• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.9
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• pp.1317-1324
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• 1998

In general, DI gasoline engine has the advantages of higher power output, higher thermal efficiency, higher EGR tolerance and lower emissions due to the operation characteristics of increased volumetric efficiency, compression ratio and ultra-lean combustion scheme. In order to apply the concept of stratified charge into direct injection gasoline engine, some kinds of methodologies have been adapted in various papers. In this study, a reflector was adapted around the injector nozzle to apply the concept of stratified charge combustion which leads the air-fuel mixture to be rich near spark plug. Therefore, the mixture near the spark plug is locally rich to ignite while the lean mixture is wholly introduced into the combustion chamber. The characteristics of combustion is analyzed with the variations of fuel injection pressure and load in a stratified -charge direct injection single cylinder gasoline engine. The obtained results are summarized as follows ; 1. The MBT spark timing approached to TDC with the increase of load on account of the increase of evaporation energy, but has little relation with fuel injection pressure. 2. The stratification effects are apparent with the increase of injection pressure. It is considered by the development of secondary diffusive combustion and the increase of heat release of same region, but proceed rapidly than diesel engine. Especially, in the case of high pressure injection (l70bar) and high load (3.0kgf m), the diffusive combustion parts are developed excessively and results in the decrease of peak pressure than in the case of middle load. 3. The index of engine stability, COVimep value, is drastically decreased with the increase of load. 4. To get better performance of DI gasoline engine development, staged optimizaion must be needed such as injection pressure, reflector, intake swirl, injection timing, chamber shape, ignition system and so on. In this study, the I50bar injection pressure is appeared as the optimum.

• Journal of ILASS-Korea
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• v.19 no.4
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• pp.182-187
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• 2014

As the regulations for Particulate Matter (PM) and Particle Number (PN) emissions from Gasoline Direct Injection (GDI) Vehicle stringent recently, a lot of studies have been made on the emission characteristics of PM and PN. In this study, PM and PN emission characteristics were compared to GDI and Multi Port Injection (MPI) Vehicles using the Condensation Particle Counter (CPC) measurement equipment. And driving mode is divided into normal driving mode (CVS-75, NEDC, NIER 6, NIER 9) and a constant speed driving mode (10 km/h, 35 km/h, 80 km/h, 110 km/h) to evaluate the characteristics in the various operating conditions. In the results, most of the driving mode, PM and PN were emitted from GDI Vehicle more than MPI Vehicle. However, in the constant speed mode of 110 km/h, PM and PN from MPI Vehicle were also a lot of emission. It is determined to cause a difficulty in the fuel injection control of the MPI Vehicle.

• Journal of ILASS-Korea
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• v.17 no.3
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• pp.113-120
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• 2012

It is being more serious problems that the pollutant and the greenhouse gas emitted from the internal combustion engines due to the increasing demand of automobiles. To counteract this, as one of the ways has been studied, GDI type engine, which is directly injected into the combustion chamber and burns by a spark ignition that chose the merits of both gasoline engine and diesel engine, was appeared. The combustion phenomena in this GDI engine is known to contribute to combustion stability, fuel consumption reduction and reductions of harmful substances of exhaust gas emission, when the fuel spray of atomization being favorable and the mixture formation being promoted. Accordingly, this study analyzed the affection of ambient temperature and fuel injection pressure to the fuel by investigate the visualization of combustion, combustion pressure and the characteristic of emission, by applying GDI system on the constant combustion chamber. As a result, as the fuel injection pressure increases, the fuel distribution in the combustion chamber becomes uniform due to the increase of penetration and atomization. And when ambient temperatures in the combustion chamber become increase, the fuel evaporation rate being high but the penetration was reduced due to the reduction of volume flux, and confirmed that the optimized fuel injection strategy is highly needed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.8
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• pp.1138-1144
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• 2002

Recently GDI(Gasoline Direct Injection) engine is spot-lighted to achieve higher thermal efficiency under partial loads and better performance at full loads. To realize this system, it is essential to make both stratified combustion and homogeneous combustion. Spray pattern must be optimized according to injection timing because ambient pressure in combustion chamber is varied with crank angle. In this experimental study, two types of visualization system such as laser scattering method and schlieren method were developed to clarity the spray behavior during on intake stroke. As the ambient pressure increases, thepenetration length and spray angle show a tendancy to decrease due to rising resistance caused by the drag force of the ambient air. Distribution of injected fuel on intake stroke has a significant effect on homogeneous mixture in the cylinder. These results provide the information on macroscopic wall-wet growth in the cylinder and design factors for developing GDI injector.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2002.05a
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• pp.49-59
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• 2002

For the purpose of helping development of a GDI(Gasoline Direct Injection) engine, the spray behaviors and fuel distributions were investigated in a single cylinder GDI engine. The experimental engine is a swirl type GBI engine with a SCV(Swirl Control Valve). PLIF(Planar Laser Induced Fluorescence) system with KrF Excimer laser was used for the measurement of the fuel distributions. The effects of SCV opening angle and the Injector specifications, such as the spray cone angle and the offset an91e on the fuel distributions characteristics were investigated. As a result, it was found that the SCV opening angle had a great effect on the fuel distributions in the late stage of compression process by changing flow fields in the combustion chamber.

• Journal of ILASS-Korea
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• v.25 no.4
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• pp.154-161
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• 2020

A single spray plume is the basic unit of the entire spray plume and is an important factor in understanding the spray characteristics. However, since the multi-hole GDI injector has a narrow spray angle, the superposition of the spray plumes occurs severely. Therefore, the spray uniformity and the spray atomization characteristics of a single spray plume were analyzed in this study using a single-hole GDI injector. Five single-hole GDI injectors with different nozzle hole diameters were used in the experiment. The uniformity of the spray was evaluated through the analysis of the spray pattern images. In addition, the atomization characteristics were compared using the diameter distribution of the spray droplets obtained using PDPA. As a result, the larger diameter of the nozzle hole, the less uniformity of the spray, and the injection pressure did not have a significant effect on the spray uniformity. It is judged that the surface roughness of the injector has a greater effect on spray uniformity than the diameter of the nozzle hole. Also, the size of the spray droplets increased sharply when the diameter of the nozzle hole was 230 ㎛.

• International Journal of Automotive Technology
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• v.7 no.6
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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.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.3
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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.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.3
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• pp.106-112
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• 2012

Since air pollution problem by emissions from automotive vehicles has become social issues, lean-burn gasoline direct injection (GDI) engine is focused as an alternative to meet the requirement of reinforced emission regulation and improved fuel consumption. Spray-guided type DI combustion is promising technology, which characterized by the centrally mounted injector and closely positioned spark plug, since stable lean combustion can be realized even at ultra-lean mixture condition. In the present study, the effect of multi-ignition with developed charge coil on combustion and emission characteristics was investigated in optical accessible single cylinder engine. In order to fully understand the in-cylinder phenomena and the mechanisms of emission production, optical diagnostics, such as flame visualization was also carried out at frequently using operating condition. Multi-ignition is effective to improve fuel economy but increase NOx emission at flammability limit.

• Journal of ILASS-Korea
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• v.25 no.2
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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.