• 대한설비공학회지:설비저널
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• 제17권4호
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• pp.418-425
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• 1988

종래의 전통적인 컴퓨터 프로그램에서는 속도 경계조건만을 처리할 수 있으며, 크린룸에서와 같이 넓은 출입구가 존재하는 실제적인 유동통로에서 이 속도 경계조건을 부여하기 위한 실제 속도의 측정은 간단하지 않다. 그렇다고 경계에서의 속도 분포를 가정하는 것은 물리적으로 타당하지 않는 상황을 의미할 수도 있다. 이러한 동기에서 본 연구에서는 비교적 측정이 쉬운 압력이 경계조건으로 알려졌을 때 공간 내부의 유동을 예측할 수 있는 컴퓨터 프로그램을 고안하여 문제를 해석하였다. 여기에서의 속도 경계조건은 다만 점착조건과 문제를 확정시키기 위하여 입구에서의 단면 방향 속도를 영으로 둔 것 뿐이다. 본 연구의 결과는 실용적으로 많이 이용되고 있는 간단한 Bernoulli 방정식에 의한 예측치와 비교되었으며 5% 이내의 차이로 정량적인 일치를 보았으며 이로써 본 연구의 타당성을 입증할 수 있었다. 본 연구에서는 유입구와 2개의 유출구에 압력경계조건이 부여된 크린룸 내부의 공기유동을 수치적으로 예측하고자 하였다. 유입구의 정압이 상대적으로 낮은 값을 가지는 왼쪽 유출구의 정압보다 150[Pa] 높은 경우에 왼쪽 유출구의 정압은 고정시키고 오른쪽 유출구의 정압을 0~150[Pa] 범위에서 25[Pa] 간격으로 변화시켜가면서 각 경우에 대한 크린룸내부의 유동특성과 유입구의 속도분포 그리고 2개 유출구에서의 유량분배와 크린룸 내부의 유동특성을 예측하였다. 상대적으로 높은 정압이 부여된 오른쪽 유출구로의 유량배분은 이 유출구에 부여되는 정압이 커짐에 따라 선형적으로 감소되었으나 유입구에서 역류가 형성될 수 있을 만큼 정압이 증가된 후에는 유량배분이 급격히 감소되었다.

• 한국수소및신에너지학회논문집
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• 제35권3호
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• pp.300-309
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• 2024

Hydrogen utilization in the transportation sector, which relies on fossil fuels, can significantly reduce greenhouse gas by using to hydrogen fuel cell vehicles, and its adoption depends performance of hydrogen refueling station. The present study developed a model to simulate the back-to-back filling process of heavy duty hydrogen fuel cell vehicles at hydrogen refueling stations using a cascade method. And its quantitatively evaluated hydrogen refueling station performance by simulating various mass flow rates and storage tank capacity combinations, analyzing vehicle state of charge (SOC) of vehicles. In the cascade refueling system, the capacity of the high-pressure storage tank was found to have the greatest impact on the reduction of filling time and improvement of efficiency.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2003년도 추계학술대회 논문집
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• pp.99-102
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• 2003

PIV(Particle Image Velocimetry)was used to visualize the interaction of reed valve of the reciprocating compressor. The valve is the key part which governs the efficiency, noise and reliability of the compressor, so the development of analytical model about valve performance is necessary. As the valve reed is opened and closed by pressure pulsation, the flow characteristic of the refrigerant passing the valve is very important. In the present study, a circular disk with inclination is assumed to be the valve reed of a reciprocating compressor, The mean velocity shows the vortical characteristic of this flow. It is found that the back flow is affected by the height of reed valve of reciprocating compressor.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.291-294
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• 2006

Exhaust system of steam turbines consists of an annular diffuser and a collector and connects the last stage turbine and the condenser. The system is used to transfer the turbine leaving kinetic energy to potential energy while guiding the flow from turbine exit plane to the downstream condenser. In the steam turbine exhaust system, distorted pressure profile is arisen by the nonaxisymmetric collector structure at the diffuser outlet, and this distorted pressure is propagated to the last stage LP turbine exit plane through the diffuser, then the last stage LP turbine experiences asymmetric back pressure. It is known that the pressure recovery performance of diffuser is strongly influenced by diffuser inflow condition. In this study, the effect of exhaust system due to the changing of inlet flow condition is observed by using CFD, and the interaction of last stage LP turbine and exhaust system is investigated by using actuator disk model as modeling of turbine blade row of exhaust hood inlet.

• Wind and Structures
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• 제20권3호
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• pp.449-468
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• 2015

Current wind-resistance designs of large-scale indirect dry cooling towers (IDCTs) exclude an important factor: the influence of the ventilation rate for radiator shutter on wind loads on the outer surfaces of the tower shell. More seemingly overlooked aspects are the effects of various ventilation rates on the wind pressure distribution on the tower surfaces of two IDCTs, and the feature of the flow field around them. In order to investigate the effects of the radiator shutter ventilation rates on the aerodynamic interference between IDCTs, this paper established the numerical wind tunnel model based on the Computational Fluid Dynamic (CFD) technology, and analyzed the influences of various radiator shutter ventilation rates on the aerodynamic loads acting upon a single and two extra-large IDCTs during building, installation, and operation stages. Through the comparison with the results of physical wind tunnel test and different design codes, the results indicated that: the influence of the ventilation rate on the flow field and shape coefficients on the outer surface of a single IDCT is weak, and the curve of mean shape coefficients is close to the reference curve provided by the current design code. In a two-tower combination, the ventilation rate significantly affects the downwind surface of the front tower and the upwind surface of the back tower, and the larger positive pressure shifts down along the upwind surface of the back tower as the ventilation rate increases. The ventilation rate significantly influences the drag force coefficient of the back tower in a two-tower combination, the drag force coefficient increases with the ventilation rate and reaches the maximum in a building status of full ventilation, and the maximum drag coefficient is 11% greater than that with complete closure.

• 한국대기환경학회지
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• 제14권6호
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• pp.599-606
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• 1998

Removal of toluene vapor from airstreams was studied in a biological reactor known as a biofilter. The biofilter was packed porous ceramic inoculated with thickened activated sludge (MLVSS 17,683 mg/L). The lab-scale biofilter was operated for 42 days under various experimental conditions including inlet toluene concentrations and flow rates of the contaminated air streams. Removal efficiency reached up 96.6% after 4 days from start up. Nutrient limitation was proposed as a reason for the decrease in biofilter performence. Biofilter performance decreased substantially, coincident with the buildup of back pressure due to accumulation of excess VSS within the medium bed. Practically, the bed needs to be backwashed when the overall pressure drop is greater than 460.6 Pa at SV (Space Velocity) 100 h-1. Periodic backwashing of the biofilter was necessary for removing excess biomass and attaining stable long -term high removal efficiency The removal efficiency of toluene in the biofilter decreased as the gas velocity and toluene concentration in the inlet gas increased. The maximum elimination capacity of ceramic biofilter could reach up to 444.85 g/m3. hr. When the loading of toluene exceed this critical value, substrate inhibition occurred.

• Journal of Advanced Marine Engineering and Technology
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• 제38권1호
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• pp.15-22
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• 2014

엔진 배기 저감이나 열효율 향상을 위하여 배기관에 많은 장치들이 부착되고 있다. 이러한 장치들은 배기구의 개도면적을 줄이게 되고 배기 압력을 증가시킨다. 배기압력의 증가는 원활한 가스 교환을 방해하여 엔진 성능이 저하되는 원인이 된다. 그러나 적당한 배압의 증가는 잔류가스의 효과에 의하여 질소산화물을 감소시킬 수 있다. 본 연구에서는 배기 압력 증가가 엔진 성능에 미치는 영향을 평가하기 위하여 배기관 끝단의 개도량을 변화시켜 배기 압력을 조절하면서 엔진 실험을 수행하였다. 실험 결과 무부하에서 배압이 미소하게 증가된 경우에 연료 소모율이 저감되고 동시에 질소산화물이 저감되었지만 과도하게 배압이 증가하는 경우에는 연소의 악화로 유해 배기가스가 크게 증가되었다.

• 한국생산제조학회지
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• 제20권2호
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• pp.151-156
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• 2011

This study examined the casting analysis of fuel pressure regulator of LPI vehicles. We aims to predict all the phenomenon accompanied by flow and solidification in die casting, and maximize productivity and quality through optimal casting design. As a result of comparing Types A and B of casting design, it was found that the number of overflow affected flow, flowspeed and solidification temperature. And there was a minute difference between solidification temperatures at thick section of the spare parts. Solidification began at temperatures of $624^{\circ}C{\sim}630^{\circ}C$ but after the casting was completed, temperatures at the center of the parts were $600^{\circ}C{\sim}614^{\circ}C$ Temperature of molten metal showed optimal flow at temperature of $680^{\circ}C$. It began to solidity around at $650^{\circ}C$ and to be cooled between $580^{\circ}C{\sim}550^{\circ}C$ in high speed. When the process was analysed through a computer simulation, it was found that hardness of regulators manufactured through Type B of overflow was above $H_R60$.

• Transactions on Electrical and Electronic Materials
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• 제7권4호
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• pp.184-188
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• 2006

This work describes efforts in the fabrication and testing of robust microelectromechanical systems (MEMS). Robustness is typically achieved by investigating non-silicon substrates and materials for MEMS fabrication. Some of the traditional MEMS fabrication techniques are applicable to robust MEMS, while other techniques are drawn from other technology areas, such as electronic packaging. The fabrication technologies appropriate for robust MEMS are illustrated through laminated polymer membrane based pressure sensor arrays. Each array uses a stainless steel substrate, a laminated polymer film as a suspended movable plate, and a fixed, surface micromachined back electrode of electroplated nickel. Over an applied pressure range from 0 to 34 kPa, the net capacitance change was approximately 0.14 pF. An important attribute of this design is that only the steel substrate and the pressure sensor inlet is exposed to the flow; i.e., the sensor is self-packaged.

• Journal of Advanced Marine Engineering and Technology
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• 제31권1호
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• pp.26-33
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• 2007

The intake swirl motion, as one of dominant effects for an engine combustion. is very effective for turbulence enhancement during the compression process in the cylinder of 2-valve engine. Because the combustion flame speed is determined by the turbulence that is mainly generated from the mean flow of the charge air motion in intake port system. This paper describes the experimental results of swirl flow and combustion characteristics by using the oil spot method and back-scattering Laser Doppler velocimeter (LDV) in 2-valve single cylinder transparent LPG engine using the liquid phase LPG injection. For this. various intake port configurations were developed by using the flow box system and swirl ratios for different intake port configurations were determined by impulse swirl meter in a steady flow rig test. And the effects of intake swirl ratio on combustion characteristics in an LPG engine were analyzed with some analysis parameters that is swirl ratio. mean flow coefficient, swirl mean velocity fuel conversion efficiency. combustion duration and cyclic variations of indicated mean effective pressure(IMEP). As these research results, we found that the intake port configuration with swirl ratio of 2.0 that has a reasonable lean combustion stability is very suitable to an $11{\ell}$ heavy-duty LPG engine with liquid phase fuel injection system. It also has a better mean flow coefficient of 0.34 to develope a stable flame kernel and to produce high performance. This research expects to clarify major factor that effects on the design of intake port efficiently with the optimized swirl ratio for the heavy duty LPG engine.