• 한국기계기술학회지
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• 제13권4호
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• pp.101-108
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• 2011

On cold start operation of an SI engine, a catalyst shows poor performance before it reaches activation temperature. Therefore, fast warmup of the catalyst is very crucial to reduce harmful emissions. In this study, an appropriate control strategy is investigated to increase exhaust gas temperature through changes of spark timing. Combustion stability is also considered at the same time. Exhaust gas temperature and pressure of combustion chamber are measured to investigate the effects of spark timings on cold start and idle performance. Experiments showed that retarded spark timing promotes the combustion at the end of expansion stroke and increases exhaust gas temperature during cold start.

• 한국자동차공학회논문집
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• 제9권6호
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• pp.103-111
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• 2001

During cold-start period, the reduction of exhaust emissions is a challenging task. To decrease harmful gaseous substances such as HC, it is necessary to realize a fast catalyst warm-up. In this study, the performance of dual pipe exhaust system have been carried out through different test mode. From measurement of gas temperature and HC concentration, the following conclusions were derived ; 1) Compared with single pipe, dual pipe exhaust system remarkably increase temperature of exhaust gas going through M.C.C(Main Catalytic Converter). 2) W.C.C.(Warm-up Catalytic Converter) also decreases HC emission. To reduce HC emission, it is helpful to use W.C.C. as well as dual pipe exhaust system. 3) Using finite element method, it is shown that inner parts have much higher distribution of temperature than outer parts.

• 한국대기환경학회지
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• 제16권3호
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• pp.257-264
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• 2000

An aftertreatment device which reduce exhaust gas of natural gas vehicle(NGV), NGV catalyst has important meaning as to reduce the exhaust emission. In this study, the characteristics of NGV catalyst were investigated and the effect parameters of NGV catalyst were analyzed and were predicted by changing the various parameters such as temperature, and gas concentration. The conversion efficiency of NGV catalyst converter was also predicted by Pd-loading, mass flow rate and gas composition.

• 한국정밀공학회지
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• 제25권3호
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• pp.115-125
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• 2008

Recently, Exhaust Gas Recirculation (EGR) system which re-flow a cooled exhaust gas from vehicles burning diesel as fuel to a combustion chamber of engine has been used to solve the serious air pollution. For the design and mass production of EGR system, it is essential to ensure structural integrity evaluation. The EGR system consisted of ten dimpled oval core rectangular tubes, two fix-plates, two coolant pipes, shell body and two flanges in this study. To confirm the safety of the designed system, finite element modeling about each component such as the dimpled oval core tube with the dimpled shape and others was carried out. The reliability of EGR system against exhaust gas flow with high temperature was investigated by flow and pressure analysis in the system. Also, thermal and strength analysis were verified the safety of EGR system against temperature change in the shell and tubes. Furthermore, modal analysis using ANSYS was also performed. From the results of FE analysis, there were confirmed that EGR system was safe against the flow of exhaust gas, temperature change in EGR system and vibration on operation condition, respectively.

• 한국자동차공학회논문집
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• 제12권1호
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• pp.55-60
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• 2004

Residual gas acts as a diluent which results in reducing the in-cylinder temperature as well as the flame speed, significantly affecting fuel economy, NOx emissions and combustion stability. Therefore it is important to determine the residual gas fraction as a function of the engine operating parameters accurately. However, the determination of the residual gas fraction is very sophisticated due to the unsteady state of induction and exhaust process. There has been little work toward the development of a generally applicable model for quantitative predictions of residual gas fraction. In this paper, a simple model for calculating the residual gas fraction in SI engines was suggested. The amount of fresh air was evaluated through AFR and fuel consumption. After this, from the intake temperature and pressure, the amount of total cylinder-charging gas was estimated. The residual gas fraction was derived by comparing the total charging and fresh air. This results coincide with measured EGR value very well.

• Journal of Advanced Marine Engineering and Technology
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• 제28권2호
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• pp.315-331
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• 2004

The effects of intake mixture temperature on performance and exhaust emissions under four kinds of engine loads were experimentally investigated by using a four-cycle. four-cylinder. swirl chamber type. water-cooled diesel engine with scrubber EGR system operating at three kinds of engine speeds. The purpose of this study is to develop the scrubber exhaust gas Recirculation (EGR) control system for reducing $\textrm{NO}_{x}$ and soot emissions simultaneously in diesel engines. The EGR system is used to reduce $\textrm{NO}_{x}$ emissions. And a novel diesel soot-removal device of cylinder-type scrubber with five water injection nozzles is specially designed and manufactured to reduce soot contents in the recirculated exhaust gas to the intake system of the engine. The influences of cooled EGR and water injection. however. would be included within those of scrubber EGR system. In order to survey the effects of cooled EGR and moisture on $\textrm{NO}_{x}$ and soot emissions. the intake mixtures of fresh air and recirculated exhaust gas are heated up using a heater with five heating coils equipped in a steel drum. It is found that intake and exhaust oxygen concentrations are decreased, especially at higher loads. as EGR rate and intake mixture temperature are increased at the same conditions of engine speed and load. and that $\textrm{NO}_{x}$ emissions are decreased. while soot emissions are increased owing to the decrease in intake and exhaust oxygen concentrations and the increase in equivalence ratio. Thus ond can conclude that $\textrm{NO}_{x}$ and soot emissions are considerably influenced by the cooled EGR.

• International Journal of Automotive Technology
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• 제7권7호
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• pp.763-768
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• 2006

Emission reduction in the cold start period of SI engines is crucial to meet stringent emission regulations such as SULEV Emissoin reduction is the starting point of the study in the which the variable valve timing (VVT) technology may be one promising method to minimize cold start emissions while maintaining engine performance. This is because it is possible to change valve overlap and residual gas fraction during cold start and idle operations. Our previous study showed that spark timing is another important factor for reducing cold-start emissions since it affects warm-up time of close-coupled catalysts (CCC) by changing exhaust gas temperature. However, even though these factors may be favorable for reduction of emissions, they may deteriorate combustion stability in these operating conditions. This means that the two variables should be optimized for best exhaust emissions and engine stability. This study investigated the effects of valve and spark timings in idle performance such as combustion stability and exhaust emissions. Experiments showed that valve timings significantly affected engine stability and exhaust emissions, especially CO and $NO_x$, due to change in residual gas fraction within the combustion chamber. Spark timing also affects HC emissions and exhaust gas temperature. Yet it has no significant effects on combustion stability. A control strategy of proper valve timing and spark timing is suggested in order to achieve a reduction in exhaust emissions and a stable operation of the engine in a cold start and idle operation.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 2000년도 THE THIRD INTERNATIONAL CONFERENCE ON AGRICULTURAL MACHINERY ENGINEERING. V.III
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• pp.639-646
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• 2000

Hot air heater with light oil combustion is the most common heater for greenhouse heating in the winter season in Korea. However, since the heat efficiency of the heater is about 80%, considerable unused heat in the form of exhaust gas heat discharges to atmosphere. In order to capture this exhaust gas heat a heat recovery system for plant bed heating in the greenhouse was built and tested in the hot air heating system of greenhouse. The system consists of a heat exchanger made of copper pipes, ${\phi}\;12.7{\times}0.7t$ located inside the rectangular column of $330{\times}330{\times}900mm$, a water circulation pump, circulation plastic pipe and a water tame The total heat exchanger area is $1.5m^2$, calculated considering the heat exchange amount between flue gas and water circulated in the copper pipes. The system was attached to the exhaust gas path. The heat recovery system was designed as to even recapture the latent heat of flue gas when exposing to low temperature water in the heat exchanger. According to performance test it can recover 45,200 to 51,000kJ/hr depending on the water circulation rates of 330 to $690{\ell}$/hr from the waste heat discharged. The exhaust gas temperature left from the heat exchanger dropped to $100^{circ}C$ from $270^{circ}C$ by the heat exchange between the water and the flue gas, while water gained the difference and temperature increased to $38^{circ}C$ from $21^{circ}C$ at the water flow rate of $690{\ell}$/hr. And, the condensed water amount varies from 16 to $43m{\ell}$ at the same water circulation rates. This condensing heat recovery system can reduce boiler fuel consumption amount in a day by 34% according to the feasibility study of the actual mimitomato greenhouse. No combustion load was observed in the hot air heater.

• 대한기계학회논문집B
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• 제26권6호
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• pp.833-841
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• 2002

The present study examined the possibility of NOx reduction in the high temperature industrial furnaces, duct burner of gas turbine cogeneration and two-stage gas turbine combustor. The experimental study was carried out for the non-premixed flame of second stage combustor with the variations of oxygen concentration in the hot exhaust gas of first stage combustor. It also examined the flammability range, temperature and NOx, $CO_2$, $O_2$formation in the combustor with respect to oxygen concentration in which the fuel(natural gas) is supplying into the hot exhaust gas. The results show that the inner temperature of flame reaches 1,20$0^{\circ}C$ at EGR $O_2$23% and that 15ppm of NOx at EGR $O_2$15.5% increases up to 60ppm at EGR $O_2$23%. It is believed that Fenimore＇s prompt NOx mechanism is more influential on the NOx formation than Zeldovich＇s thermal NOx mechanism does.

• Journal of Advanced Marine Engineering and Technology
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• 제37권8호
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• pp.822-828
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• 2013

고체산화물형 연료전지는 운전온도가 고온이기 때문에 연료전지 시스템으로 공급되는 가스의 열관리 문제가 중요하다. 본 연구에서는 선박 배기가스의 폐열을 선박 전원용 500kW급 SOFC 시스템으로 공급되는 연료, 가스 및 물을 가열하는 열원으로 활용한 경우에 연료전지 애노드 및 캐소드로 공급되는 가스의 온도특성에 관하여 검토하였다. 본 연구에서 제안한 연료전지 시스템에서는 선박의 배기가스를 활용하지 않고 연료전지에서 배출되는 배기가스만으로 연료전지 시스템으로 공급되는 가스의 가열원으로 활용한 경우의 애노드 및 캐소드로 공급되는 가스의 온도가 963K로 가장 높음을 알 수 있었다. 또한 엔진의 출력(배기가스의 유량)은 연료전지 스택으로 공급되는 가스의 온도에 큰 영향을 미치지 않음을 알 수 있었다.