• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.2
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• pp.161-168
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• 2016

CNG engine has been used as a transportation because of higher thermal efficiency and lower CO2 and particulate matter. However its out put power is decreased due to cylinder-to-cylinder variation during the supply of air-fuel mixture to the each cylinder. It also causes noise and vibration. So in this study, 1D engine simulation model was validated by comparison with experiment data and 3D CFD simulation was conducted to steady-state flow analysis about each manifold geometry. Then, the effects of various intake manifold geometries on variation were evaluated by using 1D-3D coupling analysis at engine speed of 2100 rpm range in 12 L CNG engine. As a result, variation was improved about 4 % though 3D CFD analysis and there was a variation within 3 % using 1D-3D coupling analysis.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.3
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• pp.141-147
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• 2012

A direct injection diesel engine with large amount of exhaust gas recirculation was used to investigate low temperature diesel combustion. Pilot injection strategy was adopted in low temperature diesel combustion to reduce high carbon monoxide and hydrocarbon emissions. Combustion characteristics and exhaust emissions of low temperature diesel combustion under different pilot injection timings, pilot injection quantities and injection pressures were analyzed. Retarding pilot injection timing, increasing pilot injection quantity and higher injection pressure advanced main combustion timing and increased peak heat release rate of main combustion. As a result of these strategies, carbon monoxide and hydrocarbon emissions were reduced. Soot emission was slightly increased with retarded pilot injection timing while the effect of pilot injection on nitrogen oxides emission was negligible under low combustion temperature condition. Spatial distribution of fuel from the spray targeting visualization was also investigated to provide more insight into the reason for the reduction in carbon monoxide and hydrocarbon emissions.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.1
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• pp.53-60
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• 2012

As enforced by the regulation on the improving fuel efficiency and increased the demand on green technology, many interests are focused on electric vehicles and hybrid vehicles. Thus the technology development in electrification of vehicle operation system, including steering and braking field, is actively progressive. Especially electric power steering substitutes for hydraulic power steering rapidly in the market, which is more complex and bigger in packaging volume compared with electric power steering system. The core component in electric power steering system is a motor, which is required to be silent and powerful to guarantee required system performance. Brushless synchronous motors are widely used and many variations of the motors are introduced in the market, while the performance of each type is not well defined or studied for electric power steering system. In this paper, recent developments in brushless synchronous motor are reviewed and compared applying finite element analysis in electromagnetic field. As results, each characteristic of different types of brushless synchronous motors is compared and summarized for optimized selection in electric power steering system.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.6
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• pp.140-145
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• 2012

Recently, various after-treatment systems, such as LP-EGR(Low Pressure-Exhaust Gas Recirculation), SCR(Selective Catalytic Reduction) and LNT(Lean NOx Trap), were developed to obey the stringent emission regulations of diesel engine. There are many researches on LP-EGR system because it has advantages of NOx reduction and low fuel consumption. But, condensation water is generated in internal of intercooler tube and it contains various types of anion that cause the corrosion of aluminium tube. In this study, it is examined that the condensation water effects on corrosion of aluminium tube. And method for improvement of corrosion characteristics is investigated using the dipping and electrochemical test.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.5
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• pp.9-19
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• 2010

Every car manufacturer desires to reduce the new car development time spent in improving the safety, NVH, lightweight, reliability and environment friendly features of the car. Other considerations such as planning, exterior and interior styling, packaging, color, and material selection increase the complexity of the car design process. This paper proposes a personal DDP (Digital Design Process) to utilize the engineering analysis and design/styling software for car design. DDP can be efficiently used by a team of car research center or a studio with small number of engineers, helping ordinary engineers becoming ambidextrous in design as well as engineering applications. The concept model starts from idea sketch, rendering, and 3D surface model with CAS (Computer Aided Styling) to the final safety estimation by using proposed DDP based on engineering technology (CAD, CAE). The concept model proposed a hydrogen fuel cell sports coupe which could be available within next 10 years. The proposed DDP can not only reduce the new car development time but also be adapted into designing of varied products such as aircraft, yacht, electrical equipment and sports gear.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.6
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• pp.120-127
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• 2014

Robustness and controllability are the key factors in internal combustion engine commercialization. This study focuses on the combustion strategy to commercialize the low temperature diesel combustion technology. Various LTC combustion methods such as PPCI, MK and highly diluted mixing controlled LTC were conducted on 6.0L heavy duty diesel engine. To find the best feasible LTC strategy, emission level, fuel consumption and combustion safety during the combustion mode change were considered. Experiments were carried out under various engine operating conditions; engine speed & load, EGR level, injection timing. Finally, this study suggests realizable LTC combustion strategy; moderate EGR level and slight early injection are possible to considerably lower PM, NOx emission and expand LTC operating range up to 50% load without CO and HC emission.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.6
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• pp.113-119
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• 2014

For the robust design of Motor Driven Power Steering (MDPS) systems, it is important to consider energy efficiency from every aspect such as system configuration and current flow, etc. If design optimization is not considered, it has many problems on a vehicle. For example, when evaluating steering test, particularly the Catch-up test which turning the steering wheel left or right quickly, steering effort should be increased rapidly. Also a vehicle might have poor fuel efficiency. In this study, it is calculated energy consumption for each component of the steering system and analyzed factors of energy consumption. As a result, this paper redefines a method to estimate steering input torque using characteristics of vehicle electric components and then conducts an analysis of contribution for the Catch-up.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.4
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• pp.106-112
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• 2013

Compression ratio is an important factor affecting engine performance and emission characteristics since thermal efficiency of spark ignition engine can be theoretically improved by increasing compression ratio. In order to evaluate the effect of compression ratio change in HCNG engine, natural gas engine was employed using HCNG30 (CNG 70 vol%, hydrogen 30 vol%). Combustion and emission characteristics of CNG and HCNG fuel was analyzed with respect to the change of compression ratio at each operating condition. The results showed that thermal efficiency improved and $CH_4$, $CO_2$ emission decreased with the increase in compression ratio while $NO_x$ emissions were decreased at a certain excess air ratio condition. Higher thermal efficiency and further reduction of exhaust emissions can be achieved by the increase of compression ratio and the retard of spark timing.

• International Journal of Automotive Technology
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• v.6 no.4
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• pp.315-322
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• 2005

This work was performed to investigate the effect of a split injection on spray characteristics of fuel sprays injected from a common rail system. In order to analyze the spray behavior and atomization characteristics at various rates of split injections, the injection durations of pilot and main injections were varied in experiments. The injection rate of split injection was measured to study the effect of the pilot injection on the main injection. By using a Nd:YAG laser and an ICCD camera, the development of the injected spray was visualized at various elapsed time from the start of injection. The microscopic characteristics such as SMD and axial velocity were analyzed by using a phase Doppler particle analyzer system. The results indicate that the ambient gas flow generated by the pilot injection affects the behavior of main spray, whereas the effect of pressure variation on the main spray is little. The spray tip penetration of a main spray with pilot injection is longer than that of the single injection by the effect of ambient gas flow. Also the main spray produces larger droplets than the pilot spray due to a small relative velocity between the droplets and ambient gas.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.1
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• pp.24-31
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• 2002

An experimental study was conducted to investigate the effects of EGR (Exhaust Gas Recirculation) variables on performance and emission characteristics in a 2-liter 4-cylinder spark-ignition LPG fuelled engine. The effects of EGR on the reduction of thermal loading at exhaust manifold were also investigated because the reduced gas temperature is desirable for the reliability of an engine in light of both thermal efficiency and material issue of exhaust manifold. The steady-state tests show that the brake thermal efficiency increased and the brake specific fuel consumption decreased with the increase of EGR rate in hot EGR and with the decrease of EGR temperature in case of cooled EGR, while the stable combustion was maintained. The increase of EGR rate or the decrease of EGR temperature results in the reduction of NOx emission even in the increase of HC emission. Furthermore, decreasing EGR temperature by $180^{\circ}C$ enabled the reduction of exhaust gas temperature by $15^{\circ}C$ in cooled EGR test at 1600rpm/370kPa BMEP operation, and consequently the reduction of thermal load at exhaust. The optimization strategy of EGR application is to be discussed by the investigation on the effect of geometrical characteristics of EGR-supplying pipe line.