• Title/Summary/Keyword: hydraulic model testing

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On the Analysis of Dynamic Characteristics of Pipe Supporting Hydraulic Snubber in Electric Power Plant with State-space Model and Impulse Testing (상태공간 모델과 임펄스 시험에 의한 발전소 배관지지용 유압완충기의 동특성 해석)

  • Lee, Jae-Cheon;Im, Mun-Hyeok;Hwang, Tae-Yeong
    • Journal of the Korean Society for Precision Engineering
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    • v.19 no.10
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    • pp.130-138
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    • 2002
  • This paper presents the modeling and analysis of dynamic characteristics of hydraulic snubber in electric power plant. The nonlinear state-space model of 14th order to describe the dynamics of the snubber was established by Simulink. The simulation results show that the hydraulic snubber reacts as like the conventional shock absorbers against the high pulse shock load. The snubber also shows the peculiar characteristics to the small step load, which temporarily lock the control valves up, however maintain same steady-state pressures of all internal chambers in the long run. Two case studies for the analysis of the snubber were addressed. Practical pulse testing method was also proposed to identify the frequency response characteristics of the snubber.

On the Analysis of Dynamic Characteristics of Pipe Supporting Hydraulic Snubber in Electric Power Plant with State-space Model and Impulse Testing (상태공간 모델과 임펄스 시험에 의한 발전소 배관지지용 유압완충기의 동특성 해석)

  • Lee, Jae-Cheon;Hwang, Tae-Yeong
    • 연구논문집
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    • s.31
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    • pp.89-99
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    • 2001
  • This paper presents the modeling and analysis of dynamic characteristics of hydraulic snubber in electric power plant. The nonlinear state-space model of 14th order to describe the dynamics of the snubber was established by Simulink. The simulation results show that the hydraulic snubber reacts as like the conventional shock absolvers against the high pulse shock load. The snubber also shows the peculiar characteristics to the small step load, which temporarily lock the control valves up, however maintain same steady-state pressures of all internal chambers in the long run. Two case studies for the analysis of the snubber are addressed. Practical pulse testing method was also proposed to identify the frequency response of the snubber.

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Modeling and testing for hydraulic shock regarding a valve-less electro-hydraulic servo steering device for ships

  • Jian, Liao;Lin, He;Rongwu, Xu
    • International Journal of Fluid Machinery and Systems
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    • v.8 no.4
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    • pp.318-326
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    • 2015
  • A valve-less electro-hydraulic servo steering device (short: VSSD) for ships was chosen as a study object, and its mathematic model of hydraulic shock was established on the basis of flow properties and force balance of each component. The influence of system structure parameters, changing rate of motor speed and external load on hydraulic shock strength was simulated by the method of numerical simulation. Experiment was designed to test the hydraulic shock mathematic model of VSSD. Experiment results verified the correctness of the model, and the model provided a correct theoretical method for the calculation and control of hydraulic shock of valve-less electro-hydraulic servo steering device.

Case study comparisons of computational fluid dynamics modeling versus tracer test to evaluate the hydraulic efficiency of clearwell (정수지 내 추적자 실험과 CFD(전산유체역학)의 상관관계 분석)

  • Kim, Tae-Kyun;Choi, Young-June;Jo, Young-Mahn
    • Journal of Korean Society of Water and Wastewater
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    • v.25 no.5
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    • pp.635-642
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    • 2011
  • Hydraulic efficiency was a vital component in evaluating the disinfection capability of clearwell. Current practice evaluates these system based on the tracer test only. In this paper, CFD(Computational Fluid Dynamics) was applied on the clearwell for alternating or supplementing the tracer test. The baffle factor derived from the CFD modeling closely matched the values obtained from full scale tracer testing. And, for suggesting proper numerical model in clearwell; the turbulence model, discretization scheme, convergence criteria were investigated through separate simulation runs. The model validation was conducted by comparing the simulated data with experimental data. In the turbulence model, the realizable ${\kappa}-{\varepsilon}$ model and the standard ${\kappa}-{\varepsilon}$ model were found to be more appropriate than RNG ${\kappa}-{\varepsilon}$ model. The residuals of convergence criteria should be used as not $10^{-3}$ but $10^{-4}$ or $10^{-5}$. In discretization scheme, the difference of simulated values in 1st, 2nd, 3rd upwind scheme was found to be insignificant. Moreover, the result of this study suggest that CFD modeling can be a reliable alternative to tracer testing for evaluating the hydraulic efficiency.

A Study on Derivation of Optimal Specifications and Verification of Performance of Hydraulic Propulsion Propeller for Small Dredger (소형 준설선 유압 추진기의 최적 제원 도출 및 성능 검증에 관한 연구)

  • Baek, Do Sun;Yang, Kyong Uk
    • Journal of Drive and Control
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    • v.18 no.4
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    • pp.43-51
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    • 2021
  • In this study, we designed a hydraulic propulsion propeller system that allows dredged materials to be carried out by the dredger to the disposal place. The proposed model equation was used to formulate the screw propeller specifications considering the resistance to the dredger, and the quantitative specifications of the hydraulic propulsion propeller were determined through the numerical analysis programs. In addition, based on the proposed results, we were able to determine the specifications of the hydraulic system that was used for the hydraulic motor in the propulsion propeller device and then manufactured the hydraulic propulsion propeller. To guarantee the reliability of the proposed model equation, an external testing agency was invited and verified that the hydraulic propulsion propeller based on the proposed model equation could achieve the target speed in the dredger.

The Movable Hydraulic Model Test for Exchange of Intake Weir in the Nakdong River (낙동강 취수보개체를 위한 이동상 수리모형실험)

  • 김성원
    • Journal of Environmental Science International
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    • v.9 no.1
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    • pp.35-42
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    • 2000
  • In this study, the movable bed model testing was carried out so as to analyze bed profile changes including predicting scouring and deposition of bed profile and to solve hydraulic problems affecting with bed and both-bank between upstream and downstream of intake weir in the Nakdong river channel. The movable bed model testing consists of fundamental test, movable model test and numerical analysis method respectively. The fundamental test was enforced to analyze relationship of discharge and sediment load in the tilting flume. When the movable model test was worked, it was shown that sediment budget between input sediment load and output sediment load was balanced exactly. As a result of movable model test, it was presented that scouring and deposition changes in quantities between the upstream and downstream of modification weir were less than those of nature and planning weir. Finally, numerical analysis method was operated by 1-dimensional bed profile changes model ; HEC-6 model so as to complement unsolving hard problems during movable model test. So, modification weir will sustained the stable bed profile changes than any other weirs in the study channel.

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Performance Optimization of High Specific Speed Pump-Turbines by Means of Numerical Flow Simulation (CFD) and Model Testing

  • Kerschberger, Peter;Gehrer, Arno
    • International Journal of Fluid Machinery and Systems
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    • v.3 no.4
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    • pp.352-359
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    • 2010
  • In recent years, the market has shown increasing interest in pump-turbines. The prompt availability of pumped storage plants and the benefits to the power system achieved by peak lopping, providing reserve capacity, and rapid response in frequency control are providing a growing advantage. In this context, there is a need to develop pumpturbines that can reliably withstand dynamic operation modes, fast changes of discharge rate by adjusting the variable diffuser vanes, as well as fast changes from pumping to turbine operation. In the first part of the present study, various flow patterns linked to operation of a pump-turbine system are discussed. In this context, pump and turbine modes are presented separately and different load cases are shown in each operating mode. In order to create modern, competitive pump-turbine designs, this study further explains what design challenges should be considered in defining the geometry of a pump-turbine impeller. The second part of the paper describes an innovative, staggered approach to impeller development, applied to a low head pump-turbine project. The first level of the process consists of optimization strategies based on evolutionary algorithms together with 3D in-viscid flow analysis. In the next stage, the hydraulic behavior of both pump mode and turbine mode is evaluated by solving the full 3D Navier-Stokes equations in combination with a robust turbulence model. Finally, the progress in hydraulic design is demonstrated by model test results that show a significant improvement in hydraulic performance compared to an existing reference design.

Estimation of Hydraulic States Caused by Gate Expansion in Asan Bay (아산만 방조제 배수갑문 확장사업에 따른 주변해역 수리현상 변화 검토)

  • Park, Byong-Jun;Lee, Sang-Hwa
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.20 no.2
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    • pp.184-193
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    • 2008
  • The gate expansion was planed to increase discharge capacity of gate structure at sea dike in Asan Bay. So it was estimated for changing of hydraulic states in Pyeongteak Harbor Zone caused by gate expansion, using Delft3D, FLOW-3D and hydraulic physical scale model testing. In result, the influence of gate expansion was indicated to be weak.

Flow/Pressure/Power Control of Hydraulic Pump Utilizing Switching Control Mode (스위칭 제어 모드를 이용한 유압펌프의 유량/압력/동력 제어)

  • Jung, D.S.;Kim, H.E.
    • Transactions of The Korea Fluid Power Systems Society
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    • v.4 no.4
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    • pp.8-14
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    • 2007
  • The electro-hydraulic pump is usually used in testing equipments which require one control function. But until now, it is not applied to industrial equipments which are exposed to severe working environment and require various control functions. This paper proposes a technique which controls continuously flow, pressure and power by utilizing switching control mode. Mathematical model is developed from the continuity equation for the pressurized control volume and the torque balance for the swash plate motion. To simplify the model we make the linear state equation by differentiating the nonlinear model. We analyze the stability and disturbance by using the state variable model. Finally, we review the control performances of flow, pressure and power by tests using PID controller.

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A Study on the Hydraulic System Circuit Analysis and Modeling of the Hydrostatic Tire Roller (유압 구동방식 타이어 롤러를 위한 유압 시스템 회로분석 및 모델링에 관한 연구)

  • Kim, Sang-Gyum;Park, Chun-Shic;Kim, Jung-Ha
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.27 no.4
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    • pp.432-439
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    • 2003
  • In this research, we are trying to develop the new hydraulic driven tire roller which is conventionally operated by mechanical transmission system. The reason why we would like to develop it is that tire roller is one of the most useful machine for the road construction site and also imported totally from overseas. In this paper, we conceptualize the new hydraulic system and derive the equations of motion for dynamic analysis. And we investigate system modeling by using DAQ system. Finally, we will design the controller, which can manage the hydraulic circuit of steering and traction mechanism system. The advent of modern high-speed computers coupled with the application of high-fidelity simulation technology can be used to create “virtual prototypes of construction equipment. Tests conducted on these virtual prototypes may be used to augment actual machine testing, thereby lowering costs and shortening time to production. So, we studied tire roller to integrate development technology. In System Analysis, We formulate hydraulic driving system model and hydraulic steering system model. Also, We integrate DAQ system to acquire experimental result in real tire roller equipment.