• 동력기계공학회지
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• 제8권1호
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• pp.18-23
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• 2004

The direct injection diesel engine is one of the most efficient thermal engines. For this reason DI diesel engines are widely used for heavy-duty applications. But the world is faced with very serious problems related to the air pollution due to the exhaust emissions of diesel engine. So, that is air pollution related to exhaust gas resulted from explosive combustion should be improved. Exhaust Gas Recirculation(EGR) is a proven method to reduce NOx emissions. In this study, the experiments-were performed at various engine loads while the EGR rates were set from 0% to 20%. The emissions trade-off and combustion of diesel engine are investigated. Hot and cooled EGR are achieved without cooling and with cooling respectively. It was found that the exhaust emissions with the EGR system resulted in a very large reduction in oxides of nitrogen at the expense of higher smoke emissions. Also, the reduction rates of NOx emissions for hot and cooled EGR are similar at load 20%.

• 연구논문집
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• 통권29호
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• pp.29-38
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• 1999

In comparison with gasoline engine, LPG direct injection engine has some advantages not only in emission and fuel efficiency but also in prevention of power decrease and back fire etc. which are disadvantages of conventional LPG engine. In this study, comparision tests of the incylinder spray and combustion characteristics between of LPG and gasoline fuels were performed in the RCEM as a basic research for the development of future LPG engine with low emission and high fuel efficiency During the direct injection of LPG fuel and gasoline into the inside of RCEM, spray development characteristics according to the injection condition have been photographed by the high speed shadow graph methods. The conditions for the optimum mixture distribution of LPG and gasoline fuels are achievable at the selected ignition timing, respectively.

• 한국수소및신에너지학회논문집
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• 제13권3호
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• pp.233-241
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• 2002

To achieve hydrogen power system with high performance and stable operation, the COVimep of hydrogen fueled engine with direct injection was evaluated with the change of engine speed, injection timing, air-fuel equivalence ratio and spark timing. And the cause of cycle variation was analyzed by using coefficient of variation in combustion period defined in this study. the results showed that the cycle variation of hydrogen fueled engine is mainly dependent on the early combustion period.

• Journal of electromagnetic engineering and science
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• 제8권3호
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• pp.134-137
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• 2008

This paper proposes a novel quadrature VCO(QVCO) based on direct back-gate second harmonic coupling. The QVCO directly couples the current sources of the conventional LC VCOs through the back-gate instead of front-gate to generate quadrature signals. By the second harmonic injection locking, the two LC VCOs can generate quadrature signals without using on-chip transformer, or stability problem that is inherent in the direct front-gate second harmonic coupling. The proposed QVCO is implemented in $0.18{\mu}m$ CMOS technology operating at 2 GHz with 5.0 mA core current consumption from 1.8 V power supply. The measured phase noise of the proposed QVCO is - 63 dBc/Hz at 10 kHz offset, -95 dBc/Hz at 100 kHz offset, and -116 dBc/Hz at 1 MHz offset from the 2 GHz output frequency, respectively. The calculated figure of merit(FOM) is about -174 dBc/Hz at 1 MHz offset. The measured image band rejection is 46 dB which corresponds to the phase error of $0.6^{\circ}$.

• 한국자동차공학회논문집
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• 제7권7호
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• pp.76-85
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• 1999

GDI(Gasoline Direct Injection( engine technology is well known as a new technology since it can improve fuel consumption and meet future emission regulations. But the GDI has many difficulties to be solved, such as complexity of injection control mode, unburned hydrocarbon, and restricted power. A 2-D shape combustion chamber was adopted to investigate mixture formation and combustion characteristics of GDI engine. Spray and combustion experiments were performed by changing the injection timing. injection pressure an din-cylinder flow in Rapid Compression and Expansion Machine(RCEM).Through the experiments, the detailed characteristics of fuel spray and combustion was analyzed by visualizing the in-cylinder phenomena according to the change of injection condition, and the optimal fuel injection timing and fuel injection pressure were obtained.

• 한국자동차공학회논문집
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• 제19권5호
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• pp.29-34
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• 2011

This study investigates the potential of DME/Diesel dual fuel engine for reducing emissions with same power. Dual fuel engine controls the combustion using two different fuels, DME and diesel with different auto-ignition timings. In the previous work, the caracteristics of combustion and emissions under single cylinder engine and ignition is done by compression ignition. Pre-mixture is formed by injecting low-pressure DME into an intake manifold and high-pressure fuel (diesel or DME) is injected directly into the cylinder. Both direct diesel injection and port fuel injection reduced the significant amount of Smoke, CO and NOx in the homogeneous charge compression ignition engine due to present of oxygen in DME. In addition, when injecting DME directly in cylinder with port DME injection, there is no changes in emissions and energy consumption rate even operated by homogeneous charge compression ignition.

• 수산해양기술연구
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• 제52권1호
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• pp.65-71
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• 2016

Injection rate, injection quantity and injection timing of fuel are controlled precisely by electric control in CRDI system. Particularly, injection rate being influenced with injection pressure affects to spray characteristics and fuel-air ratio, so it is a very important factor in diesel combustion. In this study, injection rates in accordance with injection pressure at a constant ambient pressure were measured with Zeuch's method. Under the same condition, non-evaporating spray images were taken with a high speed camera and analyzed carefully with Adobe Photoshop CS3. Macroscopic spray characteristics and breakup processes in the spray could be found from the examined and analyzed data. Injection start time and injection period were practically affected with injection pressure. Also, initial injection rate, spray penetration, spray angle and breakup of high density droplets region in the spray were affected with injection pressure. The results and techniques of spray visualization and injection rate measurement in this study would be practically effective to study a high pressure diesel spray for common rail direct injection system.

• 한국안전학회지
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• 제25권6호
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• pp.53-59
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• 2010

A fatigue damage caused by cyclic load is considered as one of the important failure mechanisms that threaten the integrity of structures and components in a nuclear power plant. In ASME code section III NB, the fatigue analysis procedure and standard S-N curves for the class 1 components are described and these criteria should be met at the design step of components. As the current ASME S-N curves are based on the very conservative assumptions such as a local stress concentration effect, immoderate transient frequencies and a constant Young's modulus, however, they can not precisely address the fatigue behavior of components. In order to find out the technical solution for these problems, a number of researches and discussion have been carried out continuously at home and abroad over the decades. In this study, detailed fatigue analyses for DVI nozzle with various mesh density of finite elements were performed to evaluate effect of stress concentration factors on the fatigue analysis procedure and the excessive conservatism of stress concentration factors are confirmed through the analysis results.

• 동력기계공학회지
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• 제21권1호
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• pp.63-69
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• 2017

The combustion characteristics of gasoline and diesel were tested in a compression ignition engine. Both fuels were used with same common rail injection system. Combustion experiment showed that low load condition of 0.45 MPa IMEP (indicated mean effective pressure) was tested in metal and optical engines. The gasoline combustion showed higher hydrocarbon and carbon monoxide emissions but lower soot emission compared with diesel combustion. NOx emissions were very high at late injection timing but significantly decreased at early injection timing due to the lean combustion resulted from vigorous mixing process. Direct combustion visualization showed that the diesel combustion was dominated by diffusion combustion exhibiting soot incandescence and the gasoline combustion was mostly consisted of premixed combustion showing blue chemiluminescence.

• 동력기계공학회지
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• 제15권1호
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• pp.5-10
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• 2011

The spatial fuel vapor distribution of the homogeneous charge by a 6-hole injector was examined in a optically accessed single cylinder direct injection spark ignition(DISI) engine. The effects of in-cylinder charge motion, and fuel injection pressure, and coolant temperature were investigated using a planar LIF (Laser Induced Fluorescence) technique. It was confirmed that the in-cylinder tumble flow played a little more effective role in the spatial fuel vapor distribution than the swirl flow during the compression stroke at 10 mm and 2 mm planes under cylinder head gasket and the increased fuel injection pressure activated spatial distributions of the fuel vapor. In additions, richer mixtures were concentrated around the cylinder wall by the increase of the coolant temperature.