• Journal of Ocean Engineering and Technology
• /
• v.33 no.5
• /
• pp.394-399
• /
• 2019

Plywood is a laminated wood material where alternating layers are perpendicular to each other. It is used in a liquefied natural gas (LNG) carrier for an insulation system because it has excellent durability, a light weight, and high stiffness. An LNG cargo containment system (LNG CCS) is subjected to loads from gravity, sloshing impact, hydrostatic pressure, and thermal expansion. Shear forces are applied to an LNG CCS locally by these loads. For these reasons, the materials in an LNG CCS must have good mechanical performance. This study evaluated the shear behavior of plywood. This evaluation was conducted from room temperature ($25^{\circ}C$) to cryogenic temperature ($-163^{\circ}C$), which is the actual operating environment of an LNG storage tank. Based on the plywood used in an LNG storage tank, a shear test was conducted on specimens with thicknesses of 9 mm and 12 mm. Analyses were performed on how the temperature and thickness of the plywood affected the shear strength. Regardless of the thickness, the strength increased as the temperature decreased. The 9 mm thick plywood had greater strength than the 12 mm thick specimen, and this tendency became clearer as the temperature decreased.

• Journal of the Korean Society of Safety
• /
• v.28 no.2
• /
• pp.1-5
• /
• 2013

Liquefied Natural Gas is liquefied at the condition of atmosphere pressure and cryogenic temperature. LNG is exposed very long time under the cryogenic temperature and high pressure, and it is very important to retain the structural safety in this envelopment. Until now, the material which are composing the storage tank of LNG ship has experimented at room temperature, so it is not enough to apply for the design at the cryogenic temperature. The purposes of this study are investigated mechanical properties for aluminum alloy. To evaluate tensile and fatigue test for aluminum alloy, it was considering static and fatigue conditions at room and cryogenic temperature. S-N curves were designed at both temperature respectively. Also, P-S-N curve was performed statistical method by JSME-S002.

• Journal of Advanced Marine Engineering and Technology
• /
• v.35 no.6
• /
• pp.802-808
• /
• 2011

One of the important mechanical properties of cryogenic temperature structure material is fracture toughness. Research on normalization of fracture toughness test method is becoming very important issue with development of cryogenic structural elements. Specially, mechanical properties estimation by each micro-structure of welding department is important because it can cause unstable fracture when use under cryogenic environment in case of welding department. In this study, fracture toughness estimation test was carried out to unloading compliance method and sensitization heat-tread minimized test specimen at liquid nitrogen (77K), liquid helium (4K), 293K temperature to STS-316L base metal and weld metal.

• Journal of Advanced Marine Engineering and Technology
• /
• v.37 no.4
• /
• pp.384-390
• /
• 2013

The sizes of cryogenic vessels and storage tanks are becoming bigger due to strong demands from semiconductor and LCD industry as well as high-tech electronic industry. Conventional level and pressure gauges used for cryogenic vessels were analog types which made exact measurement difficult for the remained quantity at lower levels due to their poor accuracy. In this study, a design for a digital type gas level gauge which can measure the pressure and level inside of the cryogenic liquefied gas storage tanks has been proposed by using a differential pressure sensor, in which the measured data are monitored by a host PC and are transferred to a mobile printer for data confirmation at local station.

• Journal of the Korean Society for Precision Engineering
• /
• v.34 no.4
• /
• pp.247-251
• /
• 2017

Titanium alloy has been widely used in the aerospace industry because of its high strength and good corrosion resistance. During cutting, the low thermal conductivity and high chemical reactivity of titanium generate a high cutting temperature and accelerates tool wear. To improve cutting tool life, cryogenic machining by using a liquid nitrogen (LN2) jet is suggested. In cryogenic jet cooling, evaporation of LN2 in the tank and transfer tube could cause pressure fluctuation and change the cooling rate. In this work, cooling uniformity is investigated in terms of liquid nitrogen jet pressure in cryogenic jet cooling during titanium alloy turning. Fluctuation of jet spraying pressure causes tool temperature to fluctuate. It is possible to suppress the fluctuation of the jet pressure and improve cooling by using a phase separator. Measuring tool temperature shows that consistent LN2 jet pressure improves cryogenic cooling uniformity.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.43 no.11
• /
• pp.1028-1034
• /
• 2015

Solenoid valves for space launch vehicles require the strict limitations on the size, weight and current consumption comparing to industrial solenoid valves. The preliminary design of a cryogenic and high pressure solenoid valve for propellant tank pressurization which can ensure the operation of solenoid valve under such strict limitation conditions was preformed. The Copper and Constantan materials in coil design have used to prevent the excessive rise of the current at cryogenic state. The measured current of solenoid valve at cryogenic temperature satisfies a design requirement.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.9 no.3
• /
• pp.66-73
• /
• 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. In this study liquid nitrogen was used instead of liquid oxygen as a simulant. 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).

• Journal of Ocean Engineering and Technology
• /
• v.32 no.5
• /
• pp.380-385
• /
• 2018

With the tightening of environmental regulations (i.e., IMO Tier III), natural gas (NG) has been spotlighted as an eco-friendly fuel with few air pollutants other than nitrogen oxides (NOx) and sulfur oxides (SOx). For reasons of economic efficiency, it is mainly stored and transported in a liquid state at $-163^{\circ}C$, which is a cryogenic temperature, using a liquefied gas storage tank. Accordingly, it is necessary to reduce the boil-off gas (BOG) occurrence due to the heat flow according to the temperature difference between the inside and outside of the storage tank. Therefore, in this study, a BOG measurement test on an independent-type storage tank made up of SUS304L was carried out. The test results showed the tendency for BOG occurrence according to the temperature under different filling ratios.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.23 no.5
• /
• pp.43-52
• /
• 2019

Cryogenic propellant rockets utilize a natural circulation loop of cryogenic fluid to cool the engine inlet temperature before launch. The geometric information about the circulation system, such as length and diameter of the pipes and the heat input to the system, defines the mass flow rate of the natural circulation loop. We performed experiments to verify the natural circulation mass flow rate and compared the results with the analytical results. The comparison of the mass flow rate between experiments and numerical simulations showed a 12% offset. We also included a prediction of the natural circulation flow rate in the low-gravity section and in the acceleration section in the upper stage of the launch vehicle. The oxygen tank should have 100 kPa(a) of pressure in the acceleration section to maintain a high flow rate for the natural circulation loop. In the low-gravity section, there should be an optimal tank pressure that leads to the maximum natural circulation flow rate.

• Advances in Energy Research
• /
• v.3 no.1
• /
• pp.31-43
• /
• 2015

This paper compares the performance of JP-8(Jet Propellant) fuel and liquefied petroleum gas (LPG) and natural gas in the F110 GE100 jet engine. The cost of natural gas usage in gas turbine engines is lower than JP-8 and LPG. LPG cost is more than JP-8. LPG volume is bigger than JP-8 in the same flight conditions. Fuel tank should be cryogenic for using natural gas in the aircraft. Cost and weight of the cryogenic tanks are bigger. Cryogenic tanks decrease the move capability of the aircraft. The use of jet propellant (JP) is the best in available application for F110 GE 100 jet engine.