• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.16-19
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• 2011

An experimental study on the spray characteristics of Gas-centered swirl coaxial injectors(GCSCI) for high-performance staged combustion rocket engines has been carried out using cold flow tests. In this study, water and gaseous nitrogen are used as working fluids and a back-lit photography technique with image processing for the measurements of spray characteristics. Our study is focused on the effect of injector geometries like as gap thickness of liquid nozzle and gas nozzle and momentum flux ratio for fundamental understanding of the injectors.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.2
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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.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.353-356
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• 2006

Convective heat transfer coefficient was measured around a secondary jet ejected into the supersonic flow field. Wall temperature distribution was measured on the surface, which the constant heat flux condition is applied. According to jet to freestream momentum ratio, the secondary flow was penetrated into the supersonic flow field. During the test, two dimensional thermal image of a wall temperature is taken by an infra-red camera. Experiments were performed under the testing condition of freestream Mach number of about 3, stagnation pressure of 630 kPa and Reynolds number of $3.0{\times}10^6$.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.2
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• pp.47-53
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• 2007

Convective heat transfer coefficient was measured around a circular secondary jet ejected into the supersonic flow field. The wall temperature measurement around a injection nozzle was conducted using infra-red camera. The constant heat flux is applied to the wall around a secondary nozzle. According to jet to freestream momentum ratio, the injection flow penetrates into the supersonic flow field. The measured temperature is used to calculate the convective heat transfer coefficient.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.6
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• pp.462-473
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• 2001

Due to the coupling between momentum and energy transport theoretical analysis of the loop performance is very complicate, therefore it is necessary that these problems be solved by experimental investigation before applying th loop thermosyphon to heat exchanger design. The evaporator and condenser of the loop thermosyphon were made of carbon-steel, and distilled water was used as working fluid in the experiments. From the experimental data correlations of heat transfer coefficient for evaporator and condenser sections were obtained. For heat fluxes in th range of 13~78kW/$m^2$, the correlation equations of heat transfer coefficients in evaporator and condenser predict the experimental behavior to within $\p$\pm$5% and\;\pm20$% respectively.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.1
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• pp.54-61
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• 1999

The fully developed turbulent momentum and heat transfer induced by the roughness elements on the outer wall surfaces in concentric annuli are analytically studied on the basis of a modified turbu-lence model. The resulting momentum and heat transfer are discussed in terms of various parame-ters such as the radius ratio the roughness density Reynolds number and Prandtl number accord-ing to the heating condition. The study shows that certain artificial roughness elements may be used to enhance heat transfer rates with advantage from the overall efficiency point of view.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.1
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• pp.28-35
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• 2018

In order to analyze the flammability limit and structure of the gaseous methane-gaseous oxygen diffusion flame formed through a shear coaxial injector, combustion experiments were carried out according to the condition of injector recess and propellant mass-flow rate. As a result, it was confirmed that stable anchored flame was observed even at the high oxygen Reynolds number as the propellant momentum flux ratio increased, and that the recess had no significant influence on the flame shape and flammability limit. The anchored flame visualized through a chemiluminescence showed the maximum OH radical emission intensity at a specific position, irrespective of the propellant injection condition, and the radical intensity was greatly reduced by the injector recess.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.4
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• pp.59-70
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• 2021

An experimental study was conducted to observe the spray characteristics for different flow rates and rotating speeds of a rotating fuel nozzle of a slinger combustor. The water spray ejected from the nozzle orifice was visualized using a high-speed camera and a light source. It was confirmed that the atomization was improved, as the flow rate decreased and rotating speed increased. The characteristic maps for the spray characteristics and performance parameters showed that the aerodynamic Weber number and the liquid-air momentum flux ratio were associated with the liquid primary breakup, and the liquid-air momentum flux ratio and Rossby number were closely correlated with the liquid ejection mode.

• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.298-303
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• 2002

Dispersion of coolant jets in a film cooling flow field is the result of a highly complex interaction between the film cooling jets and the mainstream. In order to investigate the effect of blowing ratios on the film cooling of turbine blade, cylindrical body model was used. Mainstream Reynolds number based on the cylinder diameter was $7.1{\times}10^4$. The effect of coolant flow rates was studied for blowing ratios of 0.7, 0.9, 1.2 and 1.5, respectively. The temperature distribution of the cylindrical model surface is visualized by infrared thermography (IRT). Results show that the film-cooling performance could be significantly improved by the shaped injection holes. For higher blowing ratio, the spanwise-diffused injection holes are better due to the lower momentum flux away from the wall plane at the hole exit.

• International Journal of Naval Architecture and Ocean Engineering
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• v.3 no.4
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• pp.286-292
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• 2011

In order to design a shear coaxial injector of solid particles for underwater propulsion system, basic experiments on gas-liquid shear coaxial injector are necessary. In the gas-liquid coaxial injector self-pulsation usually occurs with an intense scream. When self-pulsation occurs, mass flow rate oscillation and intense scream are detected by the interactions between the liquid and gas phase. Self-pulsation must be suppressed since this oscillation may cause combustion instabilities. Considerable research has been conducted on self-pulsation characteristics, but these researches are conducted in swirl coaxial injector. The main objective of this research is to understand the characteristics of self-pulsation in shear coaxial injector and reveal the mechanism of the phenomenon. Toward this object, self-pulsation frequency and spray patterns are measured by laser diagnostics and indirect photography. The self-pulsation characteristics of shear coaxial injector are studied with various injection conditions, such as the pressure drop of liquid and gas phase, and recess ratio. It was found that the frequency of the self-pulsation is proportional to the liquid and gas Reynolds number, and proportional to the L/d.