• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.16-17
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• 2006

In order to obtain spherical fine powder, we have developed a new method of high-pressure water atomization system using swirl water jet with the swirl angle $(\omega)$. The effect of nozzle apex angle $(\theta)$ upon the morphology of atomized powders was investigated. Molten copper was atomized by this method, with $\omega=0.2$ rad (swirl water jet) and $\omega=0$ rad (conical water jet). It was found that the median diameter $(D_{50})$ of atomized powders decreased with decreasing $(\theta)$ down to 0.35 rad in each $\omega$, but under ${\theta}<\;0.35$ rad, $D_{50}$ increased abruptly with decreasing $\theta$ for $\omega=0$ rad, while it was still decreased with decreasing $(\theta)$ for $\omega=0.2$ rad.

• Journal of computational fluids engineering
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• v.12 no.3
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• pp.8-12
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• 2007

An optimized bidet nozzle design to form the required swirl water jet is proposed with the help of numerical analysis. The bidet can do the cleaning process of human body by water injection and the speed/pressure/injection angle/magnitude of swirl intensity of water jet determine the cleaning capability and personal subjective feeling. The objective of this research is to design optimal water injection nozzle to make stable swirl intensity. The effect of individual design variables are analyzed from the basic design and the final design is deduced to make high performance water jet within the pre-determined operation conditions.

• 한국전산유체공학회:학술대회논문집
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• 2007.04a
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• pp.68-71
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• 2007

An optimized bidet nozzle design to form the required swirl water jet is proposed with the help of numerical analysis. The bidet can do the cleaning process of human body by water injection and the speed/pressure/injection angle/magnitude of swirl intensity of water jet determine the cleaning capability and personal subjective feeling. The objective of this research is to design optimal water injection nozzle to make stable swirl intensity. The effect of individual design variables are analyzed from the basic design and the final design is deduced to make high performance water jet within the pre-determined operation conditions.

• Journal of ILASS-Korea
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• v.1 no.1
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• pp.21-27
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• 1996

This experimental study was to investigate spray angles and drop sizes in an external mixed twin-fluid swirl jet nozzle. Twin-fluid swirl jet nozzle with swirlers designed four swirl angles such as $0^{\circ},\;22.5^{\circ},\;45^{\circ},\;64.2^{\circ}$ was employed. A PDA system was utilized for the measurement of drop size and mean velocity. Water and air were used as the working fluids in this experiment. The mass flow rate of water was fixed as 0.03 kg/min, and air flow rates were controlled to have the air/liquid mass ratio from 1.0 to 6.0. As a result, swirl angle controlled to spray angles and drop sizes. It was found that swirl angle was increased with spray angle and with decreased SMD. However, the effect of swirl angle was reduced at large air/liquid mass ratio(Mr=6.0).

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.82-85
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• 2009

In the development of Liquid Rocket Engine(LRE) systems, it is essential to understand the spray characteristics which influence mainly the performance and the stability of combustion. The injectors for this study have a recessed Liquid-swirl/Gas-centered jet coaxial type. For the similarity with actual conditions, the experimental conditions are calculated by using the momentum ratio as a matching parameter, and the stimulants of fuel and oxidizer are gaseous nitrogen and water respectively. The spray fields were measured by means of a photographic technique. Moreover, an effect of the momentum ratio has been investigated.

• International Journal of Fluid Machinery and Systems
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• v.4 no.1
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• pp.47-56
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• 2011

Our previous experimental and numerical investigations of decelerated swirling flows in conical diffusers have demonstrated that water jet injection along the symmetry axis mitigates the pressure fluctuations associated with the precessing vortex rope. However, for swirling flows similar to Francis turbines operated at partial discharge, the jet becomes effective when the jet discharge is larger than 10% from the turbine discharge, leading to large volumetric losses when the jet is supplied from upstream the runner. As a result, we introduce the flow-feedback approach for supplying the jet by using a fraction of the discharge collected downstream the conical diffuser. Experimental investigations on mitigating the pressure fluctuations generated by the precessing vortex rope and investigations of pressure recovery coefficient on the cone wall with and without flow-feedback method are presented.

• Journal of computational fluids engineering
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• v.20 no.1
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• pp.10-15
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• 2015

In this study, the characteristics of water treatment mixer with various propeller profiles are numerically invesitgated. The computation was conducted by solving the incompressible Navier-Stokes equations on unstructured tetrahedral elements with k-${\varepsilon}$ turbulence model. It was found that the spreading angle and swirl magnitude of the jet are important factors for the mixer efficiency, since they clearly characterize the propeller and the frontal surface area of the propeller but not so much affected by the skew angle if it exceeds 30 degrees. The case1 and case2 models are found to show the best propeller efficiency. The case2 with low blade angle, however, requires the lowest power input for the same discharge capacity as the case1.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.6
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• pp.3403-3409
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• 2014

Hot-firing tests were carried out using a mixing head with 19 swirl coaxial injectors and a combustion chamber with internal cooling channels. The propellants of liquid oxygen and kerosene(Jet A-1) were burned in a range of chamber pressures (59~82 bar) and mixture ratios (2.0~3.0). The temperature of water used as the cooling fluid was measured at the inlet and outlet of the cooling channels, and the heat flux was calculated. The aim of this study was to examine the effect of combustion instability on heat transfer in a subscale thrust chamber, and detect the temperature variation of cooling water. During several hot-firing tests, combustion instability was encountered which caused a 5~20% increase in heat flux. The peak heat flux took place in the initial stages of combustion instability.

• International Journal of Naval Architecture and Ocean Engineering
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• v.2 no.1
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• pp.24-33
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• 2010

Design of a Pump Jet Propulsor (PJP) was undertaken for an underwater body with axisymmetric configuration using axial/low compressor design techniques supported by Computational Fluid Dynamics (CFD) analysis for performance prediction. Experimental evaluation of the PJP was earned out through experiments in a Wind Tunnel Facility (WTF) using momentum defect principle for propulsive performance prior to proceeding with extensive experimental evaluation in towing tank and cavitation tunnel. Experiments were particularly conducted with respect to Self Propulsion Point (SPP), residual torque and thrust characteristics over a range of vehicle advance ratio in order to ascertain whether sufficient thrust is developed at the design condition with least possible imbalance torque left out due to residual swirl in the slip stream. Pumpjet and body models were developed for the propulsion tests using Aluminum alloy forged material. Tests were conducted from 0 m/s to 30 m/s at four rotational speeds of the PJP. SPP was determined confirming the thrust development capability of PJP. Estimation of residual torque was carried out at SPP corresponding to speeds of 15, 20 and 25 m/s to examine the effectiveness of the stator. Estimation of thrust and residual torque was also carried out at wind speeds 0 and 6 m/s for PJP RPMs corresponding to self propulsion tests to study the propulsion characteristics during the launch of the vehicle m water where advance ratios are close to Zero. These results are essential to assess the thrust performance at very low advance ratios to accelerate the body and to control the body during initial stages. This technique has turned out to be very useful and economical method for quick assessment of overall performance of the propulsor and generation of exhaustive fluid dynamic data to validate CFD techniques employed.