• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.5
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• pp.45-57
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• 2002

In this paper, the results gained by applying many impingement models to the cylinder and flat plate were analyzed in comparison with the experimental data to study a spray/wall interaction phenomena. To begin with, the behavior of spray injected normal to the wall was analysed using three different impingement models ; Naber and Reitz model(NR model), Watkins and Wang model(WW model) and Park and Watkins model(PW model) in the present calculation. The results obtained from these models were compared with experimental data of Katsura et. al. The results indicated that PW model was in better agreement with experimental data than the NR and WW model. Also f3r spray injected at 30DEG , the result of three models were compared with experimental data of Fujimoto et. al. The results showed that m model overpredicted the penetration in the radial direction because this model was based on the inviscid jet analogy. WW model did not predicted the radius and height of the wall spray effectively. It might be thought that this discrepancy was due to the lack of consideration of spray film velocity occurred at impingement site. The result of PW model agrees with the experimental data as time goes on. In particular, a height of the spray droplets was predicted more closely to the experimental data than the other two models. The results of PW model in which the spray droplets were distributed densely around the edge of droplet distribution shaped in a circle had an agreement with the experimental data of Fujimoto et. al. Therefore, it was concluded that PW model performed better than M and WW model for prediction of spray behavior. The numerical calculation using PW model performed to the cylinder similar to the real shape of DI engine. The results showed that vortex strength near the wall in the cylinder was stronger than that in the case of flat plate. Contrary to the flat plat, an existence of the side wall in the cylinder caused the tangential velocity component to be reduced and the normal velocity component to be increased. The flow tends to rotate to the inside of cylinder going upward to the right side wall of cylinder gradually as time passes. Also, the results showed that as the spray angle increases, the gas velocity distribution and the tumble flow seemed to be formed widely.

• 연구논문집
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• s.25
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• pp.129-135
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• 1995

This study discribes characteristics of water spray for extinguishment of gasoline pool fire. Experiments are carried out for the gasoline pool fire in a small tank with a diameter of 150mm and a height of 8mm. Droplet size, spray pressure, amount of water which reaches the flame base and velocity of water spray are measured to find extinguishment conditions and air entrainment due to the water spray is visualized. Critical conditions of water spray for extinguishment of gasoline pool fire is quantitatively shown.

• Journal of ILASS-Korea
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• v.7 no.3
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• pp.12-17
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• 2002

In this paper, spray and combustion characteristics of a liquid-fueled ramjet engine were experimentally investigated. The spray penetrations were measured to clarify the spray characteristics of a liguid jet injected transversely into the subsonic vitiated airstream, which is maintained a high velocity and temperature. The spray penetrations are increased with decreasing airstream velocity, increasing airstream temperature, and increasing air-fuel momentum ratio. To compensate our results of penetrations, the new experimental equation were modified from Inamura's equation. In the case of insufficient penetration, the combustion phenomenon in ram-combustor were unstable. Therefore, the temperature distribution was slanted to the low wall of the ram-combustor. These trends gradually disappeared as the length and air temperature of the combustor became longer. Combustion efficiency increased when the length of the combustor was long and the air temperature was high. Especially, stable flame region is enlarged when the length of the combustor was long and the air temperature was high. Type Abstract here. Type Abstract here.

• Journal of ILASS-Korea
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• v.28 no.4
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• pp.198-206
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• 2023

In this study, visualization of in-cylinder spray behavior and spark channel stretching by air flow characteristics depending on engine operating conditions were investigated. For in-cylinder spray behavior, increase in engine rpm did not alter the counter-clockwise air flow direction and location of in-cylinder dominant air flow but increased average air flow velocity, which hindered spray propagation parallel to the piston surface. When injection timing was retarded, direction of in-cylinder dominant air flow was changed, and average air flow velocity was reduced resulting in an increase in spray penetration length and change in direction. For spark channel stretching, increase in air flow speed did not affect spark channel stretch direction but affected length due to increase in spark channel resistance and limitation of energy ignition coil can handle. Change in air flow direction affected spark channel stretch direction where the air flow was obstructed by ground electrode which caused spark channel direction to occur in the opposing direction of air flow. It also affected spark channel stretch length due to change in air flow speed around the spark plug electrode from the interaction between the air flow and ground electrode.

• Journal of ILASS-Korea
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• v.29 no.1
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• pp.32-37
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• 2024

Macroscopic visualization of non-evaporating sprays was experimentally conducted to investigate spray tip penetration and spray angle under low-density conditions, corresponding to an early injection strategy. Furthermore, injectors with varying injection angles (146° and 70°) and numbers of holes (8 and 14) were employed to examine the impact of injector configuration. Compared to the baseline injector, 8H146, which has 8 holes and a 146° injection angle, the spray tip penetration of the 8H70 injector was found to be longer. This can be attributed to higher momentum due to a smooth flow field between the sac volume and the nozzle inlet, which is located closer to the injector tip centerline. The increase in velocity led to intense turbulence generation, resulting in a wider spray angle. Conversely, the spray tip penetration of the 14H70 injector was shorter than that of the 8H70 injector. The competition between increased velocity and decreased nozzle diameter influenced the spray tip penetration for the 14H70 injector; the increase in momentum, previously observed for the 8H70 injector, contributed to an increase in spray tip penetration, but a decrease in nozzle diameter could lead to a reduction in spray tip penetration. The spray angle for the 14H70 injector was similar to that of the 8H146 injector. Moreover, injection rate measurements revealed that the slope for a narrow injection angle (70°) was steeper than that for a wider injection angle during the injection event.

• International Journal of Automotive Technology
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• v.6 no.1
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• pp.9-14
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• 2005

An experimental investigation has been carried out to reveal the atomization process of the diesel fuel spray. The spray injected through a single hole nozzle was taken by a camera on the opposite side of a stroboscope for macroscopic observation or a nanolite for microscopic observation. The effect of nozzle aspect ratio was analyzed with disintegration phenomena of the diesel spray. Based on the enlarged spray photograph, atomization process was observed in detail and further the spray cone angle was measured under various ambient pressures. The result shows that atomization of diesel spray in early stage of injection is mainly progressed in the vicinity of spray periphery region except the region close to the nozzle exit and spray head region. The spray cone angle is nearly constant under the pressurized condition, while it decreases with elapsing time under the atmospheric condition.

• Journal of ILASS-Korea
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• v.10 no.1
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• pp.10-16
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• 2005

To investigate the effect of shockwave on diesel spray characteristics under ultra high pressure injection, the velocity of spray tip and shock wave were investigated using the visualization of spray by schlieren method. Spray characteristics such as the spray radius, height, and droplets size were analyzed. It is found in this study that shock wave, produced by ultra high injection pressure, propagates faster than spray tip. Spray radius of right side of nozzle tip was shorter than that of left side and spray height of right side of nozzle tip was thicker than that of left side. Droplets sue was increased at 414MPa in injection pressure because of pressure gradient between inner and outer of tile spray caused by shockwave.

• Journal of the Society of Disaster Information
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• v.17 no.1
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• pp.120-127
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• 2021

Purpose: In this study, the effect of changes in the variables related to water droplets on the spray density on the floor in the analysis of the water mist fire protection system using FDS was analyzed. Method: When the spray of the water mist nozzle was analyzed in FDS, Particles Per Seconds, Particle Velocity, Size Distribution, and Spray Pattern Shape that can be set in relation to droplets were input to review the analyzed results. Result: In the analysis results, when the number of particles per second was set above a certain value, the spray density of the floor was similar. In the case of Particle Velocity, as the velocity decreases, the spray density of the central portion increases but decreases at a distance of 0.15m or more. From the analysis of the change in the size distribution function, it was found that an increase in the 𝛾 value increases the spray density of the central part, but the value at a remote location decreases. Compared to the result of applying the Gaussian distribution, the median value decreases dramatically when the uniform distribution is applied, but the value at the adjacent position increases. Conclusion: Variables related to the droplet properties of the FDS affect the spray density of the floor. Therefore, in order to increase the reliability of results before performing analyses such as fire suppression or cooling, a sufficient review of input variables is required.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.3
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• pp.566-574
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• 1988

A study is described for obtaining real time in situ size and velocity measurements of the spray-droplet using crossed-beam interferometry. The optical arrangement is similar to dual-beam laser Doppler velocimetry(LDV). Droplets passing trough the probe volume scatter light to the collecting lens placed at 90.deg. off-axis angle. The dual-beam light scatter is analyzed by the geometric optics theory to relate the scattered fringe pattern to droplet diameter. The droplet size measurement is based upon the signal visibility. As the system is based on the Doppler effect, a single component of velocity is velocity is extracted concurrent with the size information. The validity of the method is evaluated by comparing its performance to widely accepted but limited technique, the collection method. By using 90.deg. off-axis scatter detection angle, the measurement of the droplet size and velocity distributions, and the local correlations between droplet sizes and velocities in relatively dense spray environments are made possible.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.943-948
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• 2000

The Twin-fluid Swirl Nozzles are used in many parts of the industry to produce homogeneous spray. This study is to investigate the effects of outer air swiller and inner water swiller on atomization of liquid.. The experiment was carried out with increasing air-flow rate at constant liquid-flow rate and with changing outer air swiller angle and inner water swiller angle. A Particle Dynamics Analyzer(PDA) was used to measure drop size, mean and ms values of axial velocity, number density and Sauter mean diameter(SMD). The axial mean velocity and SMD of droplets were measured along the center line and radial directions. It was found that the higher air flow-rate resulted in the smaller Sauter mean diameter of liquid spray and the higher axial mean velocity of droplets. This experimental results will be conveniently used for the preliminary design stage of twin-fluid nozzle development.