• 한국자동차공학회논문집
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• 제22권3호
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• pp.210-219
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• 2014

The MPI dual injection engine can enhance the fuel efficiency and engine power. By using one injector per one intake port, MPI dual injection engine has an excellent fuel atomization and targeting injection. As the basic research for the MPI Dual injection engine design, this research was investigated in order to understand the characteristic of the in-cylinder flow and fuel behavior according to engine temperature condition and the fuel type in the MPI dual injection engines. The 3D unsteady CFD simulation for the MPI Dual injection engine was performed using STAR-CD. The engine operating condition was 2,000 rpm/WOT. The parameters for this study were fuel types, fuel temperatures and wall temperatures. As a result, the intake air amount, evaporated fuel in the cylinder and the fuel film on the wall were presented according to parameters that depend on the fuel properties and engine wall temperature. Also, the results were influenced by in-cylinder flow such as the intake flow, back flow and so on.

• 한국분무공학회지
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• 제4권2호
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• pp.19-32
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• 1999

The present study investigated the forms and behaviors of fuel during intake and compression process, and the initial flame stability in a lean burn engine modified as a single cylinder engine equipped with quartz windows for visualization. PLIF(Planar Laser Induced Fluorescence) method with KrF Excimer laser was used for measuring the fuel distributions. The principal design concept of the lean burn nin in this study is the axial stratification in the fuel distribution via fuel injection during intake process and different shapes of intake ports; helical and straight. The experiments showed that fuel flowed in as a vapor state in the early part of intake process and lots of this mixture mated down along the intake valve side cylinder wall, but in the latter part, a lot of fuel flowed in as a liquid state and this fuel stayed in the upper part of cylinder, after that the dense fuel cloud moved upward in the early of part compression process. It became clear that the fuel flowed in via straight port had a important role in the axial fuel stratification.

• 에너지공학
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• 제13권2호
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• pp.118-127
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• 2004

본 연구는 배기량이 16.7ι인 V8형 터보차져 인터쿨러 직접분사식 디젤기관에서 흡기포트의 선회유동과 연료분사계 및 과급기가 기관성능 및 배출가스특성에 미치는 영향을 실험적으로 고찰하며 성능을 개선하는데 있다. 일반적으로 기관의 출력을 높이기 위하여 과급기 및 인터쿨러를 장착하여 과급공기를 냉각시켜 과급효율을 더욱 높인 TCI디젤기관이 보편화되고 있다 본 연구의 결과로서 흡기포트의 선회비가 2.25인 경우에서 압축비 17.5, re-entrant 8.5$^{\circ}$ 형 연소실, 노즐분공경 $\Phi$0.33*3+$\Phi$0.35*2, 노즐돌출량 3.18mm, 분사시기 BTDC 12$^{\circ}$CA, 과급기 T042(압축기 0.6A/R+46Trim, 터빈 1.0A/R+57Trim)경우가 기관성능 및 NO$_{x}$ 농도의 배출특성을 고려할 때 운전영역에서 가장 우수하여 흡기포트, 분사계 및 과급기에 대한 각 인자를 적정화할 수 있었다.

• 한국자동차공학회논문집
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• 제6권4호
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• pp.86-100
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• 1998

The impingement of the fuel spray on the wall within the combustion chamber in compact high-pressure injection engines and on the intake port wall in port-fuel-inje- ction type engines is unavoidable. It is important to understand the characteristics of impinging spray because it influences on the rate of fuel evaporation and droplet distrib- ution etc. In this study, the numerical study for the characteristics of spray/wall interaction is performed to test the applicability and reliability of spray/wall impingement models. The impingement models used are stick model, reflect model, jet model and Watkins and Park's model. The head of wall-jet eminating radilly outward from the spray impingement site contains a vortex. Small droplets are deflected away from the wall by the stagnation flow field and the gas wall-jet flow. While the larger droplets with correspondingly higher momentum are impinged on the wall surface and them are moved along the wall and are rolled up by wall-jet vortex. Using the Watkins and Park's model the predicted results show the most reasonable trend. The rate of increase of spread and the height of the developing wall-spray is predicted to decrease with increased ambient pressure(gas density).

• 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.

• 한국수소및신에너지학회논문집
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• 제33권3호
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• pp.255-260
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• 2022

Hydrogen gas fuel was applied to a small-sized two stroke engine for a mobile power source instead of gasoline fuel. Port fuel supply showed a limitation in terms of power due to the back fire at the engine intake manifold. So in this study, hydrogen direct injection system was applied to overcome this drawback by using a low pressure direct gas injector. The result from this strategy showed that hydrogen direct injection improved fuel efficiency as well as torque and power comparing to the port fuel supply system.

• 한국자동차공학회논문집
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• 제11권3호
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• pp.20-27
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• 2003

In this paper, the fuel transport characteristics during transient condition was studied by using a Fast Response Flame Ionization Detector(FRFID). The quantitative measurement method for the inducted fuel mass into cylinder is studied. The inducted fuel mass into the cylinder was estimated by using calculated air-fuel ratio by hydrocarbon concentration of cylinder and air flow model. In order to estimate the transportation of injected fuel from the intake port into cylinder, the wall wetting fuel model was used. The two coefficient $\alpha$,$\beta$) of the wall-wetting fuel model was determined from the measured fuel mass that was inducted into the cylinder at the first cycle after injection cut-off To reduce an air/fuel ratio fluctuation during rapid throttle opening, the appropriate fuel injection rate was obtain from the wall wetting model with empirical coefficients. Result of air/fuel ratio control, air/fuel excursion was reduced.

• 한국자동차공학회논문집
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• 제9권2호
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• pp.67-74
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• 2001

A synchronized secondaty air injection method has been developed to hydrocarbon emission by injecting secondary air intermittently into exhaust port. The method has been tested in a single cylinder spark-ignition engine operating at cold-steady / cold-start conditions. Effects of air injection timing, intake pressure and engine air-fuel ratio have been investigated at cold-steady condition. Also, hydrocarbon emission and exhaust gas temperature with catalytic conberter are compared with a continuous SAI method and base condition at cold-start condition. Resules show that hydrocarbon reduction rate and exhaust gas temperature are sensitive to the timing of synchronized SAI. At cold-steady condition, HC emission is minimum at engine air-fuel ratio of 10. At cold-start condition, the accumulated hydrocarbon emission during the first 120 s decreases about 56% and 22% with the synchronized and continuous SAI, respectively, compared to that of base condition.

• 한국자동차공학회논문집
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• 제13권4호
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• pp.182-189
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• 2005

In order to investigate the effect of premixed gasoline, diesel fuel, and n-heptane charges on the combustion and exhaust emission characteristics in a direct injection (DI) diesel engine, the experimental studies are performed. The premixed fuels are injected into the premixing chamber that installed upstream of the intake port in order to minimize the inhomogeneity effect of premixed charge. The injection nozzle for directly injected fuel is equipped in the center of the combustion chamber. The air temperature control system is equipped in the intake manifold to examine the effect of air temperature. The experimental results of this study show premixing fuel is effective method to reduce the NOx and soot emissions of diesel engine. NOx emissions are linearly decreased with increasing premixed ratio for the three kinds of premixed fuels. The heating of intake air $(80^{\circ}C)$ reduced the deterioration of BSFC in high premixed ratio, because it promotes evaporation of premixed diesel droplet in the premixing chamber.

• 한국자동차공학회논문집
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• 제8권6호
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• pp.31-39
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• 2000

In this paper, characteristics of a port injection type LPG fuel system were investigated to adopt the system to a spark ignition engine through rig test. Engine combustion characteristics for limited conditions and the precise control method of LPG fuel supply were also studied. As a basic experiment, the effects and the relationships of parameters such as orifice area, fuel delivery pressure, fuel temperature and flow coefficient were established. From this, one dimensional compressible flow equation can be applied to control gaseous fuel flow rate by setting pressure difference between vaporizer and manifold to a certain range, for example about 1.2 bar in a naturally aspirated engine. The combustion analysis results of LPG engine were also compared with those of gasoline engine according to spark timing and load change. At part load and stoichiometric condition, the MBT spark timing of LPG fueled engine is retarded by 2$^{\circ}$ - 4$^{\circ}$CA compared to that of gasoline engine. On the contrary, the spark timing of LPG fueled engine can be advanced by 5$^{\circ}$- 10$^{\circ}$ CA at WOT, which results from higher Octane Number and burned fraction of LPG fuel compared to gasoline.