• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.663-664
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• 2008

In this study, A special quality analysis and experiment for low power consumption type pneumatic on-off micro valve was performed. And flow characteristics of the micro valve by stroke change was numerically investigated. As a result, it is shown that magnetic force(2.4N) is exerted enough to move poppet with 0.3mm stroke with 0.01 seconds of response time, and that there is no magnetic force emitted by yoke.

• Journal of the Korean Society of Propulsion Engineers
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• v.4 no.2
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• pp.39-45
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• 2000

A Thruster valve operates to supply fuel into thruster chamber. Very quick on-off operation of thruster valve results in unsteady flow of fuel in the propellant supplying system. Then fuel kinetic force, elastic material of propellant line, compressibility of fuel cause the flow field to pulsate. The pressure oscillation arising from resonance would damage the weak part of the thruster valve and other propellant supplying equipment. Pressure drop and fuel flowrate through propellant suppling system were measured, and pressure oscillation were triggered at the thruster valve inlet.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.11
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• pp.5371-5376
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• 2013

The role of a main starting air valve is to supply compressed air to the diesel engine for starting the stopped diesel engine of a ship and cut off the air during normal operation. In this study, the main starting air valve with 80mm size was designed based on the developed valve with 50mm size. The concept design of the 80A main starting air valve was completed by using CATIA. Then, fluid analysis was performed to investigate the flow characteristics such as pressure and velocity distribution. Sequentially, structural analysis using FSI was performed. In this study, ANSYS CFX and ANSYS Workbench are utilized. The heavy weight of the body can deteriorate the strength performance of neighbor elements, leading to undesirable effect on flow characteristics. Thus, in this research, a lightweight design of the body was suggested satisfying strength requirement. The weight of the suggested design was reduced by 7kg, and the strength satisfied its requirement.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.3
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• pp.412-420
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• 2003

This study describes the merits of PWM control of hydraulic system using high speed on-off valves. Generally, Electro-hydraulic valves can be classified into two classification: valves which are controlled by analog signal and which are controlled by digital. The former includes hydraulic servo valves and proportional valves which require A/D converters as interface to digital computer and too costly and sensitive to oil contamination because of complexity in structures. The latter includes high speed on-off valves which do not require A/D converters because they are normally operated in a pulse width modulation(PWM) method, and are low in price and robust to oil contamination because of their simple structures. The objectives of this study is to analyze the limit cycle which regularly appear in the position control system using 2/2way high speed on-off valves and to give a criterion for the stability of this system. The nonlinear characteristics of PWM and cylinder friction of this system are described by harmonic linearization and the effects of parameter variations to the system stability are simulated.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.2
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• pp.110-118
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• 2021

In a liquid rocket engine system, the flow of oxidizer into the combustion chamber is controlled by the main oxidizer shut-off valve. When the valve is closed, the oxidizer flows via the recirculation line, not into the combustion chamber. In this situation, the measured pressure could be much higher than a design value because of the water hammer phenomenon. In this paper, the experiments on the water hammer in the recirculation line with different initial conditions were conducted in order to study the pressure wave produced in each case. According to the experimental results, characteristics of the pressure wave in the recirculation line depend on the initial condition. To be specific, the pressure surge is maximized in case that the shock is condensation-oriented in the end of the recirculation line.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.2
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• pp.85-91
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• 1998

This paper describes an study electric injection system for diesel engines. It is needed effective fuel injection which controls the solenoid valve of fuel pump. To solve this, this paper proposes DCC-PWM method which can realize fast reply and low holding current for solenoid valve on/off. For the proposed design method, simulation tools of ACSL are used to analyze the system. And the single-chip microcomputer is used to reduce the size of controller and to improve flexibility. And the systems validity can be verified through the experimental results.

• Journal of Biosystems Engineering
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• v.23 no.5
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• pp.427-438
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• 1998

In Korea, rotary implements are mainly utilized in the tillage operation. The attitude control system for rolling phenominon of tractors, which in caused due to uneven ground surfaces and sinkage of tractor wheels, is one of the most important control systems in agricultural tractors. The attitude control system of a rotary implement, attached on tractors, was designed and fabricated in this study. The control system was largely composed of four main units; a setting unit, a detection unit, a controller and a hydraulic unit. The implement was controlled by control signals from a computer proportional to controlled errors, on/off action of two directional solenoide valve and lift cylinder on the right lift rod. Response characteristic experiments for the control system fabricated in this study were carried out indoors and outdoors. The results of experiments showed the response characteristics sufficient to use as the attitude control system of rotary implements for agricultural tractors.

• Journal of the Korean Society of Safety
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• v.34 no.4
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• pp.41-48
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• 2019

In October 2018, a large fire occurred after an explosion in an internal floating roof tank (IFRT) that stores gasoline by wind lantern in Goyang city, Gyeonggi-do. Although there was no casualty damage, the fire inside the tank lasted for 17 hours, and caused a great wave socially, and it was a chance to review the safety of the atmospheric storage tank. In this study, the necessity of installing a flame arrester at peripheral vents was examined through the calculation of the size of ventilation pipe and ventilation rate of internal floating roof tanks in terms of the function of the peripheral vent. Next, the necessity of the emergency shut-off valve linked with the high-level alarm to prevent the overflow of the atmospheric storage tank was confirmed by LOPA. Finally, safety measures to prevent overpressure, flame propagation and overflow which cause major accidents in atmospheric storage tank are suggested.

• Journal of Mechanical Science and Technology
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• v.20 no.9
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• pp.1339-1345
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• 2006

The development of an accurate and energy saving electro-pneumatic regulator that may be applied to a variety of practical pressure control applications is described in this paper. A novel modified pulse width modulation (MPWM) valve pulsing algorithm allows the electro-pneumatic regulator to become energy saving system. A comparison between the system response of conventional PWM algorithm and that of the modified PWM (MPWM) algorithm shows that the control performance is almost the same, but energy saving is greatly improved by adopting this new MPWM algorithm. The effectiveness of the proposed control algorithm is demonstrated through experiments with various reference trajectories.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.7
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• pp.40-45
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• 2001

This paper proposes a methodology for the small-displacement-movement of a piston and develops a hybrid control algorithm for the precision position control of a pneumatic rodless cylinder. The pneumatic system uses the voltage-proportional solenoid valves to minimum valve switching since the on/off type valves are create diffculties for accurate position control and induce a lot of valve switching. For the accurate position control a methodology for the small-displacement-movement of the piston is developed and identified experimentally. The main consideration on the development of the hybrid control law is to eliminate a stick-slip phenomenon in the pneumatic control system. This paper addresses these critical issues and presents experimental results for the pneumatic control system.