• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.10a
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• pp.229-234
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• 2004

The objective of the present study is to conduct model combustion tests for double swirl coaxial injectors to identify their combustion stability characteristics. Gaseous oxygen and mixture of methane and propane have been used as simulant propellants. Two model chambers tuned to the If acoustic resonance mode of a full-scale thrust chamber were manufactured to be used as a combustion cylinder. The main idea of the experiment is that the mixing mechanism is considered as a dominant factor significantly affecting combustion instability in a full-scale thrust chamber. Self-excited dynamic pressure values in a model chamber show different combustion stability zones with respect to a recess number. Upon test results, couplings between combustion conditions and the IT acoustic resonance mode become strengthened with the increase of a recess length.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.139-143
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• 2007

The overall results of combustion tests performed for a 30 tonf-class full-scale combustion chambers of a liquid rocket engine were described. The combustion chambers have chamber pressure of 53${\sim}$60 bar and propellant mass flow rate of 89 kg/so The combustion chamber is composed of mixing head, SUS baffle, baffle injector, ablative chamber, channel cooling chamber and regenerative cooling chamber. The test results show that the combustion characteristic velocity is in the range of 1673${\sim}$1730 m/sec and the specific impulse of the combustion chamber is in the range of 254${\sim}$263 sec. As the recess number of the injectors increases, the combustion characteristic velocity increases. And as the combustion characteristic velocity increases, the specific impulse of the combustion chamber also increases.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.10
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• pp.704-709
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• 1999

The optical properties such as luminance and color coordinates for phosphor layer were studied with applied voltage and gas pressure, Xe mixing ratio, frequency using He and Xe mixing gas in chamber like AC PDP. The luminance of red phosphor layer at constant pressure(300Toor) is increased with increasing voltage, but color purity is not varied. The luminance of red phosphor layer at constant voltage(280V)is decreased with increasing pressure, but the color purity is not varied. But the luminance is increased with increasing Xe mixing ratio at constant pressure(200Toor). And also the color purity is improved by this process. The luminance is increased up to 40kHz, but the color purity with frequency is not varied.

• Journal of the Korea Institute of Military Science and Technology
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• v.6 no.4
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• pp.113-123
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• 2003

Both numerical analysis and experiment of cold and hot tests were performed to obtain basic design data for the swirl coaxial type Injector and to predict the combustion performance. Mass distribution, mixing distribution, mixing efficiency, characteristic velocity efficiency were measured by the cold tests and numerical analysis using the commercial thermo-hydraulic program. Test and analysis variables were recess, pressure drop, velocity ratio, mixing spray, mixture ratio. Hot tests were performed for the Uni-element injector to compare the performance with the cold test results, and, hot tests for Multi-element injector were performed to compare the performance with Uni-element injector. Designed thrust of the Uni-element injector liquid rocket was 35kgf at sea level and combustion chamber pressure, 20bar. Kerosene and Lox were used as a propellant.

• Journal of the korean Society of Automotive Engineers
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• v.12 no.1
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• pp.33-39
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• 1990

This study has been conducted by experiments for distribution of concentration of helium gas, which is jetted into stationary atmosphere at the normal temperature and pressure. It is able to obtain the data for concentration of helium and air mixtures by the use of hot wire probe which has fast response. At an up stream, the concentration gradient which is attained is steep. At a down stream, the mixing time of helium and air is gradually shortened with the lapse of time in front of a jet. The arrival frequency of a jet in an unsteady area is mostly constant from 0% to 100% up to 80mm, but the time which is reaching to 100% is gradually to lengthen as a descending downstream. After starting a jet and the point of 90%, the mixing time is especially to lengthen. This reason comes from the turbulent intensity which causes for mixing of helium and air. This time difference which causes according to lengthen a jet should be considered in the design of combustion chamber.

• Journal of the Korean Society of Safety
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• v.7 no.3
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• pp.73-82
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• 1992

This paper was concerned with the risk evaluation of oxidizing substances by burning test method. The samples were prepared the heaped cone-shaped mixtures of solid oxidizing sub-stance with sawdust, and ignition of the sample was made on contact with heating wire inside the combution chamber that the temperature and humidity of atmosphere can be kept at $25^{\circ}C$ and 60% respectively. Accordingly, it were measured the combustivity effect of mixing ratio and amount of sample weight on the burning rate. As a result of burning test of these samples, it could be noticed that the case when the sawdust has so and 30 wt.% in the mixing ratio shows effective combustivity, and as the amount of sample weight was increasing, It showed more rapid burning time. So the average burning time could be obtained by considering the weighting factors to the parameters of the mixing ratio and the amount of sample weight. Finally, it was compared with the effects of cation and anion of oxidizing substances and also applied analytically to the classification and evaluation of oxidizing sub-stances as dangerous goods.

• Journal of Surface Science and Engineering
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• v.50 no.5
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• pp.373-379
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• 2017

Dry processes like evaporation and sputtering in vacuum chamber are difficult to make a uniform, large area and high quality film on thin PET substrate because of PET degradation and bad adhesion. On the other hand, wet processes like electro or electroless plating have complex processes and require high environmental cost. In this study, we successfully prepared $2{\mu}m$ Zn/Cu/Ni multilayers coated on $12{\mu}m$ polyethylene terephthalate (PET) substrate by using dry-wet mixing processes. Their surface electric resistances were evaluated around $0.2{\Omega}$ by using 4 probe measurements. Furthermore, their corrosion resistance also evaluated by natural potential test and compared with other wet, dry and mixing process samples.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.6
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• pp.51-58
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• 2003

A cycle simulation method is developed by coupling a commercial code, Ricardo's WAVE, with the SENKIN code from CHEMKIN packages to predict combustion characteristics of an HCCI engine. By solving detailed chemical kinetics the SENKIN code calculates the combustion products in the combustion chamber during the valve closing period, i.e. from IVC to EVO. Except the combustion chamber during the valve closing period the WAVE code solves thermodynamic status in the whole engine system. The cycle simulation of the complete engine system is made possible by exchanging the numerical solutions between the codes on the coupling positions of the intake port at IVC and of the exhaust port at EVO. This method is validated against the available experimental data from recent literatures. Auto ignition timing and cylinder pressure are well predicted for various engine operating conditions including a very high ECR rate although it shows a trend of sharp increase in cylinder pressure immediate after auto ignition. This trend is overpredicted especially for EGR cases, which may be due to the assumption of single-zone combustion model and the limit of the chemical kinetic model for the prediction of turbulent air-fuel mixing phenomena. A further work would be needed for the implementation of a multi-zone combustion model and the effect of turbulent mixing into the method.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.11 s.254
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• pp.1093-1100
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• 2006

Combustion stability rating of jet injector is conducted numerically using air-injection technique in a model chamber, where air is supplied to oxidizer and fuel manifolds of the model five-element injector head. A sample F(fuel)-O(oxidizer)-O-F impinging-jet injector is adopted. In this technique, we can simulate mixing process of streams flowing through oxidizer and fuel orifices under cold-flow condition without chemical reaction. The model chamber was designed based on the methodologies proposed in the previous work regarding geometrical dimensions and operating conditions. From numerical data, unstable regions can be identified and they are compared with those from air-injection acoustic and hot-fire tests. The present stability boundaries are in a good agreement with experimental results. The proposed numerical method can be applied cost-effectively to stability rating of jet injectors when mixing of fuel and oxidizer jets is the dominant process in instability triggering.

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.867-869
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• 1999

In this study, $SrBi_{2}Ta_{2}O_{9}$(SBT) thin films were etched as a function of $SF_6$/Ar gas mixing ratio in magnetically enhanced inductively coupled plasma(MEICP) system fer a fixed rf power, dc-bias voltage, and chamber pressure. The etch rate of SBT thin film was $1500{\AA}/min$ and the selectivities of photoresist (PR) and $SiO_2$ to SBT thin film were 0.48 and 0.62, respectively when the samples were etched at a rf power of 600W, a dc-bias voltage of -150V, a chamber pressure of 10 mTorr and a gas mixing ratio of $SF_6/(SF_6+A)$=0.1. In order to examine the chemical reactions on the etched surface, X-ray photoelectron spectroscopy(XPS) and secondary ion mass spectrometry(SIMS) were done.