• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.315-318
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• 2006

This paper concerns about coupled dynamic analysis of the deep-seabed mining system in launching operation. The dynamic behavior of mining system consisting of lifting pipe, buffer station, flexible conduit and self-propelled miner is simulated in time domain. The launching operation is divided into four critical phases: (1) deployment of miner and flexible conduit, (2) deployment of lifting pipe, flexible conduit and miner, (3) touch-down of miner, (4) final launching. The dynamic responses of sub-systems - miner, flexible conduit, buffer and lifting pipe - are analyzed in each launching phase. According to the changing periods of forced excitation at the top, the dynamic responses of sub-systems are diverse in their characteristics. It has been shown that the total integrated responses of sub-systems are strongly affected by the design parameters. Especially, the principal dimensions of flexible conduit seem to be significant in determining of the global response. Based on the simulation results, safe operation conditions are investigated.

• Computers and Concrete
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• v.21 no.4
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• pp.431-440
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• 2018

Fluid velocity analysis on the instability of pipes reinforced by silica nanoparticles ($SiO_2$) is presented in this paper. Mori-Tanaka model is used for obtaining the effective materials properties of the nanocomposite structure considering agglomeration effects. The well known Navier-Stokes equation is used for obtaining the applied force of fluid to pipe. Based on the Reddy higher-order shear deformation theory, the motion equations are derived based on energy method and Hamilton's principal. The frequency and critical fluid velocity of structure are calculated using differential quadrature method (DQM) so that the effects of different parameters such as volume fractions of SiO2 nanoparticles, SiO2 nanoparticles agglomeration, boundary conditions and geometrical parameters of pipes are considered on the nonlinear vibration and instability of the pipe. Results indicate that increasing the volume fractions of SiO2 nanoparticles, the frequency and critical fluid velocity of the structure are increased. Furthermore, considering SiO2 nanoparticles agglomeration, decreases the frequency and critical fluid velocity of the pipe.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.273-277
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• 2009

An oxidizer tunnel-type pipe, which shall transport oxidizer from an oxidizer tank to a turbo-pump of an engine, studied is installed through a fuel tank located under an oxidizer tank. A tunnel-type pipe can save weight compared to a detour-type pipe, however may vary the temperature of fuel stored in a fuel tank because of a broad heat transfer area. Hence in this study the characteristics of main oxidizer pipe and thermal propagation from oxidizer to a fuel tank are monitored by a cryogenic performance test with a tunnel-type pipe. In addition, the possibility of adaptation of an oxidizer tunnel-type pipe to launcher system is also analyzed.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.165-168
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• 2002

This paper describes the dynamics of the weak shock wave propagating inside some kinds of branched pipe bends. Computations are carried out by solving the two-dimensional, compressible, unsteady Euler Equations. The second-order TVD(Total Variation Diminishing) scheme is employed to discretize the governing equations. For computations, two types of branched pipe($90^{\circ}$ branch,$45^{\circ}$ branch) with a diameter of D are used. The incident normal shock wave is assumed at D upstream of the pipe bend entrance, and its Mach number is changed between 1.1 and 2.4. The flow fields are numerically visualized by using the pressure contours and computed schlieren images. The comparison with the experimental data performed for the purpose of validation of computational work. Reflection and diffraction of the propagating shock wave are clarified. The present computations predicted the experimented flow field with a good accuracy.

• The Journal of Korea Robotics Society
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• v.5 no.3
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• pp.251-261
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• 2010

In this paper, we introduce an internal pipeline exploration of an in-pipe robot, based on the landmark recognition system. The fittings of pipelines such as elbows and branches are used as the landmarks. The robot recognizes the landmarks with a vision system by using the shadows of the elements, which are generated by the specially designed illuminator on the robot. By using a simple image-processing, the robot can easily detect and distinguish these landmarks while recognizing the direction of the pipeline path. Simultaneously, all information for exploration is continuously recorded and used to reconstruct the map of the pipelines. The effectiveness of the proposed method is verified by real experiments using the in-pipe robot MRINSPECT V for moving inside of the miniature urban 8-inch gas pipeline structure.

• Journal of the Optical Society of Korea
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• v.20 no.6
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• pp.770-777
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• 2016

It has been a challenge for researchers to accurately measure high temperature creep strain online without damaging the mechanical properties of the pipe surface. To this end, a noncontact method for measuring high temperature strain of a main steam pipe based on digital image correlation was proposed, and a system for monitoring of high temperature strain was designed and developed. Wavelet thresholding was used for denoising measurement data. The sub-pixel displacement search algorithm with curved surface fitting was improved to increase measurement accuracy. A field test was carried out to investigate the designed monitoring system of high temperature strain. The measuring error was less than $0.4ppm/^{\circ}C$, which meets actual measurement requirements for engineering. Our findings provide a new way to monitor creep damage of the main steam pipe of a boiler of an ultra-supercritical power plant in service.

• ETRI Journal
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• v.20 no.4
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• pp.380-394
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• 1998

A numerical study has been performed to predict the characteristics on the transient operation of the heat pipe with multiple heaters for electronic cooling. The model of the heat pipe was composed of the evaporator section with four heaters, insulated transport section, and the condensor section with a conductor which is cooled with uniform heat flux condition to surrounding. The governing equations and the boundary conditions were solved by the generalized PHOENICS computational code employing the finite volume method. Two test cases are investigated in present study; Case 1 indicates that the 1st and 2nd heaters among four heating sources are heated off, while the 3rd and 4th heaters are heated on. Case 2 is the inverse situation switched from heating location of Case 1. The results show that the transient time to reach the steady state is shorter for Case 1 than for Case 2. Especially, the temperature difference of the heater during switching operation is relatively small compared to the maximum allowable operating temperature difference in electronic system. Hence, it is predicted that the heat pipe in present study operates with thermally good reliability even for switching the heaters.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.6
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• pp.7-14
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• 2008

The main objective of sewer rehabilitation is to improve its function while eliminating inflow/infiltration (I/I). If we can identify the amount of I/I for an individual pipe, it is possible to estimate the I/Is of sub-areas clearly. However, in real, the amount of I/I for an individual pipe is almost impossible to be obtained due to the limitation of cost and time. In this study, I/I occurrence of each sewer pipe is estimated using AHP (Analytic Hierarch Process) and RPDM (Rehabilitation Priority Decision Model for sewer system) was developed using the estimated I/I of each pipe to perform the efficient sewer rehabilitation. Based on the determined amount of I/I for an individual pipe, the RPDM determines the optimal rehabilitation priority (ORP) using a genetic algorithm for sub-areas in term of minimizing the amount of I/I occurring while the rehabilitation process is performed. The benefit obtained by implementing the ORP for rehabilitation of sub-areas is estimated by the only waste water treatment cost (WWTC) of I/I which occurs during the sewer rehabilitation period. The results of the ORP were compared with those of a numerical weighting method (NWM) which is the decision method for the rehabilitation priority in the general sewer rehabilitation practices and the worst order which are other methods to determine the rehabilitation order of sub-areas in field. The ORP reduced the WWTC by 22% compared to the NWM and by 40% compared to the worst order.

• Journal of Hydrogen and New Energy
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• v.8 no.2
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• pp.91-97
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• 1997

The goals of this research are to understand the $NO_x$ emission in direct injected diesel engine with premixed hydrogen fuel. Hydrogen fuel was supplied into the test engine through the intake pipe. Amount of hydrogen-supplemented fuel was 70 percent basis heating value of the total fuel. The effects of intake air temperature on $NO_x$ emission were studied. The intake air temperature was controlled by flow rate of liquid nitrogen. The major conclusions of this work include : (i) the tested engine was run without backfire under 70 percent hydrogen fuel supplemented. (ii) radicals of nitrogen gas in the intake pipe were increased by 30 percent and cylinder gas temperature was decreased by 24 percent as the intake air temperature were changed from $23^{\circ}C$ to $0^{\circ}C$ ; and (iii) $NO_x$ emission per unit heating value of supplied fuel was decreased by 45 percent with same decrease of intake air temperature.

• Journal of the Korean Society of Safety
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• v.39 no.1
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• pp.27-32
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• 2024

This study analyzed cases of hydrogen (H₂) and natural gas (CH₄) leakage from a hydrogen-blended natural gas pipeline to determine a range of leakage characteristics, including leakage type, pipe material, pipe diameter, pressure, and damage size. Based on the results of this analysis, five hydrogen-blended natural gas leakage scenarios were selected. The national vision for a carbon-neutral society by 2050 is a very important strategic objective and promotes environmentally sustainable economic development in the age of the climate crisis. Accordingly, zero-carbon and low-carbon policies are being promoted in various fields, including energy production, consumption, and industrial processes. Hydrogen-blended natural gas is eco-friendly and is considered an important step towards carbon neutrality, with various countries including the United States and several European countries conducting empirical research to further investigate its potential. In Korea, a national research project commenced in April 2023 to verify and demonstrate the life cycle safety of blending hydrogen into the natural gas network. The results of this study will provide important data for the analysis of the damage impacts caused by the leakage of hydrogen-blended natural gas, such as the diffusion of gas clouds, fires, and gas explosions.