• Journal of the Korea Institute of Military Science and Technology
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• v.5 no.1
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• pp.107-115
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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 liquid 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 sufficient penetration must be considered to make a stable flame.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.1
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• pp.251-262
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• 1995

The goal of this study is to provide fundamental information on the design of a new diesel injector system. The cylindrical disk spray was made by an impinging disk insited below the exit of air-assist atomizor. The disintegration processes on a twin-fluid atomization by air-assist atomizor were investigated. Liquid jet was disintegrated at the condition that wavelength was equal and longer than the circumference of the liquid jet, .lambda. .geq. .pi.do. However, the wavelength and the diameter of the liquid jet were decreased according to the increasing of air velocity. The relative density distribution of droplets and pattern of spray by impinging disk were investigated with a C-CCD. Optimum design conditions for cylindrical disk spray were also achieved. The pattern of cylindrical spray can classified according to the size of the disk and the distance from the nozzle tip to the disk. When the space of the disk and the nozzle tip was narrow and the diameter of the disk was larger than that of the air orifice of the nozzle exit, the good distribution of spray could be achieved. When the air flowrate was constant, the spray width was decreased according to the increasing of the liquid flowrate. When the liquid flowrate was constant, the spray width was decreased according to the increasing of the air flowrate.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.6
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• pp.59-66
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• 2013

Spray characteristics of single round jet with liquid nitrogen and coaxial spray with liquid nitrogen and gaseous argon were observed. Shadowgraph method was used for spray visualization, and density gradient magnitude image was used to analyse the result. In subcritical condition, irregularity of the jet surface was harder in the coaxial spray. In supercritical condition, diffusion of nitrogen injected from shear coaxial injector was faster than single jet. Jet diameter was induced by averaging images, in supercritical condition, difference of diameter of coaxial jet was rapidly decreased than that of single jet.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.10
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• pp.1011-1016
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• 2008

Jet-A spray and combustion were numerically analyzed in annular type combustor model using KIVA3V. The combustor geometry have 6 dilute holes. Swirl effect and thermal NO were considered in this investigation to analyze mixing and combustion characteristics. Fuel vapor, flame temperature, NO generation were investigated for various spray angle. As increase of spray angle, Jet-A vapor appeared uniformly in primary zone and evaporation rate was increased. Mixing between fuel vapor and ambient gas was enhanced as increase of spray angle. As a result, high temperature region appeared widely and thermal NO generation rate was increased.

• Journal of the Korean Society of Industry Convergence
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• v.1 no.2
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• pp.41-48
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• 1998

This experimental study describes atomization characteristics of spray-spray impingement. Effect of the impingement location and angle on the penetration and the sauter mean diameter of the impinged spray were investigated. Experiment were performed under ranging from 50kPa to 250kPa spray pressure, ranging $30^{\circ}C$ to $135^{\circ}C$ angle on the penetration and free spray. In the case of this experimental, sauter mean diameter $D_{32}$ tends to decrease and duration of film disintegration $t_f$ to decrease, when spray pressure and angle on the penetration is increased. Sauter mean diameter $D_{32}$ were about 20% to be smaller compared with a free spray to jet-jet impingement and 30% to be smaller compared with a free spray to spray-spray impingement.

• 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 ILASS-Korea
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• v.24 no.3
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• pp.145-151
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• 2019

Viscoelastic fluid is used in various industrial sites because its cost reduction and environmental benefits by preventing formation of fine droplets that scattered around. However, viscoelastic fluids, unlike newtonian fluids, contain a shear thinning characteristic that decrease in viscosity as shear rate increases and elastic characteristic, making it difficult to predict spray breakup process. In this study we made three test fluids. Boger fluid with viscoelastic characteristics, and two newtonian fluids, were prepared to exclude shear thinning characteristics and study the effects of elastic characteristic only. Flow visualization, spray angle, and SMD were measured for three test fluids using laboratory scale impinging jet test apparatus. As a result, it was confirmed that Boger fluid, unlike the newtonian fluid, was not formed fine droplets that scattered around and the breakup process appeared differently. In addition, SMD was found to be large in Boger fluid, and the SMD according to pressure was confirmed that there is no significant difference.

• Journal of ILASS-Korea
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• v.27 no.1
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• pp.26-35
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• 2022

Electrospray is a method of atomizing fluid using high voltage supply and capable of generating continuous flow and coherent size of droplets. Electrical system and properties of fluids has enabled electrospray to have various spray modes. However, its studies have been confined only in Cone jet, which is more stable and easier to manipulate droplets' size than other spraying modes. Therefore, it is necessary to investigate and compare other spraying modes based on experimental parameters and physical properties of fluids. This research paper identified nine different spray modes. It was found out that Sauter Mean Diameter (SMD) is proportional to flow rate of fluids and maximum difference among spray modes was 1.7 times. On the other hand, SMD standard deviation had low variations on specific flow rates of fluids. Pulsed jet mode recorded the largest SMD standard deviation, while Spindle recorded the lowest.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.267-274
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• 2009

Breakup and spray formation of pressure-swirl liquid jets injected into a low-speed convective-flow are experimentally investigated. Effects of the cross-flows on the macroscopic and microscopic spray parameters are optically measured in terms of jet Weber number and liquid-to-gas momentum ratio. The liquid stream undergoes Rayleigh jet breakup at lower jet Weber numbers and a liquid sheet isn't formed because of the weak radial velocity in the swirl jet. At higher jet Weber numbers, the macroscopic spray parameter is a very weak function of the momentum ratio but the effect of the convection on the microscopic spray parameter is significant through the secondary breakup with increasing in the liquid-to-gas momentum ratio. The convective-flow promotes bag/plume breakup and the spray formation, and its effect is more distinct at higher momentum ratio.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.3
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• pp.1-8
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• 2012

A water-flow test was carried out for the nonimpinging-type injector to be equipped on 70 N-class liquid-rocket engine under development. Breakup patterns of injector-spray transit from a smooth jet to wavy one as the injection angle increases, whereas spray-breakup lengths are inversely proportional to the injection pressure. It is confirmed that there exist ruffles on the surface of liquid column, which could be caught through the instantaneous spray images captured by high-speed camera. A phenomenon of spray shedding amplified at the specific pressure level of 0.93 MPa was an unexpected behavior of the injected stream and it is to be investigated further.