• 한국화재소방학회논문지
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• 제30권2호
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• pp.92-97
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• 2016

본 연구는 필드모델에서 소모된 연료에 기초하여 화학적 화염높이를 산정하기 위한 방법을 검토하고자 한다. 높이 방향으로 HRRPUL의 누적값과 연료농도에 따른 계산 알고리즘을 FDS 해석결과에 적용하였으며 평균화학적 화염높이는 알고리즘을 적용한 순간화염높이의 시간평균을 통해 산정하였다. 연료농도에 기초한 평균화염높이는 HRRPUL의 누적값에 의해 계산된 화염높이와 10% 이내의 상향예측범위에서 일치된 결과를 보였다. 이러한 연구는 전산화재해석모델에서 정량적인 화염높이를 산정하고 보다 상세한 화재거동특성을 이해하는데 기여하고자 한다.

• 대한조선학회논문집
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• 제45권4호
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• pp.345-352
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• 2008

The motion of a projectile initiated by the release of highly pressurized air is simulated presuming the flow field as a two dimensional one. The effects of water compressibility on projectile movements are investigated, comparing results based on the Fluent VOF model where water is treated as an incompressible medium with those from the presently developed VOF scheme. The present model considers compressibility of both air and water. The Fluent results show that the body moves farther and at higher speeds than the present ones. As time proceeds, the relative difference of speed and displacement between the two results drops substantially, after acoustic waves in water traverse and return the full length of the tube several times. To estimate instantaneous accelerations, however, requires implementation of the water compressibility effect as discrepancies between them do not decrease even after several pressure wave cycles.

• 수산해양교육연구
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• 제28권4호
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• pp.1143-1151
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• 2016

To study the dispersion process and residence time of anthropogenic pollutant in Masan bay, a three-dimensional hydrodynamic model coupled to a particle tracking model, EFDC, is applied. Particle tracking model simulated the instantaneous release of particles emulating discharge from river and wastewater treatment plant to show the behaviour of pollutant in terms of water circulation and water exchange. Modelled outcomes for water circulation were in good agreement with tidal elevation and current data. The results of particle tracking model show that over half of particles released from northern Masan bay transport to out of area while the particles from Dukdong wastewater treatment plant transport to northern area. This meant pollution source from inside and outside of the northern area can affect water quality of northern Masan bay.

• 한국화재소방학회논문지
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• 제18권2호
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• pp.57-67
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• 2004

Diesel 버스가 대체적으로 주류를 이루는 일반버스들에 대한 위험도 평가결과 첫째, 순간적인 누출이 일어날 빈도는 1.4E-3/bus/year이었으며, 이로 인한 하부사상으로 Fireball의 결과를 초래할 확률은 1.7E-4이었다. 또한 그 중 CNG 버스에서 순간적인 누출이 일어날 수치는 0.002 event/year로 나타났다. 둘째, 균열에 기인되어 점차적인 누설이 일어날 빈도는 3.7E-s/year로 평가되었으며, 이에 대한 하부사상으로서 jet flame의 결과를 초래할 확률은 1.2E-3으로 나타났다. 또한 CNG 버스에서 점차적인 누출이 일어날 수치는 0.04 event/year이었다. 아울러 피해 예측 면에서 CNG버스와 디젤버스의 운송거리에 대해 화재 사상자들을 비교하였을 때, 디젤버스는 0.091 Fire fatalities/100-million miles이었으며, CNG버스는 대략 0.17 Fire fatalities/100-million miles이었다. 이 의미는 화재로 인한 치명적인 사상자수를 비교했을 때 CNG버스는 디젤버스에 비해 평균 두 배가 위험하다는 것을 보여 주는 것이고, 결국 CNG버스들이 디젤버스들에 비해 주요 화재에 대해 민감하다는 것을 말해 주는 것이다. 본 연구에서 CNG버스들의 위험도를 평가하기 위해 사용된 총칭적인 모델들과 고장 데이터들은 적정하다. 그러나 CNG버스와 관련된 연구에 있어서 더욱 더 정확한 결과를 제공하기 위해서는 향후 더 정확한 물리적인 면에 기초한 모델들과 CNG버스에 대한 자료 확충 및 데이터베이스화가 요구된다.

• 한국자동차공학회논문집
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• 제22권2호
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• pp.60-66
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• 2014

A control oriented model of the Lean $NO_x$ trap (LNT) was developed to determine the timing of $NO_x$ regeneration. The LNT model consists of $NO_x$ storage and reduction model. Once $NO_x$ is stored ($NO_x$ storage model), at the right timing $NO_x$ should be released and then reduced ($NO_x$ reduction model) with reductants on the catalyst active sites, called regeneration. The $NO_x$ storage model simulates the degree of stored $NO_x$ in the LNT. It is structured by an instantaneous $NO_x$ storage efficiency and the $NO_x$ storage capacity model. The $NO_x$ storge capacity model was modeled to have a Gaussian distribution with a function of exhaust gas temperature. $NO_x$ release and reduction reactions for the $NO_x$ reduction model were modeled as Arrhenius equations. The parameter identification was optimally performed by the data of the bench flow reactor test results at space velocity 50,000/hr, 80,000/hr, and temperature of $250-500^{\circ}C$. The LNT model state, storage fraction indicates the degree of stored $NO_x$ in the LNT and thus, the timing of the regeneration can be determined based on it. For practical purpose, this model will be verified more completely by engine test data which simulate the NEDC transient mode.

• International Journal of Automotive Technology
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• 제8권4호
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• pp.437-444
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• 2007

This paper experimentally investigates the effects of oxygen-enriched air (OEA) on the running behaviors of an LPG SI engine during both start/warm-up (SW) and hot idling (HI) stages. The experiments were performed on an air-cooled, single-cylinder, 4-stroke, LPG SI engine with an electronic fuel injection system and an electrically-heated oxygen sensor. OEA containing 23% and 25% oxygen (by volume) was supplied for the experiments. The throttle position was fixed at that of idle condition. A fueling strategy was used as following: the fuel injection pulse width (FIPW) in the first cycle of injection was set 5.05 ms, and 2.6 ms in the subsequent cycles till the achieving of closed-loop control. In closed-loop mode, the FIPW was adjusted by the ECU in terms of the oxygen sensor feedback. Instantaneous engine speed, cylinder pressure, engine-out time-resolved HC, CO and NOx emissions and excess air coefficient (EAC) were measured and compared to the intake air baseline (ambient air, 21% oxygen). The results show that during SW stage, with the increase in the oxygen concentration in the intake air, the EAC of the mixture is much closer to the stoichiometric one and more oxygen is made available for oxidation, which results in evidently-improved combustion. The ignition in the first firing cycle starts earlier and peak pressure and maximum heat release rate both notably increase. The maximum engine speed is elevated and HC and CO emissions are reduced considerably. The percent reductions in HC emissions are about 48% and 68% in CO emissions about 52% and 78%; with 23% and 25% OEA, respectively, compared to ambient air. During HI stage, with OEA, the fuel amount per cycle increases due to closed-loop control, the engine speed rises, and speed stability is improved. The HC emissions notably decrease: about 60% and 80% with 23% and 25% OEA, respectively, compared to ambient air. The CO emissions remain at the same low level as with ambient air. During both SW and HI stages, intake air oxygen enrichment causes the delay of spark timing and the increased NOx emissions.