• 한국자동차공학회논문집
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• 제23권1호
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• pp.97-104
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• 2015

This study is a part of the high pressure injection system development on the Turbo GDI engine in order to reduce smoke emission in case of using the low volatile(high DI) fuel which is used as normal gasoline fuel in the US market. Firstly, theoretical approach was done regarding gasoline fuel property, performance, definition of particle matters and its creation as well as problems of the high DI fuel. In this experimental study, 2L Turbo GDI engine was selected and optimized system parameter was inspected by changing fuel, fuel injection mode (single/multiple), fuel pressure, distance between injector tip and combustion chamber, start of injection, intake valve timing in engine dyno at all engine speed range with full load. In case of normal gasoline fuel, opacity was contained within 2% in all conditions. On the other hands, in case of low volatile fuel (high DI fuel), it was confirmed that the opacity was rapidly increased above 5,000 rpm at 14.5 ~ 20 MPa of fuel pressure and there were almost no differences on the opacity(smoke) between 17 MPa and 20 MPa fuel pressure. According to the SOI retard, smoke decrease tendency was observed but intake valve close timing change has almost no impact on the smoke level in this area. Consequently, smoke decrease was observed and 16% at 6000rpm respectively with injector washer ring installed. By removing injector washer to make injector tip closer to the combustion chamber, smoke decrease was observed by 46% at 5,500 rpm, 42% at 6,000 rpm. It is assumed that the fuel injection interaction with cylinder head, piston head, intake and exhaust valve is reduced so that impingement is reduced in local area.

• International Journal of Automotive Technology
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• 제7권6호
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• pp.675-680
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• 2006

In the direct injected gasoline engine, atomized spray is desired to achieve efficient mixture formation needed to good engine performance because the injection process leaves little time for the evaporation of fuels. Therefore, substantial understanding of global spray structure and quantitative characteristics of spray are decisive technology to optimize combustion system of a GDI engine. The combustion and emission characteristics of gasoline-fueled stratified-charge compression ignition(SCCI) engine according to intake temperature and compression ratio was examined. The fuel was injected directly to the cylinder under the high temperature condition resulting from heating the intake port. With this injection strategy, the SCCI combustion region was expanded dramatically without any increase in NOx emissions, which were seen in the case of compression stroke injection. Injection timing during the intake temperature was found to be an important parameter that affects the SCCI region width. The mixture stratification and the fuel reformation can be utilized to reduce the required intake temperature for suitable SCCI combustion under each set of engine speed and compression ratio conditions.

• 한국자동차공학회논문집
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• 제23권3호
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• pp.299-306
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• 2015

Turbocharged gasoline direct injection engine is one of promising technologies in the automotive industry. However, reduction in turbo-lag under transient operation is one of important challenging points to improve drivability. Engine transient performance was investigated in a 4-cylinder 2.0 L turbo-gasoline direct injection (T-GDI) engine using Inconel and TiAl (Titanium Aluminide alloy) turbine wheel turbochargers. The TiAl turbocharger performed superior transient boost pressure and torque rises under various engine transient operation conditions. These were mainly due to lower turbine rotational inertia of TiAl turbocharger. The Maximum boost pressure and torque build up were founded in 1500 rpm and 2000 rpm, instant load change from 20% to 100% of pedal position.

• 한국자동차공학회논문집
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• 제20권4호
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• pp.39-45
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• 2012

Today gasoline engines for vehicular application are not only faced with stringent emission regulation but also with increasing requirements to better fuel economy, while guaranteeing power density. The spray-guided type gasoline direct injection (GDI) engine has an advantage of improved thermal efficiency and lower harmful emissions. Centrally mounted high pressure injector and adjacent spark plug allow stable lean combustion due to the flexible mixture stratification. In the present study, the performance and emissions characteristics of developed spray-guided type GDI combustion system were evaluated at various excess air ratio conditions. The specific fuel consumption and nitrogen oxides ($NO_x$) emissions were reduced due to the achievement of stable lean combustion under flammability limit. Multiple injection strategy was not helpful to improve fuel consumption while further reduction of $NO_x$ emissions was possible.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.472-477
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• 2003

This study was performed to investigate the behavior of vapor phase of fuel mixtures with different piston cavity diameters in a optically accessible engine. The images of vapor phases were measured in the motoring engine using exciplex fluorescence method. The conventional engine was modified as GDI engine with swirl flow. Fuel was injected into atmospheric nitrogen to prevent quenching phenomenon by oxygen. Injection pressure is 5.1MPa. Two dimensional spray fluorescence image of vapor phases was acquired to analyze spray behavior and fuel distribution inside of cylinder. Three injection timings were set at BTDC $180^{\circ}$, $60^{\circ}$and $60^{\circ}$. With a fuel injection timing of BTDC $60^{\circ}$, fuel-rich mixture was concentrated in near the cavity center. With a fuel injection timing of BTDC $60^{\circ}$, fuel-rich mixture level in the center region was highest in the S-type during the late compression stroke. With a fuel injection timing of BTDC $180^{\circ}$, fuel was not affected in a piston cavity and generally distributed as homogeneous mixture.

• 한국자동차공학회논문집
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• 제22권3호
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• pp.75-80
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• 2014

In previous study, make an attempt to estimate exhaust valve seat and seat-ring wear acceleration factor for engine durability test with measuring and consideration of wear mechanism. But found abnormal initial wear rate in exhaust valve seat-ring. And have to improve exhaust valve seat-ring wear rate for reliability reason, because next GDI/Turbo engine is based on this engine and GDI/Turbo engine have higher combustion pressure and higher thermal load. In this study, Trying to find the cause of abnormal wear factor, improve valve-train durability by change specification & design of parts and verify variant parts for improving durability of valve-train. And then I would like to propose a design guide line of valve-train system in a reliability point of view, besides make a complement of previous study.

• 한국분무공학회지
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• 제25권2호
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• pp.60-67
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• 2020

Despite its benefit in engine thermal efficiency, gasoline-direct-injection (GDI) engines generate substantial particulate matter (PM) emissions compared to conventional port-fuel-injection (PFI) engines. One of the reasons for this is that the spray collapse caused by the spray-to-spray interaction forms the locally rich fuel-air mixture and increases the fuel wall film. Previous studies have investigated the spray collapse phenomenon through the macroscopic observation of spray behavior using laser optical techniques, but it is somewhat difficult to understand the interaction between sprays that is initiated in the near-nozzle region within 10 mm from the nozzle exit. In this study, the spray structure, droplet size and velocity data were obtained using an X-ray imaging technique from the near-nozzle to the downstream of the spray to investigate the spray-to-spray interaction and discuss the effects of spray collapse on local droplet size and velocity distribution. It was found that as the ambient density increases, the spray collapse was promoted due to the intensified spray-to-spray interaction, thereby increasing the local droplet size and velocity from the near-nozzle region as a result of droplet collision/coalescence.

• 한국분무공학회지
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• 제22권1호
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• pp.8-12
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• 2017

Recently, manufacture and sales of passenger car with GDI (Gasoline Direct injection) were dramatically increased in Korea. In this study, investigation on the exhaust emission characteristics of GDI vehicles according to mileage were conducted by using chassis dynamometer and emission analyzer. Test cars selected 5 types with G4FD engine (1600 cc) and emissions of total 14 vehicles analyzed. Measurement and evaluation on emissions (CO, NOx, NMOG, $CO_2$) characteristics of GDI vehicles with mileages from 40,000 to 80,000 km in certification driving cycle (CVS-75) were carried out in this study. It is revealed that emission results of all test cars shows below emission standard, NMOG emission value of about 80,000 km doubled that of 40,000 km and emission increased by accumulated mileage. Also, increasing pattern of NOx emissions shows when the vehicle mileages was increased and $CO_2$ emission increasing trend obviously do not show according to mileages.

• 한국자동차공학회논문집
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• 제16권2호
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• pp.166-174
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• 2008

Numerical study on the impingement process and the fuel film formation of the hollow-cone fuel spray was conducted under vaporization condition, and the effect of the wall cavity angle on spray-wall impingement structure was investigated. A detailed understanding of this phenomena will help in designing injection systems and controlling the strategies to improve engine performance and exhaust emissions of the Gasoline Direct Injection (GDI) engine. The improved Abramzon model was used to model the spray vaporization process and the Gosman model was adopted for modeling of spray-wall impingement process. The calculated results of the spray-wall impingement process were compared with experimental results. The velocity field of the ambient gas, the Sauter Mean Diameter (SMD) and the generated fuel film on the wall, which are difficult to obtain by the experimental method, were also calculated and discussed. It was found that the radial distance after the wall impingement and the SMD decreased with increasing the cavity angle and the temperature.

• 대한기계학회논문집B
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• 제39권9호
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• pp.727-734
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• 2015

세계적으로 유가 상승에 따른 내연기관의 에너지 변환 효율을 높이고자 하는 연구가 활발히 진행되고 있다. 가솔린엔진에서 높은 열효율을 실현하기 위해서는 희박연소에 의한 비열비의 증가 및 단열화염온도의 저감에 의한 열효율 향상이 필수적이다. 직접분사식 가솔린 엔진은 연료를 직접 연소실에 공급하고 정밀한 연소제어를 통해 희박 연소가 가능하게 하지만 희박연소 한계의 확대와 안정된 희박연소제어가 요구된다. 희박연소 엔진에 대한 삼원촉매의 배출가스 저감특성은 높은 공기과잉률 및 낮은 배기가스 온도로 인해 매우 제한적이다. 이에 효과적인 삼원촉매의 개발을 위해 승용 차량용 엔진의 주요 연비시험 운전조건인 2000 rpm BMEP 2bar 조건에서 공기과잉률의 변화에 따른 배출가스 반응 및 생성 특성을 비교하였다. 희박연소 조건에서 $NO_2$가 생성되었으며, $NO_2$의 비율은 공기과잉률이 증가할수록 증가하고 $N_2O$는 감소하였다.