• Journal of Mechanical Science and Technology
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• 제16권2호
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• pp.219-226
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• 2002

Natural gas is considered to be a promising alternative fuel for passenger cars, truck transportation and stationary engines providing positive effects both on the environment and energy security. However, since the composition of natural gas fuel varies with location, climate and other factors, it is anticipated that such changes in fuel properties will affect emission characteristics and performance of CNG (Compressed Natural Gas) engines. The purpose of the present study is to investigate the effects of the difference in gas composition on the engine performance and emission characteristics. The results show that THC (Total Hydrocarbon) decreases with increasing Wl (Wobbe Index) and MCP (Maximum Combustion Potential). On the other hand, it is observed that NOx slightly increases as Wl and MCP increase. The TLHV (Total Lower Heating Value of Intake) is proposed in this study as a potential index for compatibility of gas fuels in a CNG engine. There is a variation in power up to 20% depending on the composition of gas when the A/F ratio and spark timing are flexed for a specific gas fuel.

• Journal of Advanced Marine Engineering and Technology
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• 제32권6호
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• pp.847-853
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• 2008

Although combustion is essential in most energy generation processes, it is one of the major causes of air pollution. Circle fin exhaust pipes were designed to study the effect of cooling the recirculated exhaust gases (EGR) of Diesel engines on the chemical composition of the exhaust gases and the reduction in the percentages of pollutant emissions. The designs adopted in this study were exhaust pipes with solid and hollow fins around them direct surface force measurement in water using a nano size colloidal probe Technique The direct force measurement between colloidal surfaces has been an essential topic in both theories and applications of surface chemistry. As particle size is decreased from micron size down to true Carbon nano Colloid size (<10nm), surface forces are increasingly important. Nanoparticles at close proximity or high solids loading are expected to show a different behavior than what can be estimated from continuum and mean field theories. This paper use Water and CNC fluid at normal cooling system of EGR. Experimental result showed all good agreement at Re=$2.54{\times}10^{4}$.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.903-908
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• 2001

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 formulated. The effects of engine operating parameters on the residual gas were also investigated. 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 fraction was derived by comparing the total charging and fresh air. This results coincide with measured value very well.

• 동력기계공학회지
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• 제12권5호
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• pp.34-39
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• 2008

The combustion purpose of diesel engine is to reduce the emission of green gas and to produce high output. Generally, the regulation matter of emission gas is largely diveded by 'THC', 'NOx', 'CO' and 'PM'. Among those matters, the most problem is to disgorge into 'PM', the character of diesel combustion. Diesel PM can be controlled using Diesel Particulate Filter, which can effectively reduce the level of soot emissions to ambient background levels. $NO_2$ generated by the DOC is used to combust the carbon collected in the DPF at low temperature. To certificate DPF device that is suitable to domestic circumstances, it is necessary to exactly evaluate the DPF devices according to the regulation of DPF certificate test procedure fur retrofit. To do carry out the above-mentioned description the understanding of that regulation like the standard of PM reduction is needed. In this study the test procedure including test cycle and BPT test condition was examined, and also the test result for specific DPF was analyzed. In every test like field test, PM reduction efficiency test and Seoul-10 mode test, no defect was showed.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• 제4권4호
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• pp.201-208
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• 2000

The reduction of NO by hydrocarbons was investigated over Cu/Al$_2$O$_3$catalysts using a stainless steel flow reactor under highly oxidising diesel exhaust conditions(up to 15%). Three different Cu loadings(1,5 and 10wt.%) on an $Al_2$O$_3$support were prepared and characterized using spectroscopic techniques. The catalytic activity tests show that different Cu loadings as well as temperature, oxygen, and hydrocarbon concentration levels significantly influence the NO reduction. Increasing Cu loadings up to 5 and 10wt.% decreases the catalytic activities for NO reduction due to the formation of a bulk crystalline CuO phase, as observed from XRD and SEM images. In particular, the visualization of the copper dispersion on the surface using the SEM-BEI technique provides information on the extent of copper saturation, particle size, and the effects on NO reduction. However, the lower Cu loading(1 wt.%) increases the catalytic activity with a temperature window of 720-810K, thereby favoring the formation of well dispersed isolated Cu species, e.g. Cu(sup)2+ ions, which is related to selective NO reduction. The effects of other reaction parameters, such as oxygen, the hydrocarbon level and type, and byproduct emissions are further discussed.

• 대한기계학회논문집B
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• 제28권12호
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• pp.1467-1474
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• 2004

Recently, with respect to an increase of energy consumption, many countries have tried to develop alternative fuels. In the United States, less than 10 percent of motor fuels will be displaced by alternative fuels by year 2010, with about 25 percent of the replacement fuels from renewable resources. But the level of exhaust gas is not decreased to the result of an increase of diesel vehicles. Moreover, emission regulations are being intensified by advanced countries such as America and Europe. Because Biodiesel is similar to diesel fuel, it is essential to judge the environmental and health effects deriving from the use of Biodiesel in diesel engine. Therefore, this research could be conformed whether both Biodiesel 20% and Biodiesel 100% are influenced on emission according to sulfur contents by applying DOC. As a result of using the Biodiesel, this research could be conformed though Nox was increased, CO, HC and PM were decreased, and also estimated to compare diesel fuel with the Biodiesel in accordance with engine performance and emission characteristics.

• 한국분무공학회지
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• 제19권3호
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• pp.142-148
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• 2014

In this study, characteristics of gaseous pollutants and particulate matter were investigated on the condition of DPF regeneration and normal DPF condition. THC, CO, $CO_2$, NOx, and $CH_4$ were analyzed by MEXA-7200H and CVS-7100 respectively. Particulate Matter (PM) was measured by difference in weight of Membrane filter. Particle Number (PN) was measured by CPC analyzer. And Sulfate, Nitrate, Organic were measured by Aerosol Mass Spectrometer (AMS). As a result, gaseous pollutants and particulate matter were detected in higher concentration during DPF regeneration than normal DPF condition. And the PN increased by 94%, the fuel consumption was reduced by 29% on DPF generation process. Sulfate, Nitrate and Organic were undetectable level during normal DPF condition. But the highest concentration of Sulfate, Nitrate and Organic were measured as $100{\mu}g/m^3$, $20{\mu}g/m^3$ and $15{\mu}g/m^3$ respectively on DPF regeneration condition. VOCs concentrations (Benzene, Toluene, Ethylbenzene, Xylene) were analyzed by using PTR-MS. Benzene and Toluene emission have little or no change depending on DPF regeneration. But the Ethylbenzene and Xylene have comparatively low emissions on DPF regeneration.

• 한국산학기술학회논문지
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• 제17권2호
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• pp.137-146
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• 2016

EGR율이 증가할수록 $NO_X$ 저감에는 효과적이나, 과도한 EGR율은 오히려 불완전 연소의 주원인이 된다. 엄격한 배기규제를 만족하기 위해서는 엔진의 운행 조건에 최적화된 정밀한 EGR 밸브의 위치 제어가 뒷받침 되어야 한다. 따라서 본 연구에서는 EGR 밸브 용 모터 특성 분석을 위해 수학적 모델링과 제어 이론에 대해 연구하고, 마이크로칩 개발 툴을 이용하여 EGR 밸브용 모터의 위치를 제어하기 위한 단계로서 PWM(Pulse Width Modulation)의 듀티(duty)비의 입력 값에 따른 밸브 위치를 측정하여 개폐 구간 별 EGR 밸브 모터 특성을 분석하였다.

• 한국연소학회:학술대회논문집
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• 대한연소학회 2003년도 제27회 KOSCO SYMPOSIUM 논문집
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• pp.251-256
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• 2003

The capability of pilot injection with small fuel quantity at all engine operating conditions is one of the main feature of the common rail system. The purpose of the pilot injection is to lower the engine noise and to reduce the NOx emissions. This study describes the pilot spray structure characteristics of the common-rail diesel injectors, solenoid-driven and piezo-driven type, with different electric driving characteristics So, three common-rail injectors with different electric current wave were used in this study. The pilot spray characteristics such as spray speed, spray tip penetration, and spray angle were obtained by spray images, which is measured by the back diffusion light illumination method with optical system for high-speed temporal photography. Also the CFD analysis was carried out for fuel behavior under high pressure in between needle and nozzle of solenoid-driven injector to know the condition of initial injection at experiment test. It was found that pilot injection of common-rail system was effected by rate of injection and temperature of injected fuel and electrical characteristic of the driven injector.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제44회 KOSCO SYMPOSIUM 초록집
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• pp.201-202
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• 2012

The isothermal flow structure and mixing characteristics of a hybrid/dual swirl jet combustor for micro-gas turbine were numerically investigated. Location of pilot nozzle, angle and direction of swirl vane were varied as main parameters with constant fuel flow rates for each nozzle. As a result, the variation in location of pilot nozzle resulted in significant change in turbulent flow field near burner exit, in particular, center toroidal recirculation zone (CTRZ) as well as turbulent intensity, and thus flame stability and emission characteristics might be significantly changed. The swirl angle of $45^{\circ}$ provided similar recirculating flow patterns in a wide range of equivalence ratio (0.5~1.0). Compared to the co-swirl flow, the counter-swirl flow leaded to the reduction in CTRZ and fuel-air mixing near the burner exit and a weak interaction between the pilot partially premixed flame and the lean premixed flame. With the comparison of experimental results, it was confirmed that the case of co-swirl flow and swirl $angle=45^{\circ}$ would provided an optimized combustor performance in terms of flame stability and pollutant emissions.