• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1287-1289
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• 1995

For the analysis of hot gas flow due to arc in puffer type $SF_6$ gas circuit breakers(GCBs), a program has been developed by adding function for arcing to the Fluid-in Cells(FLIC) method, which is often used for a two dimensional compressible flow problems, utilizing a simplified enthalpy flow arc model available for arcing. In this paper, the results of arc modelling for 800kV GCB are presented and compared with that of cold gas flow in the interrupters. It is shown that the nozzle clogging is the dominating factor in the pressure rise of the puffer chamber. It permits to estimate the dielectric strength of interrupters.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.135-140
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• 2006

In the experimental study of $N_2$ purge cold flow test of impinging(FOOF) injector for determining of instability region, the whistling sound which has a specific frequency is generated. The frequency of whistling is proportional to the gas flow velocity in part of the oxidizer orifice and due to the coupling of the vibrating gas column and the natural frequency of pipe-orifice shape, the discontinuous jumping phenomena arises. The whistling phenomena have no effect on the combustion instability. Compared the damping factor of 1T1L mode with the hot fire test, the instability region of $N_2$ purge cold flow test is very much like that. It means that flow instability by impinging or mixing of jet is the main reason of combustion instability of impinging injector(FOOF) in the hot firing test.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.30.2-31
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• 2020

We present the properties of circumnuclear gas associated with the AGN located in the center of Abell 1644-South. A1644-S is the main cluster in a merging system, which is also known for gas sloshing in its core as seen in X-ray. The X-ray emission of A1644-S shows a rapidly declining profile, indicating the presence of cooling gas flow. This flow of cool gas may fuel the supermassive black hole embedded in the brightest cluster galaxy, leading to the activation of the central AGN. Indeed, we find a parsec-scale bipolar jet feature in the center of A1644-S in our recent KaVA observation, which implies that its central AGN is likely to have been (re)powered quite recently. In order to verify the hypothesis that cooling gas flow in the cluster core can (re)activate the central AGN, we probe the cold gas properties of the central 1 kpc region of A1644-S using the archival VLA and ALMA data. Based on the spatially resolved morphology and kinematics of HI and CO gas, we challenge to identify inflow/outflow gas streams and clumps. We study the role of circumnuclear cool gas in fueling the centrally located cluster AGN in the cool-core environment. We also discuss how the feedback due to the (re)powered AGN affects the surrounding medium.

• Journal of the Korean Society for Railway
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• v.10 no.5
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• pp.563-568
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• 2007

A separate triangular bar type differential pressure flow meter was developed for measuring exhaust gas flow rate from Diesel engine. Three kinds of the separate triangular bar flow meters whose aerodynamic angles are different one another are made and evaluated, respectively. The experimental results show that an aerodynamic shape has a effect on the pressure difference between upstream and downstream at the flow meter, that is, the thinner the shape of the separate triangular bar flow meter is, the smaller the pressure difference at the flow meter is. The separate triangular bar type flow meter was calibrated at both cold and high temperature of the gas flow. A burner system was designed for raising the gas temperature and it was well operated in controlling the gas temperature. An empirical correlation between mass flow rate and differential pressure at the separate triangular bar flow meter was obtained and the empirical correlation was also corrected by the gas temperature.

• Journal of Power System Engineering
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• v.11 no.1
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• pp.56-62
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• 2007

This paper represents the cold energy for liquefied nitrogen gas and cascade refrigerator. In this study, the vaporizer of liquefied nitrogen gas has the fin coil tube type with the dimension of inside diameter of 10mm and outside diameter of 12mm. Also, the total length of vaporizer is 20,000mm. The main experimental parameters are the mean velocity in duct and the supplied flow-rates of liquefied nitrogen gas. For the cascade refrigeration system, the refrigerants are ethane(R 170) in the high pressure stage and R 22 in the low pressure stage.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2817-2822
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• 2007

The purpose of this paper is to study the influence of operating condition and ejector geometries on the hydrodynamics and on the mass transfer characteristic of ejector. The CFD results were validated with available experimental data. Flow field analyses and predictions of ejector performance were also carried out. Variation on the operating conditions was made by varying the gas-liquid flow rate ratio in the range of 0.2 to 1.2. The ejector configuration was also varied on the length to diameter ratio of mixing tube ($L_M/D_M$) in the range of 4 to 10. CFD studies show that at $L_M/D_M$ 5.5, the volumetric mass transfer coefficient increases with respect to gas flow rates. Meanwhile, at $L_M/D_M$ 4, the plot of volumetric mass transfer coefficient to gas-liquid flow rates ratio reach maximum at gas-liquid flow rates ratio of 0.6. This study also shows that volumetric mass transfer coefficient decrease with respect to the increase of mixing tube length.

• Journal of ILASS-Korea
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• v.26 no.1
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• pp.9-17
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• 2021

Six shear coaxial injectors with different recess length and taper angle were manufactured. Cold-flow tests on the injectors were performed at room temperature and pressure using water and air as simulants. By changing the water mass flow rate and air mass flow rate, spray images were taken under single-injection and bi-injection. Breakup length and spray angle were analyzed from instantaneous and averaged spray images using image processing techniques. For all the injectors, the breakup length generally decreased as the momentum flux ratio increased at the same gas mass flow rate. The injectors with 7.5° taper angle usually had the longest breakup length and the smallest spray angle. When the taper angle was 15° or more, it hardly affected breakup length and spray angle. The recess length did not influence breakup length but its effect on spray angle depended on the taper angle.

• 한국연소학회:학술대회논문집
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• 2001.06a
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• pp.9-16
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• 2001

When large size nozzle with low jet velocity is used, the buoyancy effect arises from the density difference among propane, air, and burnt gas. Flame characteristics in such buoyant jets have been investigated numerically to elucidate the effect of buoyancy on lifted flames. It has been demonstrated that the cold jet has circular cone shape since upwardly injected propane jet decelerates and forms stagnation region. In contrast to the cold flow, the reacting flow with a lifted flame has no stagnation region by the buoyancy force induced from the burnt gas. To further illustrate the buoyancy effect on lifted flames, the reacting flow with buoyancy is compared with non-buoyant reacting flow. Non-buoyant flame is stabilized at much lower height than the buoyant flame. At a certain range of fuel jet velocities and fuel dilutions. an oscillating flame is demonstrated numerically showing that the height of flame base and tip vary during one cycle of oscillation. Under the same condition. non-buoyant flame exhibits only steady lifted flames. This confirms the buoyancy effect on the mechanism of lifted flame oscillation.

• Journal of the Korean Institute of Gas
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• v.15 no.3
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• pp.1-5
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• 2011

For the hydrogen liquefaction, the large amount of energy is consumed, because precooling, liquefaction and ortho/para conversion heats should be eliminated. In this paper the basic design and thermal analysis are carried out to reduce the energy consumption by using LNG cold energy for precooling process in hydrogen liquefaction processes. The LNG cold energy utilization for hydrogen precooling enables not only to get energy saving for liquefaction, but to recover the wasted cold energy to sea water at the LNG terminal. The results show that the energy saving rate for liquefaction using LNG cold energy is almost 75% of current industrial hydrogen liquefaction plant. The demand flow-rate of LNG is only 15T/D for 1T/D hydrogen liquefaction.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.9
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• pp.666-673
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• 2009

The turbulent swirling flow field characteristics of a gun-type gas burner with a combustion chamber were investigated under the cold flow condition. The velocities and turbulent quantities were measured by hot-wire anemometer system with an X-type probe. The turbulent swirling flow field in the edge of a jet seems to cause a recirculation flow from downstream to upstream due to the unbalance of static pressure between a main jet flow and a chamber wall. Moreover, because the recirculation flow seems to expand the main jet flow to the radial and to shorten it to the axial, the turbulent swirling flow field with a chamber increases a radial momentum but decreases an axial as compared with the case without a chamber from the range of about X/R=1.5. As a result, these phenomena can be seen through all mean velocities, turbulent kinetic energy and turbulent shear stresses. All physical quantities obtained around the slits, however, show the similar magnitude and profiles as the case without a chamber within the range of about X/R=1.0.