• Journal of ILASS-Korea
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• v.15 no.1
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• pp.8-16
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• 2010

This paper present the diesel spray characteristics at different injection system parameters in a HSDI diesel engine. The spray characteristics was calculated by the coupled simulation of fuel injection system model and three-dimensional KIVA-3V code with TAB spray model. The relevant injection parameters are accumulator volume, control chamber initial volume, control orifice diameter, needle valve diameter and nozzle chamber initial volume, etc. Parametric investigation with respect to twelve relevant injection parameters showed that there was a significant advantage in varying control chamber initial volume, control chamber orifice diameter, and nozzle chamber orifice diameter with respect to effect the SMD and fuel injection speed. Consequently, in order to design the fuel injection system for spray characteristics, it seems reasonable to suppose to be optimized the fuel injection system.

• Journal of ILASS-Korea
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• v.25 no.1
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• pp.1-7
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• 2020

In the common rail fuel injection system, which is the core of diesel high efficiency and NO_X reduction, injection strategies such as high pressure injection of fuel, accurate injection rate control, and multistage injection are important to increase fuel atomization. In this study, the bypass type piezo injector for the electronic control based common rail injection system applied to diesel fuel vehicle was studied. In particular, the injection rate and internal fuel flow characteristics of the high-pressure injector according to the piezo stacking number and applied voltage were analyzed by theoretical numerical method. When the applied voltage changes, it is determined that additional fuel flow through the bypass compensates for the reduced valve driving force due to the change in the driving voltage.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.6
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• pp.23-29
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• 2004

This work was conducted to figure out the atomization characteristics of three types of bio-diesel fuels using a common-rail injection system. The process of spray development was visualized by using a spray visualization system composed of a Nd:YAG laser and an ICCD camera, The spray tip penetrations were analyzed based on the frozen images from the spray visualization system. On the other hand, the microscopic atomization characteristics such as the distributions of SMD and axial mean velocity were measured by using a phase Doppler particle analyzer system, It is revealed that the sprays of the bio-diesel fuels have larger SMD than that of diesel fuel mainly due to high viscosity of bio-diesel. Different characteristics of bio-diesel fuels were also measured in spray tip penetrations according to the fuels and mixing ration.

• Journal of Power System Engineering
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• v.6 no.1
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• pp.5-11
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• 2002

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.4
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• pp.26-31
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• 2006

An experimental investigation of an early injection strategy was conducted on a small single cylinder common-rail DI diesel engine to reduce the oxides of nitrogen($NO_x$) emission. The main objectives of this study were to investigate the emissions, performance and combustion characteristics in a diesel engine with early and two-stage injections. The two- stage injection was conducted to reduce the wall-wetting of early injected fuels on the cylinder wall or to promote the ignition of premixed charge. The engine test was performed at conditions of 1500rpm, injection timing ranging from TDC to BTDC $80^{\circ}$. The experimental results show that $NO_x$ emissions were decreased in both cases of early injection and two stage injection compared to the conventional diesel combustion by the near TDC injection. However, soot and products of incomplete products (i.e. HC and CO) are slightly increased. Also, the second injection near TDC promoted the ignition of premixed fuel, therefore, IMEP was increased.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.6
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• pp.137-143
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• 2007

An object of this study is to understand the application characteristics in accordance with changes of EGR rate, applying BD20 reformed by ultrasonic energy irradiation to common-rail diesel engine. BD containing about 10% oxygen has attracted attention due to soaring crude oil prices and environmental pollution. This oxygen decreases soot by promoting combustion, but it also increases NOx. To make up for this problem, an EGR system is applied so that NOx might be decreased. In that case, engine power is lowered and exhaust gas is raised. However, the reformed fuel by ultrasonic energy irradiation is changed physically and chemically, promotes combustion, and thus solves such a problem. As the results of the experimemt, we could identify the optimum EGR rate by investigating the engine performance and the characteristics of exhaust materials in accordance with the EGR rate after ultrasonic energy irradiation to BD20 and applying it to common-rail diesel engine. The optimum EGR rate that can satisfy both engine performance and characteristics of exhaust materials was in the range of 15%.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.4
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• pp.1-7
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• 2013

DME spray characteristics were investigated about varied ambient pressure and fuel injection pressure using the DME common rail fuel injection system when the nozzle holes diameter is varied. The common rail fuel injection system with DME cooling system was used since DME has properties of compressibility and vaporization in atmospheric temperature. The fuel injection quantity and spray characteristics were measured. The spray analysis parameters were spray shape, penetration length, and spray angle at six nozzle holes. Three types of injector were used, the nozzle holes diameter were 0.166 mm (Injector 1), 0.250 mm (Injector 2), and 0.250 mm with enlargement of orifice hole from 0.6 mm to 1.0 mm (Injector 3). The fuel injection pressure was varied by 5MPa from 35 to 70MPa when the ambient pressure was varied 0, 2.5, and 5MPa. When using Injector 3 in comparison to the others, the DME injection quantity was increased 1.69 ~ 2.02 times. Through this, it had the similar low heat value with diesel which was injected Injector 1. Among three types of injector, Injector 3 had the fastest development velocity of penetration length. In case of spray angle, Injector 2 had the largest spray angle. Through these results, only the way enlargement the nozzle holes diameter is not the solution of DME low heat value problem.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.1
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• pp.53-59
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• 2011

The using of diesel engine will be increased in the world for fuel economy. But diesel engine emits harmful emissions such as much NOx, smoke etc. In this study, experiments were performed to investigate the spray characteristics of diesel spray in a common-rail system according to fuel temperature, injection pressure, injection period and fuel viscosity etc. using a high speed video camera. Diesel oil has different spray patten due to injection pressure and injection period in a common-rail system. A Filter pressure was influenced by fuel temperature which was turned to fuel viscosity related to a fluid flowing. The effect of the bio-diesel fuel mixing ratio on the spray and atomization characteristics was also investigated at various experimental conditions. It shows that the droplet atomization characteristics of bio-diesel fuel showed deteriorated results as the mixing ratio of biodiesel increased because of the high viscosity.

• Journal of Energy Engineering
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• v.27 no.2
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• pp.49-54
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• 2018

The common rail diesel engine used in this study is a remanufactured waste engine. The fuel injection timing of the waste engine is set to be suitable for the operating conditions of the vehicle. However, the engine of a generator is operated at a constant speed and mainly at partial load. Therefore, it is necessary to change the fuel injection timing suitable for the power generation engine, and the cost and the time required for such change must be minimized as much as possible. As a result of the analysis, it was confirmed that the fuel efficiency improves according to the fuel injection timing suitable for the engine for the generator, thereby increasing the performance and fuel efficiency.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.3
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• pp.146-153
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• 2011

American NREL (National Renewable Energy Laboratory) reported that BDF20 could reduce PM, CO, SOx, and cancerogenic matters by 13.6%, 9.3%, 17.6%, and 13% respectively, compared to diesel fuel. BDF20 has been being tested on garbage trucks and official vehicles at Seoul City, which is positive on air environment, but negative on combustion by higher viscosity in winter season. This study investigated the combustion characteristics by applying pilot injection for improving the deterioration of combustibility caused by the higher viscosity of the BDF20 with the combustion flames taken by a high-speed camera and the cylinder pressure diagram. A 4-cycle single-cylinder diesel engine was remodeled to a visible 2-cycle engine taking the flame photographs, which has a common-rail injection system. The test was done laboratory temperature at $5{\sim}6^{\circ}C$. The results obtained are summarized as follows, (1) In the case of without pilot injection, the flame propagation speed was slowed and the maximum combustion pressure became lower. The phenomena became further aggravated as the fuel viscosity gets higher. (2) In the case of with pilot injection, early stage of combustion such as rapid ignition timing and flame propagation was activated since intermediate products formed by pilot injection act as a catalyst for combustion of main fuel.