• Journal of ILASS-Korea
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• v.15 no.4
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• pp.182-188
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• 2010

Significant real fluid behaviors including rapid property changes take place where high pressure combustion devices such as rocket engines. The flamelet model is the reliable approach to account for the real fluid effects. In the present study, the flamelet equations are extended to treat the general fluids over transcritical and supercritical states. The real fluid flamelet model is carried out for the gaseous hydrogen and cryogenic liquid oxygen flames at the wide range of thermodynamic conditions. Based on numerical results, the precise discussions are made for effects of real fluid, pressure, and differential diffusion on the local flame structure.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1705-1709
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• 2005

The hydraulic LSD which uses the principle of gear pump is packed with viscous oil in tight container. When a slip occurs on one wheel, the hydraulic LSD generates torque caused by high oil pressure in the container. In this study, two dimensional(2-D) side pinion gear model was developed for hydraulic LSD. Using that model the flow analysis was conducted to preestimate pressure distributions of the side pinion gear according to the variations in the design factors such as oil viscosity, gear gap and rpm. Then, applying the obtained pressure distributions on the side pinion gear, finite element analysis was conducted to evaluate the torque characteristics. From the analysis results, the torque characteristics according to the design factor variations were evaluated.

• Fire Science and Engineering
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• v.29 no.6
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• pp.6-12
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• 2015

This study used CONTAM modeling to analyzed analyze the stack effect in high-rise buildings for the terrain and weather conditions of Seoul and Jeju. The differential pressure caused by the stack effect is a function of the indoor and outdoor temperature difference and the height of the vertical shaft. Jeju is considered more stable than Seoul, because it is warmer than Seoul in winter. The differential pressure in Jeju is about 60% that of Seoul in for the same height of buildings in winter. However, Jeju is an island and the neutral plane is raised by over 56% by strong winds, although there is less differential pressure caused by the stack effect in Jeju than in Seoul. Due to the raised neutral plane, the region and magnitude of negative pressure in the lower part is larger in Jeju than in Seoul.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.949-952
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• 2011

Study on differential pressure in the chamber of cannon by adjusting the mass flow of ignition-gas has been conducted using the 1-D interior ballistics numerical code called IBcode. In case of large-caliber cannon, high temperature ignition-gas is injected to the chamber through the side hole of the primer to ignite the propellant. Therefore, mass flow of injected ignition-gas affects the propellant combustion in the chamber. Mass flow of each side hole of the current primer was uniformly distributed. In this study, differences of propellant combustion with different mass flow of each side hole have been imposed. Results in case of the mass flow increase in the direction to the base show that the differential pressure decreases compared to the uniformed mass flow.

• 제어로봇시스템학회:학술대회논문집
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• 1987.10b
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• pp.358-363
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• 1987

It is widely noted that pressure feedback systems have been devised to damp the fluid resonance effectively in precision speed control-for large inertia system. A compensation technique preserving the natural output disturbance discrimination characteristics at lower frequencies is proposed The load pressure across positive displacement acceleration. The technique involves feeding back load differential pressure, sensed by pressure transducers, though a simple analog compensatory circuit (high pass filter). The effectiveness of the damping is determined by the filter time donstant and loop gain. Nonlinear total hydraulic simulation results verify the possibility of linear model predictions of extending the closed loop bandwidth beyond the uncompensated frequency.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3074-3079
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• 2007

The conventional control valves have been used at the locations occurring high differential pressure and high temperature which causes cavitation, flashing, severe vibration due to abrupt flow change, and sudden pressure drop. Previous studies concerning control valves focused to prevent damage of valve trim due to the internal leak and low flow rate. The newly designed helical trim of control valve has been installed at the location of high pressure change and high temperature in a power plant, and operated for evaluation. It is confirmed that the new control valve developed in this study generates flow characteristics in comparison with previous helical trim of control valves.

• Journal of the Korean Society for Railway
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• v.10 no.5
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• pp.563-568
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• 2007

A separate triangular bar type differential pressure flow meter was developed for measuring exhaust gas flow rate from Diesel engine. Three kinds of the separate triangular bar flow meters whose aerodynamic angles are different one another are made and evaluated, respectively. The experimental results show that an aerodynamic shape has a effect on the pressure difference between upstream and downstream at the flow meter, that is, the thinner the shape of the separate triangular bar flow meter is, the smaller the pressure difference at the flow meter is. The separate triangular bar type flow meter was calibrated at both cold and high temperature of the gas flow. A burner system was designed for raising the gas temperature and it was well operated in controlling the gas temperature. An empirical correlation between mass flow rate and differential pressure at the separate triangular bar flow meter was obtained and the empirical correlation was also corrected by the gas temperature.

• International Journal of Air-Conditioning and Refrigeration
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• v.13 no.3
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• pp.119-127
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• 2005

Liquid pressure amplifiers have been proposed as an energy saving technology for vapor compression refrigeration systems configured with direct-expansion evaporators. The technology utilizes a refrigerant pump in the high pressure liquid line as a means of maintaining a suitable pressure differential across the expansion valve while lowering condensing pressure to achieve the reduction of compressor energy consumption. Applications have been proposed on systems ranging from small unitary air-conditioning to large supermarket and commercial refrigeration systems. This paper clarifies the role of such a device in a vapor compression refrigeration system. Limitations are presented and discussed. Finally, results of detailed analyses are presented to quantify the energy consumption both with and without a liquid pressure amplifier in a unitary air conditioning system. The estimated energy savings associated with the installation of a liquid pressure amplifier are minimal.

• Journal of the Semiconductor & Display Technology
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• v.18 no.4
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• pp.129-133
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• 2019

In this paper, we developed a system to monitor the storage capacity of suction-type device such as vacuum cleaner or crop harvesters. The monitoring system consists of load cells and a differential pressure sensor which simultaneously monitor the weight and volume of the stock. Since weighing objects stored in storage containers alone cannot fully monitor the level of filling, more accurate monitoring can be achieved by monitoring volume and fusion with weight information. The volume was monitored using a phenomenon in which the flow rate of the inhaled air varies depending on the volume of the object filled in the storage container. In this paper, we developed a system to monitor the storage in three stages: low, medium and high.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.230-231
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• 2005

As environmental problems are important, automotive industries are developing various techniques to prevent air pollution. One of these is Positive Crankcase Ventilation (PCV) system. It removes blowby gas which includes about 30% hydrocarbon of total generated quantity. In this system, a PCV valve is attached in a manifold suction tube to control the flow rate of blowby gas which generates differently according to various operating conditions of an automotive engine. As this valve is very important, designers are feeling to design it because of both small size and high velocity. For this reason, we numerically investigated to understand both spool dynamic motion and internal fluid flow characteristics. As the results, spool dynamic characteristics, i.e. displacement, velocity, acting force, increase in direct proportion to the magnitude of differential pressure and indicate periodic oscillating motions. And, the velocity at the orifice region decreases according to the increase of differential pressure because of energy loss which is caused by the sudden decrease of flow area at the orifice region and the increase of flow volume in the front of spool head. Finally, the mass flow rate at the outlet decreases with the increase of spool displacement. We expect that PCV valve designers can easily understand fluid flow inside a PCV valve with our visual information for their help.