• Journal of Energy Engineering
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• v.24 no.1
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• pp.149-163
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• 2015

In this study, we conducted study on the confirmation of thermal-hydraulic safety for Mast assembly with Computational Fluid Dynamics(CFD) analysis. Before performing the natural convection analysis for the Mast assembly by using CFD code, we validated the CFD code against two benchmark natural convection data for the evaluation of turbulence models and confirmation of its applicability to the natural convection flow. From the first benchmark test which was performed by Betts et al. in the simple rectangular channel, we selected standard k-omega turbulence model for natural convection. And then, calculation performance of CFD code was also investigated in the sub-channel of rod bundle by comparing with PNL(Pacific Northwest Laboratory) experimental data and prediction results by MATRA and Fluent 12.0 which were performed by Kwon et al.. Finally, we performed main natural convection analysis for fuel assembly inside the Mast assembly by using validated turbulence model. From the calculation, we observed stable natural circulation flow between the mast assembly and pool side and evaluated the thermal-hydraulic safety by calculating the departure from nucleate boiling ratio.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5B
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• pp.547-558
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• 2008

With the advent of super cargo ship due to the explosive increase in the amount of cargo shipped via seas, some mega ports are under construction in South Korea, to accommodate the super cargo ship, and some of them already enter their final phase. To sustain the harbor tranquility, mega ports usually comprise huge vertical type breakwaters which are intrinsically vulnerable to the attack of long waves. In this rationale, we present the chamber type breakwater with a circular curtain wall - Eco-breaker 2, to alleviate the reflection of long waves and numerically investigate the hydraulic characteristics of Eco-breaker 2. As a wave driver, we use the Navier-Stokes eq., the most robust wave driver, using SPH (Smoothed Particle Hydrodynamics) and LES (Large Eddy Simulation). For the verification of numerical results, we also carried out hydraulic model test. It is shown that Eco-breaker 2 can effectively alleviate the reflection of long waves with its inherited large organized eddies encompassing the water chamber and some region off the curtain wall of varying size. It is also shown that the scope and strength of large organized eddies strongly depends on the incident wave period, and the reflection coefficient can be lowered to 0.18 by tuning the size of water chamber such that resident time at the chamber is just short of the half period of incident waves. Based on these results, we present the specification of Eco-breaker 2 to boost its use on the development of water environment friendly harbor worldwide.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.424-429
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• 2018

In this study, an expansion joint that is susceptible to waterhammer was tested for its vibration durability. The operation data for the hydraulic actuator was the expansion length of the expansion joint when the waterhammer occurred. In the case of the vibration durability test, the internal temperature status of the expansion joint was assumed to be a stress factor and a lifespan prediction model was assumed to follow the Arrhenius model. A test was carried out by increasing the internal temperature status at $30^{\circ}C$, $50^{\circ}C$, and $65^{\circ}C$. By a linear transformation of the lifespan data for each temperature, a constant value and activation energy coefficient was induced for the Arrhenius equation and verified by comparing the value of a lifetime prediction model with the experimental value at $85^{\circ}C$. The failure modes of the ongoing or finished test were leakage, bellows separation, and internal deformation. In the future, a composite lifespan prediction model, including two more stress factors, will be developed.

• Structural Engineering and Mechanics
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• v.16 no.3
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• pp.241-257
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• 2003

The first seismically isolated structure in Taiwan was completed in early 1999. Seven new bridges of the Second National Freeway located at Bai-Ho area, a region which is considered to be of high seismic risk, have been designed and constructed with lead-rubber seismic isolation bearings. Since this is the first application of seismic isolation method to the practical construction in Taiwan, field tests were conducted for one of the seven bridges to evaluate the assumptions and uncertainties in the design and construction. The test program is composed of ambient vibration tests, forced vibration tests, and free vibration tests. For the free vibration tests, a special test setup composed of four 1000 kN hydraulic jacks and a quick-release mechanism was designed to perform the function of push-and-quick release. Valuable results have been obtained based on the correlation between measured and analytical data so that the analytical model can be calibrated. Based on the analytical correlation, it is concluded that the dynamic characteristics and free vibration behavior of the isolated bridge can be well captured when the nonlinear properties of the bearings are properly considered in the modeling.

• Journal of Biosystems Engineering
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• v.29 no.5 s.106
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• pp.407-418
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• 2004

There are several different types of continuously variable transmission(CVT) such as toroidal drive, belt drive, hydrostatic drive, hydro-mechanical drive. The toroidal CVT is an alternative to the manual transmission, HST, power-shift gear trans-missions or other CVTs. The driver of the CVT tractor doesn't have to operate a shia lever since the CVT controller automatically controls the speed of tractor. Thus, it is much easier to operate the CVT tractor. The fuel efficiency of CVT tractor can be increased since the controller responds quickly to the change in external load on the wheel during field operation. This study was conducted to develop the hardwares and softwares for the toroidal CVT controller which control the variator and the range clutches. The hardware consisted of a measurement system, hydraulic system and computer. And the PID controller was developed using the simulation model of the CVT control system. Through the simulation, the control coefficients for the PID controller were selected. Finally, the performance of the CVT control system was evaluated by step response test and torque response test. The settling time of the CVT control system appeared to be fast enough for field operations.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.41-45
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• 2009

The small-sized bi-propellant thruster using a high concentrated hydrogen peroxide and kerosene as the oxidizer and fuel was designed and fabricated in this study. The water cold-flow test was performed to verify the performance characteristics of the injector. The mixing head assembly used in this model thruster was designed as a structure to combine igniter, injectors and film cooling, which are capable of regulating each mass flowrate. This maximize the experimental verification and efficiency of the design optimization. Finally, the mass flowrate and spray pattern of injector were evaluated by the hydraulic test. Therefore, the design validity of the mixing head was verified.

• International Journal of Highway Engineering
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• v.8 no.2 s.28
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• pp.95-104
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• 2006

Hysteresis is a common feature exhibited in hydraulic properties of an unsaturated soil. This study focuses on hysteresis observed in a compacted weathered granite subgrade soils based on the pressure plate laboratory tests. It was found that the Soil-Water Characteristics Curve of a soil is hysteretic and unique. The results also show that the wetting and drying curves predicted using the Fredlund and Xing model is quite close to the laboratory-measured results. For a specific matric suction, water content or coefficient of permeability on a wetting curve is always lower than those found on a drying curve.

• Nuclear Engineering and Technology
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• v.46 no.5
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• pp.655-666
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• 2014

The CUPID code has been developed at KAERI for a transient, three-dimensional analysis of a two-phase flow in light water nuclear reactor components. It can provide both a component-scale and a CFD-scale simulation by using a porous media or an open media model for a two-phase flow. In this paper, recent advances in the CUPID code are presented in three sections. First, the domain decomposition parallel method implemented in the CUPID code is described with the parallel efficiency test for multiple processors. Then, the coupling of CUPID-MARS via heat structure is introduced, where CUPID has been coupled with a system-scale thermal-hydraulics code, MARS, through the heat structure. The coupled code has been applied to a multi-scale thermal-hydraulic analysis of a pool mixing test. Finally, CUPID-SG is developed for analyzing two-phase flows in PWR steam generators. Physical models and validation results of CUPID-SG are discussed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.533-536
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• 2010

It has been manufactured the a prototype of the oxygen rich preburner which can be used for a small high performance liquid rocket engine. Based on the model designed and analyzed by KARI a series of the work was made. First, the layout was drawn and then two kinds of the test specimen were devised and manufactured for the hydraulic and pressure test respectively. It was confirmed that the details in designing and manufacturing the preburners. All of them efforts may help establish the bases to develop high performance liquid rocket engine.

• Nuclear Engineering and Technology
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• v.53 no.7
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• pp.2251-2260
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• 2021

The motion control of the divertor maintenance system of the China Fusion Engineering Test Reactor (CFETR) was studied in this paper, in which CFETR Multi-Functional Maintenance Platform (MFMP) was simplified as a parallel robot for the convenience of theoretical analysis. In order to design the motion controller of parallel robot, the kinematics analysis of parallel robot was carried out. After that, the dynamic modeling of the hydraulic system was built. As the large variation of heavy payload on MFMP and highly nonlinearity of the system, A Fuzzy-PID controller was built for self-tuning PID controller parameters by using Fuzzy system to achieve better performance. In order to test the feasibility of the Fuzzy-PID controller, the simulation model of the system was built in Simulink. The results have showed that Fuzzy-PID controller can significantly reduce the angular error of the moving platform and provide the stable motion for transferring the divertor.