• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1401-1406
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• 2004

In this paper, we present the theoretical and numerical results of scavenge characteristics in a small prechamber of an HCCI(Homogeneous Charge Compression Ignition) engine. Two theoretical models are proposed in prediction of the scavenge time and the efficiency ; one is the non-mixing models in which it is assumed that the input gas($CH_{4}$) and the existing gas(air) do not mix with each other, and the other is the fully-mixed model in which the two gases are assumed to mix completely before ejecting to the ambient air. Focus is also given to the effect on the scavenge performance of the size of the chamber oulet.

• Journal of computational fluids engineering
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• v.10 no.2
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• pp.21-29
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• 2005

In this paper, we present the theoretical and numerical results of scavenge characteristics in a small subchamber of an HCCI(Homogeneous Charge Compression Ignition) engine. Two theoretical models are proposed in prediction of the scavenge time and the efficiency; one is the non-mixing model in which the input gas(CH4) and the existing gas(air) do not mix at all, and the other is the fully-mixed model in which the two gases are assumed to mix completely before ejection. Focus is also given to the effect on the scavenge performance of the size of the chamber outlet.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.3
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• pp.445-452
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• 2020

The air cleaning unit of K00 IFV(or Infantry Fighting Vehicle) has important roles to make sure the engine of the vehicle works precisely as filtering foreign substances in the air such as dust and sands. The entire components including scavenge fan which is one of the important inner part of the air cleaning unit are developed so that we can produce it domestically and don't need to import it from P^⁎⁎ Co., the original maker in United Kingdom. This paper introduces a few verification processes including cleaning efficiency and reliability. As this core unit has developed successfully the improvement of military strength and logistics support can be expected. And design capability, manufacturing skills, maintenance ability of tracked weapon system will be increased thanks to the accumulated technical knowledge obtained from this developing project. Foreign currency savings and reducing operational cost can be expected as well in military industry.

• Atmosphere
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• v.29 no.5
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• pp.609-614
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• 2019

Cloud seeding experiment has been proposed as a way to alleviate severe air pollution problem because, if successful, artificially produced precipitation through cloud seeding could scavenge out some portion of air pollutants. As a first step to verify the practicality of such experiment, seedability of the clouds observed in Seoul is assessed by examining statistical characteristics of some relevant meteorological variables. Analyses of 9 years of Korea Meteorological Agency Seoul station data indicate that as PM₁₀ mass concentration increases, cloud amount, liquid water path, and ice water path decrease, but the difference between temperature and dew point temperature tends to increase. Such finding suggests that cloud seeding becomes less feasible as air pollution becomes more severe in the Seoul metropolitan area, at least in a statistical sense. For some individual severe air pollution events, however, seedable clouds may exist and indeed cloud seeding experiments can be successful. Therefore, detailed investigation on cloud seedability for individual severe air pollution events are highly required to make a concrete assessment of cloud seeding as a way to alleviate severe air pollution problem.

• 기계와재료
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• v.24 no.2
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• pp.18-26
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• 2012

지구 환경오염문제가 대두되면서 세계 각국에서는 환경오염을 최소화하려는 움직임이 활발히 이루어지고 있다. 국제해사기구(IMO)에서는 해양 대기오염의 상당량이 선박에서 배출되는 배기가스에 의한 것으로 판단하고 있으며, 이에 따라 선진국을 중심으로 선박관련 환경규제 및 선박 배기가스 배출기준을 점차적으로 강화해 가고 있고, 친환경 선박 및 기자재 개발을 적극적으로 진행하고 있다. 현재 선박에 적용 가능한 NOx 제거장치로는 ECR(Exhaust Gas Recirculation), SCR(Selective, Catalytic Reduction), SAM(Scavenge Air Moistening) 등이 개발되었으며, 연소온도 조절 및 촉매 환원반응 등을 이용하여 NOx를 제거하고 있다. 현재 개발된 탈질설비 중 현실적으로 가장 적합한 것은 SCR시스템으로 인식되고 있으나, 연료효율 감소로 인하여 가스연료를 이용하거나 새로운 연료개발 등 사용연료에 변화를 주는 방법들이 미래의 대안으로 제시되고 있다.

• Special Issue of the Society of Naval Architects of Korea
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• 2013.12a
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• pp.103-109
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• 2013

The Present work focuses on application of Organic Rankine Cycle - Waste heat Recovery System (ORC-WHRS) for marine diesel engine. ORC and its combined cycle with the engine were simulated and its performance was estimated theoretically under the various engine operation conditions and cooling water conditions. The working fluid, R245fa, was selected for the consideration of the heat source temperature, system efficiency and safety issues. According to the thermodynamic analysis, ~13.1% of system efficiency of the cycle was performed and it is about 4% of the mechanical power output of the considering Marine Diesel Engine. Also, addition of evaporator and pre-heater were studied to maximize output power of Organic Rankine Cycle as a waste heat recovery system of the marine diesel engine.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.5
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• pp.52-57
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• 2018

Most current ships have adopted on-board diesel generators to produce electricity, but the overall efficiency of equipment is down to about 50% due to thermal losses from operations such as exhaust gas, jacket water cooler, scavenge air cooler, etc. Recently, fuel cells have been highlighted as a promising technology to reduce the effect on the environment and have a higher efficiency. Therefore, this paper suggested a solid oxide fuel cell (SOFC)-gas turbine (GT) using waste heat from a SOFC and SOFC-GT-steam turbine (ST) with Rankine cycle. To compare both configurations, the fuel flow rate, current density, cell voltage, electrical power, and overall efficiency were evaluated at different operating loads. The overall efficiency of both SOFC hybrid systems was higher than the conventional system.

• Reproductive and Developmental Biology
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• v.31 no.1
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• pp.49-53
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• 2007

Astaxanthin is a kind of carotenoid compounds, having a antioxidant and anti-inflammatory activities. The antioxidative mechanism by which carotenoid scavenge free radicals has been clearly elucidated, but has not tried for the development of mammalian preimplantation embryo. This study was conducted to investigate the antioxidative effect of astaxanthin on in vitro development of porcine in vitro fertilized embryos. Porcine embryos derrived from in vitro fertilization (IVF) were cultured in 5% $CO_{2} in air at $38.5^{\circ}C$ in PZM-3 medium supplemented with different dosages of astaxanthin ($0,\;1,\;5\;and\;10{\mu}M$) and taurine (0, 1, 2.5 and 5 mM) as a positive control, and execute to compare the effects of various antioxidants such as taurine, melatonin and asculatin on in vitro development. The proportions of embryos developed to the blastocyst stage were increased when $1\;and\;5\;{\mu}M$ of astaxanthin (26.6 and 23.4%, respectively) and 1 and 2.5 mM taurine (25.8 and 26.4%, Respectively) were supplemented, compared to controls (p<0.05). Also, various antioxidant-treated groups were significantly higher rates of blastocysts (astaxanthin, 27.4%; taurine, 29.1%; melatonin, 26.8%; aesculetin, 27.9%, respectively) than control (18.8%). There was no difference in mean cell number of blastocysts between antioxidants and control. This result indicates that astaxanthin has an antioxidant feature when porcine IVF embryos were cultured in vitro.

• Journal of Power System Engineering
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• v.12 no.4
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• pp.5-11
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• 2008

The RI gasoline engine haying a sub-chamber had a high cycle variation due to the difficulty of the residual gas scavenge in the sub-chamber. To solve this problem and improve the combustion performance of RI engine, we devised a method to inject directly CNG fuel into the sub-chamber. A DI diesel engine of single cylinder was converted into a RI-CNG engine and an electronic control unit for the engine was manufactured. In this study, the combustion characteristics of the RI-CNG engine were investigated with the injection timings and air excess ratios at the load conditions of 50% throttle open rate and 1700rpm. As the results from this study, the RI-CNG engine worked reliably under the condition of the ignitable lean limit of $\lambda=1.7$ by showing the $COV_{imep}$ below about 5%. And the highest thermal efficiency could be obtained in the injection timing that produced the high imep and the low $COV_{imep}$ at the same time. The CO emission concentration indicated very low values and the THC and $NO_x$ showed an opposite pattern. With a view to improving the thermal efficiency and reducing the harmful emissions, the proper control region of the ignition timing and the mixture ratio were nearly ATDC $20^{\circ}\sim50^{\circ}$ and $\lambda=1.4$ respectively.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.7
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• pp.711-719
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• 2012

A thermodynamic analysis and a feasibility study on the organic Rankine cycle (ORC) as a waste heat recovery system for a marine diesel engine were carried out. The ORC and its combined cycle with the engine were simulated, and its performance was estimated theoretically using R245fa. A parametric study on the performance of the ORC system was carried out under different temperature conditions of the heat transfer loop and specification of the heat exchanger. According to the thermodynamic analysis, ~10% of the thermal efficiency of the cycle was able to be realized with the low temperature heat source below $250^{\circ}C$. The electric power output of the ORC was estimated to be about 4% of the mechanical power output of the engine, considering additional pumps for cooling water and circulation of the heat transfer medium. According to the present study, the electric power generated by the ORC is about 59%-69% of the required power, and it is possible to reduce the fuel consumption under normal seagoing conditions.