• Journal of Power System Engineering
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• v.14 no.2
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• pp.34-39
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• 2010

Recently, technical trend for machine tools is focused on enhancement of speed and accuracy. High speedy processing causes thermal and structural deformation of objects from the machine tools. Water cooler has to be applied to machine tools to reduce the thermal negative influence with accurate temperature controlling system. Existing On-Off control type can't control temperature accurately because compressor is operated and stopped repeatedly and causes increment of power consumption and decrement of the expected life of compressor. The goal of this study is to minimize temperature error in steady state. In addition, control period of an electronic expansion valve were considered to increment of lifetime of the machine tools and quality of product with a water cooler. PI controller is designed using type of hot-gas bypass for precise control of temperature. Gain of PI is decided easily by method of critical oscillation response, excellent performance of control is shown with 4.24% overshoot and ${\pm}0.2^{\circ}C$error of steady state. Also, error range of temperature is controlled within $0.2^{\circ}C$although disturbance occurs.

• 유공압시스템학회:학술대회논문집
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• 2010.06a
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• pp.7-11
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• 2010

Various transmission technologies have been developed to satisfy environmental issues recently. Especially, the technology of the proportional control solenoid valve (PCSV) to ensure high level performance by electronic control has been studied. This study builds an analysis process for designing of the PCSV and characteristic predictions.

• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.161-166
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• 2007

Various thermostatic valves have been used widely in Korea for conservation of heating energy and enhancement of thermal comfort in residential buildings. But heating control performances of thermostatic valves extensively vary with the design and operational conditions of the heating system, climate condition and others. An experimental method was carried out in this study to analyze heating control characteristics by temperature sensing methods of thermostatic valves for various parameters, such as supply temperatures and flow rate of hot water, the position of room thermostats and outdoor air temperatures. As a result, the heat flow rate per day of S-Valve($34^{\circ}C$-Type) of water temperature sensing method was liked that of C-Valve of indoor air temperature sensing method with stage 3.3 of room thermostat in case supply temperature of hot water was $45^{\circ}C$, flow rate was 1.3 L/min and outdoor air temperature was $7.8^{\circ}C$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.2 no.2
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• pp.45-48
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• 2001

It is a quite duality concerning to control the temperature of single crystalline growth as it does when we get most of heat treating products. It is also important factor to control the temperature when we make the $Al_2$O$_3$(single crystalline) used to artificial jewels. glass of watches, and heat resistant transparent g1asses. Thus, it is a major interest to get the proper temperature in accordance with the time process while we are making mixture of oxygen and hydrogen to have the right temperature. In this paper. we will study of electrical valve positioning system with DC-Motor for the gas mixture to improve the quality of products.

• The KSFM Journal of Fluid Machinery
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• v.11 no.2
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• pp.13-19
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• 2008

Butterfly valves are widely used as control valves for industrial process. For the definition of optimum configuration of the valve, wide range of related studies has been actively conducted in the case of working fluids of water or air under the normal temperature. Recently, internal flow and performance characteristics of cryogenic butterfly valve for LNG carrier take a growing interest in the field of research and development. Therefore, present study is aimed to investigate the internal flow and performance characteristics of the cryogenic butterfly valve because the study result for the valve can be hardly found at present. Part 1 of this paper describes the study result of a butterfly valve model under the condition of the normal temperature. Succeeding Part 2 of this paper will describe the internal flow characteristics of a cryogenic butterfly valve for LNG carrier. The results of Part 1 show that pressure loss coefficients and flow rate coefficients obtained by the present experiment and CFD analysis agree well each other. Moreover, internal flow visualization for the valve by CFD analysis and PIV measurement have revealed complicated flow patterns of the internal flow field in detail.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.7-12
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• 2000

The automatic turbine startup system provides turbine control based on thermal stress. During the startup, control system monitors and evaluates main components of turbine using damage mechanism and life assessment. In case of valve chest, the temperature of inner/outer wall is measured by thermo-couples and the safety of these values are evaluated by using allowable ${\Delta}T$ limit curve during the startup. Because allowable ${\Delta}T$ limit curve includes life assessment, it is possible to apply this curve to turbine control system. In this paper, low cycle fatigue damage and combined rupture and low cycle fatigue damage criterion proposed for yielding the allowable ${\Delta}T$ limit curve of CV(control valve) chest. To calculate low cycle fatigue damage, the stress analysis of valve chest has peformed using FEM. Automatic turbine startup to assure service life of CV was achieved using allowable ${\Delta}T$ limit curve.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.1
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• pp.1-6
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• 2002

The automatic turbine startup system provides turbine control based on thermal stress. During the startup, control system monitors and evaluates main components of turbine using damage mechanism and life assessment. In case of valve chest, the temperature of inner/outer wall is measured by thermo-couples and the safety of these values are evaluated by using allowable △T limit currie during the startup. Because allowable ΔT limit curve includes life assessment, it is possible to apply this curve to turbine control system. In this paper, low cycle fatigue damage, combined rupture and low cycle fatigue damage criterion were proposed for yielding the allowable ΔTf limit curve of CV(control valve) chest. To calculate low cycle fatigue damage, the stress analysis of valve chest has been performed using FEM. Automatic turbine startup to assure service life of CV was achieved using allowable ΔT limit curve.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.11
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• pp.1077-1084
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• 2017

Camshaft engines designed for constant engine loads have been applied to existing marine diesel engines. However, due to environmental regulations, electro-hydraulic servo mechanisms, which have a loaddependent cylinder liner jacket water cooling system (LDCL-JWCS), have been recently developed to individually control the temperature of the cylinders depending on the engine load. In this system, the 3-way valve, which prevents low temperature corrosion by reducing the temperature difference between the upper and lower parts of the cylinder, has been employed, but the outlet mass flow of the existing valve is low. In this study, the design of the internal shape of the 3-way valve was performed by analyzing the effects of the design parameters of the valve shape on the performance (i.e., the outlet mass flow rate and temperature). The proposed model was verified by comparing its performance to that of existing marine diesel engine valves.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.10
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• pp.1026-1030
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• 2010

This paper summarizes the activities performed for the development of a BLDC(Brushless Direct Current) motor driven cryogenic thrust control valve with application to KSLV-II rocket engine. The developed thrust control valve can modulate the flow rate of liquid oxygen under cryogenic temperature of 90K and high pressure of 113.2 bar with the help of electro-mechanical actuator driven by a BLDC motor. This valve can be applied to an engine combustion test after minor change because all development certification test have been performed successfully.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.951-955
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• 2004

Piezoelectric(PZT) actuator can substitute for solenoid which is used in fluid control field because it has faster response times and no possibility of explosion. Besides, it is available in a high temperature and it has low energy consumption. In this study, pneumatic micro valve, bimorph type PZT actuator using the softner type PZT, carbon plate as a shim and its controller circuit were suggested and investigated. Performance tests and characteristics analysis, such as displacement, force, hysteresis and frequency properties, were carried out. The displacement of the actuator measured at the end point was 63 ${\mu}m$., force of the actuator was 0.052 N and maximum operating frequency was 15Hz. Also, characteristics of the micro valve with PZT actuator were evaluated in a testing system. The results show that the suggested PZT actuator is suitable for micro valve.