• Proceedings of the KSME Conference
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• 2005.11a
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• pp.98.2-98.2
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• 2005

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.841-842
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• 2010

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.1
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• pp.67-73
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• 2011

The purpose of this study is to investigate experimentally the spray-atomization and combustion-emission characteristics of biodiesel-DME blended fuel. In this study, two types of test fuels pure biodiesel (BD100) and blended fuel (B-DME20) were used, and the spray and combustion characteristics of different fuel compositions were analyzed. DME constitutes 20% and biodiesel constitutes 80% (by mass fraction) of the blended fuel. The overall spray characteristics, spray tip penetration, and cone angle were evaluated using frozen spray images. In addition, the combustion and emission characteristics were analyzed on the basis of the evaluated data for a single-cylinder CI engine with common-rail injection system. It was revealed that the injection profiles of both the test fuels for a given injection pressure showed similar trends. However, the injection profiles of the blended fuel (B-DME20) indicated shorter ignition delay than those of biodiesel.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.1
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• pp.1-8
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• 2011

In recent years, there has been an interest in early-injection diesel engines as it has the potential of achieving a more homogeneous and leaner mixture close to TDC compared to standard diesel engine. The more homogeneous mixture may result in reduced NOx and soot emissions and higher efficiency in homogeneous charge compression ignition engines. While earlier studies have shown that a reduction in NOx emissions from HCCI engine is possible, there are some significant problems including the control of ignition timing and combustion rate. In order to investigate the effect of EGR and hydrogen enriched gas on combustion characteristics and emissions, an experiments with single cylinder CRDi engine were carried out concerning the formation of various premixed charge, which can achieved by early injection, EGR and hydrogen enriched gas. EGR was not effective to further reduce NOx and PM emissions. It was found that NOx emissions were decreased with an introduction of hydrogen enriched gas and an adequate diesel fuel amount.

• Transactions of the Korean hydrogen and new energy society
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• v.28 no.1
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• pp.98-105
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• 2017

In recent years, compression ignition engine has been equipped with some control devices such as common rail injection system and turbocharger. In order to control the large number of input parameter appropriately in consideration of $NO_x$, HC and engine power as the engine output objectives. The model construction which reproduces the characteristic value of $NO_x$, HC and engine power from input parameter is needed. In this research, the stepwise method was applied to construct the compression ignition engine model. By using the preliminary experimental data of single cylinder compression ignition engine, the prediction model of $NO_x$, HC and engine power on single injection compression ignition engine was built and compared with the main experimental data.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.3
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• pp.43-49
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• 2013

This work investigated the effects of engine speed and injection timing on combustion and emissions characteristics in a partially premixed charge compression ignition (pPCCI) engine fueled with DME. pPCCI engine especially has potential to achieve more homogeneous mixture in the cylinder, which results in lower NOx and smoke emission. In this study single cylinder engine was equipped with common rail and injection pressure is 700 bar. Total injected fuel mass is 64.5 $mm^3$ per cycle. The amount of pilot injection of the entire injection 12.5% is tested. Results show that NOx emission is decreased while IMEP is increased as the retard of injection timing. Besides, NOx emissions are slightly rised as well as IMEP is increased with the increase of engine speed.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.2
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• pp.158-165
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• 2008

The combustion and exhaust emissions characteristics of a liquefied petroleum gas-di-methyl ether compression ignition engine with a variable valve timing device were investigated under various liquefied petroleum gas injection timing conditions. Liquefied petroleum gas was used as the main fuel and was injected directly into the combustion chamber. Di-methyl ether was used as an ignition promoter and was injected into the intake port. Different liquefied petroleum gas injection timings were tested to verify the effects of the mixture homogeneity on the combustion and exhaust emission characteristics of the liquefied petroleum gas-di-methyl ether compression ignition engine. The average charge temperature was calculated to analyze the emission formation. The ringing intensity was used for analysis of knock characteristics. The combustion and exhaust emission characteristics differed significantly depending on the liquefied petroleum gas injection and intake valve open timings. The CO emission increased as the intake valve open and liquefied petroleum gas injection timings were retarded. However, the particulate matter emission decreased and the nitrogen oxide emission increased as the intake valve open timing was retarded in the diffusion combustion regime. Finally, the combustion efficiency decreased as the intake valve open and liquefied petroleum gas injection timings were retarded.

• Journal of ILASS-Korea
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• v.19 no.4
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• pp.204-210
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• 2014

Experimental study was conducted to investigate the effect of EGR(exhaust gas recirculation) on engine noise using single cylinder combustion ignition engine. Under constant engine rotary speed of 1200 RPM, 8 mg fuel quantity was injected with 15, 18 and 21% of oxygen ratio and 1400 bar of injection pressure. Using the in-cylinder pressure data acquired by a piezoelectric transducer, the engine performance parameters were calculated. Radiated engine noise measured for 10 seconds was analyzed using spectral characteristics and sound quality metrics such as loudness, sharpness, roughness. From the obtained engine performance parameters and sound quality metrics, effect of oxygen ratio of the premixed air, start of injection timing on frequency characteristic and sound quality metrics were analyzed. Correlation analysis was conducted between MPRR(maximum pressure rise rate), RI(ringing intensity) and sound quality metrics. RI was identified as the most important factor having influence on the sound quality metrics.

• Journal of ILASS-Korea
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• v.25 no.2
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• pp.45-50
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• 2020

Recently, global warming and environmental pollution are becoming more important, and fuel economy is becoming important. Each automobile company is actively developing various new technologies to increase fuel efficiency. CVVD(Continuously Variable Valve Duration) system means a device that continuously changes the rotational speed of the camshaft to change the valve duration according to the state of the engine. In this paper, VVT(Variable Valve Timing) and CVVD were applied to a single-cylinder diesel engine, and the characteristics of intake and exhaust flow rate and in-cylinder pressure characteristics were analyzed by numerical analysis. In order to analyze the effect of CVVD on the actual engine operation, the study was performed by setting the valve control and injection pressure as variables in two sections of the engine operating region. As a result, In the case of applying CVVD, the positive overlap with the exhaust valve is maintained, thus it is possible to secure the flow smoothness of air and increase the volumetric efficiency by improving the flow rate. The section 2 condition showed the highest peak pressure, but the pressure rise rate was similar to that of the VVT 20 and CVCD 20 conditions up to 40 bar due to the occurrence of ignition delay.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.5
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• pp.32-39
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• 2004

HCCI (Homogeneous Charge Compression Ignition) combustion has a great advantage in reducing NOx (Nitrogen Oxides) and PM (Particulate Matter) by lowering the combustion temperature due to spontaneous ignitions at multiple sites in a very lean combustible mixture. However, it is difficult to make a diesel-fuelled HCCI possible because of a poor vaporability of the fuel. To resolve this problem, the two-stage injection strategy was introduced to promote the ignition of the extremely early injected fuel. The compression ratio and air-fuel ratio were found to affect not only the ignition, but also control the combustion phase without a need for the intake-heating or EGR (Exhaust Gas Recirculation). The ignition timing could be controlled even at a higher compression ratio with increased IMEP (Indicated Mean Effective Pressure). The NOx (Nitrogen Oxides) emission level could be reduced by more than 90 % compared with that in a conventional DI (Direct Injection) diesel combustion mode, but the increase of PM and HC (Hydrocarbon) emissions due to over-penetration of spray still needs to be resolved.