• 한국자동차공학회논문집
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• 제17권2호
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• pp.75-81
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• 2009

A study was performed to investigate the characteristics of two-phase jet injected into subsonic cross-flow using the external mixed gas blast two-phase nozzle. The shadowgraph method was adopted for the cross-flow jet visualization and PDPA system was used to measure droplet size, velocity, and volume flux. The atomization of two-phase jet is initially determined according to gas to liquid mass flow-rate ratio and the Reynolds number of cross-flows. The highest penetration trajectories of two-phase jet injected into cross-flow are governed by the momentum ratio at subsonic cross-flow. As GLR of two-phase jet injected into cross-flow increases, the droplet size decreases and the distribution area of volume flux increases. The distribution of volume flux that influenced by the counter vortex pair at the downstream of cross-flow is symmetric in shape of horseshoe.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 제33회 추계학술대회논문집
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• pp.82-85
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• 2009

우주발사체용 액체추진기관 개발에 있어서, 분사기는 연소성능과 안정성을 결정짓는 매우 중요한 요소로써 이에 대한 분무특성 이해는 필수적으로 이루어져야 한다. 본 연구에서 알아보고자 하는 분사기는 중앙에서 기체산화제를 제트로 분사하고 외부에서 액체연료를 와류(스월)형으로 분사하는 형태이다. 분무형상은 리세스별로 CCD 카메라를 이용한 직접사진기법을 통해 측정하였다. 실제 연소조건과의 모사를 위해 기체질소와 물을 사용하였고, 운동량비를 주요 상사인자로 두어 대기압 수류 시험조건을 도출하여 분무특성을 알아보았다. 또한 기체-액체 운동량비의 영향을 알아보기 위한 연구가 추가적으로 이루어졌다.

• 한국항공우주학회지
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• 제43권1호
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• pp.8-22
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• 2015

지금까지 인젝터의 수치적 시뮬레이션은 대부분 Eulerian 기법의 바탕위에서 이루어져 왔다. 그러나 액체제트의 미립화현상과 복잡한 공기와의 경계면 변화를 나타내는데 있어 기존의 기법들이 갖는 선천적인 단점이 존재하며 따라서 본 연구에서는 새로운 Smoothed Particle Hydrodynamics(SPH)라는 입자 기법을 도입하였다. 수치적 시뮬레이션을 위해 먼저 해석을 위한 SPH 코드를 개발하였으며 본 논문에서는 인젝터 문제를 정확하게 나타내는데 있어 필수적인 알고리즘중 하나인 다상유동모사에 대한 검증문제가 제시 되어 있다. 마지막으로 다양한 인젝터 종류 중 하나인 액체-액체 동축형 스월 인젝터에 대한 시뮬레이션이 수행되었으며 실제실험과의 비교를 진행하였다.

• 한국분무공학회지
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• 제4권2호
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• pp.47-52
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• 1999

The prediction of the critical Reynolds number in the stability curie of liquid jet was mainly analyzed by the empirical correlations and the experimental data through the literature. The factors affecting the critical Reynolds number include Ohnesorge number, nozzle length-diameter ratio, ambient pressure and nozzle inlet type. The nozzle inlet type was divided into two groups according to the dependence of the critical Reynolds number on the length-to-diameter ratio of nozzle. The empirical correlations for the critical Reynolds number as a function of above factors mentioned are newly proposed.

• 한국공작기계학회논문집
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• 제11권5호
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• pp.88-92
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• 2002

This research is about slurry wear of SM45C and SUS304, which using standard sand and KUM river sand. The results are as follows ; 1. Mass loss rates of both standard sand and KUM river sand were linearly increased as increasement of time and velocity. 2. The average diameter of sand from relatively, less wear rate and portion of larger particles. 3. Wear resistance was linear with time and velocity of liquid jet regardless of type of sand. Also, it was able to evaluate with the formula, $HV^2$/E calibrated with n, the velocity index. 4. The wear surface in liquid jet experiment was smooth. The maximum wear depth was observed at the location 2~4mm apart from the center in the condition of $90^{\circ}$ of collision angle 6mm of nozzle diameter, and 20mm of collision distance. The sectional shape in radial appeared as 'W'shape.

• 한국분무공학회지
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• 제15권4호
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• pp.189-194
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• 2010

This study has been mainly motivated to numerically model the transcritical mixing and reacting flow processes encountered in the liquid propellant rocket engines. In the present approach, turbulence is represented by the extended k-$\varepsilon$ turbulence model. To account for the real fluid effects, the propellant mixture properties are calculated by using SRK (Souve-Redlich-Kwong) equation of state model. In order to realistically represent the turbulence-chemistry interaction in the turbulent non-premixed flames, the flamelet approach based on the real fluid flamelet library has been adopted. Based on numerical results, the detailed discussions are made for the real fluid effects and the precise structure of the transcritical cryogenic liquid nitrogen jet and gaseous hydrogen/liquid oxygen coaxial jet flame.

• 한국분무공학회지
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• 제26권1호
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• pp.33-39
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• 2021

Y-jet nozzle has a wide fuel flow rate range and turn-down ratio, thus, it is used in industrial boilers, furnace and agricultural atomizer. However, it has asymmetrical spray characteristics due to the nozzle design factors. Therefore, in this study, asymmetric spraying characteristics of the elliptical Y-jet nozzle was studied by using the lab-scale spray apparatus. As a result, the elliptical Y-jet nozzle had lower gas mass flow rate than circular Y-jet nozzle at same gas pressure, because of bigger shear stress due to the wider inner surface at the elliptical Y-jet nozzle. Larger SMD was measured on the elliptical Y-jet nozzle than the circular Y-jet nozzle. When SMD was measured in the X_Axis direction at the same gas mass flow rate, the elliptical Y-jet nozzle with an aspect ratio of 2:1 showed greater asymmetry than the others.

• 대한기계학회논문집
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• 제19권6호
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• pp.1529-1538
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• 1995

In this study, a liquid sheet type co-axial nozzle has been used to investigate the turbulent atomization characteristics which could result in the experimental data to be used in designing a jet nozzle with high performance. Image processing technique and immersion sampling method were employed to measure droplet size. In atomizing characteristics, droplet size distributions and absolute droplet sizes, SMD(Sauter Mean Diameter) have been investigated in the wide ranges of flow field depending upon the air-water mass ratios. And the comparisons between the present data and the semi-empirical curves have been conducted semi-empirical correlation for SMD has been derived in the present analysis.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 춘계학술대회논문집
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• pp.321-328
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• 2009

Free surface impinging jet on a moving plate, which is applicable to cooling of hot metals in a steel-making process, is investigated numerically by solving the Navier-Stokes equations in the liquid and gas phases. The free surface of liquid-gas interface is tracked by a level-set method which is improved by incorporating the ghost fluid approach based on a sharp-interface representation. The method is further improved by employing a nonequilibrium $\kappa-\varepsilon$ turbulence model including the effect of low Reynolds number. The computations are made to investigate the effects of the nozzle pitch, moving velocity of plate and jet velocity on the interfacial motion and the associated flow and temperature fields.

• 한국분무공학회지
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• 제11권2호
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• pp.105-112
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• 2006

A unique feature of fluidic atomizers is that the nozzle geometry produces a thin capillary Jet which is forced to oscillate on a 2-dimensional plane through the use of a passive feedback mechanism. The objective of the current work is to characterize the influence of the stagnation pressure at the nozzle exit, jet oscillation and stretching on the breakup properties of the capillary ligament. To achieve this, shadow graph technique is used to measure size, shape, velocity and the number density of the droplets as a function of the position within the spray fan. The breakup length, defined as the radial distance from the breakup point, is analyzed as a function of the non-dimensional parameters. Finally, a kinematic model is developed to simulate the breakup of the oscillating jets at low stagnation pressures. Using the existing jet breakup theories, the model is used to predict the size and diameter distribution of the droplets after primary atomization.