• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 춘계학술대회
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• pp.339-344
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• 2005

A PEMFC system model for FCEV was constructed and simulated numerically to examine the heat/water flow of the system and air/fuel humidification process for various operation conditions (ambient pressure /temperature/humidity, operating temperature, power load). We modeled PEMFC stack which can generate maximum electricity of about 80 kW. This stack consists of 400 unit cells and each unit cell has $250cm^2$ reacting area. Uniform current density and uniform operating voltage per each cell was assumed. The results show the flow characteristics of heat and water at each component of PEMFC system in macro-scale. The capacity shortage of the radiator occurred when the ambient was hot $(over\;40^{\circ}C)$ and power level was high (over 50 kW). In spite of some heat release by evaporation of water in stack, heat unbalance reached to 20kW approximately in such a severe operating condition. This heat unbalance could be recovered by auxiliary radiators or high speed cooling fan with additional cost. In cold environment, the capacity of radiator exceeded the net heat generation to be released, which may cause a problem to drop the operating temperature of stack. We dealt with this problem by regulating mass flow rate of coolant and radiator fan speed. Finally, water balance was not easily broken when we retrieved condensed and/or unused water.

• 한국자동차공학회논문집
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• 제10권1호
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• pp.17-23
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• 2002

In order to reduce exhaust emissions from diesel engine under wide operating range, an experimental study based on a new concept of combustion called HCDC(Homogeneous Charge Diesel Combustion) was conducted. In this concept, most of the fuel is supplied as premixed homogeneous charge and the rest is directly injected into a cylinder to ignite. In this study we compared combustion characteristics of an HCDC engine with those of conventional diesel engines. At high premixed fuel ratio and high load range, it was observed that premixed combustion heat release rate was low and diffusion combustion duration was shorten. from this experiment, it was found that NOx is reduced by the lower maximum temperature and soot is reduced by rapid combustion during diffusion combustion phase.

• 대한기계학회논문집B
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• 제32권7호
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• pp.513-517
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• 2008

A parametric study was made to understand the fundamentals of combustion of CNG fuel in a constant volume chamber in the respect of swirl effect, and the numbers of spark ignition. Optical devices were applied for the visualization of the physics of combustion, and combustion pressures and exhaust emission were measured at several equivalence ratios by controlling speeds of a swirling motor. When the speed of a swirling motor was raised the combustion conditions were improved. The corresponding maximum combustion pressure and heat release rate were increased and the speed of flame propagation was getting faster. This research may contribute to improve the performance of CNG engine and reduce emissions in future.

• 설비공학논문집
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• 제14권3호
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• pp.247-253
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• 2002

In this study, reduced-scale experiments were conducted to analyze smoke movement in tunnel fire with roof vent. The 1/20 scale experiments were carried out under the Froude scaling using gasoline pool fire ranging from 7.3 to 15.4 cm in diameter with total heat release rate from 1.0 to 8.46kw. In case of 1 m high vent, smoke front reached to the tunnel exit at about 16 sec delayed with ventilation. The delay time grew longer with the vent height. The temperature after the vent was lower than that without the vent. The exit temperature declined maximum of $20^{\circ}C$ after passing the vent. It was confirmed that the thickness of smoke layer was maintained uniformly under the 25% height of the tunnel through the visualized smoke now by a laser sheet and the digital camcorder.

• 오토저널
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• 제10권3호
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• pp.45-50
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• 1988

The measurement system of the pressure in engine cylinder is developed with the aids of the microcomputer, A/D converter and simple electrical circuits. The experiment is performed in 4 cycle single cylinder Gasoline engine. When data for the pressure progress is sampled, clock signal or signal from the crank angle is used as trigger. The variation of the pressure during the cycles can be well obtained experimentally. So, the informations which are necessary in the combustion analysis, i.e. expansion pressure, indicated mean effective pressure, the magnitude and time of the maximum pressure ignition time, the rate of pressure rise and heat release and combustion rates can be obtained by the calculation using experimental data. Also, the informations about the after-burning process, the existence of the detonation waves and end time of combustion can be investigated from this study.

• 터널과지하공간
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• 제20권2호
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• pp.92-96
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• 2010

본 연구에서는 지하공간에서 화재 발생시 배연장비의 연기배출 성능을 평가하기 위하여 실험을 실시하였다. 배연장비로는 이동식 송풍기를 사용하였으며 가연물질로는 에탄올을 사용하였다. 한 변의 길이가 80cm의 정사각형 화원을 사용하였으며 최대 열방출률은 약 460 kW이다. 급기방식 배연의 영향을 평가하였다. 급기방식의 경우 실내의 가시도 향상 및 온도감소 효과를 확인할 수 있었다.

• 한국안전학회지
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• 제32권5호
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• pp.32-40
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• 2017

The current status of Performance-Based Design (PBD) implemented in 4 wide areas (Seoul, Gyeonggi, Incheon and Busan) over the past 5 years was reviewed with regard to the number of PBD implementation and target buildings. Then, detailed status related to fire scenarios, input information for fire simulation, and grid size were analyzed with the pre-review for the PBD. As a result, the domestic PBD was mainly applied to the mixed occupancy. In the fire simulations performed on the identical fire scenario and fire space, the maximum heat release rate (HRR) varied significantly depending on the PBD designer. Various combustibles were also considered for the identical fire source, and their combustion properties also showed considerable uncertainty. In addition, the applicability of accurate input information for predictive models of heat and smoke detectors was examined. Finally, the average grid size for the fire simulation using Fire Dynamics Simulator (FDS) was analyzed, and the improvement of PBD to minimize designer dependency was proposed.

• 한국자동차공학회논문집
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• 제3권5호
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• pp.122-134
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• 1995

The present study was investigated combustion characteristics of methane-air mixtures at stratified charge in a constant volume combustion chamber. The main results obtained from this study can be summarized as follows. In case of ${\phi}_s=1.0$, total burning times greatly affected rather than initial time of pressure increase and maximum combustion pressure. In case of ${\phi}_t=1.0$, initial time of pressure increase and total burning times were affected considerably in comparison with the case of ${\phi}_s=1.0$. Also, even the very lean mixture which total equivalence ratio is ${\phi}_t=0.69$(${\phi}_s=1.0$, ${\phi}_m=0.65$), by changing configuration of the critical passage-hole and using a stratified mixture, it is possible to decrease substantially the initial time of pressure increase. total burning times and NOx concentration without deteriorating combustion characteristics such as maximum combustion pressure, rate of heat release etc. in comparison with the use of single chamber(in case of ${\phi}=1.0$) only. Specifically, our trends were revealed remarkably in the case of Type D which is reduced a flame contact area of sub-chamber side of the passage-hole.

• Advances in nano research
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• 제16권2호
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• pp.127-140
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• 2024

Upon direct/indirect exposure to flame or heat, composite structures may burn or thermally buckle. This issue becomes more important in the natural fiber-based composite structures with higher flammability and lower mechanical properties. The main goal of the present study was to obtain an optimal eco-friendly composite system with low flammability and high thermal buckling resistance. The studied composite consisted of polypropylene (PP) and short abaca fiber (AF) with eggshell powder (ESP) and halloysite clay nanotubes (HNTs) additives. An optimal base composite, consisting of 30 wt.% AF and 70 wt.% PP, abbreviated as OAP, was initially introduced based on burning rate (BR) and the Young's modulus determined by horizontal burning test (HBT) and tensile test, respectively. The effects of adding ESP to the base composite were then investigated with the same experimental tests. The results indicated that though the BR significantly decreased with the increase of ESP content up to 6 wt.%, it had a very destructive influence on the stiffness of the composite. To compensate for the damaging effect of ESP, small amount of HNT was used. The performance of OAP composite with 6 wt.% ESP and 3 wt.% HNT (OAPEH) was explored by conducting HBT, cone calorimeter test (CCT) and tensile test. The experimental results indicated a 9~23 % reduction in almost all flammability parameters such as heat release rate (HRR), total heat released (THR), maximum average rate of heat emission (MARHE), total smoke released (TSR), total smoke production (TSP), and mass loss (ML) during combustion. Furthermore, the combination of 6 wt.% ESP and 3 wt.% HNT reduced the stiffness of OAP to an insignificant amount by maximum 3%. Moreover, the char residue analysis revealed the distinct differences in the formation of char between AF/PP and AF/PP/ESP/HNT composites. Afterward, dilatometry test was carried out to examine the coefficient of thermal expansion (CTE) of OAP and OAPEH samples. The obtained results showed that the CTE of OAPEH composite was about 18% less than that of OAP. Finally, a theoretical model was used based on first-order shear deformation theory (FSDT) to predict the critical bucking temperatures of the OAP and OAPEH composite plates. It was shown that in the absence of mechanical load, the critical buckling temperatures of OAPEH composite plates were higher than those of OAP composites, such that the difference between the buckling temperatures increased with the increase of thickness. On the contrary, the positive effect of CTE reduction on the buckling temperature decreased by raising the axial compressive mechanical load on the composite plates which can be assigned to the reduction of stiffness after the incorporation of ESP. The results of present study generally stated that a suitable combination of AF, PP, ESP, and HNT can result in a relatively optimal and environmentally friendly composite with proper flame and thermal buckling resistance with no significant decline in the stiffness.

• Journal of Advanced Marine Engineering and Technology
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• 제38권7호
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• pp.868-876
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• 2014

본 논문에서는 함정에 탑재된 추진용 엔진에 사용되는 디젤연료(MDO)의 분사상태를 가시화가 가능한 단기통 디젤엔진에 적용시켜 전 후 분사시기에 따른 연소특성, 일산화탄소(CO) 및 탄화수소(HC) 배출특성을 규명하고, 연소과정의 가시화를 통하여 연소특성을 분석하는데 초점을 두었다. 전 분사시기가 주 분사시기 쪽으로 지연될수록 실린더 내부 평균유효압력($P_{me}$) 및 최고압력($P_m$)은 상승했으나, 주 분사의 방열율은 저감되고, 일산화탄소 및 탄화수소의 발생량 또한 감소하였다. 후 분사시기가 빨라질 경우 주 분사에 의해 형성된 고온, 고압 하에서 연소가 이루어짐에 따라 실린더 내부 평균유효압력 및 최고압력은 증가하였고, 일산화탄소 및 탄화수소 배출수준 또한 증가하였다. 연소과정을 분석한 결과, 전 분사시기가 늦어질수록 주 분사 시 발생되는 착화지연은 매우 짧아지며, 화염강도는 매우 상승하였다. 분사시기에 관계없이 후 분사 시 착화지연 현상은 발생하지 않았으며, 후 분사시기가 늦어질수록 화염의 강도는 점점 떨어졌다.