• International Journal of Fluid Machinery and Systems
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• v.2 no.4
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• pp.286-294
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• 2009

Hydroelectric power plants are known for their ability to cover variations of the consumption in electrical power networks. In order to follow this changing demand, hydraulic machines are subject to off-design operation. In that case, the swirling flow leaving the runner of a Francis turbine may act under given conditions as an excitation source for the whole hydraulic system. In high load operating conditions, vortex rope behaves as an internal energy source which leads to the self excitation of the system. The aim of this paper is to identify the influence of the full load excitation source location with respect to the eigenmodes shapes on the system stability. For this, a new eigenanalysis tool, based on eigenvalues and eigenvectors computation of the nonlinear set of differential equations in SIMSEN, has been developed. First the modal analysis method and linearization of the set of the nonlinear differential equations are fully described. Then, nonlinear hydro-acoustic models of hydraulic components based on electrical equivalent schemes are presented and linearized. Finally, a hydro-acoustic SIMSEN model of a simple hydraulic power plant, is used to apply the modal analysis and to show the influence of the turbine location on system stability. Through this case study, it brings out that modeling of the pipe viscoelastic damping is decisive to find out stability limits and unstable eigenfrequencies.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.7
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• pp.653-665
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• 2001

The characteristics of the pulsating flow in a hydraulic pipe have been investigated. It is necessary to study the power control of the power transmission system in the landing gear system of aircraft and the design of robots. In this system, the power transmission pipeline is composed of a hydraulic system, and the operating flow is unsteady flow. The wave equation varying with frequency is analyzed in order to investigate the characteristics of unsteady flow in such a pipe. This wave equation involves the propagation coefficient in terns of frequency and viscosity. The theoretical result of this wave equation are compared with experimental result. Each wave equation, varying with the propagation coefficient, is analyzed theoretically. then, a sinusoidal wave generator is built in order to make better sinusoidal waves, and a rectifier is built to eliminate the noise from the hydraulic pump. The theoretical results of the wave equation in the flow of viscous fluid agree well with experimental results.

• 한국금형공학회:학술대회논문집
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• 2008.06a
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• pp.61-66
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• 2008

The hydraulic system have been used much in a heavy machine which high power source is desired. In the case of the heavy press machine and the injection molding machine, the use of the hydraulic power is essential especially for increasing productivity and getting the good products. Because the hydraulic circuit is very complex and the system parameters are uncertain, the development of the simulation model for hydraulic system is not easy in the heavy machine. In this case, Many researchers have used a commercial program for analysis and development in a major field of study. In this paper, the aim is to develop the simulation model of the hydraulic system with various commercial program for trajectory tracking. And adaptive control method is applied to the simulation model for the trajectory tracking of a cylinder motion. Load on the cylinder is modeled in ADAMS program, the hydraulic circuit including pump, spool valve and cylinder is modeled in AMESim program and a controller is designed in MatLab/simulink program. The suggested model is applied for the tracking of a cylinder motion, and through computer simulation, its trajectory tracking performance is illustrated.

• Nuclear Engineering and Technology
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• v.52 no.7
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• pp.1417-1428
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• 2020

The design of a nuclear reactor core requires basic thermal-hydraulic information concerning the heat transfer regime at which onset of nucleate boiling (ONB) will occur, the pressure drop and flow rate through the reactor core, the temperature and power distributions in the reactor core, the departure from nucleate boiling (DNB), the condition for onset of flow instability (OFI), in addition to, the critical velocity beyond which the fuel elements will collapse. These values depend on coolant velocity, fuel element geometry, inlet temperature, flow direction and water column above the top of the reactor core. Enough safety margins to ONB, DNB and OFI must-emphasized. A heat transfer package is used for calculating convection heat transfer coefficient in single phase turbulent, transition and laminar regimes. The main objective of this paper is to study the possibility of power upgrading of WWR-S research reactor from 2 to 10 MW_th. This study presents a one-dimensional mathematical model (axial direction) for steady-state thermal-hydraulic design and analysis of the upgraded WWR-S reactor in which two types of plate fuel elements are employed. FOR-CONV computer program is developed for the needs of the power upgrading of WWR-S reactor up to 10 MW_th.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10b
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• pp.1611-1616
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• 1991

A high power stewart platform is designed and manufactured to simulate the 6 degrees of freedom motion of moving vehicle. This paper describes the design of such a motion system including kinematic and kinetic analysis, real time servo control mechanical and hydraulic system configuration, and techniques of regeneration of test records. Discussions are also presented for an algorithm called remote parameter control, which has been developed to compensate the dynamic delay of the electro-hydraulic servo actuators and the nonlinearities of stewart platform.

• Transactions of The Korea Fluid Power Systems Society
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• v.8 no.2
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• pp.1-7
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• 2011

An inverted pendulum mounted on a cart and actuated by a hydraulic servo cylinder was designed and built. Position information of the cart was acquired via a potentiometer and a angle of the pendulum was sensed by an incremental encoder. These were collected by a DAQ board and processed through the Real-Time Windows Target software(included in simulink). A simulink graphical program was implemented as a controller of the hydraulic system that governed the motion of the cart in order to maintain vertical balance of the inverted pendulum. The purpose of this study is to develop an electro-hydraulic inverted pendulum system for a modeling and controling the intrinsic unstable system. The simulation results were compared with the experimental and verified.

• Transactions of The Korea Fluid Power Systems Society
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• v.8 no.2
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• pp.23-28
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• 2011

This paper investigates the motion control of a hydraulic motor-load system using the Simple Adaptive Control (SAC) method. The plant transfer function has been modelled mathematically. The open-loop responses have been obtained experimentally in order to identify the design parameters of transfer function. The hydraulic motor-load system has been modelled using the 3D CAD and imbedded in the hydraulic circuit simulation program to verify the overall performance. The experimental results confirm that the SAC method gives a good tracking performance compared to the PID control.

• Transactions of The Korea Fluid Power Systems Society
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• v.5 no.2
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• pp.14-19
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• 2008

Hydraulic excavator consists of booms, arms, bucket, and cylinder. The cylinder make these structures moved and the cushion parts of cylinder in operation absorb the great impact which is stemmed from high velocity and pressure at cushion parts of cylinders. The cushion technology of cylinders has a great effect on the operator's comfortable as well as protecting equipment from damage by suppressing the inertia of the hydraulic excavator. In this study, three hydraulic cylinders have different shapes of a cushion ring, respectively. we studied optimal cushion pattern by analyzing the change of cushion pressure and time, according to supply pressure and velocity variations.

• Journal of Power System Engineering
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• v.6 no.2
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• pp.82-87
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• 2002

For the dynamic behavior evaluation of a semi-active vibration control system, it is very important to use an accurate mathematical model for the hydraulic damper applied to the control system. In this study, a mathematical model for a symmetric type hydraulic damper was suggested. In this model, the effects of gas volume and oil temperature variation on the bulk modulus of oil were considered. The dynamic behavior of the damper was investigated by experiments and simulations. It was confirmed that the pressure variation, damping force, and mean pressure variation could be estimated with comparatively good precision by the suggested mathematical model. Moreover, it was shown that excessive pressure rise can be generated by the oil expansion due to the heat energy transformed from the exciting energy of the damper for a short period of the damper operation.

• Transactions of The Korea Fluid Power Systems Society
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• v.6 no.2
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• pp.14-21
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• 2009

The typical hydraulic hoisting system of the rack-bar type sluice gate is composed of a hydraulic supply unit using an uni-directional pump, a direction control valve, a hydraulic motor, a counter balance valve, and flow control valves. Here, the hydrostatic transmission is applied to the hoisting system of rack-bar type sluice gate to simplify the operation of gate such that the upward and downward direction of gate is simply controlled by the direction of pump rotation. The new hydraulic hoisting system is composed of a bi-directional pump, a hydraulic motor, two counter balance valves, two check valves, two pilot-operated check valves, two relief valves and a shuttle valve. The characteristics of a suggested system are analyzed by computer simulations.