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RISS 인기검색어
- 검색키워드
- 저자 : Torbjørn K. Nielsen (검색결과 4 건)
- 무료
- 기관 내 무료
- 유료
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Simulation model for Francis and Reversible Pump Turbines
Torbjørn K. Nielsen 한국유체기계학회 2015 International journal of fluid machinery and syste Vol.8 No.3
When simulating the dynamic behaviour of a hydro power plant, it is essential to have a good representation of the turbine behaviour. The pressure transients in the system occurs because the flow changes, which the turbine defines. The flow through the turbine is a function of the pressure, the speed of rotation and the wicket gate opening and is, most often described in a performance diagram or Hill diagram. In the Hill diagram, the efficiency is drawn like contour lines, hence the name. A turbines Hill diagram is obtained by performance tests on scaled model in a laboratory. However, system dynamic simulations have to be performed in the early stage of a project, before the turbine manufacturer has been chosen and the Hill diagram is known. Therefore one have to rely on diagrams for a turbine with similar speed number. The Hill diagram is drawn through measured points, so for using the diagram in a simulation program, one have to iterate in the diagram based on curve fitting of the measured points. This paper describes an alternative method. By means of the Euler turbine equation, it is possible to set up two differential equations which represents the turbine performance with good enough accuracy for the dynamic simulations. The only input is the turbine’s main geometry, the runner blade in- and outlet angle and the guide vane angle at best efficiency point of operation (BEP). In the paper, simulated turbine characteristics for a high head Francis turbine, and for a reversible pump turbine are compared with laboratory measured characteristics.
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Fast Transition from Pump to Turbine Mode of Operation
Magni F. Svarstad,Torbjørn K. Nielsen 한국유체기계학회 2018 International journal of fluid machinery and syste Vol.11 No.3
The reversible pump turbine (RPT) is a suitable machine to control fluctuations in the energy market. The usage of RPTs for this purpose will increase the number of operational mode changes of the machine. In order to reduce the response time of the machine, fast transitions between the modes of operation are necessary. Therefore, increased knowledge of how the machine operates during these fast transitions is needed. This includes the investigation of the transient characteristics for the whole operating range of the machine. This paper presents experimental results from a fast transition from pump to turbine mode. The flow rate is measured by the use of a modified pressure time method. The resulti ng transient characteristics are compared with steady state characteristics. Experiments have been preformed on a model scale reversible pump turbine in the Waterpower Laboratory at the Norwegian University of Science and Technology (NTNU). The results show that the pressure pulsations are highest at low discharge in both pump and turbine mode of operation and at runaway speed in turbine. Oscillations at runaway speed is reduced with lower opening degree on the guide vanes. The results also show a difference between the steady state and transient characteristics in the pump mode due to the inertia of the water masses.
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Influence of Guide Vane Setting in Pump Mode on Performance Characteristics of a Pump-Turbine
Deyou Li,Hongjie Wang,Torbjørn K. Nielsen,Ruzhi Gong,Xianzhu Wei,Daqing Qin 한국유체기계학회 2017 International journal of fluid machinery and syste Vol.10 No.2
Performance characteristics in pump mode of pump-turbines are vital for the safe and effective operation of pumped storage power plants. However, the head characteristics are different under different guide vane openings. In this paper, 3-D steady simulations were performed under 13mm, 19mm and 25mm guide vane openings. Three groups of operating points under the three GVOs were chosen based on experimental validation to investigate the influence of guide vane setting on flow patterns upstream and downstream. The results reveal that, the guide vane setting will obviously change the flow pattern downstream, which in turn influences the flow upstream. It shows a strong effect on hydraulic loss (power dissipation) in the guide and stay vanes. It is also found that the hydraulic loss mainly comes from the flow separation and vortices. In addition, in some operating conditions, the change of guide vane opening will change the flow angle at the runner inlet and outlet, which will change the Euler momentum (power input). The joint action of Euler momentum and hydraulic loss results in the change of the head characteristics.
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Blade passage modeling strategy for hydraulic turbine
Ruzhi Gong,Chirag Trivedi,Ole G. Dahlhaug,Torbjørn K. Nielsen 한국유체기계학회 2017 International journal of fluid machinery and syste Vol.10 No.4
CFD has played a significant role to investigate the performance and improve the design of hydraulic turbines; however, the improvement of CFD method demands powerful computer resources including time, CPU, memory, and commercial licenses. In present work, both global and local parameters of a high head Francis turbine were studied using several geometrical and interface modelling approaches. The aim of the work is to find suitable strategy for designers to simulate the hydraulic turbines to balance the numerical accuracy and the requirement of computational resources. The geometrical modelling approaches include combinations of turbine components such as, spiral casing, distributor, runner and draft tube. The interface modelling approaches includes, stage, Frozen rotor and transient rotorstator types. The study showed that the proper combinations of both approaches can effectively reduce the numerical error.
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