• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.676-681
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• 2001

We usually divide the noise of exhaust system into pulsation noise and flow noise. Pulsation noise is the shock wave to occur when the burning gas of low pressure emits and include harmonic having basic frequency as the exhaust cycle of engine. Flow noise is the noise that is produced when gas flow emits into the atmosphere through the pipe and has the character of frequency like pink noise which has the high level of high frequency component. A muffler is divided into reflective type and absorptive type. We usually use the muffler compounding the property of them. In this study, it is the case of transfer matrix method that a muffler is compounded to analyze the elements of each section according to sound wave's proceed direction. But we use simple model. So, we use finite element method that takes short time to analyze. Acoustic analysis gives us transfer matrix to use FEA of SYSNOISE and we use STAR-CD for fluid analysis. We made database that is based on analytical results about the muffler of expansion type, extended type, offset type, reverse type, and perforated type and developed the muffler design system to perform work efficiently.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.6
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• pp.460-466
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• 2009

The mixing method of water and chemicals is significant in a small-scale water supply system because drinking water should be supplied with a certain quantity of remaining chemicals maintained. In the present study, the concentration distribution and the mixing index were obtained from four models, which were to find out the optimal mixing method of water and chemicals. The two models brought the good mixing effects out of the four, one for providing chemicals from the center of water supply pipe and the other for setting up the semicircle block at the downstream of the chemicals-providing pipe. As a result, the mixing effect was found out to be increased due to the diffusion and the disturbance of flows. In conclusion, these numerical results are expected to contribute to designing the optimal mixing system.

• Nuclear Engineering and Technology
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• v.52 no.4
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• pp.755-763
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• 2020

The critical flow phenomenon has been studied because of its significant effect for design basis accidents in nuclear power plants. Transition points from thermal non-equilibrium to equilibrium are different according to the geometric effect on the critical flow. This study evaluates the uncertainty parameters of the critical flow model for analysis of DBA (Design Basis Accident) with the MARS-KS (Multi-dimensional Analysis for Reactor Safety-KINS Standard) code used as an independent regulatory assessment. The uncertainty of the critical flow model is represented by three parameters including the thermal non-equilibrium factor, discharge coefficient, and length to diameter (L/D) ratio, and their ranges are determined using large-scale Marviken test data. The uncertainty range of the thermal non-equilibrium factor is updated by the MCDA (Model Calibration through Data Assimilation) method. The updated uncertainty range is confirmed using an LBLOCA (Large Break Loss of Coolant Accident) experiment in the LOFT (Loss of Fluid Test) facility. The uncertainty ranges are also used to calculate an LBLOCA of the APR (Advanced Power Reactor) 1400 NPP (Nuclear Power Plants), focusing on the effect of the PCT (Peak Cladding Temperature). The results reveal that break flow is strongly dependent on the degree of the thermal non-equilibrium state in a ruptured pipe with a small L/D ratio. Moreover, this study provides the method to handle the thermal non-equilibrium factor, discharge coefficient, and length to diameter (L/D) ratio in the system code.

• Special Issue of the Society of Naval Architects of Korea
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• 2013.12a
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• pp.30-34
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• 2013

Prevention of exhaust gas back flow becomes a great interest to shipyards and shipowners in large container carriers because exhaust gas pollutes cargoes, flows back into the deck house and the engine room area through fresh air intakes and fan rooms, gives harmful damages to the crew's health and also gives thermal damages to electric equipments on the navigation deck. The phenomena of exhaust gas back flow has been studied with the analysis of sea trial records and wind tunnel tests and the height of the exhaust gas pipe, the front area of the deck house, the inflow speed and the position of the radar mast platform has been confirmed as the principal factors of exhaust gas back flow phenomena. The simple empirical formula to estimate exhaust gas back flow phenomena and the design guidances of exhaust gas related structures on deck has been introduced. In future, parametric studies for the exhaust gas back flow factors will be carried out with the CFD analysis. The results of this study will be the guide for development of the prevention method of exhaust gas back flow phenomena for large container carriers.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.8
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• pp.991-998
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• 2013

The fuel injection pipe of a common rail system used in a clean diesel vehicle plays a role in supplying fuel from a rail to the injector of each cylinder connecting the engine under a repeated internal pressure. The fuel injection pressure is increased to over 200 MPa for satisfying EU emission standards and improving fuel efficiency, and a heading process and an autofrettage process are required for preventing folding defects and improving fatigue life. In this study, the flow stress and SN data of the material of the pipe are obtained through a tensile test and a fatigue test. The heading process for checking the folding defects of pipe ends is performed by using FEA. Furthermore, the optimal design of the autofrettage process for improving fatigue life considering not only the compressive residual stresses of the inner surface but also the tensile residual stresses of the outer surfaces of the pipe under the repeated internal pressure is performed by using FEA. To verify the process design, fatigue analysis for the autofrettaged pipe is performed.

• Journal of Biosystems Engineering
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• v.32 no.6
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• pp.430-439
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• 2007

This study was carried out to(1) visualize the installation effect of an anti-wind net; (2) evaluate structural stability of typical anti-wind nets in Jeju; and (3) present the optimal specification of pipes in an anti-wind net for maximum instant wind velocities of 40 m/s and 45 m/s. The analyses were done for anti-wind nets with a mesh of 4 mm and a height of 3 m by using CFX and ANSYS. The results showed that the wind went down due to flow resistance when passing through an. anti-wind net. The anti-wind net with the supporting pipe being installed every two main columns was certainly unstable because the main column not sustained by the supporting pipe became cantilever. With regard to the position of a fixing point of the supporting pipe, von Mises stress on pipes was certainly increased as vertical positions of the supporting pipe were changed to be too lower or higher than an adequate position but there was little difference according to horizontal positions. The adequate vertical position was $2{\sim}2.5\;m$ high from the ground. For a maximum instant wind velocity of 40 m/s, the optimal specification of pipes was a main column of ${\varphi}48.1{\times}2.1$ t@2,000, cross beams(bottom and top) of ${\varphi}26.7{\times}1.9\;t$, cross beams(center) of ${\varphi}33.5{\times}2.1$ t/2ea and a supporting pipe of ${\varphi}31.8{\times}1.5$ t@2,000. In case of a maximum instant wind velocity of 45 m/s, the optimal specification of pipes with structural stability was a main column of ${\varphi}48.6{\times}3.25$ t@2,000, cross beams(bottom and top) of ${\varphi}26.7{\times}1.9\;t$, cross beams(center) of ${\varphi}48.1{\times}2.1$ t/2ea and a supporting pipe of ${\varphi}31.8{\times}1.5$ t@2,000.

• 한국연소학회:학술대회논문집
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• 2006.10a
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• pp.299-303
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• 2006

From the analysis of fly ash, which contains unburned carbon, collected from the coal-fired Yong Hung power station, most particles are turned out to be hollow cenosphere and agglomerated soot particles. The sooting potential from six coals used in the plant were investigated with CPD model. The results show that the higher potential presented to Peabody, Arthur, Shenhua coals rather than other coals. It is necessary to measure the coal flow rates at each coal feeding pipe for four burner levels since they affect the extent of mixing of soot with oxidant, in turn, the oxidation rate of soot particles. The unbalance in coal flow rate was found in several coal pipes. We successfully reduced unburned carbon in ash by increasing the excess air and changing the SOFA yaw angle.

• Journal of Power System Engineering
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• v.13 no.2
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• pp.30-35
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• 2009

Numerical Calculations for dimensionless pressure drop (friction factor times Reynolds number) have been obtained for fully developed laminar flow of MPL(Modified Power Law) fluid in isosceles triangle pipes. The solutions are valid for Pseudoplastic fluids over a wide range from Newtonian behavior at low shear rates through transition region to power law behavior at higher shear rates. The analysis identified a dimensionless shear rate parameter which for a given set of operating conditions specifies where in the shear rate range a particular system is operating, i.e., Newtonian, transition or power law region. The numerical calculation data of the dimensionless pressure drop for the Newtonian and power law regions are compared with previously published asymptotic results presenting within 0.16 % in Newtonian region and 2.98 % in power law region.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.1
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• pp.17-23
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• 2006

This study is to investigate the pressure wave characteristics and the maximum pressure rise generated by instantaneous valve closure at the end of the straightening polybutylene piping system. Experiments were conducted under the following conditions: initial pressure $1\~5$ bar, flow velocity $\~0.5-3.0m/s$ and water temperature $25^{\circ}C$. Results indicated that the peak pressure generated by quick valve closure reached Joukowsky's value. We also found that the maximum pressure rise and the pressure history depended on not only initial steady pressure but also flow velocity.

• Journal of the KSME
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• v.16 no.3
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• pp.277-283
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• 1976

An analytical study on the effects of initial turbulence intensities and Reynolds Number on the transition flow of a circular tube is conducted in Part I;Analysis of Transition Flow. In this second report, however, the effects of tripping wire on the developing regions of a horizontal pipe are studied experimentally and the results of analytical and experimental studies are compared. The agreements between the two results are relatively good. The diameter of the apparatus tube in the experimental works is 76.25mm. and the length is about 7m. The tripping wire diameters used in the experiments are 1.0,1.5,2.0,2.5mm., etc. From the experimental works, the relations between tripping wire size; o.e., diameter and Reynolds Number are proposed for the given thbe diameter.