• Journal of Advanced Marine Engineering and Technology
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• v.39 no.9
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• pp.870-875
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• 2015

Diesel engines are widely used due to superior power and fuel consumption, however there are many challenges in exhaust gas management. Exhaust gas recirculation (EGR) is the most effective technique for reducing mono-nitrogen oxide (NOx) emissions in a diesel engine, in comparison with other catalytic technologies. In addition, the technology has a number of advantages in terms of economic efficiency and implementation. In this study, the effects on the power and exhaust characteristics of diesel engines equipped with EGR systems were investigated. It was found that as the EGR rate increased, horsepower expressed as IHP and BHP decreased. The net effect of the application of EGR was measured at various engine speeds. EGR technology caused decreases in BHP of around 9% during low engine speed and 3.5% during high engine speed. Additionally, NOx emissions reduced as the EGR rate increased, and increased as engine speed increased. However, smoke emissions increased as the EGR rate increased, and decreased as engine speed increased. The optimum operating conditions and ERG rate to simultaneously achieve minimum NOx and smoke emissions were investigate. It was found that as the EGR rate increased, optimal operating speed for minimal NOx and smoke also increased. Keywords: Diesel engine, Exhaust gas recirculation, Power perfomance, Emission characteristics, NOx, Smoke

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.7
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• pp.8-15
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• 2014

In order to satisfy stringent future emission regulation in diesel engines, systematic approaches to mitigate the harmful exhaust emissions were developed, such as engine hardware, fuel injection equipment, engine control, and after-treatment system. In this study, to improve the nano-particle and NOx emissions from a state-of-the-arts diesel engine, effect of various EGR and fuel injection pressure with combustion analysis were evaluated. Size-resolved nano-particle and NOx emissions showed trade-off characteristics with various EGR rate and increment of fuel injection pressure.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.7
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• pp.722-728
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• 2005

In this paper, the effects of ethanol blended gasoline on emissions and their catalytic conversion efficiency characteristics were investigated in a multiple-point EFI gasoline engine, The results show that with the increase of ethanol concentration in the blended fuels, THC emissions were drastically reduced by up to thirty percent, And brake specific fuel consumption was increased, but brake specific energy consumption could be improved. However, unburned ethanol and acetaldehyde emissions increased. Pt/Rh based three-way catalysts were effective to reduce acetaldehyde emissions, but had low catalytic conversion efficiency for unburned ethanol. The effect of ethanol on CO and NOx emissions and their catalytic conversion efficiency had close relation to the engine's speed, load and air/fuel ratio. Furthermore fuels blended with thirty percent ethanol by volume could dramatically reduced THC CO and NOx emissions at idle speed.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.7
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• pp.823-832
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• 2007

This paper presents the static characteristics of EGR-WI combined system. The water injection system was statically characterized by recording the engine exhaust outlet $NO_x$ emissions for comparison with baseline $NO_x$ emissions. Effects of the water injection system on CO and HC emissions and fuel consumption were examined. The research engine used for these experiments was a 103 kW turbocharged, intercooled, 2.5 L VM Motori CIDI engine equipped with a cooled EGR system. Water injection in the intake system demonstrated the potential for significant reductions in engine outlet $NO_x$ emissions. The system has reduced engine outlet $NO_x$ emissions by 40-50%, but caused significant increases in CO and HC emissions, particularly at low loads. Fuel consumption effects were minimal.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.1
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• pp.117-124
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• 2011

Automotive engines require strategies to fulfill the emission regulations in terms of NOx and PM. A dramatic reduction in NOx and PM emissions could be achieved with high pressure injection, innovative combustion strategies and EGR. Recently, Lean NOx Trap (LNT) and Urea-SCR are considered as more practical strategy to suppress the engine-out emissions substantially for copying with severe regulation. These systems need to reduce the reducing agent injection system which has a huge impact on NOx purification efficiency. In this paper, different three injectors have been used to investigate spray characteristics and engine emission test was conducted to clarify the effect of these injectors on the NOx reduction.

• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.183-190
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• 2002

In order to reduce NOx emissions in the 20kw class microturbines under development, the low NOx characteristics, as being an application to the lean premixed combustion technology, have been investigated. The study has been conducted at the conditions of high temperature and pressure. Air from a compressor with the temperature of 500K to 650K and the pressure of 0.3bar gauge to 0.7bar gauge, was supplied to the combustor through an air preheat-treatment. Sampling exhaust gases were measured at the immediate exit of the combustor. for the effect of temperature on NO and CO emissions. though NOx was increased, CO was decreased with increasing inlet air temperature. With increasing inlet air pressure, NOx and CO were increased also. NOx was decreased, but CO was increased with increasing inlet air mass flow rate. The test has been performed on the equivalent ratios of 0.10 to 0.25 in a lean region. NOx was increased with increasing equivalent ratios, but CO was decreased as an influence of flame temperature. In the very lean region of the equivalent ratio below 0.12, CO was increased suddenly, due to instability. As the results of this study, NOx and CO are found to be reduced to the similar level at the same time when operated at optimal conditions.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.3
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• pp.7-12
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• 2012

Cooled EGR system is widely used to reduce NOx emissions in diesel engine. But when EGR rate was increased, combustion stability was worsened and PM level was increased. So determining optimized control point of EGR rate is important. In order to determine this point, it is important to figure out the effect of EGR system on the exhaust emissions. In this research, NOx and PM emissions were analyzed with various coolant temperature supplied to the EGR cooler at several positions such as downstream of turbocharger, upstream and downstream of DPF. Effects of some variables such as EGR rate, hot / cooled EGR and change of injection timing were estimated. And $CO_2$ emissions were measured at exhaust and intake manifold to calculate EGR rate at each engine operating condition. Also combustion analysis was performed in each engine operating conditions. In the result of this study, there was trade-off between NOx emissions and PM emissions. When EGR rate was increased, combustion pressure was decreased and COV of IMEP was increased.

• 한국연소학회:학술대회논문집
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• 2012.04a
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• pp.107-109
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• 2012

A quasidimensional model is developed with the surrogate mechanism of isooctane and n-heptane to predict knock and emissions of a homogeneous GDI engine. It is composed of unburned and burned zone with the latter divided into multiple zones of equal mass to resolve temperature stratification. Validation is performed against measured pressure traces, NOx and CO emissions at different load and rpm conditions. Comparison is made between the empirical knock model and predictions by the chemistry model in this work.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.12
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• pp.1199-1206
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• 2015

In this study, the exhaust gas of a diesel engine operating on biodiesel(BD) fuel(a mixture of diesel and soybean oil) was investigated for different fuel mixing ratios in the range of BD3 to BD100. The experiments were conducted using injection pressures of 400, 600, 800, 1000, and 1200 bar. The Pearson correlation coefficient and Spearman rank-order correlation coefficient were used to quantify the NOx and Soot emissions based on the fuel mixing ratio and injection pressure. Consequently, the Pearson correlation coefficient obtained for NOx and Soot emissions according to the mixing ratio and injection pressure was -0.811 and the corresponding Spearman rank-order correlation coefficient was -0.884, which indicated that the correlation of the NOx and Soot emissions was linear. Thus, the NOx and Soot have a trade-off relationship. Moreover, at each injection pressure, the Pearson correlation coefficient was a negative number, which indicated an inversely proportional relationship between NOx and Soot.

• Journal of Energy Engineering
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• v.25 no.4
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• pp.53-61
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• 2016

Unburned Carbon(UBC) and NOx emissions from High-moisture coal and Dried coal were investigated in Drop Tube Furnace(DTF). When the same amount of the High-moisture coal and Dried coal were oxidized in DTF, the results show that UBC and NOx emissions of Dried coal case is higher than High-moisture coal case. As the moisture in coal decreases from 40% to 10%, the average gas temperature increases but the moisture concentration in DTF decreases. As the wall temperature increases from $900^{\circ}C$ to $1500^{\circ}C$, the UBC decreases and NOx emissions increases. Especially, the difference for UBC between High-moisture coal and Dried coal decreases with increasing wall temperature.