• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.79-84
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• 2004

This paper report our preliminary results of characterizing the jet structures of kerosene injection into quiescent atmosphere and a Mach 2.5 crossflow at various preheat temperature. A heating system has been designed and tested that can prepare heated kerosene of 0.8 kg up to 670 K at a pressure of 5.5 ㎫. Temperature measurement near the injector shows that the temperature of pressurized kerosene can be kept constant during the experimental duration. Comparison of kerosene jet structures in the preheat temperature range of 290-550 K demonstrates that with injection pressure of 4 ㎫ the jet plume turns into vapor phase completely at injection temperature of 550 K, while keeping the penetration depth essentially unchanged. The results suggest that the injection of vaporized fuel would improve the performance of a liquid hydrocarbon-fueled supersonic combustor because the evaporation process is now omitted.

• Journal of Energy Engineering
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• v.12 no.2
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• pp.74-83
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• 2003

In the advanced nuclear power plants including APR1400, the SDVS (Safety Depressurization and Vent System) is adopted to increase the plant safety using the concept of feed-and-bleed operation. In the case of the TLOFW (Total Loss of Feedwater), the POSRV (Power Operated Safety Relief Value) located at the top of the pressurizer is expected to open due to the pressurization of the reactor coolant system and discharges steam and/or water mixture into the water pool, where the mixture is condensed. During the condensation of the mixture, thermal-hydraulic loads such as pressure and temperature variations are induced to the pool structure. For the pool structure design, such thermal-hydraulic aspects should be considered. Understanding the phenomena of the submerged steam jet condensation in a water pool is helpful for system designers to design proper pool structure, sparger, and supports etc. This paper reviews and evaluates the steam jet condensation in a water pool on the physical phenomena of the steam condensation including condensation regime map, heat transfer coefficient, steam plume, steam jet condensation load, and steam jet induced flow.

• Applied Science and Convergence Technology
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• v.25 no.3
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• pp.51-55
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• 2016

The surface treatment of a titanium implant is investigated with a non-thermal atmospheric pressure plasma jet. The plasma jet is generated by the injection of He and $O_2$ gas mixture with a sinusoidal driving voltage of 3 kV or more and with a driving frequency of 20 kHz. The generated plasma plume has a length up to 35 mm from the jet outlet. The wettability of 4 different titanium surfaces with plasma treatments was measured by the contact angle analysis. The water contact angles were significantly reduced especially for $O_2/He$ mixture plasma, which was explained with the optical emission spectroscopy. Consequently, plasma treatment enhances wettability of the titanium surface significantly within the operation time of tens of seconds, which is practically helpful for tooth implantation.

• Fire Science and Engineering
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• v.23 no.6
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• pp.111-115
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• 2009

Acetone LIF and Rayleigh scattering measurements were performed to identify the entrainment of ambient air in the buoyant jet qualitatively. The air entrainment near nozzle exit was enhanced with increasing both an axial distance and Reynolds number. The results supported that the air entrainment had to be considered in isothermal model for the development of its accuracy. Also, this paper provided an isothermal model based on the ideal plume, of which radiative heat loss fraction was assumed to 0.35 and the entainment of isothermal jet was considered. This simple model could be used in compartment or semi-enclosure fires such as tunnel, and it is more reliable because of introducing entrainment effect in isothermal jet.

• Journal of Korea Water Resources Association
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• v.32 no.2
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• pp.153-162
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• 1999

In this study, mixing and dilution characteristics of vertical multijet discharged by multiport diffuser into stagnant water are investigated. The results obtained from the experiment of multiport diffuser performed in the three dimensional flume are as follows. As far as merging process of multiport diffuser is concerned, merging starts at about z/l = 3 although merging length is dependent upon stability condition and thereafter lateral temperature distribution becomes gradually uniform which is typical distribution of plane jet. Analyses of experimental data for minimum dilution show that characteristics of minimum dilution are described based on three regions which are jet region where momentum is dominated, intermediate region, and plume region where buoyancy is dominated. Minimum dilution coefficient in plume region of multiport diffuser obtained in this study is 15% higher than that of plane diffuser. This is because individual jet of multiport diffuser entrains more ambient water before merging is occurred, and therefore dilution increases.

• Nuclear Engineering and Technology
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• v.29 no.1
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• pp.45-57
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• 1997

The direct contact condensation phenomenon, which occurs when steam is injected into the subcooled water, has been experimentally investigated. Two plume shapes in the stable condensation regime are found to be conical and ellipsoidal shapes depending on the steam mass flux and the liquid subcooling. Divergent plumes, however, are found when the subcooling is relatively small. The measured expansion ratio of the maximum plume diameter to the injector inner diameter ranges from 1.0 to 2.3. By means of fitting a large amount of measured data, an empirical correlation is obtained to predict the steam plume length as a function of a dimensionless steam mass flux and a driving potential for the condensation process. The average heat transfer coefficient of direct contact condensation has been found to be in the range 1.0~3.5 ㎿/$m^2$.$^{\circ}C$. Present results show that the magnitude of the average condensation heat transfer coefficient depends mainly on the steam mass fin By using dynamic pressure measurements and visual observations, six regimes of direct contact condensation have been identified on a condensation regime map, which are chugging, transition region from chugging to condensation oscillation, condensation oscillation, bubbling condensation oscillation, stable condensation, and interfacial oscillation condensation. The regime boundaries are quite clearly distinguishable except the boundaries of bubbling condensation oscillation and interfacial oscillation condensation.

• Journal of computational fluids engineering
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• v.16 no.1
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• pp.36-41
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• 2011

Numerical simulation of air-launched rockets from a helicopter was conducted to investigate the aerodynamic interference between air-launched rocket and helicopter. For this purpose, a three-dimensional inviscid flow solver has been developed based on unstructured meshes. An overset mesh technique was used to describe the relative motion between rocket and rocket launcher. The flow solver was coupled with six degree-of-freedom equation to predict the trajectory of free-flight rockets. For the validation, calculations were made for the impinging jet with inclined plate. The rotor downwash of helicopter was calculated and applied to simulation of air-launched rocket. It is shown that the rotor downwash has non-negligible effect on the air-launched rocket and its plume development.

• Advances in aircraft and spacecraft science
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• v.3 no.3
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• pp.243-257
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• 2016

The increase of air traffic volume has brought an increasing amount of issues related to carbon and NOx emissions and noise pollution. Aircraft manufacturers are concentrating their efforts to develop technologies to increase aircraft efficiency and consequently to reduce pollutant discharge and noise emission. Ultra High By-Pass Ratio engine concepts provide reduction of fuel consumption and noise emission thanks to a decrease of the jet velocity exhausting from the engine nozzles. In order to keep same thrust, mass flow and therefore section of fan/nacelle diameter should be increased to compensate velocity reduction. Such feature will lead to close-coupled architectures for engine installation under the wing. A strong jet-wing interaction resulting in a change of turbulent mixing in the aeroacoustic field as well as noise enhancement due to reflection phenomena are therefore expected. On the other hand, pressure fluctuations on the wing as well as on the fuselage represent the forcing loads, which stress panels causing vibrations. Some of these vibrations are re-emitted in the aeroacoustic field as vibration noise, some of them are transmitted in the cockpit as interior noise. In the present work, the interaction between a jet and wing or fuselage is reproduced by a flat surface tangential to an incompressible jet at different radial distances from the nozzle axis. The change in the aerodynamic field due to the presence of the rigid plate was studied by hot wire anemometric measurements, which provided a characterization of mean and fluctuating velocity fields in the jet plume. Pressure fluctuations acting on the flat plate were studied by cavity-mounted microphones which provided point-wise measurements in stream-wise and spanwise directions. Statistical description of velocity and wall pressure fields are determined in terms of Fourier-domain quantities. Scaling laws for pressure auto-spectra and coherence functions are also presented.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.5
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• pp.716-722
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• 2017

The present study numerically investigates the effect of obstacles located in the trajectory of fire plume flow on heat flow characteristics by using Fire Dynamics Simulation (FDS) software in an underground combined cycle power plant (CCPP). Fire size is taken as 10 MW and two different locations of fire source are selected depending on the presence of an obstacle. As the results, when the obstacle is in the trajectory of fire plume, hot plume arrives at the ceiling about 5 times slower in the upper of the fire in comparison to the results without obstacle. In addition, the average propagation time of ceiling jet increases by about 70 % with the distance from the ceiling in the upper of the fire, and it increases mainly about 4 times at the distance of 10 m. Consequently, it is noted that the analysis of heat flow characteristics in the underground CCPP considering fire scenarios is essential to develop the fire detection system for initial response on evacuation and disaster management.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 1996.11a
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• pp.72-75
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• 1996

The objectives of this paper investigate the effect of installed spacing on the activation of spot type heat detection devices. The flow of hot gases under a ceiling resulting from the impingement of a fire plume activates heat detectors and sprinklers. Local temperature and velocity in this ceiling jet are usually expressed with the function of a ceiling height, the distance from a fire location and the heat release rate of fire. And detectors having different. RTI respond in different ways to the same temperature and velocity of ceiling jet. Thus great care should be taken to decide installed spacing of heat detection devices by considering above effects.