• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.4
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• pp.181-187
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• 2013

Performance of DI diesel engine with high fuel injection method is directly related to its emission characteristics and fuel consumption. In this study, numerical model of 3rd generation piezo-driven injector was designed to analyze the hydraulic performance. Also the injection response characteristics was investigated by using the AMESim simulation code. From this study, it was shown that 3rd generation piezo-driven injector had a faster response and had better control capability due to its hydraulic bypass-circuit that has potential to higher hydraulic characteristics and improved accuracy of injected fuel quantity.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.2
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• pp.137-143
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• 2011

This paper describes the effects of biodiesel blended fuel on the engine combustion and emission characteristics in a four cylinder CRDI(Common-rail direct injection) diesel engine. In this work, the biodiesel-diesel blended fuel(20% of biodiesel and 80% of ULSD(ultra low sulfur diesel) by volume ratio, BD20) and ULSD fuel are used under the various injection pressures and engine speeds. The experimental results of BD20 and ULSD fuel show that NOx emissions were increased and soot emissions were decreased with the increase of injection pressure. In particular, NOx emissions were slightly increased for the BD20 fuel, however, soot emissions were significantly reduced compared to the ULSD fuel. When the engine speed is increased from 1000rpm to 2000rpm, NOx emissions are decreased at all tested conditions, and soot emissions are largely increased at lower injection pressure.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.5
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• pp.169-175
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• 2013

CRDi technology of diesel engine was developed from in the early 2000s due to a need to increase fuel efficiency and environment care. Especially, high-pressure fuel injection system in CRDi system which has a fuel injection unit including an injector, a fuel pump and common-rail, etc. becomes possible to make the exhaust gas clean as well as power improvement. In this study, comparison of dynamic characteristics of servo-hydraulic piezo-driven injector with 3-way and bypass-circuit type was analyzed by using the AMESim code. As results of this study, it found the bypass-circuit inside servo-hydraulic piezo injector can cause a faster injection response than that of the 3-way type. Also it was shown that bypass-circuit type had better control capability due to hydraulic bypass system.

• Journal of the Korean Applied Science and Technology
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• v.34 no.4
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• pp.974-985
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• 2017

Although the number of registered cars in South Korea is about 22million but, there is no national standard for automobile reference fuel in South Korea. Reference fuel is the fuel used for certificating vehicle performance, emissions and fuel economy. Now, domestic market fuels are used as reference fuel. However, the quality of domestic market fuel is constantly changing by seasonal and fuel manufacturers. It may effect vehicle performance, emissions and fuel efficiency test result. On this study, market diesel fuel quality was monitored and reference fuel standard(draft) was set by reflecting market fuel monitoring result. Reference fuel standard(draft) was applied to CRDI engine.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.3
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• pp.351-358
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• 2006

The capability of high pressure injection with small fuel quantify at all engine operating conditions is one of the main feature in common rail fuel injection system, which is used in small and light-duty Diesel engine. The key parameter for the better atomized fuel sprays and multiple injections of this common rail fuel injection control, that can be freely selected irrespective of the engine speed and load is the mechanism controlling the needle energizing and movement in high pressure Diesel injector. In the electro-hydraulic injector, the injection nozzle is being opened and closed by movement of the injector's needle which is balanced by pressure between the nozzle seat and the needle control chamber. This study describes the macroscopic spray structure characteristics of the common rail Diesel injectors with different electric driving method i.e. the solenoid-driven and piezo-driven type. The macroscopic spray characteristics such as spray tip speed. spray tip penetration and spray cone angle were investigated by the high speed spray, which is measured by the back diffusion light illumination method with optical system for the high speed temporal photography in a constant volume chamber pressurized by nitrogen gas. As the results, the prototype piezo-driven injector system was designed and fabricated for the first time in domestic case and the effect of injector's needle response driven by different drive type was compared between the solenoid and piezo-driven injector It was found therefore. that the piezo-driven injector showed faster needle response and had better needle control capability by altering the electric input value than the solenoid-driven injector.

• Journal of ILASS-Korea
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• v.20 no.2
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• pp.88-94
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• 2015

Recently, exhaust gas regulation has been gradually strengthened due to depletion of fossil fuels and environmental problem like a global warming. Due to this global problem, the demand for eco-friendly vehicle development is rapidly increasing. A clean diesel vehicle is considered as a realistic alternative. The common-rail fuel injection system, which is the key technology of the clean diesel vehicle, has adopted injection strategies such as high pressure injection, multiple injection for better atomization of the fuel. In addition, the emission regulations in the future is expected to be more stringent, which a conventional engine is difficult to deal with. One of the way for actively proceeding is the study of alternative fuels. Among them, the bio-diesel has been attracted as an alternative of diesel. So, in this study, spray characteristics of bio-diesel was analyzed in the common-rail fuel injection system with three injectors driven by different operating mechanism.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.2
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• pp.118-125
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• 2009

Calculation of indicated mean effective pressure(IMEP) requires high cylinder pressure sampling rate and heavy computational load. Because of that, it is difficult to implement in a conventional electronic control unit. In this paper, a cylinder pressure based real-time IMEP estimation method is proposed for controller implementation. Crank angle at 10-bar difference pressure($CA_{DP10}$) and cylinder pressure difference between $60^{\circ}$ ATDC and $60^{\circ}$ BTDC($DP_{deg}$) are used for IMEP estimation. These pressure variables can represent effectively start of combustion(SOC) and fuel injection quantity respectively. The proposed IMEP estimation method is validated by transient engine operation using a common-rail direct injection diesel engine.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.2
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• pp.123-134
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• 2012

A typical cooling system of an engine relies on a water pump that circulates the coolant through the system. The pump is typically driven by the crankshaft through a mechanical link with engine starting. In order to reduce the friction and warm-up time of an engine, the clutch-type water pump (CWP) was applied in 2.0 liter diesel vehicle. The clutch-type water pump can force cooling water to supply into an engine by the operation of an electromagnetic clutch equipped as the inner part of pump system. The onset of CWP is decided by temperature of cooling water and engine oil. And, the control logic for an optimal operation of the clutch-type water pump was developed and applied in engine and vehicle tests. In this study, the warm-up time was measured with the conventional water pump and clutch-type water pump in engine tests. And the emission and the fuel consumption were evaluated under NEDC mode in vehicle tests. Also, tests were carried out for the various temperature conditions starting the operation of CWP. From the results of the study, the application of CWP can improve the fuel consumption and $CO_2$ reduction by about 3%.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.3
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• pp.45-51
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• 2012

This work was investigated 2-stage injection strategy on combustion and emissions in a direct injection compression-ignition engine fueled with DME. Single cylinder engine was equipped with common rail. Injection pressure was 700bar, dSOI between the main injection and the pilot injection was varied. Diesel was used as compared fuel of DME in all cases. The results was shown that maximum pressure was higher than all cases and its amount of DME and diesel was similar. Regardless the pilot injection, the main fuel injection timing was same. The heat release rate of the main injection for diesel was high while that of pilot injection for DME was high. The THC was very low regardless of the fuel type and injection strategy. In the single injection, NOx was increased to retard of main injection timing regardless of the fuel type. NOx emissions was decreased with the retardation of the main injection timing regardless of the fuel type in the case of 2-stage injection strategy.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.2
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• pp.91-99
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• 2014

The common-rail injectors are the most critical component of the CRDI diesel engines that dominantly affect engine performances through high pressure injection with exact control. Thus, from now on the advanced combustion technologies for common-rail diesel injection engine require high performance fuel injectors. Accordingly, the previous studies on the numerical and experimental analysis of the diesel injector have focused on a optimum geometry to induce proper injection rate. In this study, computational predictions of performance of the diesel injector have been performed to evaluate internal flow characteristics for various needle lift and the spray pattern at the nozzle exit. To our knowledge, three-dimensional computational fluid dynamics (CFD) model of the internal flow passage of an entire injector duct including injection and return routes has never been studied. In this study, major design parameters concerning internal routes in the injector are optimized by using a CFD analysis and Response Surface Method (RSM). The computational prediction of the internal flow characteristics of the common-rail diesel injector was carried out by using STAR-CCM+7.06 code. In this work, computations were carried out under the assumption that the internal flow passage is a steady-state condition at the maximum needle lift. The design parameters are optimized by using the L16 orthogonal array and polynomial regression, local-approximation characteristics of RSM. Meanwhile, the optimum values are confirmed to be valid in 95% confidence and 5% significance level through analysis of variance (ANOVA). In addition, optimal design and prototype design were confirmed by calculating the injection quantities, resulting in the improvement of the injection performance by more than 54%.