• Calibration and uncertainty analysis of pressure sensors used for dynamic measurements 

      Melaaen, Aase Sørum (Master thesis, 2017)
      Dynamic calibration of pressure sensors is challenging. Often, steady-state calibration is applied on pressure sensors used to measure dynamical measurements. Steady-state calibration does not represent the dynamic behavior ...
    • Experimental study of a Francis turbine under variable-speed and discharge conditions 

      Trivedi, Chirag; Agnalt, Einar; Dahlhaug, Ole Gunnar (Journal article; Peer reviewed, 2018)
      This work investigates the unsteady pressure fluctuations in a hydraulic turbine that are observed during steep ramping. Although hydraulic turbines are expected to operate seamlessly during steep ramping, the resulting ...
    • Experimental Study of a Low-Specific Speed Francis Model Runner during Resonance 

      Agnalt, Einar; Østby, Petter Thorvald Krogh; Solemslie, Bjørn Winther; Dahlhaug, Ole Gunnar (Journal article; Peer reviewed, 2018)
      An analysis of the pressure in a runner channel of a low-specific speed Francis model runner during resonance is presented, which includes experiments and the development of a pressure model to estimate both the convective ...
    • Fatigue loads in a Francis turbine runner 

      Lødemel, Eirik (Master thesis, 2019)
      Utvidelsen av fornybare energikilder i det europeiske energimarkedet fører til en økende etterspørsel etter regulerbare energikilder som kan stabilisere nettfrekvensen. Vannkraft kan fungere som en regulerbar energikilde, ...
    • Fatigue loads in a Francis turbine runner 

      Lødemel, Eirik (Master thesis, 2019)
      Utvidelsen av fornybare energikilder i det europeiske energimarkedet fører til en økende etterspørsel etter regulerbare energikilder som kan stabilisere nettfrekvensen. Vannkraft kan fungere som en regulerbar energikilde, ...
    • Fluid structure interaction of Francis-99 turbine and experimental validation 

      Østby, Petter Thorvald Krogh; Agnalt, Einar; Haugen, Bjørn; Billdal, Jan Tore; Dahlhaug, Ole Gunnar (Journal article; Peer reviewed, 2019)
      The ability to predict a francis runners dynamic response to the exciting forces is paramount to avoid unwanted disintegration of the turbines components. In this article, each of the principal factors contributing to the ...
    • Investigations of unsteady pressure loading in a Francis turbine during variable-speed operation 

      Trivedi, Chirag; Agnalt, Einar; Dahlhaug, Ole Gunnar (Journal article; Peer reviewed, 2017)
      Current study was aimed to investigate the unsteady pressure loading in a model Francis turbine under variable-speed configurations. Focus was to investigate the time-dependent characteristic frequencies and the pressure ...
    • On the Rotor Stator Interaction Effects of Low Specific Speed Francis Turbines 

      Agnalt, Einar; Iliev, Igor; Solemslie, Bjørn Winther; Dahlhaug, Ole Gunnar (Journal article; Peer reviewed, 2019)
      The rotor stator interaction in a low specific speed Francis model turbine and a pump-turbine is analyzed utilizing pressure sensors in the vaneless space and in the guide vane cascade. The measurements are analyzed relative ...
    • Onboard measurements of pressure pulsations in a high head Francis model runner 

      Agnalt, Einar; Solemslie, Bjørn Winther; Dahlhaug, Ole Gunnar (Journal article; Peer reviewed, 2019)
      Over the last years, there have been several incidents with cracks in high head Francis turbines. These cracks are understood to be related to pressure pulsations, vibration modulus and the combination of these. In this ...
    • Pressure measurements inside a Francis turbine runner 

      Agnalt, Einar (Master thesis, 2016)
      Over the last years, there have been several incidents with cracks in high head Francis turbines. These cracks are understood to be related to pressure pulsations, vibration modulus and combination of these. In this paper, ...
    • Pressure Pulsation and Stresses in a Francis Turbine Operating at Variable Speed 

      Sannes, Daniel Braathen (Master thesis, 2018)
      The introduction of new intermittent energy sources on the electrical grid increases the need of regulated power to ensure stability of grid frequency. Hydropower has the unique possibility to deliver both stability and ...
    • Pressure Pulsations and Fatigue Loads in High Head Francis Turbines 

      Solemslie, Bjørn Winther; Trivedi, Chirag; Agnalt, Einar; Dahlhaug, Ole Gunnar (Journal article; Peer reviewed, 2019)
      The Norwegian power system today includes a relatively large percentage of Francis turbines with a head of above 300m, in the world. This leads to a need to maintain and develop the national competence regarding the ...
    • Rotor-Stator Interaction in Low-Specific Speed Francis Turbines 

      Agnalt, Einar (Doctoral theses at NTNU;2019:219, Doctoral thesis, 2019)
      Several breakdowns in hydropower plants with low specific speed Francis runners have been reported. These breakdowns are understood to be related to pressure pulsations, vibration modulus and the combination of these. One ...
    • The Rotor-Stator Interaction Onboard a Low Specific speed Francis Turbine 

      Agnalt, Einar; Solemslie, Bjørn Winther; Storli, Pål-Tore Selbo; Dahlhaug, Ole Gunnar (Journal article; Peer reviewed, 2020)
      Over the last years, several breakdowns in hydropower plants with low specific speed Francis runners have been reported. One of the main excitation forces in such runners is the pressure fluctuations originating from the ...
    • Signature analysis of characteristic frequencies in a Francis turbine 

      Trivedi, Chirag; Agnalt, Einar; Dahlhaug, Ole Gunnar; Brandåstrø, Bård Aslak (Journal article; Peer reviewed, 2019)
      The present work investigates the unsteady pressure fluctuations in a model Francis turbine that are observed during steady state operation. Focus of the present study is to correlate pressure fluctuations between stationary ...
    • Variable-speed operation and pressure pulsations in a Francis turbine and a pump-turbine 

      Iliev, Igor; Trivedi, Chirag; Agnalt, Einar; Dahlhaug, Ole Gunnar (Journal article; Peer reviewed, 2019)
      The paper presents result from model measurements of the efficiency and pressure pulsation intensities for two low-specific-speed hydraulic turbines operated at variable speed, namely, one splitter-bladed Francis turbine ...