• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2010.11a
• /
• pp.741-747
• /
• 2010

Vent-relief valve performed as a safety-valve combination for liquid propellant feeding system of space launch vehicle, which can vent the vaporized oxygen vapor during both filling cryogenic oxidizer into tank and flight. We have designed vent-relief model by using the AMESim code to predict dynamic characteristics and simulate pneumatic behavior of valve. To validate valve model we have compared by opening time in vent model, and opening/closing pressure by mathematical methods and improved the accuracy through numerical flow analysis by using FLUENT code. In this study, we had verified design parameters and analyzed operating performances. We can use these analysis results to precedent development study on propellant feeding system of Korea Space Launch Vehicle.

• Current Industrial and Technological Trends in Aerospace
• /
• v.9 no.1
• /
• pp.130-138
• /
• 2011

A vent relief valve performs as a safety valve, which ensures ventilation of propellant tank during filling and protection from tank overpressure after filling. Because of the reliability and cost saving, the virtually same vent relief valve has been used on all US cryogenic liquid fueled launch vehicles. Some modification to the valve has been applied to satisfy the various mission requirements of launch vehicles. This paper reviews the main technology trends of the vent relief valve applied to the propellant feed system for launch vehicle with respect to design and manufacture. This paper also introduces the operating technology of vent relief valve applied for launch vehicles of advanced countries in space development.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2017.05a
• /
• pp.213-217
• /
• 2017

Since more than 30% of the liquid rocket engine failures occur during the start-up process, and the Space Shuttle Main Engine (SSME) is especially sensitive to small changes in propellant conditions, a 2% error in the valve position or a 0.1sec timing error could lead to significant damage of the engine, simulation modeling of start-up process is important. However, there are many difficulties associated with engine start-up process caused by nonlinear mass flow and heat transfer characteristics associated with filling an unconditioned engine system with cryogenic propellants. In this paper, we modelled a SSME simulation model using partially Computational Fluid Dynamics (CFD) method to solve these problems and checked the performance by comparing with the performance of the simulation model using the lumped method under the state of normal condition.

• Journal of the Korean Ceramic Society
• /
• v.35 no.11
• /
• pp.1148-1154
• /
• 1998

Ga K-edge EXAFS spectra of PbO-Ga2O3 glasses were recorded at liquid nitrogen temperature and analyz-ed in order to quantitatively understand the medium-range-order arrangement around gallium in the glasses. The second peak was generated from a backscattering of the neighbor balliums and the Ga-Ga distance is ~3.13 A with Ga coordination number of ~2.7 Therefore GaO4 tetrahedra are connected through the cor-ner~sharing mode and form their own clusters made of the tetrahedra sharing more than 3 corners while some chains or rings are also present. These connection schemes of the GaO4 tetrahedra are believed to form the substantial part of the network structure.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.26 no.7
• /
• pp.545-549
• /
• 2013

To realize the high-Tc superconducting (HTS) DC cable system, it is important to study not only high current capacity and low loss of conductor but also optimum electrical insulation at cryogenic temperature. A model HTS DC cable system consists of a HTS conductor, semi-conductor, cooling system and insulating materials. Polypropylene laminated paper (PPLP) has been widely adopted as insulating material for HTS machines. However, the fundamental insulation characteristics of PPLP for the development of HTS DC cable have not been revealed satisfactorily until now. In this paper, we will discuss mainly on the breakdown characteristics of 3 sheets PPLP in liquid nitrogen ($LN_2$). The characteristics of the diameter, location of butt-gap, distance between butt-gap length, pressure effect, polarity effect under DC and impulse voltage were studied. Also, the DC polarity reversal breakdown voltage of mini-model cable was measured in $LN_2$ under 0.4 MPa.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2004.10a
• /
• pp.178-183
• /
• 2004

Thermal stratification phenomena in the liquid oxygen tank of launch vehicle is caused by heat influx from ambient and non-equilibrium heat and mass transfer in the cryogenic tank. The thermal stratification study is needed for designing vent system, tank insulation, pump inlet. In this paper by investigating buoyancy driven boundary layer flow by side wall heating, one dimensional analysis of thermal stratification is peformed. thermal gradient is described with time.

• Progress in Superconductivity and Cryogenics
• /
• v.11 no.1
• /
• pp.64-68
• /
• 2009

To keep the superconducting (SC) magnet coils of KSTAR at proper operating conditions, not only the coils but also other cold components, such as thermal shields (TS), magnet structures, SC bus-lines (BL), and current leads (CL) must be maintained at their respective cryogenic temperatures. A helium refrigeration system (HRS) with an exergetic equivalent cooling power of 9kW at 4.5K without liquid nitrogen $(LN_2)$ pre-cooling has been manufactured and installed for such purposes. In this proceeding, we will present the commissioning and initial operation results of the KSTAR HRS. Circuits which can simulate the thermal loads and pressure drops corresponding to the cooling channels of each cold component of KSTAR have been integrated into the helium distribution system of the HRS. Using those circuits, the performance and the capability of the HRS, to fulfill the mission of establishing the appropriate operating condition for the KSTAR SC magnet coils, have been successfully demonstrated.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.26 no.4
• /
• pp.54-63
• /
• 2022

A 3-tonf class liquid rocket engine that powers the upper stage of a small launcher and lifts 500 kg payload to 500 km SSO is designed. The small launcher is to utilize the flight-proven technology of the 75-tonf class engine for the first stage. A combination of liquid oxygen and liquid methane has been selected as their cryogenic states can provide an extra boost in specific impulse as well as enable a weight saving via the common dome arrangement. An expander cycle is chosen among others as the low-pressure operation makes it robust and reliable while a specific impulse of over 360 seconds is achievable with the nozzle extension ratio of 120. Key components such as combustion chamber and turbopump are designed for additive manufacturing to a target cost. The engine system provides an evaporated methane for the autogenous pressurization system and the reaction control of the stage. This upper stage propulsion system can be extended to various missions including deep space exploration.

• Korean Chemical Engineering Research
• /
• v.52 no.5
• /
• pp.574-580
• /
• 2014

Storage tanks of Carbon dioxide ($CO_2$) carriers utilized for the purpose of carbon capture and storage (CCS) into subsea strata have to undergo a pre-cooling session before beginning to load cryogenic liquid cargos in order to prevent physical and thermal deterioration of tanks which may result from cryogenic $CO_2$ contacting tank walls directly. In this study we propose dynamic model to calculate the tank inflow of $CO_2$ gas injected for precooling process and its dynamic simulation results under proportional-integral control algorithm. We selected two cases in which each of them had one controlled variable (CV) as either the tank pressure or the tank temperature and discussed the results of that decision-making on the pre-cooling process. As a result we demonstrated that the controlling instability arising from nonlinearity and singularity of the mathematical model could be avoided by choosing tank pressure as CV instead of tank temperature.

• Journal of Energy Engineering
• /
• v.26 no.3
• /
• pp.105-112
• /
• 2017

A lot of piping systems have been used from nuclear power systems to water supply systems. The maintenance of the piping systems is needed to ensure proper operation of the piping systems. Failure of the large pipe systems especially such as KDHC(Korea District Heating Corporation) can be a matter directly related to the enterprise productivity and profitability. It can also lead to very important issues in promoting public safety and convenience. Therefore a method of quick and safety repairs have been emerged as the most important problem. In this study, freezing seal isolation method using liquid nitrogen cryogenic refrigerant was developed for the maintenance of a pre insulated heat transport pipe of KDHC with a diameter of 300 mm. In this study, by employing computational analysis techniques we performed the flow and heat transfer analysis for the targeted pre insulated heat transfer pipe and freezing seal jacket(ice-Plug) and have selected for optimal system. The detailed design model based on the results of the computational analysis finally was produced. A laboratory-scale test apparatus were designed and the freezing seal isolation self-test carried out. Also the performance assessment tests in the test bed of KDHC were carried out for on-site application.