• 한국해안·해양공학회논문집
• /
• 제31권1호
• /
• pp.9-16
• /
• 2019

유속의 크기와 블레이드의 기하학적 형상 변화에 따라 발생하는 조류발전용 쉬라우드 시스템 내 유속 변화를 분석하기 위하여 수리모형실험과 수치해석적 방법을 이용하였다. 모형실험을 통해 시스템의 유입부에서 유속 변화와 블레이드 형상변화에 따른 고유 회전수를 계측하였으며, 수치해석을 통해 쉬라우드내 유속 변화를 분석하였다. 실험 유속이 약 28% 증가하고, 익형의 형상을 적용하였을 때, 쉬라우드 유입부에서 계측된 유속은 최대 약 56% 증가하는 경향을 보였다. 한편, 익형 형상을 적용한 블레이드가 설치된 경우 유입부에서의 유속은 일반 블레이드에 비해 최대 14% 증가하는 경향을 보였으며, 회전수 역시 동일 조건에서 가장 높은 수치를 보였다. 수리실험과 수치해석 결과는 약 13%의 오차를 보였으며, 각각의 결과에서 보이는 유속 변화에 대한 경향은 유사하다. 쉬라우드 내 유속 변화를 수치해석으로 분석한 결과 유입부 대비 블레이드 앞부분에서 유속은 최대 1.7배 증가하는 경향을 보였다. 본 연구를 통해 얻은 시스템 내 유속 변화 분석 결과는 효율적인 조류발전용 쉬라우드 시스템 개발에 필요한 기초 자료를 제시할 수 있을 것으로 판단된다.

• 한국원자력학회:학술대회논문집
• /
• 한국원자력학회 1999년도 춘계학술발표회요약집
• /
• pp.104-104
• /
• 1999

The local heat transfer coefficient is experimentally investigated for the reflux condensation in a countercurrent flow between the steam-air mixture and the condensate. A single vertical tube has a geometry which is a length of 2.4m, inner diameter of 16.56mm and outer diameter of 19.05mm and is made of stainless steel. Air is used as a noncondensible gas. The secondary side is installed in the form of coolant block around vertical tube and the heat by primary condensation is transferred to the coolant water. The local temperatures are measured at 15 locations in the vertical direction and each location has 3 measurement points in the radial direction, which are installed at the tube center, at the outer wall and at the coolant side. In three different pressures, the 27 sets of data are obtained in the range of inlet steam flow rate 1.348 -3.282kg/hr, of inlet air mass fraction 11.8 -55.0%. The local heat transfer coefficient increases as the increase of inlet steam flow rate and decreases as the decrease of inlet air mass fraction. As an increase of the system pressure, the active condensing region is contracted and the heat transfer capability in this region is magnified. The empirical correlation is developed represented with the 165 sets of local heat transfer data. As a result, the Jacob number and film Reynolds number are dominant parameters to govern the local heat transfer coefficient. The rms error is 17. 7% between the results by the experiment and by the correlation.

• Nuclear Engineering and Technology
• /
• 제31권5호
• /
• pp.486-497
• /
• 1999

The local heat transfer coefficient is experimentally investigated for the reflux condensation in a countercurrent flow between the steam-air mixture and the condensate, A single vertical tube has a geometry which is a length of 2.4m, inner diameter of 16.56mm and outer diameter of 19.05mm and is made of stainless steel. Air is used as a noncondensible gas. The secondary side has a shape of annulus around vertical tube and the lost heat by primary condensation is transferred to the coolant water. The local temperatures are measured at 11 locations in the vertical direction and each location has 3 measurement points in the radial direction, which are installed at the tube center, at the outer wall and at the coolant side. In three different pressures, the 27 sets of data are obtained in the range of inlet steam flow rate 1.348∼3.282kg/hr, of inlet air mass fraction 11.8∼55.0%. The investigation of the flooding is preceded to find the upper limit of the reflux condensation. Onset of flooding is lower than that of Wallis' correlation. The local heat transfer coefficient increases as the increase of inlet steam flow rate and decreases as the increase of inlet air mass fraction. As an increase of the system pressure, the active condensing region is contracted and the heat transfer capability in this region is magnified. The empirical correlation is developed by 165 data of the local heat transfer. As a result, the Jacob number and film Reynolds number are dominant parameters to govern the local heat transfer coefficient. The rms error is 17.7% between the results by the experiment and by the correlation.

• 한국항공우주학회지
• /
• 제41권9호
• /
• pp.714-719
• /
• 2013

본 연구 대상 터보 프롭 항공기는 주어진 항공기 임무 수행을 위해 결빙 조건하에서도 운용이 가능하여야 한다. 동 연구에 적용된 터보 항공기의 공기 흡입구 계통은 정상 비행조건하에서 엔진 입구에 최대 전압력을 공급할 수 있도록 설계 및 검증이 되어야 할 뿐만 아니라 결빙조건하에서 생길 수 있는 얼음과 같은 입자가 엔진 흡입구 망으로 들어가서 엔진 화염꺼짐이나 엔진에 심각한 손상을 주지 않도록 하기 위한 관성분리기를 포함하도록 개발이 되어야 한다. 따라서 결빙 조건하에서 형상이 변하는 가변형상의 공기흡입구 조립체를 설계하고 설계 결과 확인을 위해 조립체에 대한 전산 유동 및 구조해석을 수행하였다. 이후 35% 축소형 모델을 제작하여 풍동시험을 수행하였다. 동 논문에서는 흡입구 조립체 개발과정에서 요구되는 공기역학적 설계, 잔산 유동/구조 해석 및 풍동 시험평가 결과를 기술하였다.

• 대한기계학회논문집B
• /
• 제38권12호
• /
• pp.1017-1026
• /
• 2014

Urea-SCR 머플러 시스템 입구와 촉매 전단에 설치된 다공튜브는 우레아 수용액 분무의 균일분포, SCR 촉매 활용도 증대 및 암모니아 슬립을 방지하기 위해 사용되고 있다. 다공튜브의 오리피스 면적비 변화가 머플러 챔버 내부유동 특성에 끼치는 영향이 상용 소프트웨어를 이용하여 해석적으로 조사되었다. 다공튜브 오리피스 면적비 변화는 촉매 전단에 설치된 챔버 내부의 벌크 선회유동 형성과 촉매 전단 속도분포의 균일도 지수에 큰 영향을 끼침을 보였다. 해석결과를 검증하기 위해 엔진실험이 ESC 및 ETC 모드에서 수행되었다. 엔진 실험결과 다공튜브 길이방향으로 보다 많은 유량이 흐르는 모델이 가장 높은 NOx 저감 효율을 나타냈으며, 이것은 높은 균일도지수 및 강한 선회유동을 나타내는 해석 결과와 일치됨을 알 수 있었다.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2007년도 춘계학술대회B
• /
• pp.3050-3055
• /
• 2007

A wind turbine is one of the most popular energy conversion systems to generate electricity from the natural renewable energy source and an axial-flow type wind turbine is the most popular system for the electricity generation in the wind farm nowadays. In this study, a cross-flow type turbine has been studied for the application of wind turbine for electricity generation. The target capacity of electric power generation of the model wind turbine developing on the project is 12 volts, 130A/H (about 1.56kW). The important design parameters of the model turbine impeller are the inlet and exit angle of the turbine blade, number of blade, hub/tip ratio and the exit flow angle of the casing. In this study, the radial equilibrium theorem was used to decide the inlet and exit angle of the impller blade and CFD technique was used to have the performance analysis of the designed model power turbine to find out the optimum geometry of the CPT impeller and casing. The designed CPT with 24 impeller blades at ${\alpha}=82^{\circ}$, ${\beta}=40^{\circ}$ of turbine blade angle was estimated to generate 284.6 N.m of indicated torque and 2.14kW of indicated power.

• 상하수도학회지
• /
• 제18권4호
• /
• pp.500-507
• /
• 2004

This study was conducted to evaluate the equity of the flow distribution from rapid mixing basin to the flocculation basins. Also, several types of inlet structures of the open channel affecting the flow pattern and distribution trend were studied using Computational Fluid Dynamics (CFD) simulation. For investigating the factual phenomena in distribution channel, we selected a certain domestic water treatment plant with capacity of $361,000m^3/d$. From the measurements of flow discharge, it is investigated that this existing inlet geometry resulted in significant inequitable distribution. The both largest deviations in the basins and rows were over 10%. In order to reduce the these deviation, this study suggested installing a baffle against the influent, and showed the effectiveness which the largest deviation was less than 3%. Also, it was concluded that the existing design method of open channel could be improved by three-dimensional hydrodynamic analysis for optimizing the even flow.

• Journal of the korean society of oceanography
• /
• 제36권3호
• /
• pp.72-82
• /
• 2001

The progress of giant dyke construction off the Mangyung and Donajin rivers, has yielded enormous impact on the estuarine environment, both hydrodynamically and sedimentologically. Especially the inter-dyke gap in the northern Saemankeum area, 4 km wide between Yamido and Piungdo, has acted as an artificial tidal inlet. Due to such a changed geometry, tidal regime has been reversed from being flood- to ebb-dominated with a directional change from NE-SW to E-W. As a result, a large tongue-like tidal sand bar (named Saemankeum Bar) has conspicuously grown seaward through the artificial tidal inlet. The Saemankeum Bar composed of well-sorted very fine sands (3.0-3.5${\phi}$) has grown at a rate of 1.63 km/yr for the past three yews (1996-1998). Such a rapid growth of the sand bar is attributed to enhanced sediment supply derived from the degradation of former tidal sand bars at the mouth of the Mangyung River. Eventually the reworking of the tidal sand bars also caused the pre-existing tidal channels to be wider, deeper and more straightened. All of these phenomena well examplify the critical effect of artificial modifications on the natural estuarine environments.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2007년도 추계학술대회논문집
• /
• pp.6-11
• /
• 2007

Packaged power station (PPS) is a stationary diesel engine generator set and developed for the supply of electric power to small villages, islands and factories etc. Therefore, the PPS is closely installed to residence area and sometimes cause the environmental noise problems. In this paper, environmental noise analysis was performed for the power plant with 28 sets of PPS. The initial analysis results showed the some difference between the measurement and analysis because of the inaccurate noise source data. To improve the accuracy of analysis, main noise sources were inversely estimated using the in-situ measurement data in the vicinity of PPS and steam boiler. As the results of re-analysis, the good agreement was obtained and it was concluded that the noise levels exceed the specified noise limit in residence area. In order to reduce the noise, the several methods such as geometry alteration of inlet duct, application of hybrid-type silencer and noise protection barrier were suggested and verified with the confirmed analysis model.

• 한국원자력학회:학술대회논문집
• /
• 한국원자력학회 1997년도 춘계학술발표회논문집(1)
• /
• pp.356-361
• /
• 1997

To investigate parametric effect on CHF and to get CHF data, experimental study has been performed with vertical round tubes under the condition of low pressure and low flow (LPLF). Test sections are made of Inconel-625 tube and have the geometry of 8 and 10 mm in diameter, and 0.5 and 1.0 m in heated length. All experiments have been conducted at the pressure of under 9 bar, the mass flux of under 250 kg/$m^2$ and the inlet subcooling of 350 and 450 kJ/kg, for stable upward flow with water as a coolant. Flow regime analysis has been performed for obtained CHF data with Mishima's flow regime map, which reveals that most of the CHF occur in the annular-mist flow regime. General parametric trends of the collected CHF data are consistent with those of previous studies. However, for the pressure effect on CHF, two different are observed; For relatively high mass flux, CHF increases with pressure and far lower mass flux, CHF decrease with pressure. Using modern data regression tool, ACE algorithm, two new CHF correlations for LPLF condition are developed based on local condition and inlet condition, respectively. The developed CHF correlations show better prediction accuracy compared with existing CHF prediction methods.