Ladle 내에서 기포에 따른 액상 영역의 유동학적 특성에 관한 가시적 연구

오율권,서동표,양호동 조선대학교 에너지.자원신기술연구소 2004 에너지·자원신기술연구소 논문지 Vol.26 No.2

In the present study, the gas injection system based on air-water model was designed to investigate the fluid-dynamics characteristics of liquid zone into a ladle. PIV system and camera techniques were applied to analysis flow patterns at the liquid zone. Gas flow rate is one of most important factors which could feature a flow pattern in a gas injection system. At low gas flow rate, upward bubble flow induced by buoyancy force is predominant and does not make an impact on mixing due to a weak circulation flow. However, with increasing gas flow rate, the kinetic energy of bubble increases and a strong circulation flow develops in the liquid. Such a flow in the liquid develops vortex and improve the mixing process. Due to the centrifugal force, circulation flow was well developed near both wall sides and upper region respectively.

작동유체의 등온 가열 상태에서 펌프의 이상유동 특성에 관한 실험적 연구

오율권,유영태,이용헌,서동표 조선대학교 생산기술연구소 1996 生産技術硏究 Vol.18 No.1

This study is to examine the effects of entrained air on the pump performance in a centrifugal pump. Using a 1/10 scale model pump. which is designed and manufactured to simulate two phase flow performance of the reactor coolant pumps of Y.G.N #3 and 4. a set of experiments was executed with water and air mixtures at heated state of 50℃ and at atmospheric pressure. A head loss coefficient. which is defined as a nondimensional ratio of the difference of theoretical and actual pump head coefficient in a single phase. ◁화학식 삽입▷ (원문을 참조하세요) was determined as a function of void fracrtion, α , and flow coefficient, Φ. The calibrated mass flow rates of air and water were used to calculate void fraction using the void meter of the conductivity probe type. compensate the defect of drift flux model and calculate the void fraction. In particular. the flows were stoped when the void fraction was about 0.13.

단상류와 이상류에서 펌프특성간의 상호관계 결정

오율권,김순기,김상녕,이종원 대한기계학회 1990 대한기계학회논문집 Vol.14 No.6

Using a 1/10 scale model pump, which is designed and manufactured to simulate two phase performance of reactor coolant pump of Y.G.N

고도로 과열된 액체분사의 분해의 메카니즘에 관한 연구

오율권,정낙규 조선대학교 동력자원연구소 1988 動力資源硏究所誌 Vol.10 No.2

Delay time and jet divergence angle measured were studied for slashing jets at high degrees of superheat. n-pentane, n-hexane, and ethanol were injected into nitrogen at two injection pressures and for three nozzle diameters. Proposed hypothesis for the delay time based on homogeneous nucleation are not confirmed by our experimental data. The assumption that the spray angle is related to the heat-transfer-controlled bubble growth appears to be supported by our data but important details concerning the number of bubbles in the jet and the state of the vapor in the bubble at breakup have not yet been properly explained. Both delay time and jet divergence angle are found to be sensitive to the degree of superheat and liquid properties, influenced by the liquid pressure and insensitive to jet diameter.

상반류(물/공기) 유동한계에 관한 연구

오율권,조상진,김상녕,이종원 대한기계학회 1991 대한기계학회논문집 Vol.15 No.1

A set of experiments of Counter-Current Flow Limit(CCFL or Flooding) was performed to improve the drawbacks of Wallis' Correlation which neglects the effects of channel size, channel length, injection method and the boundary conditions at the inlet of liquid and gas phase. In these experiments using water and air, the followings were found ; (i) The effects of channel size and length were quite significant. In large tubes(D>20mm), the flooding front occurred at the bottom of the channel and when the gas flow increased the front moved upward ; however, in small tubes(D<20mm), there were no upward movement of flooding front and the flooding just occurred at the liquid inlet. (ii) The effect of water inlet device was not as significant as that of channel length though the inlet boundary conditions could affect the flow development and flooding afterward. (iii) Once the flooding front reached the inlet of water injection device, an newly reduced flow condition was set up and resulted in another flooding corresponding to the new condition. 본 연구에서는 CCFL에 영향을 미치는 관의 크기, 길이, 주입구 형상 등 변화 에 대한 현상해석과 이의 영향을 고려한 관계식의 개발에 있다. 그러므로 본 실험에 서의 물의 주입량을 관에 수막(film)이 형성시킬 수 있는 유량으로 고정시킨 상태에서 공기의 유량을 증가시켜, CCFL이 발생하였을때 공기와 물의 유량을 측정하였다. 그 리고 관의 길이, 크기 그리고 물의 주입구 구조(예각, 둔간, 톱니, 다공)의 변화에 따 른 CCFL의 영향에 관하여 실험을 수행하였다.

Air-Water 모델에서 액상의 유동특성에 관한 연구

오율권,서동표,박설현 한국안전학회 2004 한국안전학회지 Vol.19 No.1

In the present study, the gas injection system based on air-water model was designed to investigate the flov< characteristics of liquid phase. A PIV system was applied to analyze the flow pattern in a ladle which gas started to rise upward from the bottom. Gas flow is one of most important factors which could feature a flow pattern in a gas injection system. As the gas injected into the liquid, the kinetic energy of bubble transfer to liquid phase and a strong circulation flow develops in the liquid phase. Such a flow in the liquid develops vortex and improve the mixing process. Due to the centrifugal force, circulation flow was well developed near both wall sides and upper region respectively. Increasing gas flow was helpful to remove dead zone but, weak flow zone still exists in spite of the increasement of gas flow rate.

배기계에서 비정상 가스의 소음특성에 관한 해석

박근욱,신문섭,장옥수,오율권 朝鮮大學校 機械技術硏究所 1998 機械技術硏究 Vol.1 No.1

일반적으로 자동차의 소음은 주로 엔진에서 발생되어서 공기를 통해 전달되는 소음과 흡·배기계를 구성하는 tube 또는 Chamber를 통하여 전달되는 소음으로 구성된다. (1) 차량소음의 주요 소음원은 흡기계의 흡기소음과 배기계의 배기소음을 들 수 있으며, 소음중 배기소음은 도시소음의 주된 요인이며 차량의 승차감을 저해하는 간접적인 원인 중의 하나이다. 따라서 일반적인 자동차에는 반드시 소음기 즉, 머플러를 부착하여 소음을 어느 정도 이하로 감소시키게 되어 있다.(2.3) 전통적으로 소음기에 대한 연구는 주로 음향필터이론에 바탕을 두고 진행되어왔으나 음향필터이론은 배기소음기의 소음감쇄작용에 대한 체계적인 이론적 설명을 제시하지는 못했다. 음향에너지의 소산(Dissipation)을 고려하지 않고 음향이론상에서 배압을 예측하는 것은 불가능하다.(4) 그로므로 본 연구에서는 내연기관의 다양한 배기시스템에 대하여, 비선형 작용을 고려하므로서 1차원 비정상 등엔트로피 분석을 이용한 특성법(5)을 사용하였으며, 이러한 분석법에 배기시스템내에서 유동현상의 완전한 처리를 위하여 준정적 유동 접근법에 근거한 경계모델을 포함시켰다. 또한 이론의 타당성을 검증하기 위하여 최근까지 연구되어져온 블로오등을 사용한 시험결과는 달리 로터리 밸브 시뮬레이터를 사용하여 압력-시간 파형을 측정하였으며 측정된 결과와 계산된 결과를 비교하여 맥동 압력파 전파 특성을 확인하였다. 본 연구의 목적은 엔진 성능과 관계된 비정상 가스유동의 거동특성을 유한진폭과 이론을 사용하여 성공적으로 예측하는 방법을 제시하는데 있으며, 각 머플러에 대한 소음감쇠특성 및 소음기의 일반적인 특성을 분석하는데 있다. This thesis describes a theoretical and experimental investigation of the pressure propagation characteristics of some basic internal combustion engine exhaust systems. The mufflers of internal combustion engine have been applied to control the exhaust noise for many years. The greatest reduction in engine noise is generally achieved through proper muffler selection. Although proper muffler selection may seem relatively simple, a numbers of considerations must be made. Additional considerations in the reduction of exhaust system noise include proper selection of piping lengths and diameters, proper mounting of exhaust system components, and proper positioning of the exhaust outlet. In the present work, account is taken of the nonlinear behavior. For sections of parallel pipe, an one-dimensional unsteady homentropic analysis is employed, and a numerical solution is obtained with the aid of a digital computer, using the concept of characteristics. This analysis is than combined with boundary models, based on a quasi-steady flow approach, to give a complete treatment of the flow behavior in the exhaust system

배관내 자유수면에서 와류현상에 대한 연구

오율권,장완호,이종원,김상녕 대한기계학회 1992 대한기계학회논문집 Vol.16 No.11

In order to prevent the decay heat removal system from failure due to air entrainment or free surface vortex in the piping system, a set of simulating experiments for the midloop operation of nuclear power plant was performed. Through these experiments, a relation between the dimensionless numbers, such as submergence H/d, froude number, reynolds number, was found. However, the effect of reynolds number was negligible for the operation conditions of Nuclear power plant. It was also found that the perturbation of the system by the disturbance such as pump start, valve operation, etc., has a strong effect on the free surface vortex. Furthermore, from a view point of reactor safery, a modified inlet device of reducer type is strongly recommendable for the prevention of air entrainment. 본 연구에서는 국내 원자력 발전소중 영광 3,4호기의 설계자료를 토대로 1/6 크기로 축소한 모델실험을 통해서 공기흡입이 발생하는 임계수위를 결정하는 상관식을 개발하였으며 또한 공기흡입구를 reducer type으로 개선함으로써 공기흡입을 방지할 수 있음을 밝혔다.

액상을 수직 상승하는 기포의 열전달 특성에 관한 실험적 연구

오율권,서동표,양호동 朝鮮大學校 機械技術硏究所 2004 機械技術硏究 Vol.7 No.2

In the present study, the gas injection system based on air-water model was designed to investigate the heat transfer characteristics of bubbles injected into a ladle. To analysis heat transfer characteristics rising bubbles, bubble temperature was experimentally measured in a gas-liquid flow region. Bubble temperature was obtained by a thermal infrared camera. Since bubble temperature is different from liquid temperature in a ladle, heat transfer occurs between gas and liquid phases. Actually, bubble temperature reaches liquid temperature in a short time after injection.

비예혼합 역류화염에서 열전대 측정을 적용하기 위한 복사보정에 관한 연구

오율권,허준영,차경옥 한국마린엔지니어링학회 2002 한국마린엔지니어링학회지 Vol.26 No.2

The temperature field of a counterflow non-premixed flame is investigated using thermocouples of two sizes. A thermal balance is performed on the thermocouple in order to calculate the magnitude of the radiation corrections involved. Both the thermocouple wire and bead are separately considered to be the relevant thermal surface to which convective heat transfer takes place, and from which radiation lasses occur. The flame is also simulated by using a detailed chemical kinetic mechanism in a previously developed computer code. The local thermo-physical properties of the gas mixture, required to calculate the corrections, are determined both from the simulation, and by approximating the properties of the mixture as those of molecular nitrogen at the measured temperatures. It is concluded that the thermocouple wire is the appropriate thermal surface to which radiation corrections apply, in the absence of information about the gas mixture, its properties can be reasonably approximated by those of nitrogen rm ($N_2$), and the radiation corrections are very sensitive to misalignments in the temperature and velocity fields.