• International Journal of Automotive Technology
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• 제5권3호
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• pp.181-188
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• 2004

A cylindrical constant-volume combustion chamber was used to investigate the flow characteristics at the spark electrode gap and the combustion characteristics of an inhomogeneous charge methane-air mixture under several parameters such as stratified pattern, initial charge pressure, ignition time and the excess air ratio of the initial charge mixture. Flow characteristics including mean velocity and turbulence intensity were analyzed by a hot-wire anemometer. The combustion pressure development, measured by a piezo-electric pressure transducer, was used to investigate the effect of initial charge pressure, excess air ratio and ignition times on combustion pressure and combustion duration. It was found that the mean velocity and turbulence intensity had the maximum value around 200-300 ms and then decreased gradually to near-zero value at 3000 ms. For the stratified patterns, the combustion rate under the rich injection (RI) condition was the fastest. Under the initial charge conditions, the second mixture was accompanied by an increase in the combustion rate, and that the higher the mass which is added in the second stage injection, the faster the combustion rate.

• 설비공학논문집
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• 제3권5호
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• pp.350-364
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• 1991

The movements of small particles distributed uniformly in a steady flow in rectangular chambers having inlets and outlets were simulated numerically. Low Reynolds number turbulent model with a two-equation ($k-{\varepsilon}$) which describes the turbulent characteristics was applied to predict the air flow pattern and particles movements under the condition of the various locations and size of ducts. The calculation results show that the prediction of recirculation zone and stagnation point of flow is important to determine the particles behavior according to the design change. These results will be useful in designing the rectangular chambers for collective protection.

• 설비공학논문집
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• 제17권4호
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• pp.333-340
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• 2005

Horizontal air-jet effect has been utilized in some air conditioning systems in order to control the contaminated air indoor. In the present study, the flow and heat transfer of the contaminated air from a range hood system has been investigated with or without horizontal air-jet effect when the hood fan is on or off. For the present numerical experiment, PAT Flow code has been used. From the present numerical simulations, it has been shown that the air jet of a range hood generates coanda effect confining the contaminated air in a certain region. Furthermore, the qualitative relation between the flow rate of the capture air jet and the distribution pattern of the contamination has been discussed.

• 농업과학연구
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• 제7권2호
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• pp.156-168
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• 1980

분무기(噴霧機) nozzle의 와실내(渦室內)에서 공기(空氣)를 수류(水流)의 중심부(中心部)로 분무(噴霧)시켜 예비미립화(豫備微粒化) 및 공기충돌식(空氣衝突式)의 미립화방식(微粒化方式)을 복합(復合)하여 고안(考案)된 air-center nozzle의 분무살포량(噴霧撒布量)의 분포도(分布度)와 분출량(噴出量)의 특성(特性)을 찾기위한 실험(實驗)을 실시(實施)하였다. 공기량(空氣量)은 소구경(小口徑) pipe 직경(直徑) 0.45mm부터 1.42mm이내로 7 수준(水準)으로 조절(調節)하였고 이의 각수준별(各水準別)로 압력(壓力)을 $0.35kg/cm^2$(5 psi)부터 $6.33kg/cm^2$(90 psi)까지 11 수준(水準)으로 조절(調節)하였다. 매실험결과(每實驗結果)는 표준(標準) nozzle 실험치(實驗値)와 비교분석(比較分析)하였고 이의 결과(結果)는 다음과 같다. Air-center nozzle은 비교적(比較的) 표준(標準) nozzle보다 안정(安定)된 살포량(撒布量) 분포형(分布型)을 유지(維持)하였다. Air-center nozzle의 분무살포량(噴霧撒布量) 분포도(分布度)는 공기량(空氣量)이 증가(增加)함에 따라서 중심부분(中心部分)으로 집중화(集中化)하였고 이 집중화정도(集中化程度)는 표준(標準) nozzle보다도 더 컸다. 이현상(現象)은 표준(標準) nozzle에 비(比)하여 도달성(到達性) nozzle형(型)에 적합(適合)함을 시사하였다. Air-center nozzle의 분출량(噴出量)은 어느 일정(一定)한 수준(水準) 이내(以內)에서 공기량(空氣量)때문에 표준(標準) nozzle의 분출량(噴出量)만큼 크지는 못하였다. 분출량(噴出量)의 감소율(減少率)은 압력(壓力)이 증가(增加)함에 따라서 둔화되었고 혼합용제(混合溶劑)속의 공기함유율(空氣含有率)이 2~3%인 저비율(低比率)일때 급속(急速)히 컸다. 이 현상(現象)은 공기(空氣)의 압축성질(壓縮性質)에 기인(基因)된 것으로 사료(思料)된다.

• 설비공학논문집
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• 제28권5호
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• pp.186-194
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• 2016

As a turbulence-enhancing device, a mixing vane installed at a spacer grid of the fuel assembly plays a role in improving the convective heat transfer by generating either swirl flow in the subchannels or cross flow between fuel rod gaps. Therefore, both configuration and arrangement pattern of a mixing vane are important factors that determine the performance of a mixing vane. In this study, in order to examine the flow distribution features inside $5{\times}5$ fuel assembly with swirl-type mixing vanes used in benchmark calculation of OECD/NEA, simulations were conducted with commercial CFD software ANSYS CFX R.14. Predicted results were compared to data measured from MATiS-H (Measurement and Analysis of Turbulent Mixing in Subchannels-Horizontal) test facility. In addition, the effect of swirl-type mixing vanes on flow pattern inside the fuel assembly was described.

• 한국환경과학회지
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• 제17권7호
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• pp.743-753
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• 2008

Gwangyang Bay is often severely confronted by photochemical pollutants due to its location and dense emissions. It is located in a basin on the south coast of the Korean peninsula and is crossed by a remarkable cluster of hills and mountains of a small horizontal scale that forms a channel. Clearly, the air flow field has a great influence on the dispersion of air pollutants. The characteristics of the wind flow patterns have an important effect on the dispersion of pollutants emitted. In these situations, the distribution of the ozone concentration is extremely complicated because of the superposition of circulations of the air flow fields, especially in complex coastal region. In this study, we examined the distribution of the high level ozone on Gwangyang Bay particularly during the episode day (for 5 years). Among these days, A high level ozone was induced by the development of a sea/land breeze local circulation system, as well as by an anabatic/catabatic flow from the mountains and valley with weakening of the synoptic wind. High level ozone distribution pattern(6 types) on Gwangyang bay is analyzed and the comparison of each pattern reveals substantial localized differences in intensity and distribution of ozone concentration from the site coherence and UPA analysis of ozone concentration. The observed VOC concentration had much difference in concentrations and daily variations between Jungdong and Samil.

• 설비공학논문집
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• 제10권4호
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• pp.398-410
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• 1998

Two-phase flow phenomena are observed in many industrial facilities and make much importance of optimum design for nuclear power plant and the liquid transportation system. The particular flow pattern depends on the conditions of pressure, flow velocity, and channel geometry. However, the research on drag reduction in two-phase flow is not intensively investigated. Therefore, experimental investigations have been carried out to analyze the drag reduction and void fraction by polymer addition in the two-phase flow system. We find that the polymer solution changes the characteristic of two-phase flow. The peak position of local void friction moves from tile wall of the pipe to the center of the pipe when polymer concentration increase. And then we predict that it is closely related with the frau reduction.

• 한국환경과학회지
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• 제21권3호
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• pp.327-337
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• 2012

Air pollution inventories are aggregated around south-eastern part of the Korean Peninsular including Busan, Ulsan, and Changwon cities. Because densely populated cities are concentrated in this region, air pollutants emitted from one of these cities tend to be impacted on the air quality of other cities. In order to clarify the seasonal movement pattern of emitted particles, several numerical simulations using WRF/FLEXPART were carried out. Four cases were selected for each season. The Weather Research and Forecasting model (WRF) reproduced atmospheric flow fields with nested grids. The seasonal pattern of air mass of study area was determined by backward and forward trajectories. As a result, the air parcel moves from northwest to southeast due to northwesterly winds in spring and winter. Also air parcel transports from south to north in summer, and moves from west to east. Because the air mass moves differently in each season, these characteristics should be considered when performing air quality analysis.

• 대한설비공학회지:설비저널
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• 제17권5호
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• pp.590-597
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• 1988

Characteristics of flow regime transitions in inclined upwards gas-liquid two-phase flow have been investigated based upon a statistical analysis of instantaneous pressure drop curves through an orifice. The probability density functions of the curves indicate distinct patterns depending upon two-phase flow regime, which are very similar to those of horizontal two-phase. The dimensionless intensity of fluctuations of the pressure drops sharply change as the flow transitions such as plug-slug, pseudo slug-slug and annular-slug take place. The effects of inclination angle on the flow regime transitions have been also investigated. The results show that the method to identify the flow pattern based upon the statistical analysis of instantaneous pressure drops is suitable for inclined flow as well as horizontal flow.

• 설비공학논문집
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• 제25권6호
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• pp.324-330
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• 2013

The main objective of this work is to experimentally investigate the effect of inlet geometries on the distribution of two-phase annular flow at header-channel junctions simulating the corresponding parts of compact heat exchangers. The cross-section of the header and the channels were fixed to $16mm{\times}16mm$ and $12mm{\times}1.8mm$, respectively. Experiments were performed for the mass flux and the mass quality ranges of $30{\sim}140kg/m^2s$ and 0.3~0.7, respectively. Air and water were used as the test fluids. Three different inlet geometries of the header were tested:no restriction (case A), a single 8 mm hole at the center (case B), and nine 2 mm holes around the center (case C) at the inlet, respectively. The tendencies of the two-phase flow distribution were different, in each case. For cases B and C (flow resistance exists), more uniform flow distribution results were seen, compared with case A(no flow resistance), due to the flow pattern change to mist flow from annular flow at the inlet, and the flow recirculation near the end plate of the header.