve closing time in case of compensation of the compression ratio was improved by around 25.1%, and the mean effective pressure was also increased by around 18.6%. Also, as the retardation of intake valve closing time increases, air quantity becomes insufficient due to a backflow phenomenon of intake air and thus thermal efficiency was decreased in a high load operation domain. The solving method of this problem is possible by supercharge. Therefore, in order to improve thermal efficiency by retardation of ntake valve closing time, the thermal efficiency improvement according to low compression is possible when there are a compensation device of a compression ratio and a supercharge device. This is a problem-solving method of low compression and high expansion cycle.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제30회 춘계학술대회논문집
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• pp.263-267
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• 2008

본 연구에서는 헬리콥터 추진시스템의 장착 성능해석 모델링 시 고려하여야 할 흡입구 모델, 블리드 공기 손실, 보기류 시스템 구동에 사용되는 출력 추출 등을 포함한 장착 성능해석을 수행하였다. 흡입구의 압력 손실은 비행마하수와 유량에 따른 압력손실 값으로 나타낸 흡입구 성능 맵을 이용하였다. 추진시스템 장착 성능해석 모델링의 검증을 위해서는 실제 시험데이터와 비교해야 하지만 데이터 확보가 어려워 상용성능해석 프로그램인 GASTURB 해석결과와 비교 하였다. 해석결과 평균오차 0.5% 이내로 본 연구에서 수행한 추진시스템의 장착 성능해석 모델링의 타당성을 검증하였다.

• 한국추진공학회지
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• 제12권1호
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• pp.51-56
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• 2008

본 연구에서는 헬리콥터 추진시스템의 장착 성능해석 모델링 시 고려하여야 할 흡입구 모델, 블리드 공기 손실, 보기류 시스템 구동에 사용되는 출력 추출 등을 포함한 장착 성능해석을 수행하였다. 흡입구의 압력 손실은 비행마하수와 유량에 따른 압력손실 값으로 나타낸 흡입구 성능 맵을 이용하였다. 추진시스템 장착 성능해석 모델링의 검증을 위해서는 실제 시험데이터와 비교해야 하지만 데이터 확보가 어려워 상용성능해석 프로그램인 GASTURB 해석결과와 비교하였다. 해석결과 평균오차 0.5% 이내로 본 연구에서 수행한 추진시스템의 장착 성능해석 모델링의 타당성을 검증하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.283-290
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• 2007

Recently, plastic products in air-intake parts of automotive engines have become very popular due to advantages that include reduced weight, constricted cost, and lower intake air temperature. However, flow-induced noise in air-intake parts becomes a more serious problem for plastic intake-manifolds than for conventional aluminum-made manifolds. This is due to the fact that plastic manifolds transmit more noise owing to their lower material density. Internal aerodynamic noise from an Idle Speed control Actuator (ISA) is qualitatively analyzed by using a scaling law, which is expressed with some flow parameters such as pressure drop, maximum flow velocity, and turbulence kinetic energy. First, basic flow characteristics through ISA passage are identified with the flow predictions obtained by applying Computational Fluid Dynamics techniques. Then, the effects on ISA passage noise of each design factors including the duct turning shape and vane geometries are assessed. Based on these results, the preliminary low noise design for the ISA passage are proposed. The current method for the prediction of internal aerodynamic noise consists of the steady CFD and the scaling laws for the noise prediction. This combination is most cost-effective, compared with other methods, and therefore is believed to be suited for the preliminary design tool in the industrial field.