• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.6
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• pp.46-52
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• 2011

Homogeneous charge compression ignition (HCCI) is the best concept able to provide low NOx and PM in diesel engine emissions. This new alternative combustion process is mainly controlled by chemical kinetics in comparison with the conventional combustion in internal combustion engine. However, HCCI engine's operation have an excessive rate of pressure rising during the combustion process. In this study, stratification condition of EGR exhaust gases was used to reduce the pressure rising during the combustion process in HCCI engine. Also, combustion characteristics and emissions characteristics were investigated using the detailed diesel surrogate reaction mechanism.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.11
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• pp.1630-1636
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• 2003

Automobile companies and research institutions in leading automobile-manufacturing nations have recently been very active with research regarding the HCCI engine for use in future vehicles. Because HCCI engines take advantage of high compression ratio and heat release rate, they exhibit high efficiency found in compression ignition engines. HCCI engines also utilize a lean air/fuel ratio resulting in low emissions of NO$_{x}$ and PM (particulate matter). The objective of this research is to determine the effects of EGR rate on the combustion processes of HCCI. for this purpose, a 4-cylinder, compression ignition engine was converted into a HCCI engine, and a heating device was installed to raise the temperature of the intake air and also to make it more consistent. In addition, a pressure sensor was inserted into each of the cylinders to investigate the differences in characteristics among the cylinders. The experimental study of the effects of EGR rate on various gas emissions, engine performance, etc. should prove to be a valuable source of information for the development of the HCCI engine.e.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.3
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• pp.70-78
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• 2000

The effects of recirculated exhaust gas on the characteristics of ;$NO_x$ and soot emissions under a wide range of engine load have been experimentally investigated by a water-cooled, four-cylinder, indirect injection, four cycle and marine diesel engine operating at two kinds of engine speeds. The purpose of the present study is to develop the EGR control system for reducing $NO_x$ and soot emissions simultaneously in diesel engines. The EGR system is used to reduce NOx emissions, and a novel diesel soot removal apparatus with a cylinder-type scrubber for the experiment system which has 6 water injectors(A water injector is made up 144 nozzles with 1.0mm in diameter) is specially designed and manufactured to reduce the soot contents in the recirculated exhaust gas to intake system of the engines. The intake oxygen concentration obtained by the intake air flow and the oxygen concentration in the recirculated exhaust gas, and the exhaust oxygen concentration measured in exhaust manifold are used to analyse and discuss the influences of EGR on NOx and soot emissions. The experiments are performed at the fixed fuel injection timing of $15.3^{\circ}$ BTDC regardless of experimental conditions. It is found that $NO_x$ emissions decrease and soot emissions increase owing to the drop of intake oxygen concentration and exhaust oxygen concentration as EGR rate rises. Also, one can conclude that it is sufficient for the scrubber EGR system with a novel diesel soot removal apparatus to reduce $NO_x$ emissions, but not to reduce soot emissions.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.6
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• pp.142-154
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• 1998

The effects of recirculated exhaust gas on the characteristic of soot emissions have been investigated by using an eight-cylinder, four-stroke, direct injection and water-cooled diesel engine operating at several loads and speeds. The experiments in this study are carried out at the fixed fuel injection timing of $38^{\circ}$ BTDC regardless of experimental conditions. The intake oxygen concentration and the mean equivalence ratio calculated by the intake air flow and fuel consumption rate are used to analyze and discuss the influences of EGR rate on soot emissions. Results of this study indicate that soot emissions increase owing to the drop of intake oxygen concentration and the rise of equivalence ratio as the EGR rate increases at a given engine load and speed, especially the high load.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.11
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• pp.83-89
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• 2008

The Effect of Space Velocity(SV) on NOx conversion rate was performed to develop NOx reduction after-treatment system. SV is calculated from engine exhaust gas volume and SCR catalyst volume. Found the Urea injection duty of maximum efficiency for NOx conversion if increase SV, NOx Conversion rate is down. Especially, when SV is more than $110,000h^{-1}$, NOx conversion rate decrease suddenly. Same case, if SV is lower than $40,000h^{-1}$, NOx conversion rate is down. Also, the characterization of Urea-SCR system was performed. Three candidate injectors for injecting Urea were tested in terms of 속 injection rate and NOx reduction rate. The performances of SCR catalytic converter on temperature were investigated. The performance of Urea-SCR system was estimated in the NEDC test cycle with and without EGR. It was found that nozzle type injector had high NOx conversion rate. SCR catalytic converter had the highest efficiency at the temperature of $350^{\circ}C$. EGR+Urea-SCR system achieved NOx reduction efficiency of 73% through the NEDC test cycle.

• 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.

• Journal of the Korean Society of Combustion
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• v.21 no.3
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• pp.32-38
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• 2016

This paper aims to predict oxidation amounts of catalyst and heat produced through passive regeneration on DPF according to different EGR rates and loads of off-road engines. Soot oxidation model and parameter assumption model were used for the test. Engine data were measureed with 25%, 50% and 75% of 1600 RPM loads and with 0% and 30% of EGR rates in order to estimate parameters. Oxygen levels calculated on the DPF downstream and oxygen levels measured were compared through all of the experimental conditions for validating the model. Oxidation rates on DPF according to different EGR rates and oxygen levels on the DPF downstream were estimateed successfully, which can be applied for off-road vehicles.

• Journal of Power System Engineering
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• v.20 no.5
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• pp.37-45
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• 2016

Exhaust gas recirculation has the advantage of being low-cost and easy to control of NOx emission. Therefore, it is most generally used to reduce NOx emission according to strengthen regulation. In the case of a non-road engine, such as the agricultural engine, since it mainly operate a middle or high-load state, NOx emission is decreased in accordance with the mapping range of the EGR rate, but results in an increase in the particulate matter which is caused to deposit and fouling problem of the EGR system. This problem has become an important issue for maintaining the performance of the engine, as well as emission performance. This study had examined the effects of cooler aging on the performance of heat transfer efficiency and NOx emission in non-road diesel engine. As a result of the EGR cooler aging during 200 hours engine operation, the cooling performance decreased about 25% compared with that of fresh cooler and the NOx emission increased about 14.6% on NRSC(non-road steady cycle) and 20% on NRTC(non-road transient cycle) compared with that of fresh cooler respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.3 no.1
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• pp.58-62
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• 2002

The efforts of EGR on performance and emissions were investigated in this study. The engine used for the tests was a six-cylinder, 11 liter, and turbo-charged, heavy-duty diesel engine with a low pressure route ECR system. The volume of recirculated gas was controlled by a manually operated valve which was installed between the turbine outlet and compressor inlet. The experiments were performed at various engine speeds and loads while the ECR rates were set at 4% and 8%. Exhaust emissions with EGR system were compared with the baseline emissions.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.1
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• pp.56-64
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• 2015

This study presents a model-based gain scheduling strategy for PI-based EGR controllers. The air-to-fuel ratio is used as an indirect measurement of the EGR rate. In order to cope with the nonlinearity and parameter varying characteristics of the EGR system, we proposed a static gain model of the EGR system using a new scheduling parameter. With the 810 steady-state measurements, the static gain model achieved 0.94 of R-squared value. Based on the static gain of the EGR system, the PI gains were robustly designed using quantitative feedback theory. Consequently, the gains of the PI controller are scheduled according to the static gain parameter of the EGR path in runtime. The proposed model-based gain scheduling strategy was validated through various operating conditions of engine experiments such as setpoint step responses and disturbance rejections.