• 한국대기환경학회지
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• 제22권3호
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• pp.383-391
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• 2006

In Korea, the major source of serious air pollution is motor vehicles. Air pollution from vehicles has been annually increased. Then the government will try to control the vehicle emission by applying the effective emission management policy for the manufactured and in-used car. It is necessary to correctly calculate the emission factor for successful propulsion of the vehicle emission control policy. In this study, correlation analysis of exhaust emissions from vehicles between CVS-75 mode and Korea mode was conducted. A total of 25 light-duty buses were tested on the chassis dynamometer system in order to measure CO, HC, NOx PM and fuel efficiency (F.E.). For the test modes, 10 different Korea modes and CVS-75 mode were used. As the result of correlation analysis between those modes, most of the correlation coefficients were higher than 0.90. On the basis of high correlation between those modes, correction factors by driving conditions were estimated. Through the results of this study, we obtained essential basic data to correct difference from those modes.

• 한국연소학회지
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• 제14권4호
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• pp.25-32
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• 2009

In commercial combustion systems, heavy oil is one of main hydrocarbon fuel because of its economical efficiency. Regarding heavy oil combustion, due to increasing concerns over environmental pollutants such as carbon monoxide, unburned hydrocarbon and nitrogen oxides, development of low pollutant emission methods has become an imminent issue for practical application to numerous combustion devices. Also a great amount of effort has been tried to developed effective methods for practical using of biomass. It is also an important issue to reduce carbon tax. In this paper, an experimental study has been conducted to evaluate the effect of biomass reburning on NOx formation in a heavy oil flamed combustion furnace. Experiments were performed in flames stabilized by a multi-staged burner, which was mounted at the front of the furnace. Experimental tests were conducted using air-carried rice husk powder and LNG as the reburn fuel and heavy oil as the main fuel. The paper reports data on flue gas emissions and temperature distribution in the furnace for several kinds of experimental conditions. NOx concentration in the exhaust has decreased considerably due to effect of reburning. The maximum NOx reduction rate was 62% when the rice husk was used by reburn fuel, however it was 59% when the LNG was used by reburn fuel. The result shows the positive possibility of biomass reburning system for optimal NOx reduction.

• International Journal of Air-Conditioning and Refrigeration
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• 제17권2호
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• pp.52-60
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• 2009

The purpose of this research is to develop high efficiency plastic plate heat exchangers which can be substituted for conventional aluminum plate heat exchangers. Four simulation models of plastic plate heat exchangers are designed and simulated: that is, flat plate type, turbulent promoter type, corrugate type and dimple type heat exchanger. The flat plate type is designed as the reference model in order to evaluate how much thermal performance increases. The turbulent promoter type is fabricated with cylindrical-type vortex generators and rib-type turbulent promoters. The corrugate type is obtained from the conventional stainless steel compact heat exchangers, which are called the herringbone-type compact heat exchangers. The dimple type has a number of dimples on its surface. In this study, the flow and heat transfer characteristics of the plastic plate heat exchanger are investigated using numerical simulation and compared with experimental results. Numerical simulation is carried out using the FLUENT code. The flows are assumed as a three-dimensional, incompressible and turbulent model. The computational analysis and experimental results both show that the friction coefficient and Nu number is highest in the corrugate type. The tendency of numerical simulation results is in good agreement with that of the experimental results.

• 한국수소및신에너지학회논문집
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• 제29권5호
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• pp.538-548
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• 2018

The thermo-acoustic instability in the combustion process of a gas turbine is caused by the interaction of the heat release mechanism and the pressure perturbation. These acoustic vibrations cause fatigue failure of the combustor and decrease the combustion efficiency. This study is to develop a segmented dynamic thermo-acoustic model to understand combustion instability of gas turbine. Therefore, this study required a dynamic analysis rather than static analysis, and developed a segmented model that can analyze the performance of the system over time using the Matlab/Simulink. The developed model can confirm the thermo-acoustic combustion instability and exhaust gas concentration in the combustion chamber according to the equivalent ratio change, and confirm the thermo-acoustic combustion instability for the inlet temperature and the load changes. As a result, segmented dynamic thermo-acoustic model has been developed to analyze combustion instability under the operating condition.

• 전력전자학회논문지
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• 제15권6호
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• pp.460-465
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• 2010

최근 화석 연료의 고갈과 이산화탄소 배출 제한으로 인하여 내연기관 자동차에서 전기 자동차로의 대한 관심이 높아지고 있다. 전기 자동차 에너지 저장 요소인 배터리 충전에 필요한 AC-DC 컨버터가 필요하며 컨버터의 필요조건 으로 넓은 출력 전압 범위, 고효율, 높은 역률 등을 들수 있다. 넓은 전압 범위와 절연을 위해 2단 구성 하였다. 앞단은 LLC 컨버터를 후단은 역률을 고려 하여 BOOST 컨버터를 이용한 PFC 회로를 구현하여 실험적으로 확인 하였다.

• Ocean Systems Engineering
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• 제10권1호
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• pp.1-23
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• 2020

Hydrodynamic Drag of Surface combatants pose significant challenges with regard to fuel efficiency and exhaust emissions. Stern flaps have been used widely as an energy saving device, particularly by the US Navy (Hemanth et al. 2018a, Hemanth Kumar and Vijayakumar 2018b). In the present investigation the effect of flap turning angle on drag reduction is numerically and experimentally studied for a high-speed displacement surface combatant fitted with a stern flap in the Froude number range of 0.17-0.48. Parametric investigations are undertaken for constant chord length & span and varying turning angles of 5° 10° & 15°. Experimental resistance values in towing tank tests were validated with CFD. Investigations revealed that pressure increased as the flow velocity decreased with an increase in flap turning angle which was due to the centrifugal action of the flow caused by the induced concave curvature under the flap. There was no significant change in stern wave height but there was a gradual increase in the stern wave steepness with flap angle. Effective length of the vessel increased by lengthening of transom hollow. In low Froude number regime, flow was not influenced by flap curvature effects and pressure recovery was marginal. In the intermediate and high Froude number regimes pressure recovery increased with the flap turning angle and flow velocity.

• 한국기계가공학회지
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• 제9권5호
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• pp.64-69
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• 2010

This study is the machining of fuel supply pipe used in large vessels. The fuel supply pipe of large vessels have effects to reduce engine exhaust because of common rail system and show excellent fuel efficiency so it is in the limelight as a vessel engine of next generation. At present, the shape of fuel supply pipe of common rail used for huge two-stroke & low-speed vessels is like a peanut hole so the second machining is necessary after the first machining. There is high error rate for machining and the materials waste caused by machining error is serious. Also, in this time the request for increasing the length of fuel supply pipe is suggested in the world market, it's judged that current methods will show higher error rate for machining. Therefore, the purpose of this study is to improve the machining process used originally. For that, the system controlling the process was developed as well as surface roughness and straightness which are evaluation items of fuel supply pipe were measured so that improved process can be observed in real time.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제34회 춘계학술대회논문집
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• pp.81-84
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• 2010

본 연구에서는 과산화수소와 케로신을 추진제로 사용하는 로켓 엔진의 혼합비에 따른 연소특성을 파악하기 위해 동축 스월형의 단일 인젝터 로켓엔진을 설계 및 제작하여 연소실험을 수행하였다. 수류실험을 통해 설계/제작된 단일 인젝터의 분무 성능을 검증하였으며, 연소 시험은 혼합비에 따른 연소성능을 특성배기속도로 평가하였다. 연소 시험은 다양한 혼합비에서 성공적으로 수행되었으며, 설계점에서의 연소 효율이 약 95% 이상이었으며 연소실 압력 섭동도 매우 작은 것으로 확인되었다.

• 한국자동차공학회논문집
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• 제11권5호
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• pp.50-59
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• 2003

It was known that high pressure injection is an effective method to enhance thermal efficiency and decrease exhaust emissions in diesel engines. If injection pressure becomes ultra high, it is predicted that there may be a suitable injection pressure which the enhancement rate of spray characteristics is moderate. Also, there may be a limit injection pressure which spray characteristics is reversed and get worse. But these are unknown. To investigate a suitable injection pressure and a limit injection pressure, ultra high pressure injection equipment(UHPIE), which can realize the injection pressure of 3,200bar, was developed. UHPIE is a basic apparatus of single shot injection, and ultra high pressure was achieved by second stage rapid compression in short time. From the evaluation of UHPIE, a injection curve like a conventional diesel engine(jerk type) was realized. Also, it was proved that repetition of experiment was excellent. Therefore it was found that there was no problem to perform the study on the ultra high pressure injection with UHPIE. Consequently, the foundation of the study on ultra high pressure injection could be established.

• 한국수소및신에너지학회논문집
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• 제21권2호
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• pp.129-135
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• 2010

Homogeneous charge compression ignition (HCCI) engines have the potential to provide both diesel-like efficiency and very low emissions of nitrogen oxide (NOx) and particulate matter(PM). However, several technical issues still must be resolved before HCCI can see application. Among these, steep pressure-rise rate which leads to narrow operating range of HCCI engine continues to be a major issue. This work investigates the combination of two methods to mitigate the excessive pressure-rise rates at high power output, namely fuel stratification and Cooled exhaust-gas recirculation (Cooled EGR), after identifying the each effects to pressure-rise rate. When applying the fuel stratification to simulation, total fuelling width of 0.15 at BDC is set as a equivalent ratio difference based on the previous research. In order to simulate the effects of cooled EGR, $CO_2$ mole fraction in pre-mixture is changed ranging from 0 to 30%. DME which has a characteristic of two-stage ignition is used as a fuel.