• Journal of Advanced Marine Engineering and Technology
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• 제37권4호
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• pp.378-383
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• 2013

가솔린엔진의 출력제어를 위해 나비형(butterfly-type) 스로틀밸브가 응용되고 있다. 그러나 기존의 나비형 스로틀밸브는 밸브 후방에서 발생하는 강한 와류현상으로 인해 매우 큰 흡입 유로의 저항을 유발하게 된다. 이러한 유로저항은 엔진의 체적효율(volumetric efficiency)을 떨어뜨려 궁극적으로 엔진의 출력과 효율에 부정적인 영향을 미치게 된다. 본 연구에서는 CFD수치해석 기법을 이용하여 기존 나비형 스로틀밸브의 문제점 개선을 위해 제안한 벤투리형(venturi-type) 가변스로틀밸브(VGTV)의 공기역학적 작동특성에 관해 알아보았으며, 본 장치의 유량과 저항계수($K_L$)의 변화특성 분석을 통해 가솔린엔진의 체적효율 개선효과를 평가하는데 연구의 목적을 두고 있다. 본 연구를 통해 기존의 나비형 스로틀밸브에 비해 새롭게 제안된 벤투리형 가변스로틀밸브의 유로저항이 평균 49.0%정도 개선된다는 사실을 알 수 있었으며, 이는 엔진의 체적효율과 출력에 매우 큰 영향을 줄 것으로 기대된다.

• Journal of Advanced Marine Engineering and Technology
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• 제24권4호
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• pp.526-534
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• 2000

In this study, the characteristics of exhaust emissions in medium speed diesel engine under various operating conditions were investigated through experiments to derive the optimum conditions for minimizing the exhaust emissions, especially, nitrogen oxides. The 355 KW$\times$1200 rpm medium speed diesel engine was intensively examined to investigate the trend of exhaust emissions in case that the parameters affecting combustion conditions such as fuel injection timing, intake air temperature and pressure, engine speed and load were changed. The exhaust emissions for 9 sets of medium speed diesel engine were analyzed in addition. From this study, NOx level could be reduced by 30~50% through the adjustment of retarded fuel injection timing, lowered intake air temperature and increased charging air pressure.

• 한국분무공학회지
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• 제6권1호
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• pp.25-34
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• 2001

Several efforts to meet the exhaust gas regulation have been undertaken by many researchers in recent years. Main researches are on development of design techniques of intake port and combustion chamber, atomisation of fuel and precise control of air-fuel ratio, post-treatment of exhaust gas and so on. Engine technology is changed from PFI to GDI to correspond with exhaust gas regulation. GDI technique makes it possible to preserve lean air-fuel ratio and control accurate air-fuel ratio. Nevertheless, It is not cleared that information of spray characteristics and atomization process are very dependent on fluctuation of pressure and change of temperature in intake stroke. In this study, a constant volume combustion chamber is manufactured to investigate various fluctuations of in-cylinder pressure for injection duration. It is taken photographs of injection process of conventional GDI injector using PMAS. Then, it was verified experimently that ambient conditions as temperature and pressure of combustion chamber have effects on process of spray growth and atomization of fuel.

• 한국분무공학회지
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• 제8권3호
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• pp.33-40
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• 2003

The low-emission and high-performance diesel combustion is an important issue in the combustion research community, In order to understand the detailed diesel flame involving the complex physical processes, it is quite desirable to diesel spray dynamics, auto-ignition and spray flame propagation. Dynamics of fuel spray is a crucial element for air-fuel mixture formation, flame stabilization and pollutant formation, In the present study, the diesel RCM (Rapid Compression Machine) and the Electric Control injection system have been designed and developed to investigate the effects of injection pressure, injection timing, and intake air temperature on spray dynamics and diesel combustion processes, In terms of the macroscopic spray combustion characteristics, it is observed that the fuel jet atomization and the droplet breakup processes become much faster by increasing the injection pressure and the spray angle, With increasing the cylinder pressure, there is a tendency that the of spray pattern in the downstream region tends to be spherical due to the increase of air density and the corresponding drag force, Effects of intake temperature and injection pressure on auto-ignition is experimently analysed and discussed in detail.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.447-452
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• 2000

The low-emission and high-performance diesel combustion is an important issue in the combustion research community. In order to understand the detailed diesel flame field involving the complex Physical Processes, It Is quite desirable to study diesel spray dynamics, auto-ignition and spray flame propagation. Dynamics of fuel spray is a crucial element for air-fuel mixture formation flame stabilization and pollutant formation. In the present study, the diesel RCM (Rapid Compression Machine) and the Electric Control injection system have been designed and developed to investigate the effects of injection Pressure, injection timing, and intake air temperature on spray dynamics and diesel combustion processes. In terms of the macroscopic spray combustion characteristics it is observed that the fuel jet atomization and the droplet breakup processes become much faster by increasing the injection pressure and the spray angle. With increasing the cylinder pressure there is a tendency that the shape of spray pattern in the downstream region tends to be spherical due to the increase of air density and the corresponding drag force. Effects of intake temperature and injection pressure on auto-ignition is experimently analysed and discussed in detail.

• 한국수소및신에너지학회논문집
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• 제34권1호
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• pp.77-82
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• 2023

The fuel cell in fuel cell electric vehicle utilizes oxygen in the atmosphere, which requires the use of an air cleaner system to minimize the intake of harmful pollutants. To estimate the performance of the air cleaner system, the pressure drop between the filter inlet and outlet is used under the rated air flow condition. In this study, the effect of sensor error in this air cleaner testing is experimentally carried out. It is found that the errors of the temperature sensor does not significantly affect the estimation of pressure drop. However, in the case of the pressure sensor, 5% sensor error results in the error of pressure drop estimation by 3%. Therefore, it is recommended that the measurement accuracy of the pressure sensor mounted in test system should be maintained at less than 5%.

• Journal of Advanced Marine Engineering and Technology
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• 제18권2호
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• pp.91-96
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• 1994

Intake gases other than air, which is composed of oxygen, nitrogen, carbon dioxide, and argon, are used to study their effects on the performance of the diesel engine experimentally. The engine is operated at constant speed and fixed fuel injection timing, and cylinder pressure and heat release rate are measured at various intake gas compositions. The results show that increase of oxygen concentration improves the performance of the engine generally. The adverse effect is observed when the oxygen concentration is increased over the critical oxygen concentration of this test, mainly because of the over-shortened ignition delay. Increase of carbon dioxide concentration degardes the performance of the engine, mainly due to the lower specific heat ratio of carbon dioxide. Adding argon gas to the intake gas improves the overall performance. Finally, it is found that two most influencing factors affecting the performance of the diesel engine in this study are ignition delay and speific heat ratio of the intake gas.

• 한국항공우주학회지
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• 제41권9호
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• pp.714-719
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• 2013

본 연구 대상 터보 프롭 항공기는 주어진 항공기 임무 수행을 위해 결빙 조건하에서도 운용이 가능하여야 한다. 동 연구에 적용된 터보 항공기의 공기 흡입구 계통은 정상 비행조건하에서 엔진 입구에 최대 전압력을 공급할 수 있도록 설계 및 검증이 되어야 할 뿐만 아니라 결빙조건하에서 생길 수 있는 얼음과 같은 입자가 엔진 흡입구 망으로 들어가서 엔진 화염꺼짐이나 엔진에 심각한 손상을 주지 않도록 하기 위한 관성분리기를 포함하도록 개발이 되어야 한다. 따라서 결빙 조건하에서 형상이 변하는 가변형상의 공기흡입구 조립체를 설계하고 설계 결과 확인을 위해 조립체에 대한 전산 유동 및 구조해석을 수행하였다. 이후 35% 축소형 모델을 제작하여 풍동시험을 수행하였다. 동 논문에서는 흡입구 조립체 개발과정에서 요구되는 공기역학적 설계, 잔산 유동/구조 해석 및 풍동 시험평가 결과를 기술하였다.

• 한국자동차공학회논문집
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• 제22권2호
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• pp.182-189
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• 2014

This paper proposes a decoupler design method to reduce interaction between exhaust gas recirculation (EGR) and variable geometry turbocharger (VGT) systems in passenger car diesel engines. The EGR valve and VGT vane are respectively used to control air-to-fuel ratio (AFR) of exhaust gas and intake pressure. A plant model for EGR and VGT systems is defined by a first order transfer function plus time-delay model, and the loop interaction between these systems is analyzed using a relative normalized gain array (RNGA) method. In order to deal with the loop interaction, a design method for simplified decoupler is applied to this study. Feedback control algorithms for AFR and intake pressure are composed of a compensator using PID control method and a prefilter. The proposed decoupler is evaluated through engine experiment, and the results successfully showed that the loop interaction between EGR and VGT systems can be reduced by using the proposed decoupler. Furthermore, it presents stable performance even off from the designed operating point.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2005년도 제24회 춘계학술대회논문집
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• pp.394-398
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• 2005

초음속 순항 추진기관인 램제트 추진기관은 $1.5\sim3$ 정도의 비행마하수를 가지는 비행체에 적용되어져 왔고, 마하수 4 이상의 고성능 램제트 추진기관에 대한 연구도 다수 이루어져 왔다. 현재는 극초음속 비행을 위한 램제트-스크램제트 엔진의 작동모드를 가지는 듀얼모드 스크램제트 엔진개발 연구가 활발히 이루어지고 있다. 본 연구에서는 고성능 램제트와 듀얼모드 스크램제트 엔진에 필요한 마하 4에서의 공기흡입구 유동에 대한 연구로서 배압, 받음각, 요각의 변화에 따른 초음속 흡입구에서의 유동 특성을 Schlieren 가시화, Oil 가시화, 압력 측정 등을 통해 파악하였다.