• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.160-160
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• 2003

• 한국가스학회:학술대회논문집
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• 2005.05a
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• pp.228-228
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• 2005

• Nuclear Engineering and Technology
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• v.28 no.2
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• pp.103-117
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• 1996

A mathematical model of vapor explosion propagation is presented. The model predict two-dimensional, transient flow fields and energies of the four fluid phases of melt drop, fragmented debris, liquid coolant and vapor coolant by solving a set of governing equations with the relevant constitutive relations. These relations include melt fragmentation, coolant-phase-change, and heat and momentum exchange models. To allow thermodynamic non-equilibrium between the coolant liquid and vapor, an equation of state for oater is uniquely formulated. A multiphase code, TRACER, has been developed based on this mathematical formulation. A set of base calculations for tin/water explosions show that the model predicts the explosion propagation speed and peak pressure in a reasonable degree although the quantitative agreement relies strongly on the parameters in the constitutive relations. A set of calculations for sensitivity studies on these parameters have identified the important initial conditions and relations. These are melt fragmentation rate, momentum exchange function, heat transfer function and coolant phase change model as well as local vapor fractions and fuel fractions.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.9
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• pp.826-834
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• 2007

A 7K60MC-S low speed diesel engine in a power plant has frequently experienced high vibration since the unit completed construction works. Up to date, no fundamental vibration solutions were reached. Hence, several vibration tests and analyses were conducted to identify the root cause of this high vibration and to suggest the optimal countermeasures for diesel engine. The 9.25 Hz and 25.4 Hz vibrations have been observed on main body during operation. The magnitude of engine upper structural vibration is generally similar in horizontal transverse direction. However, differences in the 'Fore' and 'After' vibration magnitude with the same vibration phase angle at 9.25 Hz occur due to the explosion pulsations of 7 cylinders and the Inertia momentum added by the SCR (selective catalytic reduction) duct system. It was analyzed that the excess structural vibration occurred when the natural frequency of engine body is affected by the exciting sources due to the explosion pressure and the discharge pulsation of the seven cylinders in resonance range.

• Nuclear Engineering and Technology
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• v.54 no.10
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• pp.3909-3918
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• 2022

In the event of a severe accident, the reactor core may melt due to insufficient cooling. the high-temperature core melt will have a strong interaction (FCI) with the coolant, which may lead to steam explosion. Steam explosion would pose a serious threat to the safety of the reactors. Therefore, the study of steam explosion is of great significance to the assessment of severe accidents in nuclear reactors. This research focuses on the development of a two-dimensional steam explosion integrated analysis code called SEINA. Based on the semi-implicit Euler scheme, the three-phase field was considered in this code. Besides, the influence of evaporation drag of melt and the influence of solidified shell during the process of melt droplet fragmentation were also considered. The code was simulated and validated by FARO L-14 and KROTOS KS-2 experiments. The calculation results of SEINA code are in good agreement with the experimental results, and the results show that if the effects of evaporation drag and melt solidification shell are considered, the FCI process can be described more accurately. Therefore, it is proved that SEINA has the potential to be a powerful and effective tool for the analysis of steam explosions in nuclear reactors.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.657-658
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• 2006

Although there are many numerical models to simulate fs laser ablation of metals, no model can analyze the ablation phenomena over a wide range of fluence. In this work, a numerical code for simulating the fs laser ablation phenomena of metals has been developed. The two temperature model is employed to predict the ablation rate and the crater shape of metals using phase explosion mechanism in the relatively high fluence regime. Also, the ultrashort thermoelastic model is used for the low fluence regime to account for spallation of the sample by high strain rate. It has been demonstrated that the thermoelastic stress generated within the sample can exceed the yield stress of the material even near the threshold fluence. Numerical computation results are compared with the experiment for Cu and Ni and show good agreement. Discussions are made on the hydrodynamic model considering phase change and hydrodynamic flow.

• Journal of Powder Materials
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• v.11 no.2
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• pp.105-110
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• 2004

In this study the possibility to obtain a homogeneous mixture and to produce solid solutions and intermetallic compounds of Fe and Al nano particles by simultaneous pulsed wire evaporation (S-PWE) have been investigated. The Fe and Al wires with 0.45 mm in diameter and 35 mm in length were continuously co-fed by a special mechanism to the explosion chamber and simultaneously exploded. The characteristics, e.g., phase composition, particle shape, and specific surface area of Fe-Al nano powders have been analyzed. The synthesized powders, beside for Al and $\alpha$-Fe, contain significant amount of a high-temperature phase of $\gamma$-Fe, Fe Al and traces of other intermetallics. The phase composition of powders could be changed over broad limits by varying initial explosion conditions, e.g. wire distance, input energy, for parallel wires of different metals. The yield of the nano powder is as large as 40 wt ％ and the powder may include up to 46 wt % FeAl as an intermetallic compound.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.321-339
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• 2021

Response Surface Method (RSM) has been widely used for flammable cloud size prediction as it can reduce computational intensity for further Explosion Risk Analysis (ERA) especially during the early design phase of offshore platforms. However, RSM encounters the overfitting problem under very limited simulations. In order to overcome the disadvantage of RSM, Bayesian Regularization Artificial Neural (BRANN)-based model has been recently developed and its robustness and efficiency have been widely verified. However, for ERA during the early design phase, there seems to be room to further reduce the computational intensity while ensuring the model's acceptable accuracy. This study aims to develop an integrated method, namely the combination of Center Composite Design (CCD) method with Bayesian Regularization Artificial Neural Network (BRANN), for flammable cloud size prediction. A case study with constant and transient leakages is conducted to illustrate the feasibility and advantage of this hybrid method. Additionally, the performance of CCD-BRANN is compared with that of RSM. It is concluded that the newly developed hybrid method is more robust and computational efficient for ERAs during early design phase.

• Proceedings of the Korean Society of Laser Processing Conference
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• 2000.11a
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• pp.14-18
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• 2000

No Abstract, See Full Text

• Journal of the Korean Society for Precision Engineering
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• v.23 no.1 s.178
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• pp.48-55
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• 2006