• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.04a
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• pp.23-23
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• 1998

Jet Vane Type 추력방향제어 시스템의 구조적 안정성을 검토하기 위해 시스템의 해석을 Vane, Ablation & Bracket Interface, Nozzle flange & Housing Interface 및 Fastener의 세 부분으로 나누어 수행하였다. 해석을 위한 외력조건은 유동해석을 통해 얻어진 온도 및 압력분포에 근거하였으며, Vane의 응력해석을 위해서는 상용 Software인 Patran 및 Nastran이 사용되었다. 이번 연구는 Test Model 단계로서 충분한 강도의 고정 Housing이 사용되어, 이에 대한 해석은 수행되지 않았지만 추후 Flight Model 단계에서는 함께 고려되어질 것이며, 각 경우의 Margin of Safety값들을 도출하여 구조적 안정성을 검토하였다.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.1
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• pp.36-44
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• 2018

The thermal response of carbon/phenolic used in a solid rocket nozzle liner was analyzed. In this paper, the numerical analysis of the thermal response of carbon/phenolic consists of (1) the integration equation of the boundary layer to obtain the convective heat transfer coefficient of the combustion gas on the rocket nozzle wall and (2) 1-D finite difference method for heat conduction of carbon/phenolic to calculate the ablation, char, and temperature. The calculated result was compared with the result of a blast-tube-type test motor. It is found that the calculated result shows good agreement with the thermal response of the test motor, except at the vicinity of the throat insert.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.651-663
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• 2017

Experimental results of $30^{\circ}-15^{\circ}$ nozzles were compared with numerically calculated convective heat transfer coefficients using FLUENT, Boundary Layer Integration Method and Bartz predictions. Also, the convective heat transfer coefficients were calculated by using FLUENT and boundary layer integration method for NASA HIPPO nozzles according to the characteristics of combustion gas and the correlation between pressure and pressure was compared. Finally, thermal analysis of NASA HIPPO nozzle was performed to compare the ablation thickness and char depth according to the combustion gas characteristics.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1159-1161
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• 1995

The pure PTFE nozzles may not be used in the GCB with very high interrupting capacity because of their excessive ablation and carbonization. But it is known that the nozzles with filler can show good performances at the extremely high inetrrupting currents of 50kA or 63kA. So, the manufacturing process of filled Teflon has been carefully studied. Then several specimens have been prepared for the experiments and analyses of their mechanical and electrical characteristics. Finally the high power arc tests have been conducted to the Teflon nozzle with filler of $Al_2O_3$. The results of experiments and tests show that the filled Teflon nozzle has superior mechanical characteristics, comparable electrical characteristics to a pure Teflon nozzle and a distinguished endurance against high power arcs.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.320-323
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• 2009

There is many considerations of the composition development of propellant, performance analysis according to temperature, ablation condition of heat-resistant material, etc. in the solid rocket motor development process. Performance analysis of the motor according to nozzle expansion ratio is one of this process and an important factor to decide the motor performance. A Study is verified through anlaysis, motor manufacture and test.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.05b
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• pp.7-10
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• 2004

This paper presents the electrical properties of PTFE nozzle for a electrical apparatus. In the arcing environment in a electrical apparatus, radiation is considered to be the major energy transport mechanism from the arc to the wall. The fraction of the radiation power is emitted out of the arc and reaches the nozzle wall, causing ablation at the surface and in the depth of the wall. The energy concentration in the material leads to the depolymerization and eventually leads to the generation of decomposed gas as well as some isolated carbon particles. Adding some fillers into PTFE is expected to be efficient for improving the endurability against radiation. In this experiment, three kinds of fillers that have endurance in the high temperature environment were added into PTFE. Light reflectance of fillers was investigated. Dielectric constan and dissipation factor of PTFE composites were investigated. Dielectric constant and dissipation factor of the PTFE composites increased with increasing contents of the fillers.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.2
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• pp.200-205
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• 2010

Heat-resistance of W/$Y_2O_3$ as throat insert material was evaluated to develop rocket motor keeping thrust uniformly under condition of high-temperature, high-pressure and long-burn time. Test was conducted with varying burn time, and test results were compared with CIT. Test showed that ablation rate was decreased according as burn time was increased, and that ablation rate of W/$Y_2O_3$ was about 55 % of CIT. Macro/micro structures of throat insert did not show a peculiar phenomenon by increased burn time. In addition, the vacuum heat treatment is effective for the prevention of crack in throat insert.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.887-890
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• 1997

Recently micromachining using DPSSL(Diode Pumped Solid State Laser) with 3rd harmonic wavelength is actively studied in laser machining area. Micromachining using DPSSL have outstanding advantages as UV source comparing with excimer laser in various aspect such a maintenance cost, maskless machining, high repetition rate and so on. In this study micro-drilling of PCB type substrate which consists of Cu-PI-Cu layer was performed using DPSS Nd:YAG laser(355nm, wavelength) in vector scanning method. Experimental and numerical method(Matlab simulation, FEM) are used to optimize process parameter and control machining depth. The man mechanism of this process is laser ablation. It is known that there is large gap between energy threshold of copper and that of PI. Matlab simulation considering energy threshold of material is performed to effect of duplication of pulse and FEM thermal analysis is used to predict the ablation depth of copper. This study could be widely used in various laser micromachining including via hole microdrilling of PCB, and micromachining of semiconductor components, medical parts and printer nozzle and so on.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2506-2511
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• 2007

The coupled simulation is performed to find out the interaction of arc plasmas with surrounding materials in a thermal puffer plasma chamber. In order to be more realistic, PTFE nozzle ablation and Cu electrode evaporation, which are caused by high temperature of arc plasmas, are considered together. Pressure rise and temperature inside the chamber generated during the whole arcing history are investigated with the applied currents. It is very important to define how thermal flow and mass transfer are processing between the arc plasma and surrounding materials for further understanding complex physics inside the chamber. It is concluded that the result might be very useful to understand the mechanism happened inside and to design thermal puffer plasma chambers, but further experimental studies are required to verify the results for the more practical applications.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.11
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• pp.527-532
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• 2005

During the last ten years the new interruption techniques, which use the arc energy itself to increase the pressure inside a chamber by the PTFE nozzle ablation, have displaced the puffer circuit breakers due to reduced driving forces and better maintainability. In this paper, we have investigated the thermal flow characteristics inside a thermal puffer type gas circuit breaker by solving the Wavier-Stokes equations coupled with Maxwell's equations for considering all instabilities effects such as turbulence and Lorentz forces by transient arc plasmas. These relative inexpensive computer simulations might help the engineer research and design the new interrupter in order to downscale and uprating the GIS integral.