• 한국주조공학회지
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• 제29권3호
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• pp.138-143
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• 2009

Vacuum suction is applied to the mold during pouring in the inclined gravity die casting to remove defects such as misrun and gas porosity in the brake master cylinder. Casting defects are observed after solidification and their cause is analyzed by using the calculated results with commercial solidification and flow analysis code(ZCAST). The optimum vacuum suction is -2 cmHg, and when the start time of vacuum suction is 3 seconds after pouring, better filled result is obtained by holding it for 15 seconds. Reproducibility test under the optimum conditions attained from the above pouring tests is performed, and it is confirmed that these pouring conditions can be applied to the mass production immediately.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제23회 추계학술대회 논문집
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• pp.189-192
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• 2004

소형 액체로켓엔진의 냉각특성 연구를 위한 연소시험장치를 개발하였다. 본 연소시험장치는 물과 kerosene 냉각이 가능하며, 특히 재생냉각이 가능하도록 설계되었다. 시험에 사용되는 연소기는 혼합기, 점화기, 실린더 및 노즐부가 각각 분리되어 개별 냉각이 가능하도록 설계되었다. 현재 본 연소 시험장치를 이용한 소형 액체로켓엔진의 물 냉각 및 kerosene 냉각 시험이 수행 중에 있으며, 향후 LNG(Liquefied Natural Gas) 및 기체 메탄을 이용한 재생냉각이 가능하도록 시험장치를 개량할 예정이다.

• 설비공학논문집
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• 제20권10호
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• pp.637-644
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• 2008

Auxiliary port which had been known to be used to reduce the expansion loss of a refrigeration system was applied to a R134a reciprocating compressor in a household refrigerator cycle with an intention of improving the compressor performance. Effects of the auxiliary port on the compressor performance was investigated by a computer simulation program. When a simple hole was made on the side wall of the cylinder as an auxiliary port and surrounding gas inside the compressor shell was assumed to be drawn into the cylinder through the hole, maximum COP improvement of 1.66% was obtained. With auxiliary port equipped with a plate type of check valve, maximum COP was raised to be 1.99%. COP improvement was more distinctive with decreasing the discharge pressure; COP improvement was 5% with discharge pressure of 7 bar.

• 한국재난정보학회 논문집
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• 제16권1호
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• pp.44-59
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• 2020

이 논문에서는 2층 건물 지하층의 다방에서 가스냄새가 난다고 119신고가 되어 소방대원들이 출동하여 옥상에 있는 LPG 가스통들의 밸브를 직접 잠그고 지하층 다방의 중간밸브의 잠금 상태를 확인하고 현장에 도착한 가스공급 및 설치 업자에게 안전조치를 취하도록 요구하고 철수한 후 7분 만에 가스폭발사고가 발생하여 2명이 사망하고 21명이 부상을 입은 사례를 분석하고 있다. 법원은 가스폭발사고의 원인이 규명되지 아니하였으므로 가스공급 및 설치 업자와 한국가스안전공사에 배상 책임을 물을 수 없고 안전조치를 하지 않고 철수한 소방기관에게만 배상책임이 있다고 판결하였다. 그러므로 가스가 누설된다고 119신고가 되는 경우에 출동한 소방대는 가스 밸브를 잠그고 사람들을 대피시키거나 접근하지 못하게 하고 환기를 시키는 등 안전조치를 하고 화재나 폭발가능성이 없음을 확인한 후 철수해야 한다.

• 한국자동차공학회논문집
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• 제19권1호
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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.

• 한국수소및신에너지학회논문집
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• 제13권1호
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• pp.83-89
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• 2002

The goal of this research is to understand the NOx emission in direct injected diesel engine with premixed hydrogen fuel. Hydrogen fuel was supplied into the test engine through the intake pipe. Amount of hydrogen-supplemented fuel was 70 % basis on heating value of the total input fuel. The effects of intake air temperature and exhaust gas recirculation(EGR) on NOx emission were studied. The intake air temperatures were varied from $23^{\circ}C$ to $0^{\circ}C$ by using liquid nitrogen. Also, the exhaust gas was recirculated to the intake manifold and the amount of exhaust gas was controlled by the valve. The major conclusions of this work include: ( i ) nitrogen concentrations in the intake pipe were increased by 30% and cylinder gas temperature was decreased by 24% as the intake air temperature were changed from $23^{\circ}C$ to $0^{\circ}C$; ( ii ) NOx emission per unit heating value of supplied fuel was decreased by 45% with same decrease of intake air temperature; and (iii) NOx emission was decreased by 77% with 30% of EGR ratio. Therefore, it may be concluded that EGR is effective method to lower NOx emission in hydrogen fueled engine.

• 한국자동차공학회논문집
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• 제10권1호
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• pp.24-31
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• 2002

An experimental study was conducted to investigate the effects of EGR (Exhaust Gas Recirculation) variables on performance and emission characteristics in a 2-liter 4-cylinder spark-ignition LPG fuelled engine. The effects of EGR on the reduction of thermal loading at exhaust manifold were also investigated because the reduced gas temperature is desirable for the reliability of an engine in light of both thermal efficiency and material issue of exhaust manifold. The steady-state tests show that the brake thermal efficiency increased and the brake specific fuel consumption decreased with the increase of EGR rate in hot EGR and with the decrease of EGR temperature in case of cooled EGR, while the stable combustion was maintained. The increase of EGR rate or the decrease of EGR temperature results in the reduction of NOx emission even in the increase of HC emission. Furthermore, decreasing EGR temperature by $180^{\circ}C$ enabled the reduction of exhaust gas temperature by $15^{\circ}C$ in cooled EGR test at 1600rpm/370kPa BMEP operation, and consequently the reduction of thermal load at exhaust. The optimization strategy of EGR application is to be discussed by the investigation on the effect of geometrical characteristics of EGR-supplying pipe line.

• Journal of Advanced Marine Engineering and Technology
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• 제24권2호
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• pp.57-62
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• 2000

The effect of exhaust gas recirculation(EGR) on the characteristics of exhaust gas emissions, and SFC are experimentally investigated by four-cylinder, four-cycle and direct injection marine diesel engine. In order to reduce the soot contents in the recirculated exhaust gas to intake system of the engines, a soot removal system of a cylinderical-type scrubber is specially designed and manufactured for the experimental system. (1) SFC is increased in downward convex curve style with increasing excess air ratio, it is increased with increasing EGR rate at the same excess air ratio. (2) NOx emission is reduced in downward convex curve style with increasing excess air ratio, it is reduced with increasing EGR rate at the same excess air ratio. (3) Soot emission is decreased in downward convex curve style with increasing excess air ratio, it is reduced with increasing EGR rate at the same excess air ratio. (4) CO emission is increased in nearly straight line style with increasing excess air ratio, it is increased with increasing EGR rate at the same excess air ratio. (5) HC emission is not constant tendency with increasing excess air ratio, it is increased with increasing EGR rate at the same excess air ratio.

• 한국자동차공학회논문집
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• 제20권5호
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• pp.13-18
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• 2012

This research is about the exhaust gas and driving performance test which are for CNG-Diesel dual fuel engine. The CNG-Diesel dual fuel engine converted from 2500cc diesel has two steps of injection systems; small amount of diesel is injected to mixture CNG in cylinder to ignite before CNG is injected into each intake manifold to form mixture. The amounts of output power and emission in duel fuel consumption were measured by engine dynamometer and exhaust gas analyzer. Over 90% of diesel consumption reduction, similar driving performance to current diesel engine and reduced emission on $CO_2$ and PM, respectively, were indicated through the measurements. The two steps of system were applied to vehicle to investigate exhaust gas characteristics and driving performance via NEDC mode and real driving test. Additional oxidation catalyst was applied to reduce emission on the test vehicle and the NEDC mode test showed the reduction of Co, $CO_2$, Pm and THC.

• 한국자동차공학회논문집
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• 제3권6호
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• pp.238-249
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• 1995

The gas pressure acting on the rings in internal combustion engine influences the friction and wear characteristics. Inter-ring pressure variation during engine operation results from cylinder gas flow through a piston-ring pack. The flow passages consist of ring end gaps and clearances between the ring and the piston groove. The gas flow in the clearance between the ring and the groove is directly affected by the axial motion of the ring in the groove. In this paper the asperity contact force is newly considered in the prediction of the clearence between the ring and the groove surface. This term must be taken into account physically in case that the clearance get narrow rather than asperity height between the ring and the groove surface. Finally, comparisons of calculated inter-ring gas pressures based on the analytical method are made with the measured ones. The agereement was found to be good below midium engine speed, 3000rpm. In order to obtain accurate analytical results to the extend of high rpm range, it is recommended to include oil ring motion as well as top and second ring in analytical model.