• Journal of the Korean Society of Combustion
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• v.4 no.1
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• pp.117-129
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• 1999

A method for the mixing augmentation of the transverse injection of fuel in a Scramjet combustor is suggested. Based on the fact that the main factor controlling the mixing characteristics in transverse injection is the effective back-pressure (the pressure around the injection hole) it is tried to make a flow expansion near the injection port in order to reduce effective back-pressure. A three dimensional Navier-Stokes code adopting the upwind method of Roe#s flux difference splitting scheme is used. The k-w SST turbulence model turbulence model is used to calculate the turbulent viscosity. It is shown that the reducing of the effective back-pressure make it possible to increase the penetration distance and to increase the mixing rate without excessive losses of stagnation pressure. Also, it is shown that the streamwise vorticity generated by baroclinic torque has great influences on the mixing process.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.2
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• pp.359-372
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• 1988

Characteristics of twin spray ejected from two swirl spray nozzles were studied experimentally. By using a patternator for measuring volumetric flux of drop flow at various locations inside the spray, variation of the twin spray pattern along the axial direction was studied with changing the injection pressure and the distance between the nozzles. The general findings from the experiments are as follows: (i) as axial distance from the nozzles increases, the spray pattern in x-z plane which contains both nozzles changes significantly. On the other hand the spray pattern in y-z plane which passes the midpoint between two nozzles remains almost unchanged at outer region as axial distance and injection pressure vary; (ii) at the downstream of the twin spray with spray interaction, the maximum volumetric flux in y-z plane (q$_{max}$)$_{y}$, has tendency to become larger than that of x-z plane (q$_{max}$)$_{x}$, due to a characteristic(hollow cone shape) of the constituting swirl sprays, and this trend is pronounced at higher injection pressure since the cross-section of each single spray remains hollow at the longer axial distance from each nozzle with higher injection pressure; (iii) at a certain axial distance from the nozzles, the cross-sectional shape of the boundary of the twin spray tends to be circular similar to that of the single spray with twice the flow-rate, and that distance is not proportional to the distance between two nozzles; (iv) though there are some collisions between droplets from each nozzles of twin spray, in present experimental range, the flow pattern of gas including the entrainment effect plays the key role in spray interaction.n.ion.n.

• Journal of ILASS-Korea
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• v.23 no.1
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• pp.22-29
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• 2018

The purpose of this study is to investigate the macroscopic spray characteristics and spray pattern of a gasoline direct injection (GDI) injector according to the increase of injection pressure. The macroscopic spray characteristics, such as a spray tip penetration and spray angle, were measured and analyzed from the frozen spray images, which are obtained from the spray visualization system including the high-speed camera, light-source, long-distance microscope (LDM). The spray pattern was analyzed through the deviation of the center of the spray plum and images were acquired using Nd: YAG Laser and ICCD(Intensified charge coupled device) camera. From the experiment and analysis, it revealed that the injection pressure have a significant influence on the spray tip penetration and spray pattern. However, the injection pressure have little influence on the spray angle. The increase of injection pressure induced the reduction of a closing delay. In addition, the deviation of spray center increase with the increase of injection pressure and the distance from a nozzle tip.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.5
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• pp.907-913
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• 2023

Currently, the sprinkler method is widely used as an initial suppression method in existing firefighting systems. However, this method can cause significant damage to both equipment and facilities in the hydration area. To minimize this damage, fire extinguishing monitors are being developed that can spray fire extinguishing water directly at the point of fire. These monitors are installed on the top floor of the ship, such as the Living Quarter and Ventilation System. While conventional fire extinguishing monitors focus on lightweight research with a short spray port and require a spray distance of about 40 to 45m, recent developments necessitate a longer spray port, similar to a water cannon, requiring a spray distance of about 70 to 75m. This study aims to predict the injection distance of both the existing ship-installed fire extinguisher and the long spray port fire extinguisher through hydrodynamic computer analysis, and to determine whether the injection distance has increased.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.5
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• pp.182-190
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• 1998

Behaviour of ultra-high pressure diesel spray in a constant-volume pressure chamber was studied with injection pressure ranging from 20 to 160㎫. Sprays were observed by the right angle scattering method. As a result, the spray tip penetration is first proportional to a time, and after that, it is proportional to 0.52 of the time during at the time of injection pressure and back pressure increase. An empirical correlation was made for the parameters of injection pressure, air-fuel density ratio, spray tip distance, spray angle, jet angle of spray and max. spray width.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.9
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• pp.76-83
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• 2021

This study examines the characteristics of spraying conditions based on the change in standoff distance during fine particle spraying while measuring the surface roughness, maximum depth, and maximum width of the sprayed surface. The processing shape of the sprayed surface is analyzed to understand the effects of injection pressure, nozzle diameter, standoff distance, processing shape, processing cycle, processing speed, and injection particles, which are the main factors of fine particle injection processing. Based on the derived characteristics, we attempt to determine the interrelationships of these major factors. The standoff distance is set as a variable factor and a spray machining experiment using a hexagonal shape (from among polygons) instead of square and circular shapes is conducted. Results reveal that research on the characteristics of spraying conditions could be expanded based on changes in the shapes of workpieces.

• International Journal of Automotive Technology
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• v.7 no.5
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• pp.585-593
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• 2006

The effect of the shape of the side wall on vaporization and fuel mixture were investigated for the impinging spray of a direct injection(DI) gasoline engine under a variety of conditions using the LIEF technique. The characteristics of the impinging spray were investigated under various configurations of piston cavities. To simulate the effect of piston cavity configurations and injection timing in an actual DI gasoline engine, the parameters were horizontal distance from the spray axis to side wall and vertical distance from nozzle tip to impingement plate. Prior to investigating the side wall effect, experiments on free and impinging sprays for flat plates were conducted and these results were compared with those of the side wall impinging spray. For each condition, the impingement plate was located at three different vertical distances(Z=46.7, 58.4, and 70 mm) below the injector tip and the rectangular side wall was installed at three different radial distances(R=15, 20, and 25 mm) from the spray axis. Radial propagation velocity from spray axis along impinging plate became higher with increasing ambient temperature. When the ambient pressure was increased, propagation speed reduced. High ambient pressures tended to prevent the impinging spray from the propagating radially and kept the fuel concentration higher near the spray axis. Regardless of ambient pressure and temperature fully developed vortices were generated near the side wall with nearly identical distributions, however there were discrepancies in the early development process. A relationship between the impingement distance(Z) and the distance from the side wall to the spray axis(R) was demonstrated in this study when R=20 and 25 mm and Z=46.7 and 58.4 mm. Fuel recirculation was achieved by adequate side wall distance. Fuel mixture stratification, an adequate piston cavity with a shorter impingement distance from the injector tip to the piston head should be required in the central direct injection system.

• Journal of Aerospace System Engineering
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• v.12 no.4
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• pp.81-89
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• 2018

In the present study, a numerical investigation was conducted to analyze the effect of the distance between the adjacent injectors on the characteristics of flow structure, fuel penetration, and air/fuel mixing. Numerical results were validated with experimental data using a single injection. Subsequently, the same injector geometry and properties were applied on a non-reacting flow simulation with multiple injectors. Total pressure loss, penetration height, and mixing efficiency were compared with the distance between the injectors. The results showed that each injected gas merged into a single stream, resulting in the 2D-like flow fields under the condition of short distance and lower mixing efficiency along with higher total pressure loss. When the distance between the injectors increased, total pressure loss reduced and mixing efficiency increased due to the weakening of interactions between the injected gases.

• Journal of the Korean GEO-environmental Society
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• v.3 no.3
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• pp.27-36
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• 2002

Generally, it is known that urethane injection is excellent in long-term durability and environment friendly for ground improvement. However, urethane grouting has short rise time thus the penetration distance from the injection point is so short. Therefore, urethane injection cannot be used for the site where requires ground improvement in deep location from the injection point. Other injection materials such as cement cannot be alternatives when rapid hardening is required. From this study, we improve disadvantage urethane injection by developing TAS method. From the field tests, it is ascertained that TAS increases injection distance over 10m, which is further than that of original urethane grouting. In addition, TAS has relatively short Rise-time compared to cement grouting thus instantaneous improvement can be mobilized right after the injection. Short Rise-time and long penetration distance provide excellent applicability for tunnel construction.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.361-364
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• 2009

The cooling system optimization for injection molds was studied with a response surface method in the previous research. It took so much time to find an optimum solution for a large product due to an extensive amount of calculation time for the CAE analysis. In order to use the optimization technique in the actual design process, the calculation time should be much reduced. In this study, we tried to reduce the number of design variables with the concept of the close relationship between the depth and the distance of cooling channels. The optimum ratio of the distance to the depth of cooling channels for a 2-dimensional problem was 2.0 so that the optimum ratio was again sought out for 4 industrial products. The major cooling effect of the injection molds for large products rely on baffle tubes. The optimum ratio of the distance to the depth for baffle tubes was 2.0 for the large products. The result enables us to reduce the number of the design variables by half in the cooling system optimization problem.