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  • 101.
    Thiery, Florian
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Gantasala, Sudhakar
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Aidanpää, Jan-Olov
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Numerical evaluation of multilobe bearings using the Spectral Method2017Ingår i: Advances in Mechanical Engineering, ISSN 1687-8132, E-ISSN 1687-8140, Vol. 9, nr 7Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hydropower rotors and pumps have the specificity to be oriented vertically, meaning that the bearing forces have to be evaluated at each time-step depending on the position of the rotor for dynamical analyses. If the bearing forces cannot be evaluated analytically, a suitable numerical method should be used to calculate the pressure distribution over the bearing domain. This process can be computationally expensive as it should be performed for each discrete time-step. As a result, a comparison between the spectral method, the finite difference method, and the finite element method is performed to investigate which method is more adapted to dynamical analysis of the bearing. It is observed that the spectral method has the advantage of having a reasonable simulation time for any eccentricity magnitude with a moderate number of interpolation points. However, this method should be restricted to simple bearing models such as plain bearings or multilobe bearings due to the advantage of finding a global numerical solution directly on the entire bearing/pad domain

  • 102.
    Thiery, Florian
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Gustavsson, Rolf K.
    Vattenfall Research & Development.
    Aidanpää, Jan-Olov
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Dynamics of a misaligned Kaplan turbine with blade-to-stator contacts2015Ingår i: International Journal of Mechanical Sciences, ISSN 0020-7403, E-ISSN 1879-2162, Vol. 99, s. 251-261Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Rotor-to-stator contacts can occur in hydropower systems due to mechanical and electrical misalignment as well as high unbalance forces. It can result in high impact forces and damages in case of malfunction of the machine. As a result, a real hydropower rotor is studied to evaluate the different types of dynamic motion due to multiple impacts when it is initially misaligned. In this paper, the simplicity of its blade rubbing modelling allows us to evaluate in a fast and efficient way the dynamics of this system as a function of several design parameters. It is observed that the global dynamics of the system are similar to simple bladed Jeffcott rotors when scaled with the number of blades. Since the rotor runs at its operating point, the contact forces are also evaluated at nominal speed. A parametric study - as a function of contact stiffness and damping - is performed and results are given in terms of Poincaré sections, bifurcation diagrams and maximum displacements at steady state. These simulations are used to determine if the system is safe to operate. It can be used to design hydropower rotors by choosing the operating speed in a suitable range, or to analyse if the machine can be stopped before a catastrophe occurs

  • 103.
    Thiery, Florian
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Gustavsson, Rolf K.
    Vattenfall Research & Development.
    Aidanpää, Jan-Olov
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Evaluation of Campbell diagrams for vertical hydropower machines supported by Tilting Pad Journal Bearings2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    In vertically oriented machines with tilting-pad journal bearings, there is no static load that allow tocalculate the bearing properties around a determined static position. As a result, most of simulationsare performed by solving Reynolds equation at each time-step which can result in long computationaltime. To avoid this concern, a simplified model is used that takes in account the variation of unbalanceload depending on the pad configuration. This nonlinear model is used to simulate the dynamics ofa hydropower turbine and compared with the Campbell diagram calculations used from hydropowerindustry standards. A comparison between the linear and nonlinear model is performed to evaluate howaccurate the linear model is and until which limits it can be relevant. In case of qualitative discrepancies inthe results in terms of natural frequencies and damping ratios, an improvement of the Campbell diagramcalculation is proposed to obtain a more accurate linear model.

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