• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.99-103
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• 2017

As a development test of the 75-tonf LOx/Kerosene liquid rocket engine for KSLV-II first Stage Engine, hot firing test of 75-tonf engine are performed. The current status of development test on first stage 75-tonf engine system including combustion chamber, turbopump, gas generator, propellant supply system are presented. During the 75tonf engine test campaign, the development of startup sequence of LOx-Kerosene engine system, engine startup using pyrostarter, ignition of gas generator, steady operation and engine shutdown is successfully performed. As a passenger test during engine hot firing tests, Thrust Vector Control system (TVC) of the engine are also evaluated during engine hot firing test. The results of hot firing test of 75-tonf thrust engine system will be used for the design confirmation and performance evaluation of 75 tonf engine system for KSLV-II first Stage.

• Korean Journal of Microbiology
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• v.54 no.2
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• pp.105-112
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• 2018

To compare the denitrification efficiency, this study used molasses and methanol were used as external carbon sources. Specific experimental conditions were classified according to C/N ratio conditions. The batch test showed that the denitrification efficiency increased as C/N ratios of molasses and methanol rose. The most suitable C/N ratio of molasses turned out 4:1 considering the concentration of the residue chemical oxygen demand (COD) and the denitrification efficiency, which was 91.4%. Specific denitrification rate (SDNR) drawn as a kinetic factor demonstrated that molasses and methanol showed similar SDNR values as C/N ratios of molasses and methanol increased. Under the condition of C/N ratio 4:1, 0.0292 g $NO_3{^-}-N$ removal/g mixed liquor volatile suspended solid (MLVSS)/day (molasses), 0.0299 g $NO_3{^-}-N$ removal/g MLVSS/day (methanol) were found. Sludge adapted to molasses showed that Bacterium Pseudomonas sp. and Bergeylla sp. dominated through an analysis of microbial community. In addition, some bacteria were high convergences than the variety of microbial community. Accordingly, it was assumed that molasses focus on growing microorganisms specialized in denitrification and applied as a replaceable external carbon source that can enhance denitrification performance.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.4
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• pp.74-80
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• 2005

This paper presents a misfire monitoring method by using the weight factor. According to OBD II(On-Board Diagnostics) regulations of the CARB (California Air Resources Board), an ECU (Electronic Control Unit) should detect misfires which occur in the internal combustion engine. A misfire is 1311owe4 by post-oscillations for short duration. Sometimes, the amplitude of oscillations may be as high as misfire and can be falsely detected as another misfire. To prevent this, the software designers do not attempt to detect another misfire for this short duration, during which the post oscillations exist. Because of this, ECU does not detect all the misfires and hence, the unstable state of automobile cannot be detected. If this happens for a long time, automobile may get damaged. To solve these problems, this paper suggests a new algorithm to detect misfire by using weighting factor Weighting factor is a concept to distinguish the misfire with the post oscillation and to improve the detection rate. This value of weighting factor is used for counting the misfire. This paper also shows the result of experiment done on a automobile using this software. The software is implemented using ASCET-SD which is preferred in the design of engine control. This paper's result show the possibility of improving the misfire detection by implementing this algorithm.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.1
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• pp.116-123
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• 2019

Thermal batteries are also called molten-salt batteries as the electrolyte is mainly composed of molten salt. The molten-salt electrolyte is a solid that does not conduct electricity at room temperature, but when it is melted by a pyrotechnic heat source, it becomes an excellent ionic conductor. Thermal batteries are a kind of pyrotechnic battery because they operate only when the solid electrolyte is melted by the heat energy provided by pyrotechnic materials. Pyrotechnic components used in a thermal battery include heat sources, fuse strips, and an igniter. The reliability of these pyrotechnic components critically affects the reliability and performance of the battery that must supply electricity stably to guided munitions even under extreme environmental conditions. Different igniter types offer different advantages: notch-type igniters offer improved ignition probability, whereas film-type igniters offer improved safety. The addition of metal oxides to the heat paper could improve the burn rate, and the ignition reliability could be greatly improved by using it with a flame igniter at the same time. Using a two-step reduction process, high-purity Fe particles in coral form can be safely obtained.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.4
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• pp.391-397
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• 2011

The use of Hydrogen as a fuel is receiving considerable attention and as a result, research on novel methods of hydrogen production is necessary so that the hydrogen demands in the future can be satisfied. This study presents experimental data on methanol Autothermal Reformation that quantifies the relationship between the oxygen-to-methanol ratio ($O_2/CH_3OH$) and reformer efficiency. For each catalyst configuration, the $O_2/CH_3OH$ was varied from 0.1 to 0.4, with an increment of 0.05, to investigate the effects of $O_2/CH_3OH$ on the reactor performance, including temperature profile, conversion, and efficiency. $O_2/CH_3OH$ was increased from 0.15 to 0.20, and the catalyst bed temperature increased by $235^{\circ}C$ to approximately $550^{\circ}C$. The catalyst bed temperature increased with increasing $O_2/CH_3OH$ as the reaction shifted from endothermic to exothermic reaction and as a result, excess heat, which raised the reactor temperature, was generated. The reactor performance was shown to be highly dependent on $O_2/CH_3OH$. The optimum $O_2/CH_3OH$ = 0.30 found in the experimental tests is 30% higher than the theoretical optimum of 0.23. This is attributed to a combination of factors such as the concentrations of the $O_2$ and $CH_3OH$ gas, reaction rate, catalyst effects, heat loss from the reactor, and the difference between the actual amounts of reaction products formed and the theoretical amounts of the reaction products.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.4
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• pp.394-401
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• 2005

A nonthermal plasma-assisted fuel reformer was developed and the effects of operating variables on the performance of this reformer were studied. The $H_2$-rich reformed gas from the reformer was injected into a diesel engine under an idle condition and the effects of the amount of injected gas on the NO and soot reduction were investigated. It was found that with increasing electric power consumption, the degree of facility of ignition of the reforming reaction in the reformer could be enhanced. The performance of the reformer including $H_2$ concentration, $H_2$ recovery, and energy conversion was affected only by the O/C mole ratio. This was because the equilibrium reaction temperature was governed by the O/C mole ratio. With increasing O/C mole ratio, the $H_2$ recovery and energy conversion passed through the maximum values of 33.4% and 66%, respectively, at an O/C mole ratio between 1.2 and 1.5. The reason why the $H_2$ recovery and energy conversion increased with increasing O/C mole ratio when the O/C mole ratio was lower than $1.2{\sim}1.5$ appeared to be that the complete oxidation reaction occurred more enough with increasing O/C mole ratio in this low O/C mole ratio range and accordingly the reaction temperature increased. Whereas the reason why the $H_2$ recovery and energy conversion decreased with increasing O/C mole ratio when the O/C mole ratio was higher than $1.2{\sim}1.5$ appeared to be that the complete oxidation reaction was further advanced and the $H_2$ recovery and energy conversion decreased. As the weight ratio of reformed diesel to total diesel which entered the diesel engine was increased to $18.2{\sim}23.5%$, NO and soot reduction efficiencies increased and reached as values high as 68.5% and 23.5%, respectively.

• Journal of Bio-Environment Control
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• v.31 no.4
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• pp.384-392
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• 2022

The objective of this study was to estimated nitrogen content and chlorophyll using RGB, Hyperspectral sensors to diagnose of nitrogen nutrition in apple tree leaves. Spectral data were acquired through image processing after shooting with high resolution RGB and hyperspectral sensor for two-year-old 'Hongro/M.9' apple. Growth data measured chlorophyll and leaf nitrogen content (LNC) immediately after shooting. The growth model was developed by using regression analysis (simple, multi, partial least squared) with growth data (chlorophyll, LNC) and spectral data (SPAD meter, color vegetation index, wavelength). As a result, chlorophyll and LNC showed a statistically significant difference according to nitrogen fertilizer level regardless of date. Leaf color became pale as the nutrients in the leaf were transferred to the fruit as over time. RGB sensor showed a statistically significant difference at the red wavelength regardless of the date. Also hyperspectral sensor showed a spectral difference depend on nitrogen fertilizer level for non-visible wavelength than visible wavelength at June 10th and July 14th. The estimation model performance of chlorophyll, LNC showed Partial least squared regression using hyperspectral data better than Simple and multiple linear regression using RGB data (Chlorophyll R²: 81%, LNC: 81%). The reason is that hyperspectral sensor has a narrow Full Half at Width Maximum (FWHM) and broad wavelength range (400-1,000 nm), so it is thought that the spectral analysis of crop was possible due to stress cause by nitrogen deficiency. In future study, it is thought that it will contribute to development of high quality and stable fruit production technology by diagnosis model of physiology and pest for all growth stage of tree using hyperspectral imagery.