• International Journal of Automotive Technology
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• v.7 no.4
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• pp.493-500
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• 2006

Investigation on the fuel adhering on a wall was carried out experimentally to clarify the characteristics of impinging diesel sprays. Diesel sprays were injected into a high-pressure chamber of cold state and impinged to a wall having various impingement distances and ambient pressures. Photographs of both the fuel film and the post-impingement spray were taken through a transparent wall. Adhered fuel mass on a wall was measured by means of dividing into two types of fuel state: the fuel film itself; and sparsely adhered fuel droplets. Adhering fuel ratio was predicted and further the distribution of fuel mass for impinging diesel spray was analyzed as a function of time. As result, with an increase of the ambient pressure, both the maximum fuel film diameter and the adhered fuel ratio decreased. Based on some assumptions, the adhering fuel mass increased rapidly until the fuel film diameter approached the maximum value, and then increased comparatively gradually.

• Journal of ILASS-Korea
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• v.20 no.2
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• pp.76-81
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• 2015

Swirl flow has an impact on the stabilization of the flame by the recirculation flow, improvement of the combustion efficiency. The swirl flow in the gun type burner is created by the spinner which is inside the airtube that guide the combustion air. Burner has generally the combustion device composed electronic spark plug, injection nozzle, combustion device adaptor, and spinner. These inner components change the air flow behavior passing through airtube. So, this study analyzed exhaust flow characteristics of the gun type burner according to the ratio of airtube diameter. Turbulence characteristics by the spinner was mean velocity, turbulence intensity, kinetic energy, shear stress and flattness factor of the air flow of axial direction and tangential direction from the exit of the airtube.

• 한국연소학회:학술대회논문집
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• 2002.06a
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• pp.147-153
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• 2002

Experimental investigations are performed on the stability and the structure of bluff-body stabilized hydrogen flames. The velocities of coflow air are varied from subsonic to supersonic velocity of Mach 1.8 and OH PLIF images and Schilieren images are used for analysis. Three characteristic flame modes are classified into three regimes with the variation of fuel-air velocity ratio; a jet like flame, a central-jet dominated flame and a recirculation zone flame. Stability curves are drawn to find the blowout regimes and to show that flame stability is improved by increasing the lip thickness of fuel nozzle that works as bluff-body. $Damk{\ddot{o}hler$ number is adopted in order to scale the blowout curves of each flame obtained at different sizes of the bluff-body and all blowout curves are scaled successfully regardless of its bluff-body size.

• Journal of the Korean Society of Propulsion Engineers
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• v.1 no.1
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• pp.33-45
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• 1997

Axisymmetric shear layers around a free jet is forced by co-flowing and counter-flowing secondary jets from/to an annular tube around the jet nozzle. The jet potential core extends far downstream with co-flowing secondary jets due to inhibited vortex developing and pairing. For counter-flowing cases, the axisymmetric shear layer around the jet transits from convective instability to absolute instability for velocity ratios R＝1.3～l.65 for the uniform velocity jets. Consequently, the jet potential core length increases and the turbulence level in the jet core is reduced significantly. The jets are controlled better with extension collars attached to the outer nozzle exit because the annular secondary flow is guided well by the extension collars. For the vectoring of jet, the annular tube around the jet is divided in two parts and the only one part is used for suction. The half suction makes the different shear layer around the jet and vectoring the jet by Coanda effect. The vectoring and turbulent components are varied significantly by the suction ratio. The experiments are carried out to investigate the characteristics of forced free jets using flow visualization, velocity and turbulence measurements.

• Solar Energy
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• v.15 no.1
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• pp.53-71
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• 1995

Experiments have been conducted on a planar, free surface jet of water to investigate the effects of aspect ratios(AR=6.67, 15, 26.67), average nozzle velocity($V_0=3.3m/s{\sim}78m/s$) and nozzle-to-plate spacings($Z/W=6{\sim}40$) on the characteristics of heat transfer, when 3 rectangular waterjets impinging on a flat plate which has the uniform heat flux. the scondary peaks which produced by circular jets also produced by rectangular water jets. The position of the scondary peaks depends upon the aspect ratio of nozzle. The heat transfer coefficient was subjected to the influence of aspect ratio. The heat transfer correlations and best position of nozzles which produced maximum heat transfer coefficient at stagnation point are provided.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.8
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• pp.1128-1138
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• 2000

Pumping action in ejector systems is generally achieved through the mixing of a high-velocity and high-energy stream with a lower-velocity and lower-energy stream within a duct. The design and performance evaluation of the ejector systems has developed as a combination of scale-model experiments, empiricism and theoretical analyses applicable only to very simplified configurations, because of the generic complexity of the flow phenomena. In order to predict the detailed performance characteristics of such systems, the flow phenomena throughout the operating regimes of the ejector system should be fully understood. This paper presents the computational results for the two-dimensional supersonic ejector system with a second throat. The numerical simulations are based on a fully implicit finite volume scheme of the compressible Reynolds-averaged Navier-Stokes equation in a domain that extends from the stagnation chamber to the diffuser exit. For a wide range of the operating pressure ratio the flow field inside the ejector system is investigated in detail. The results show that the supersonic ejector systems have an optimal throat area for the operating pressure ratio to be minimized.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.3
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• pp.28-39
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• 2018

In this study, numerical simulations were performed for steady and unsteady state characteristics of length effects on linear pintle nozzles using the overset grid method. Nozzles and pintles are created separately by an auto grid generation program to use the overset grid method. Appropriate turbulent models and numerical methods are selected for the validation of simulations. Pintle shapes are chosen from five types, with differences in the ratio of length and diameter. The longer the pintle length, the greater the thrust and thrust coefficient. The chamber pressure tendency of steady-state and unsteady-state are different for various pintle velocities. The thrust of the nozzle exit responds to changes in the nozzle throat in the unsteady-state, and the speed of pressure propagation wave generated by movement of the pintle is considered to predict the major factor of performance.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.5
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• pp.510-519
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• 2013

In this study, the spray characteristics of a pressure swirl atomizer classified into a liquid sheet-type swirl nozzle for Urea-SCR system were investigated experimentally with the variation of injection pressure. The length to diameter ratio ($l_o/d$) of the nozzle was 3.1, and the swirler was set inside the nozzle tip to give injecting fluid angular momentum. The injection duration of the nozzle was controlled by PWM (pulse width modulation) modes. The development processes of the spray were imaged by a 2-D PIV system, and the change of spray angle was measured. The atomization characteristics, including axial velocity and SMD, were measured using a 2-D PDA system with the injection pressures at room temperature and ambient pressure conditions. As the experimental results, the injection pressure had a significant impact on the spray structure showing a different shape around the spray leading edge, and the smaller SMD was observed with increasing injection pressures, which was similar to that of the previous work.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.134-137
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• 2009

Combustion tests of a low thrust rocket engine was performed to get combustion characteristics, which used a high concentrated hydrogen peroxide and kerosene as the oxidizer and fuel. The engine consisted of multi injector(six coaxial swirl injectors), chamber, nozzle and catalyst ignition system. The test was carried out by changing O/F ratio from 3.8 to 11.0. The experimental results showed that combustion efficiency was highest at O/F ratio from 5 to 6 and pressure fluctuations of all the range were lower than 5%.

• The KSFM Journal of Fluid Machinery
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• v.8 no.6 s.33
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• pp.26-32
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• 2005

1.6 MW class supersonic partial admission impulse turbine has been designed and tested in Korea Aerospace Research Institute for the liquid rocket engine application. The test has been performed using a high pressure air source facility in KARI. For the turbine power absorption, a hydraulic dynamometer has been used. Appropriate similarity relations are used for the determination of test condition. Various settings of turbine pressure ratio and rotational speed are tested to investigate global turbine characteristics. From measured data, parameters related to the turbine design are derived and validated.