• 한국분무공학회지
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• 제26권2호
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• pp.57-66
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• 2021

The reactivity controlled compression ignition (RCCI) is the technology that provides two different types of fuel to the combustion chamber with the advantage of significantly reducing particulate matter and nitrogen oxides emissions. However, due to the characteristics of lean combustion, combustion efficiency is worsened. The conventional type of pistons for conventional diesel combustion (CDC) has mostly been used in the researches on RCCI. Because the pistons for CDC are optimized to enhance flow and target spray, the pistons are unsuitable for RCCI. In this study, a piston that is suitable for RCCI is designed to improve combustion efficiency. The new piston was designed by considering the factors such as squish geometry, bowl depth, and surface area. The experiment was carried out by fixing the energy supply to 0.9kJ/cycle and 1.5kJ/cycle respectively. The two pistons were quantitatively compared in terms of thermal efficiency and combustion efficiency.

• 한국자동차공학회논문집
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• 제5권5호
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• pp.140-156
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• 1997

The combustion characteristics of DI Diesel engine using turbocharging and EGR are numerically studied. Computations are carried out for the wide range of trubochyarged pressures, EGR ratios, and Ar/He dilution. Numerical results indicate that the Ar/He dilution in the intake gas significantly influence the engine performance, the spray combustion process, and the pollutant formation.

• 한국연소학회:학술대회논문집
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• 한국연소학회 1999년도 제19회 KOSCO SYMPOSIUM 논문집
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• pp.21-26
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• 1999

Liquefied petroleum gas(LPG) has been used as motor fuel due to its low emissions and low cost. The fuel feeding system has been improved with stringent requirement for exhaust emissions. LPG carburation system was firstly introduced, then the system changed into a gas injection system controlled precisely, but those gas feeding system has a limitation on improving power output. In order to improve an engine performance, a multi-point port injection system was introduced recently, and a liquid direct injection system into a cylinder was suggested as a next generation system to maximize a fuel economy as well as a power. This study addresses the analysis of the LPG spray from diesel injectors. The spray images are visualized and compared with diesel sprays in a wide injection pressure range. The photographs show much wider dispersion of LPG sprays.

• 에너지공학
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• 제16권3호
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• pp.120-127
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• 2007

본 연구의 목적은 디젤연소장의 분위기조건에 따라 다성분 혼합연료의 질량분률이 분무착화 및 연소특성에 미치는 영향을 실험적으로 고찰하는데 있다. 착화 및 연소특성은 화학발광계측법 및 직접촬영법을 이용하여 분석되었다. 실험은 광계측기를 사용하여 RCEM에서 이루어졌으며, 이소옥탄, 노말 도데칸, 노말 헥사데칸으로 혼합한 다성분연료는 커먼레일 인젝터의 전자제어에 의해 RCEM의 연소실 내로 분사된다. 실험조건은 분사압력 42, 72, 112 MPa과 분위기온도 700, 800, 900 K로 하였다. 그 결과로서 착화지연은 고세탄가성분에 의존하고, 분위기온도가 낮을 경우 저비점성분 혼합비율의 증가에 따라 휘도영역이 현저하게 낮아지며, 열발생률이 증가하면서 확산연소기간을 단축시킨다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.790-795
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• 2001

Since the characteristics of combustion and pollutant in Diesel engines were mainly affected by the characteristics of in-cylinder gas flow and fuel spray, an understanding of those was essential to the design of the D.I. Diesel engines. The improvement of volumetric efficiency of air charging into combustion chamber is a primary requirement to obtain better mean effective pressure of an engine. Since the air resistances in intake and exhaust flow passages, valve lift and valve shape influence greatly to the volumetric efficiency, it is very important to investigate the flow characteristics of intake and exhaust port which develops air motion in the combustion chamber. This paper presents the results of an experimental investigation of steady flow through the various kinds of commercial cylinder head ports, and the development procedures of HHI's H21/32 prototype cylinder head ports.

• 한국분무공학회지
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• 제7권3호
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• pp.31-37
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• 2002

In previous study, diesel-methanol stratified injection system is manufactured and applied to a D.I. diesel engine in order to realize combustion improvement using methanol, which is oxygenated fuel with large latent heat. We know that NOx and soot is reduced by stratified injection of diesel fuel-methanol. Therefore, in the present study, combustion diagnosis using optical measurement is tried to make clear effect of methanol on simultaneous reduction of NOx and soot. Two-color method is used to measure flame temperature and KL value, which is approximately proportional to the soot consentration along the optical path. Laser induced scattering method was used to measure distribution of soot at two dimensional area. Also, it is compared exhaust characteristics of NOx and soot with results of optical measurement.

• 한국분무공학회지
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• 제13권1호
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• pp.28-33
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• 2008

The present study is mainly motivated to investigate the vaporization, auto-ignition and combustion processes in high-pressure diesel engines. In order to realistically simulate the dimethyl ether (DME) fueled diesel engine, the high pressure vaporization model is utilized and the interaction between turbulence and chemistry is treated by employing the Representative Interactive Flamelet (RIF) model. The detailed chemisty consisted of 336 elementary reaction steps and 78 species is used for DME/air reaction. Numerical results indicate that the RIF model with high pressure vaporization model successfully predicts the essential feature of the combustion processes and pollutants formations in the DME fueled diesel engines.

• 한국분무공학회지
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• 제3권3호
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• pp.23-32
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• 1998

The effect of reentrant type bowl geometry on combustion characteristics was investigated in a D.I. diesel engine. The main factor was the aspect ratio (Bowl Diameter / Bowl Depth) of bowl of combustion chamber, and the cylinder pressure, engine performance and emissions of the engine using the 4 kinds of the combustion chamber were meadured. Also, the combustion characteristics compared of the experimented and the calculated values which is used by the Hiroyasu's combustion model. The results are as follows; The effect of $d_c/H$ on ignition delay period are small. The smoke is corerelated to the heat release of the premixed and the diffusion combustion, i.g, the smoke decreased by decreasing the premixed combustion or increasing the diffusion combustion on cumulative heat release. The premixed combustion process has more effect than the diffusion combustion on smoke. The formal tendency of $d_c/H$ on engine performance has not appear.

• 대한기계학회논문집
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• 제19권9호
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• pp.2373-2385
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• 1995

The goals of this study are to apply exciplex method to the visualization of the fuel spray of a diesel engine and to investigate the liquid phase of fuel spray that injected at the various tips of a fuel injector. This study provides the informations for the improvement of the diesel injection system and the structures of diesel spry with the boiling of fuel droplets in combustion chamber by the exciplex method. Hexame was used as fuel for approximation to injection condition of the engine. And naphthalene and TMDP were added to the fuel for the visualization by exciplex method. Experimental injectors were 4hole, 8hole, and 1hole impinging injectors. In the injection condition of actual engine the exciplex was sufficient to catch the liquid phase signal. The spray penetration of impinging injector was small than that of actual 4 and 8hole injector but atomization was better. The upper bound of impinging injector was determined by the geometry of a cylinder head and the lower bound was determined by spray angle. On impinging injector the atomization was better at the edge of disk than at center of disk and also the mixing with environmental gas was better.

• 오토저널
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• 제13권2호
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• pp.50-66
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• 1991

There are many factors which influence on the performance of a diesel engine. The piston bowl shape and swirl ratio are important factors to enhance the fuel-air mixing and flame propagation. In this study, calculations of the flow field in the cylinder of the diesel engine were carried out using the CONCHAS-SPRAY code for different bowl shapes and swirl ratios. In the case of constant swirl ratio, vortices which affect fuel-air mixing, evaporation and flame propagation are generated more strongly and consistently in the bowl-piston type combustion chamber than in the flat piston type. With this strong squish effect, injected fuel droplets are widely diffused and rapidly evaporated in the bowl-piston type combustion chamber. Especially a strong squish is developed and large and strong vortices are generated in the edge cutted bowl piston chamber. As the swirl ratio increases, it is found that a large and strong squish and vortices are generated in the combustion chamber and also fuel droplets are diffused into the entire combustion chamber.