• Journal of the Korean Society of Industry Convergence
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• v.24 no.6_2
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• pp.787-793
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• 2021

The global demand for Liquefied Natural Gas(LNG) continues to increase and is facing a big cycle. To keep pace with the increase in international demand for LNG, the demand for LNG fueled ships is also increasing. Since LNG fuel tanks are operated in a cryogenic environment, insulation technology is very important, and although there are various types of insulation applied to Type C tanks, multi-layer insulation and vacuum insulation are typically applied. Powder insulation materials are widely used for storage and transportation of cryogenic liquids in tanks with such a complex insulation structure. In this study, compression tests at room and cryogenic temperature were performed on closed perlite, glass bubble, and fumed silica, which are representative powder insulation material candidates. Finally, the applicability to the Type C fuel tank was reviewed by analyzing the experimental results of this study.

• Progress in Superconductivity and Cryogenics
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• v.26 no.1
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• pp.25-30
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• 2024

High-temperature superconducting rotors offer advantages in terms of output-to-weight ratio and efficiency compared to conventional phase conduction motors or generators. The rotor can be cooled by conduction cooling, which attaches a cryocooler, and by refrigerant circulation, which uses circulating liquid or gas neon, helium and hydrogen. Recent work has focused on environmental issues and on high-temperature superconducting motors cooled with liquid hydrogen that can be combined with fuel cells. However, to ensure smooth supply and return of the cryogenic cooling fluid, a cryogenic rotational coupling between the rotating and stationary parts is necessary. Additionally, the development of a sealing structure to minimize fluid leakage applicable to the coupling is essential. This study describes the design and performance evaluation of a non-contact sealing method, specifically a labyrinth seal, which avoids power loss and heat load caused by friction in contact sealing structures. The seal design incorporates a spiral flow path to reduce leakage using centrifugal force, and computational fluid dynamics (CFD) simulations were conducted to analyze the flow path and rotational speed. A performance evaluation device was configured and employed to evaluate the designed seal. The results of this study will be used to develop a cryogenic rotational coupling with supply and return flow paths for cryogenic applications.

• Journal of the Korean Society for Precision Engineering
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• v.34 no.4
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• pp.237-241
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• 2017

Cryogenic machining uses liquid nitrogen (LN2) as a coolant. This machining process can reduce the cutting temperature and increase tool life. Titanium alloys have been widely used in the aerospace and automobile industries because of their high strength-to-weight ratio. However, they are difficult to machine because of their poor thermal properties, which reduce tool life. In this study, we applied cryogenic machining to titanium alloys. Orthogonal cutting experiments were performed at a low cutting speed (1.2 - 2.1 m/min) in three cooling conditions: dry, cryogenic, and cryogenic plus heat. Cutting force and friction coefficients were observed to evaluate the machining characteristics for each cooling condition. For the cryogenic condition, cutting force and friction coefficients increased, but decreased for the cryogenic plus heat condition.

• Progress in Superconductivity and Cryogenics
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• v.24 no.1
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• pp.29-33
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• 2022

Recently, development of a cryogenic fluids storage tank for storing or transporting liquid hydrogen is actively in progress. In cryogenic fluids storage tanks, hydrogen evaporates due to the extreme temperature difference inside and outside the tank. As the mass of the cryogenic fluids changes with continuous vaporization, the fluids level also changes. Therefore, there is need for a method of accurately measuring the level change in the storage tank. In the case of general cryogenic fluids, it is difficult to accurately measure the level because the dielectric constant is very low. As a method of measuring cryogenic fluids level with low dielectric constant, it can be used an Millimeter wave (MM wave) FMCW radar sensor. However, the signal sensitivity is very weak and the level accuracy is poor. In this paper, the signal sensitivity is improved by designing the horn lens antenna of the existing 80 GHz FMCW radar sensor. Horn lens antenna is fabricated by FDM/SLA type 3D printer according to horn and lens characteristics. The horn is used to increase the signal gain and the lens improves the signal straightness. This makes it possible to measure the level of cryogenic fluids with a low dielectric constant.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.3
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• pp.82-89
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• 2012

The temperature of cryogenic propellant in the propellant tank increases during flight due to heat input from surroundings. The propellant which temperature rises up over the required condition of turbo-pump remains as unusable propellant at the end of flight. In this paper the estimation method of the heat transfer coefficient at the upper layer of cryogenic propellant was presented. The heat transfer mode at the propellant upper layer was considered as conduction. Temperature distributions near propellant surface obtained from heat transfer coefficient were compared with test data to show the possibility of this method.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.168-175
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• 2005

The pressurization system in a liquid rocket propulsion system provides a controlled gas pressure in the ullage space of the vehicle propellant tanks. It is advantage to employ a hot gas heat exchanger in the pressurization system to increase the specific volume of the pressurant and thereby reduce over-all system weight. A significant improvement in pressurization-system performance can be achieved, particularly in a cryogenic system, where the gas supply is stored inside the cryogenic propellant tank. The temperature characteristic of cryogenic pressurant is very important to develop some components in pressurization system. Numerical modeling and Test data were studied using SINDA/FLUINT Program and PTF(Propellant-feeding Test Facility).

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.709-716
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• 2011

The temperature of cryogenic propellant in the propellant tank increases during flight due to heat input from surroundings. The propellant which temperature rises up over the required condition of turbo-pump remains as unusable propellant at the end of flight. In this paper the estimation method of the heat transfer coefficient at the upper layer of cryogenic propellant was presented. The heat transfer mode at the propellant upper layer was considered as conduction. Temperature distributions near propellant surface obtained from heat transfer coefficient were compared with test data to show the possibility of this method.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.918-919
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• 2015

Because of environmental regulations in emissions control area, the demand for ships to use LNG as fuel is increasing. Orders for domestic shipbuilders to produce LNG carriers are steadily increasing. However, major appliances such as spray pump, main cargo pump and others have been relied on imports. Therefore, development of pump motor using at cryogenic temperature is necessary. Operating temperature of an induction motor is at $-163^{\circ}C$. At this low temperature, the resistivity of a motor coil is quite different from normal ones, and so does the torque characteristics of motor. This paper presents a designing method of a cryogenic induction motor for LNG pump. The variation of resistivity of motor coil is considered in the design process. The heat source such as core-loss, hysteresis-loss and copper-loss are analyzed to prevent the LNG evaporation which may cause the motor failure.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.283-288
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• 2011

The spherical flange was designed to apply to a cryogenic high pressure pipe of the Liquid Rocket Engine. It is designed that the spherical flange is able to be assembled and kept airtight upto $2.5^{\circ}$ of the axial misalignment between the combined components. It increases the degree of freedom of the engine assembly. The spherical flange is composed of a ball and socket joint, a metal seal and spherical type bolts, washers. The prototype was verified by leak test at the room temperature and the cryogenic temperature. Additionally the strength test and the destructive test were performed at the room temperature.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.3
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• pp.64-69
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• 2011

The spherical flange was designed to apply to a cryogenic high pressure pipe of a liquid rocket engine. It is designed that the spherical flange is able to be assembled and kept airtight up to $2.5^{\circ}$ of the axial misalignment between the combined components. It increases the degree of freedom of the engine assembly. The spherical flange is composed of a ball and socket joint, a metal seal, spherical type bolts and washers. The prototype was verified by leak test at the room temperature and the cryogenic temperature. Additionally the strength test and the destructive test were performed at the room temperature.