• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.61-64
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• 2008

The present study of these experiments are close examination of spray characteristics that are continuous liquid jet and modulated pressure pulse liquid jet. The experiments were conducted using water, over a range of cross-flow velocities from 42${\sim}$136 m/s, with injection frequencies of 35.7${\sim}$166.2 Hz. Between continuous cross-flow jet and pressure pulsed cross-flow jet for characteristics of penetration, breakup point, spray angle and macro spray shape are investigated experimentally. In cross-flow field, main parameter of liquid jet for breakup was cross-flow stream rather than pressure pulse frequency. As oscillation of the periodic pressure that could make liquid jet moved up and down, the mixing efficiency was increased. Also, a bulk of liquid jet puff was detected at upper field of liquid surface. So, this phenomenon has a good advantage of mixing spray from concentration of center area to outer area. Because of pressure pulsation frequency, an inclination of SMD for the structured layer was evanescent. Cross-sectional characteristics of SMD at downstream area were non-structured distributions. Then cross-sectional characteristics of SMD size were about same tendency over a range that is effect of spray mixing. The tendency of volume flux value for various frequency of pressure pulse was same distribution. And volume flux was decreased when the frequency of pressure pulse increase.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.749-752
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• 2004

In a liquid-fueled ramjet engine, the insufficient mixing and evaporation result in the low combustion efficiency and combustion instability. Improving its spray characteristics and devising a means of mixing fuel droplets with air may compensate these disadvantages of liquid fuel ramjet engine. The jet penetrations of various fuel injectors were measured to investigate the spray characteristics of a liquid-fueled ramjet engine under high pressure air-stream conditions. The penetrations in high pressure conditions are smaller than the values calculated from Inamura's or Lee's equations, and, in the high pressure conditions, the jet penetrations are similar each other. In the dual hole injectors, the jet penetrations of rear orifice is rapidly increased due to the reduction of the drag, which is created by the jet column of front orifice. The jet penetration of rear orifice is increased because of the drag reduction created by the jet column of the front orifice. And, because of the drag reduction formed by the column of jet, the jet penetration in the rear orifice of dual hole injector is much larger than the jet penetration of single hole injector. As the distances of the orifice are increased, the jet penetrations of the rear orifice decrease.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.12
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• pp.4053-4061
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• 1996

Internal flow characteristics within Y-jet atomizers and the local drop size distribution and cross-sectional averaged drop size at the outside were investigated with the liquid and air injection pressures, mixing port length of atomizers, and the liquid properties taken as parameters. To examine the effect of the liquid viscosity, glycerin-water mixtures were used in this study. The liquid viscosity plays only a minor role in determining the internal flow pattern and the spatial distribution shape of drops, but the drop sizes themselves generally increase with increasing of the liquid viscosity. An empirical correlation for the liquid discharge coefficient at the liquid port was deduced from the experimental results; the liquid discharge coefficient strongly depends on the liquid flow area at the mixing point which is proportional to the local volumetric quality(.betha.$_{Y}$), and the volumetric quality was included in the correlation. Regardless of the value of the liquid viscosity, the compressible flow through the gas port was well represented by the polytropic expansion process(k=1.2), and the mixing point pressure could be simply correlated to the aspect ratio( $l_{m}$/ $d_{m}$) of the mixing port and the air/liquid mass flow rate ratio( $W_{g}$/ $W_{f}$) as reported in the previous study.udy.udy.y.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.702-704
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• 2011

For the representative of the poor performance of liquid fuel(Jet A-1), the physical properties effests of different additive ratios in the liquid fuel have been investigated. The mixed liquid fuel could be analyzed by principal factor of liquid fuel such as, density, viscosity and caloric value. This additives will be usefully applied to high energy density liquid fuel development.

• 한국전산유체공학회:학술대회논문집
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• 2004.10a
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• pp.37-41
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• 2004

Liquid injection in a Venturi Scrubber creates great effect on the dust-collection efficiency and operation cost of venturi scrubbers. We have developed a model that can numerically simulate atomization of the liquid jet in the Venturi Scrubber. This simulation consists of models on liquid column, jet surface breakup, column fracture and secondary droplet breakup. These models have been embedded in the KIVA3-V code. We have calculated such parameters as the jet penetration, jet trajectory, droplet size, velocity field and the volume flux distribution. The results are compared with the experimental data in this paper.

• Journal of ILASS-Korea
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• v.1 no.2
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• pp.66-73
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• 1996

The present study investigates experimentally the characteristics of liquid jet, which is, the spray flow in the normal direction of the air stream under the flow conditions of air velocity $110\sim125m/s$. The present study adopts with the flow visualization technique using a short duration light bulb and the image processing analyse with CCD camera. Two types of injector were used: one is a flat plate type, and the other is backward facing step type, which height are 5, 8, 10mm. Dispersion of liquid jet can be represented by gray level of CCD camera. In the upstream of liquid jet, the backward facing step shows better liquid jet penetration. However, in the downstream. mean droplet size for backward facing step injector is smaller than that for flat plate injector

• Journal of ILASS-Korea
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• v.25 no.2
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• pp.74-80
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• 2020

The jet in crossflow is a spray method used in the various air-breathing engine. In order to understand the spray characteristics in various environments, many prior studies have been conducted. However, there is a lack of understanding of the low-temperature liquid spray characteristics below 273 K. With this in mind, we tried to enhance the knowledge of the low-temperature liquid spray characteristics by identifying the penetration height of low-temperature ethanol. The experiment was conducted under phase pressure, and 273 K of air and 293, 263, and 233 K of ethanol was used. Shadowgraphy was employed to measure the liquid penetration, and Otsu's method was used to analyze the penetration height. The heights tend to decrease as the temperature of the liquid jet decreases. A correlation for the penetration height in the experimental conditions was derived and presented.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.8
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• pp.1009-1023
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• 1997

The breakup length of a liquid jet with flowrate, formed by releasing through a nozzle of circular cross-section into the atmosphere, was experimented and studied for 3 liquid nozzles of varying diameters. The experimental result was analyzed using the existing theoretical equation for predicting the breakup length. It was found that the breakup length of liquid jet depends on the velocity, and the breakup length increases with increasing of the liquid nozzle diameter. Also, the variation range of the breakup length for the same flowrate of liquid increased rapidly as velocity was increased for laminar flow, but in the turbulent flow region, it leveled off in the range of approximately 0.55-0.7 of the mean breakup length. Furthermore, when the longest smooth liquid jet was applied to the co-axial flow air blast atomizer, the effect of air flow on the flow pattern and breakup length was studied for 6 glass nozzles of different lengths and diameters. It was found that depending on the diameter of the mixing tube and liquid jet, it was possible to observe a wide range of flow patterns, such as liquid jet through flow, partial annular flow and annular flow. The liquid jet breakup length was more sensitive to the change in the length rather than the diameter of the mixing tube. As the length of the mixing tube shortens, the breakup length also shortens rapidly.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.5
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• pp.668-676
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• 2003

The effect of nozzle height on heat transfer of a hot steel plate cooled by an impinging liquid jet is not well understood. Previous studies have been based on the dimensionless parameter z/d. To test the validity of this dimensionless parameter and to investigate gravitational effects on the jet, stagnation velocity of an impinging liquid jet were measured and the cooling experiments of a hot steel plate were conducted for z/d from 6.7 to 75, and an inverse heat conduction method is applied for the quantitative comparison. Also, the critical instability point of a liquid jet was examined over a range of flow rates. The experimental velocity data for the liquid jet were well correlated with the dimensionless number 1/F $r_{z}$$^2$based on distance. It was thought that the z/d parameter was not valid for heat transfer to an impinging liquid jet under gravitational forces. In the cooling experiments, heat transfer was independent of z when 1/F $r_{z}$$^2$< 0.187(z/d = 6.7). However, it was found that the heat transfer quantity for 1/F $r_{z}$$^2$=0.523(z/d = 70) is larger 11% than that in the region for 1/F $r_{z}$$^2$=0.187. The discrepancy between these results and previous research is likely due to the instability of liquid jet.uid jet.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.12
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• pp.3377-3385
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• 1994

This paper introduces empirical correlations to obtain the gas/liquid flow rates and the spray drop size of low viscosity liquid injected by Y-jet twin-fluid atomizers. The gas flow rate is well correlated with the gas injection pressure and the mixing point pressure, based on the compressible flow theory. Similarly, the liquid flow rate is determined by the liquid injection pressure and the mixing point pressure, and a simple correlation for the liquid discharge coefficient at the liquid port was deduced from the experimental results. The mixing point pressure, which is one of the essential parameters, was expressed in terms of the gas/liquid flow rate ratio and the mixing port length. Disintegration and atomization mechanisms both within the mixing port and outside the atomizer were carefully re-examined, and a "basic" correlation form representing the mean diameter of drops was proposed. The "basic" correlation was expressed in terms of the mean gas density within the mixing port, gas/liquid mass flow rate ratio and the Weber number. Though the correlation is somewhat complicated, it represents the experimental data within an accuracy of ${\pm}15%$.EX>${\pm}15%$.