• 한국전산유체공학회:학술대회논문집
• /
• 2008.03b
• /
• pp.260-263
• /
• 2008

KEPCO(Korea Electric Power Corporation) is performing the nation's first biogas-MGT project as an effort to encourage the utilization of wasted biogas which contains useful CH4. The goals of this project are to develop the Pretreatment system of Livestock bio-gas and set up the biogas-MGT co-generation system. The project will not only utilze flared biogas as precious energy but also improve the economics of the plant a lot. The pretreatment system mainly consists of sulfur removal tower, biogas compressor and many filtering systems. A computational fluid dynamics study in the bio gas sulfur removal tower and sulfur absorption filter was carried out. Understanding of the flow in the sulfur removal tower and sulfur adsorption filter obtained by this study can be used to identify the problems in the sulfur removal tower and to improve the sulfur removal efficiency of the sulfur removal tower. Resistance material modeling is used to simulate the sulfur adsorption filter, and the resistance coefficient was adjusted to reflect the experimental pressure loss value. And the pressure loss change with the flowrate is predicted

• Transactions of the Korean hydrogen and new energy society
• /
• v.27 no.1
• /
• pp.29-35
• /
• 2016

It is important to uniformly supply the fuel gas into the reaction activity area in polymer electrolyte membrane fuel cell (PEMFC). Recent studies have shown that the cell performance can be significantly improved by employing metal foam gas distributor as compared with the conventional bipolar plate types. The metal foam gas distributor has been reported to be more efficient to fuel transport. In this study, three-dimensional computational fluid dynamics (CFD) simulations have been performed to examine the effects of metal foam flow field design on the fuel supply to the reaction site. Darcy's law is used for the flow in the porous media. By solving additional advection equation for fluid particle trajectory, the gas transport has been visualized and examined for various geometrical configuration of metal foam gas distributor.

• KEPCO Journal on Electric Power and Energy
• /
• v.5 no.2
• /
• pp.103-111
• /
• 2019

The combined cycle plant is an integration of gas turbine and steam turbine, combining the advantages of both cycles. It recovers the heat energy from gas turbine exhaust to use it to generate steam. The heat recovery steam generator plays a crucial role in combined cycle plants, providing the link between the gas turbine and the steam turbine. Simulation of the performance of the HRSG is required to study its effect on the entire cycle and system. Computational fluid dynamics has potential to become a useful to validate the performance of the HRSG. In this study a solver has been implemented in the open source code, OpenFOAM, for combustion simulation in the heat recovery steam generator. The solver is based on the steady laminar flamelet model to simulate detailed chemical reaction mechanism. Thereafter, the solver is used for simulation of HRSG system. Three cases with varying fuel injections and gas turbine exhaust gas flow rates were simulated and the results were compared with measurements at the system outlet. Predicted temperature and emissions and those from measurements showed the same trend and in quantitative agreement.

• Transactions of the Korean hydrogen and new energy society
• /
• v.33 no.4
• /
• pp.363-371
• /
• 2022

In this study, the operation characteristics of the internal reforming type molten carbonate fuel cell (MCFC) were studied using computational fluid dynamics (CFD) analysis according to the steam to carbon ratio (S/C ratio), operating temperature, and gas utilization. From the simulation results, the distribution of gas composition due to the electrochemical reaction and the reforming reaction was predicted. The internal reforming type showed a lower temperature difference than the external reforming type MCFC. As the operating temperature decreased, less hydrogen was produced and the performance of the fuel cell also decreased. As the gas utilization rate decreased, more gas was injected into the same reaction area, and thus the performance of the fuel cell increased.

• The Bulletin of The Korean Astronomical Society
• /
• v.44 no.2
• /
• pp.75.4-75.4
• /
• 2019

We present a quantitative analysis of the relationship between the gas dynamics and star formation history of DDO 210 which is an irregular dwarf galaxy in the local Universe. We perform profile analysis of an high-resolution neutral hydrogen (HI) data cube of the galaxy taken with the large Very Large Array (VLA) survey, LITTLE THINGS using newly developed algorithm based on a Bayesian Markov Chain Monte Carlo (MCMC) technique. The complex HI structure and kinematics of the galaxy are decomposed into multiple kinematic components in a quantitative way like 1) bulk motions which are most likely to follow the underlying circular rotation of the disk, 2) non-circular motions deviating from the bulk motions, and 3) kinematically cold and warm components with narrower and wider velocity dispersion. The decomposed kinematic components are then spatially correlated with the distribution of stellar populations obtained from the color-magnitude diagram (CMD) fitting method. The cold and warm gas components show negative and positive correlations between their velocity dispersions and the surface star formation rates of the populations with ages of < 40 Myr and 100~400 Myr, respectively. The cold gas is most likely to be associated with the young stellar populations. Then the stellar feedback of the young populations could influence the warm gas. The age difference between the populations which show the correlations indicates the time delay of the stellar feedback.

• Nuclear Engineering and Technology
• /
• v.55 no.7
• /
• pp.2697-2711
• /
• 2023

In this study, the validity of reducing the number of gas turbine stages designed for a nitrogen Brayton cycle coupled to a sodium-cooled fast reactor was assessed. The turbine performance was evaluated through computational fluid dynamics (CFD) simulations under different off-design conditions controlled by a reduced flow rate and reduced rotational speed. Two different multistage gas turbines designed to extract almost the same specific work were selected: two- and three-stage turbines (mid-span stage loading coefficient: 1.23 and 1.0, respectively). Real gas properties were considered in the CFD simulation in accordance with the Peng-Robinson's equation of state. According to the CFD results, the off-design performance of the two-stage turbine is comparable to that of the three-stage turbine. Moreover, compared to the three-stage turbine, the two-stage turbine generates less entropy across the shock wave. The results indicate that under both design and off-design conditions, increasing the stage loading coefficient for a fewer number of turbine stages is effective in terms of performance and size. Furthermore, the Ellipse law can be used to assess off-design performance and increasing exponent of the expansion ratio term better predicts the off-design performance with a few stages (two or three).

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.38 no.9
• /
• pp.773-779
• /
• 2014

A qualitative and quantitative analysis on flame dynamics is required to model combustion instability characteristics in gas turbine lean premixed combustors. The current paper shows the flame transfer function modeling results using CFD(Computational Fluid Dynamics) techniques for the flame dynamics study. It is generally known that flame shapes determine the basic characteristics of the flame transfer function. The comparisons of the modeled flame shapes with the measured ones were made using the optimized heat transfer conditions. Modeling results of the flame transfer function show the close behaviors to the measured data with a reasonable accuracy if the flame geometry can be exactly captured.

• Membrane Journal
• /
• v.33 no.6
• /
• pp.447-453
• /
• 2023

The performance of computer systems and the development of various computer simulation programs have made it possible to analyze chemical systems composed of more complex elements, and accordingly, research using molecular dynamics simulation is being actively conducted. Research on calculating the gas permeation characteristics of polymer membranes by molecular dynamics, which was previously conducted mainly through experiments, is receiving attention for gas barrier membranes used in food packaging and pharmaceuticals. Recently, there has been a report that a gas barrier effect appears when a coating film is made using silk fibroin, and in this study, a study was conducted using molecular dynamics simulation to confirm whether an oxygen barrier effect appears when a composite film is made using silk fibroin. We built a single model, calculated the gas permeation characteristics, and compared it with the experimental value to confirm that the model reflects the actual experimental results. Actual composite membrane models were then built and the gas movement path within the polymer was analyzed. As a result, oxygen molecules were found that they could not pass through and was blocked in the fibroin region. Therefore, the composite membrane with silk fibroin has excellent oxygen barrier property and is expected to be useful in food packaging, etc.

• Applied Science and Convergence Technology
• /
• v.26 no.6
• /
• pp.184-188
• /
• 2017

Polymer deposition pattern on the ceramic lid surface is analyzed by numerical modeling. Assumption was made that is affected by gas flow pattern from the horizontal and vertical nozzles, temperature profile from the finger-like branches made of graphite and electrostatic potential effect. Calculated results showed gas flow dynamics is less relevant than two others. Temperature and electrostatic effects are likely determining the polymer deposition pattern based on our numerical simulation results.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.12
• /
• pp.125-130
• /
• 2019

A gas-spring has been used in many areas and its use is increasing because it can be designed for a range of purposes. In this study, the behavior of a piston with an orifice hole inside the gas-spring cylinder was predicted using computational fluid dynamics (CFD). The piston was designed to reduce the reaction force if the gas-spring is compressed and to move at a low speed when it is returned. The analysis showed that if the initial gas pressure in the gas-spring is increased to a certain level, the speed of the piston would not decrease with time but will remain constant. The effects of orifice hall size on the piston return speed were investigated. Reducing the size of the orifice hole will increase the pressure difference on both sides of the piston, reduce the piston speed, and make it more constant. On the assumption of a constant speed of the piston, a theoretical solution to the return speed of the piston was derived according to the initial gas pressure, and the results for several initial gas pressures were compared with those of CFD. Comparison studies showed similar results for both methods.