• International Journal of Precision Engineering and Manufacturing
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• v.2 no.1
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• pp.56-61
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• 2001

This work is concerned with the development of a new plaster die casting process the combines pressurization and vibration for the prototyping of die-castings, and also with a plaster die-casting machine that has a structure quite similar to that of an ordinary die casting machine. The machine utilized an air cylinder for pressurization and a magnetic actuator for vibration. A rapid prototyped pattern is made by the LOM process to prepare a plaster mold. In the process, a plunger int he developed machine simultaneously pressurizes and vibrates the molten metal to fill the plaster mold completely and to facilitate the creation of nuclei in the molten metal, respectively. The developed machine produced a prototype of an end clutch cover with a remarkable improvement in mechanical properties.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.91.1-91.1
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• 2005

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.6
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• pp.649-654
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• 2010

A three-dimensional numerical study of the WIG-effect vehicle with a direct-underside-pressurization (DUP) system and a propeller is performed to analyze the aerodynamic forces and moments acting on the vehicle. The computational model includes all the compartments of a WIG-effect vehicle, including a propeller in the middle of the fuselage and an air chamber under the fuselage. The DUP system and propeller help considerably reduce the take-off speed and minimize the effect of the hump drag when the vehicle accelerates to take off on water. The airflow is accelerated by a propeller, and the air then enters the air chamber through a channel in the middle of the fuselage, this air helps increase the lift since the dynamic pressure of air is converted to static pressure. However, the air accelerated by the propeller produces excessive drag and creates yawing moment. It is found that the effect of yawing and rolling moments on static stability is negligible.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.116-121
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• 2006

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. Therefore a significant improvement in pressurization system performance can be achieved, particularly in a cryogenic system. For this study air and $CN_2$ are employed as external fluid and pressurant respectively Numerical analysis on the pressurant discharging characteristics have been compared with the experimental results performed at the PTF(Propellant-feeding Test Facility). It is shown that the discrepancy of analytic and experimental results is within about ${\pm}15%$. It is estimated that the temperature drop rate of cryogenic pressurant immersed liquid oxygen can be predicted using this analytic approach method.

• Fire Science and Engineering
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• v.33 no.3
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• pp.74-83
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• 2019

In the U.S., the pressurization of elevator shaft was developed in 1972 to allow vulnerable people, such as the elderly and weak who could not use escape stairs in case of fire, to evacuate. It is an advantage in terms of space saving by not using vertical ducts. This study drew the problem of the pressurization of elevator shaft based on the existing domestic patents and proposed improvements. The smoke control volume calculation method is proposed by using vertical modeling. Leakage gaps in elevator doors need to be reviewed through experimental data or actual data. The evacuation floor was divided, the openings in the elevator machine room were automatically closed to the fire signal and the relief damper was installed to improve the performance. The improved method functions as the smoke control damper supplying the air flow rather than maintaining the differential pressure. To increase reliability of the research results, the procedure was performed to verify by using Contam.

• Aerospace Engineering and Technology
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• v.12 no.2
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• pp.83-90
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• 2013

In this paper, the energy flows related to cryogenic propellant tank ullage were understood and pressurization efficiency of the tank was calculated using propellant feeding test data with the help of calculation program. The related energy flow terms and calculation method of each terms were described. Three test data of different tank pressure and incoming pressurant temperature were used. Under the test conditions, the pressurization efficiency was low in the range of 13.9%~19.3%. The proportion of energy loss to the incoming pressurant energy was in the range of 55.2%~67.6%. The energy loss to the propellant tank wall was the biggest one. If the temperature of incoming pressurant was the same, the rates of each energy flows to the incoming energy were almost the same regardless of the propellant tank pressure. The collapse factor of propellant tank was calculated using test data, and the relation of it to the heat loss rate was observed.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.2
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• pp.54-61
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• 2007

Propellant pressurization system in liquid rocket propulsion system plays a role supplying pressurant gas at a controlled pressure into the ullage space of propellant tanks. The most important design parameter for such propellant pressurization system is the temperature of pressurant gas fed from pressurant tank. Such pressurant is gaseous state, of which density is very sensitive to the temperature of pressurant. Generally for the propulsion system, which requires high thrust and is consisted of cryogenic propellant the pressurant is stored at high density and high pressure to reduce the weight of pressurant tanks, which are placed inside of cryogenic propellant tank. That is called cryogenic storage pressurization system. This study investigates the temperature variation of pressurant at the time when the pressurant is coming out of pressurant tank experimentally as well as numerically. Fluids used in this study are air and liquid oxygen as outer fluid and gaseous nitrogen and gaseous helium as pressurant respectively.

• Fire Science and Engineering
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• v.30 no.5
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• pp.87-92
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• 2016

Amid the growing number of high-rise complex buildings in Korea, efficient smoke prevention technology in a fire is required and as an alternative of a mechanical smoke control system in high-rise buildings, the use of a smoke control system using sandwich pressurization has been on the rise. In such a system, the appropriate pressure difference and the data for designing the air supply and exhaust flow rate are necessary to prevent the spread of smoke and offer a tenable evacuation environment. As part of such effort, this paper presents a field test process and result after testing a building where such a smoke control system using sandwich pressurization has been installed. A ventilation rate of 6 cycles per hour were applied to simulate the air exhaust flow rate on a fire floor and the air supply flow rate on the floors above and below the fire floor. As a result of the system operation, pressure difference of approximately 260 Pa between the 12th floor of a fire and the 13th floor was generated. The over pressure of the experiment has a serious effect on the evacuation or fire compartment so that it is necessary to examine the improvement.

• KIEAE Journal
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• v.14 no.5
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• pp.117-121
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• 2014

Even though a study of airtightness performance of apartment and detached house have been done constantly, there are few of studies of multi-family housing which increasing every year. Therefore, this study analyzed airtightness performance of 20 households of one room in Daejeon to investigate airtightness performance standard. All experiments were performed under the same conditions except sealing windows to investigate airtightness performance without sealing windows (natural condition) and airtightness performance with sealing windows of studio apartment. As results, (1) average ACH50 without sealing windows was 19.2/h for pressurization, and 12.8/h for depressurization and (2) average ACH50 with sealing windows was 16.0/h for pressurization, and 10.7/h for depressurization and ACH50 in both condition, ACH50 under pressurization was about 50% higher than that under depressurization. Throughout this experiment, we can figure out that about 16% of air infiltration rate is occurred in windows, and the other 84% is occurred in rest of places such as Junction structure, socket and ventilating opening.

• The Journal of Engineering Geology
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• v.32 no.3
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• pp.389-399
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• 2022

Observations on the influence of the fluid infiltration on the breakdown pressure during laboratory hydraulic fracturing tests, along with an analysis of the applicability of the breakdown pressure prediction for cylindrical samples using Quasi-static and Linear Elastic Fracture Mechanics approaches were carried out. These approaches consider fluid infiltration through the so-called radius of fluid infiltration or crack radius, a parameter that is not a material property. Two sets of tests under pressurization rate controlled and injection rate controlled tests were used to evaluate the applicability of these methods. The difficulty of the estimation of the radius of fluid infiltration was solved by back calculating this parameter from an initial set of tests, and later, the obtained relationships were used to predict breakdown pressures for a second set of tests. The results showed better predictions for the injection rate than for the pressurization rate tests, with average errors of 3.4% and 18.6%, respectively. The larger error was attributed to differences in the testing conditions for the pressurization rate tests, which had different applied vertical pressures. On the other hand, for the tests carried out under constant injection rate, the Linear Elastic Fracture Mechanics solution reported lower errors compared to the Quasi-static solution, with values of 3% and 3.8%, respectively. Moreover, a sensitivity analysis illustrated the influence of the radius of fluid penetration or crack radius and the tensile strength on the breakdown pressure, suggesting a need for a careful estimation of these values. Then, the calculation of breakdown pressure considering fluid infiltration in cylindrical samples under triaxial conditions is possible, although larger data sets are desirable to validate and derive better relations.