• International Journal of Fluid Machinery and Systems
• /
• v.2 no.3
• /
• pp.260-268
• /
• 2009

The effects of acoustic modes in the penstock on the self-excited oscillation in hydraulic power system were studied by assuming a finite sound velocity in the penstock. The flow in the draft tube is considered to be incompressible assuming that the length of the draft tube is smaller than the wavelength of the oscillation. It was found that various acoustic modes in the penstock can become unstable (amplified) by the diffuser effect of the draft tube or the effect of swirl flow from the runner. Their effects on each mode are discussed.

• Land and Housing Review
• /
• v.13 no.1
• /
• pp.141-150
• /
• 2022

Responding to the increasing demand for research on seismic resistance of structures triggered by a large-scale earthquake in Korea, the Ministry of the Interior and Safety revised the typical application of the existing seismic design standards with the national seismic performance target enhanced. Therefore, in this paper, the dam body of the aged Test-Bed and the penstock with fluid were modeled by the three-dimensional finite element method by introducing several variables. The current seismic design standard law confirmed the safety of the dam structure and penstock against seismic waves. As a result of the 3D finite element analysis, the stress change due to the water impact of the penstock was minimal, and it was confirmed that the effect of the hydraulic pressure was more significant than the water impact in the earthquake situation. When the hydrostatic pressure is in the form of SPH, it was analyzed that the motion of the fluid and the location of stress caused by the earthquake can be effectively represented, and it will be easier to analyze the weak part. As a result of the analysis, which considers penstock's corrosion, the degree of stress dispersion gets smaller because the penstock is embedded in the body. The stress result is minimal, less than 1% of the yield stress of the steel. In addition, although there is a possibility of micro-tensile cracks occurring in the inlet of the dam, it has not been shown to have a significant effect on the stress increa.

• Water for future
• /
• v.6 no.1
• /
• pp.29-35
• /
• 1973

For the simplicity in the analytical solution, the simple surge tank has been chosen for the test where an unsteady flow is porduced by suddenly closing the valve controlling the discharge. The valve is loated immediately downstream from the surge tank. Momentumn equations in the penstock and in the surge column are measured recored on the oscillograph and then the calibration of surge column heights and scale readings on the oscillograph trace are made. The diameter of the penstock are determined by the trial and error method. The water levels in the surge column are computed by numerical integration of the differential equation of the surge tank. The relationships between the results from the experiment and numerical computation are figured, compared and discussed.

• Journal of Korean Society of Disaster and Security
• /
• v.14 no.1
• /
• pp.9-21
• /
• 2021

Recently, the importance of eco-friendly power generation facility using renewable energy has newly appeared. Hydropower plant is a very important source of electricity generation and supply which is very important to secure safety because it is commonly connected with multi facility and operated on a large scale. In this study, a scenario-based analysis method was suggested to assess vulnerability of a penstock system caused by water hammer commonly occurred in the operation of hydropower plants. A hypothetical hydropower plant was used to demonstrate the applicability of a transient analysis model. In order to verify reliability of the model, the prediction of pressure behaviors were compared with the results of commercial model (SIMSEN) and measured data, then a real hydroelectric power plant was applied to develop all potential water hammer scenarios during the actual operation. The scenario-based simulation and vulnerability assessment for water hammer in the penstock system were performed with internal and external load conditions. The simulation results indicated that the vulnerability of a penstock system was varied with the operating conditions of hydropower facilities and significantly affected by load combination consisting of different load scenarios. The proposed numerical method could be an useful tool for the vulnerabilityty assessment of the hydropower plants due to water hammer.

• International Journal of Fluid Machinery and Systems
• /
• v.7 no.2
• /
• pp.42-53
• /
• 2014

Phase resonance in Francis type hydraulic turbine is studied. The phase resonance is a phenomenon that the pressure fluctuation in the penstock of hydraulic turbine installation can become very large when the pressure waves from each guide vane caused by the interaction with the runner vane reach the penstock with the same phase. Experimental and numerical studies have been carried out using a centrifugal fan. In the present study, comparisons between the pump mode and the turbine mode operations are made. The experimental and numerical results show that the rotational direction of the rotor does not affect characteristics of the pressure fluctuation but the propagation direction of the rotorstator interaction mode plays an important role. Flow rate fluctuations through the stator are examined numerically. It has been found that the blade passing flow rate fluctuation component can be evaluated by the difference of the fluctuating pressure at the inlet and the outlet of the stator. The amplitude of the blade passage component of the pressure fluctuation is greater at the stator inlet than the one at the stator outlet. The rotor-stator interaction mode component is almost identical at the inlet and the outlet of the stator. It was demonstrated that the pressure fluctuation in the volute and connecting pipe normalized by the flow rate fluctuation becomes the same for pump and turbine mode operations, and depends on the rotational direction on the interaction mode.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2008.05a
• /
• pp.1-8
• /
• 2008

The paper describes the process and issues encountered during the design and construction of seven kilometres of canal to convey 2.5 cumecs of flow to two power stations. The location of the scheme above the primary reservoir of the Waipori Hydropower scheme in Otago, New Zealand, utilising an existing stream diversion into this reservoir, means that no new water abstraction or diversion consents were required. This mini hydro development associated with the existing Waipori scheme was partly justified by an allocation of carbon credits. The scheme controls are slightly more complicated than many canal and penstock schemes as the canal lengths are considerable in relation to the gradient.

• Journal of Ocean Engineering and Technology
• /
• v.5 no.1
• /
• pp.64-70
• /
• 1991

The design theory of roller gate has been systematized laying more emphasis on practical formulas than theoretical ones and the design procedure of the existing gate facilites is reviewed and analyaed on economical viewpoint and safety factor. The design theory of timoshenko, the thechnical standards for hydraulic gate and penstock of Japan, and the design standards for waterworks structures of Germany are applied to the study of optimal design of a gate leaf. In this study, gate leaf which is now being operated for water control at the seadike, estuary dam and reservoir dam are adopted as a mode, and a new design method by the computer is proposed through the variation of design elements within practical ranges. As a result, safety factor and economical design can be made by using T-beams to the horizontal and vertical beam of the gate leaf instead of H-beams used in the existing seadike roller gate at Asan, and total weight of gate leaf is reduced by the present optimization.

• Proceedings of the KIPE Conference
• /
• 2018.11a
• /
• pp.15-17
• /
• 2018

본 논문은 DFIG기반의 가변속 양수발전소의 조속기, 터빈-수압관(penstock), 발전기/컨버터 및 시스템 제어기를 모델링하였으며, 발전기/컨버터 모델은 하나의 전류원과 임피던스로 등가화 되었다. 최적 운전 조건을 위한 터빈의 속도와 게이트 위치 지령치는 시스템 제어기를 통해서 얻을 수 있으며, 계통 전력의 지령치를 통해서 발전기/컨버터 모델의 전류 지령치를 만들며. 터빈 회전속도와 게이트 위치는 DFIG의 속도와 지령 속도의 비교를 통해 출력된다. 시뮬레이션 모델링을 통해 전력의 지령치 변화에 따라 계통의 전력과 터빈의 응답성을 확인하였다.

• 유체기계공업학회:학술대회논문집
• /
• 2005.12a
• /
• pp.613-616
• /
• 2005

In general, the hollow jet valve, the fixed cone valve had been used for the urgency released or maintenance of the flow rate. Nowadays, the butterfly valve, the gate valve are applied in economic performance and operation maintenance more than the hollow jet valve, the fixed cone valve. However, in the case of butterfly valve, it should be required the strict application standard to the cavitation coefficient because the structural axis and disk were situated in pipe channel and the occurring the shock problem by Karman Vortex. And, the judgment data for choice were slight lowdown in water supply and drainage facilities standard or Japanese penstock technology standard, various standard of KOWACO etc. Therefore. there were investigated the valve inside phenomenon (cavitation, disk chattering, vibration) by velocity of flow and the stability examination of body by high velocity of flow through flow scale model test using the numerical analysis and PIV to establish the applicable extensibility of the butterfly valve for the urgency released valve.

• International Journal of Fluid Machinery and Systems
• /
• v.10 no.1
• /
• pp.1-8
• /
• 2017

Bifurcation refers to wye division of penstock to divide the flow symmetrically or unsymmetrically into two units of turbine for maintaining economical, technical and geological substrates. Particularly, water shows irrelevant behavior when there is a sudden change in flow direction, which results into the transition of the static and dynamic behavior of the flow. Hence, special care and design considerations are required both hydraulically and structurally. The transition induced losses and extra stresses are major features to be examined. The research on design and analysis of bifurcation is one of the oldest topics related to R&D of hydro-mechanical components for hydropower plants. As far as the earlier approaches are concerned, the hydraulic designs were performed based on graphical data sheet, head loss considerations and the mechanical analysis through simplified beam approach. In this paper, the multi prospect approach for design of Bifurcation, incorporating the modern day's tools and technology is identified. The hydraulic design of bifurcation is a major function of dynamic characteristics of the flow, which is performed with CFD analysis for minimum losses and better hydraulic performances. Additionally, for the mechanical design, a simplified conventional design method as pre-estimation and Finite Element Method for a relevant result projections were used.