• Journal of Energy Engineering
• /
• v.16 no.3
• /
• pp.103-112
• /
• 2007

Flood issue for nuclear power plants designed and built in 1970 is extremely severe for main steam header compartment and main feedwater line region of intermediate building and lower floor. A calculation for flood level at the main feedwater line isolation compartment is now performing by hand calculation. But, this methodology is quite conservative assumption. The goal of this study was to develop method to analyze flowrate using the RETRAN-3D computer code, and the developed method was applied to flood level analysis following main feedwater line break. As a result of analysis, flood level was low remarkably.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.33 no.8
• /
• pp.56-64
• /
• 2005

It is prerequisite that we have to fomulate the nonlinear mathematical modeling to design the guidance and control system of rotorcraft-based unmanned aerial vehicle using a small-scaled commercial helicopter. The small-scaled helicopters are very different from the full-scale helicopters in dynamic behavior such as high rotation speed and high frequency dynamic characteristics. In this paper, the formulation of the mathematical model of the small-scaled helicopter to minimize the complexity is presented by component and source build-up approach. It is linearized at the trim condition of hovering and forward flight and analyzed the flight modes. The results of this approach have general trends but a little difference. To verify this approach, it is necessary to compare this theoretical model with experimental results by system identification using flight test as a next research topic.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.2 no.1
• /
• pp.1-12
• /
• 1998

Industrial ejector system is a facility to transport, to compress or to pump out a low pressure secondary flow by using a high pressure primary flow. An advantage of the ejector system is in its geometrical simplicity, not having any moving part, compared with other fluid machinery. Most of the previous works have been performed experimentally and analytically. The obtained data. are too insufficient to improve our current understanding on the detailed flow field inside the ejector. In order to provide more comprehensive data on this ejector flow field, two-dimensional computations using Reynolds-averaged Navier-Stokes equations were performed for a very wide range of operating pressure ratio of the supersonic ejector with a secondary throat. The current results showed that the supersonic ejector system has an optimum pressure ratio for the secondary flow total pressure to be minimized. The numerical results clearly revealed the shock system, shock/boundary layer interaction, and secondary flow entrainment inside the supersonic ejector.

• Journal of the Society of Naval Architects of Korea
• /
• v.38 no.3
• /
• pp.41-46
• /
• 2001

The very large vessels like VLCC and container ship have been built recently and those vessels have smaller structural strength in comparison with the other convectional skips. As a result the fatigue destruction of upper deck occurs a frequently due to the springing phenomenon at the encountering frequencies. In this study, the hydrodynamic loads are calculated by three-dimensional source distribution method with the translating and pulsating Green function. A ship is longitudinally divided into 23 sections and the added mass, damping and hydrodynamic force of each section is calculated. focusing only on the vertical motion. Stiffness matrix is calculated by the Euler beam theory. The calculation is carried out for Esso Osaka.

• Resources Recycling
• /
• v.28 no.1
• /
• pp.32-39
• /
• 2019

The present study investigated hydration of alkali activated slag incorporating sulfate as a form of anhydrite by employing thermodynamic modeling using the Gibbs free energy minimization approach. Various parameters were evaluated in the thermodynamic calculations, such as presence of sulfide, precipitation/dissolution of AFt/AFm phase, and the effect of oxic condition on the predicted reaction. The calculations suggested no significant difference in the void volume and chemical shrinkage, which might influence the performance of the mixtures, in spite of various changes of the parameters. Although the types of hydration products and their amount varied according to the input conditions, their variations were smaller range than that induced by water-to-binder ratio. Moreover, it did not affect the amount of C-(N-)A-S-H which was the most important hydration product.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.34 no.10
• /
• pp.24-31
• /
• 2006

In this paper, mechanical behavior of unidirectional composites with flexible matrix was predicted by geometrical non-linear finite element analysis. Two typical idealized unit cells of square and hexagonal fiber arrays were modeled and these were subjected to different loadings. The stress-strain behavior of composites was predicted from which the effective properties were calculated. The hyperelasticity of polyurethane matrix was considered using Mooney-Rivlin model. In result, the stress-strain behavior of flexible composites shows non-linearity, especially it is remarkable under transverse normal and shear loading conditions. In this cases, there are great difference between square and hexagonal fiber array models.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.16 no.4
• /
• pp.753-764
• /
• 1992

The steam generator water level is difficult to control at low power due to its reversed responses to the feedwater flow, which are well known as the shrink and swell phenomena. With regard to this problem a new control scheme has been studied by which the level transients could be kept within permissible ranges at low power. The relations between the various input conditions to steam generator and the level transients have been examined to be expressed in the form of process transfer functions. Analog filters have been incorporated to be expressed in the process with proper control constants. This control scheme allows the prediction of level variation together with the corresponding feedwater rate and results in mider transients with good stabilites.

• Journal of the Korean Vacuum Society
• /
• v.13 no.3
• /
• pp.132-138
• /
• 2004

We used the self-consistent one-dimensional model applied to FCT algorithm and FEM method in a wire-cylinder type reactor to study the characteristics of corona discharge plasma in air at the atmospheric pressure. At the pulsed do voltage and do voltage, we studied the changes of the characteristic of plasma by computing electron density profile according to the changes of voltage and the size of reactor. The changes of active radius from this result are compared with the data of Peek's. The numerical simulation results for a corona discharge plasma explain the physical mechanism of the discharge process and could be used to obtain the optimized parameters for designing the plasma reactor for pollution abatement.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
• /
• 2012.04a
• /
• pp.66-69
• /
• 2012

Field Model에 의한 화재해석방법은 화재현상을 지배하는 망정식윤 직접 해석하기 때문에 Zone model에 비해 공간내의 상세 정보를 제공함과 동시에 다양한 화재형태에 내해 보편적인 적용이 가능하다. Field model은 해석영역을 구성하는 격자점에 대해 이산화된 지배 방정식을 해석하는 과정에서 차분방법이나 격자의 크기에 따라 수치오류가 발생할 수 있다. 특히 격자수는 계산시간에 영향을 미치는 가장 중요한 인자이기 때문에 효율적인 계산을 위해서는 격자크기의 최적화가 이루어져야 한다. 본 연구에서는 구획공간 화재의 최적 격자크기 선정을 위해 격자해상도(Grid Resolution)에 따른 해석결과의 독립성을 비교분석하고 이를 통해 구획공간화재에 대한 격자 최적화 방법에 대해 논의하고자 한다. 화재크기 및 특성 길이에 따른 격자의존성을 파악하기 위해 ISO-9705 표준화재실에 내해 적용된 격자크기는 최소 3 cm에서 최대 30 cm까지 총 7 종류의 격자크기에 대해 FDS 해석이 수행되었다. 해석결과, 환기량이 충분한 화재에 대해서도 격자해상도가 16보다 작은 경우 출입구의 유동은 격자에 따른 독립성을 확보하지 못하는 것으로 나타났으며 화재발열량이 증가함에 따라 독립적인 해석해를 얻기 위해서는 더 큰 격자해상도를 요구하는 것으로 나타났다. 따라서 현재 실무에서 격자최적화를 위해 사용되고 있는 격자선정법에 대한 재검토가 필요하며 화재특성 및 구획공간 조건에 따른 최적격자 조건을 도출하기 위한 추가적인 연구가 필요하다.

• Journal of the Korean Institute of Gas
• /
• v.7 no.1 s.18
• /
• pp.10-18
• /
• 2003

Consequence model has been suggested to evaluate consequence of city gas accident considering actual situation. Through event tree analysis(ETA), probable accidents were summarized and listed. Then release rate was calculated both sonic and subsonic conditions. Among city gas accidents, fire damage is the dominant one and mainly discussed; fatality, burning injury, and damage to building were estimated using the consequence model suggested. With an appropriate conditions, calculating total cost by accident was suggested.