Abstract
Pelton turbines are important machines for power generation from a renewable energy source such as water. For power rates below 20 MW, the rotor of Pelton turbines is usually in horizontal position. Considering ideal mounting and operating conditions, there are no axial forces acting on the rotor. In practice, there is an hydraulic force due to the difference between nozzle centerline and bucket centerline, and there is a magnetic force due to the difference between axial position of stator and rotor magnetic field centers. These forces are supported by bearings. In this article, a nonlinear dynamic model considering these axial forces and bearings behavior is presented and solved for two different actual Pelton turbines. The nonlinear dynamic model allows determining and evaluating the source of axial motion and therefore provides valuable information in order to reduce it when the axial displacement is high enough to produce damage.
Highlights
Pelton turbines are widely used all over the world for electric power generation. is type of turbines with horizontal rotors is commonly used for power rates below 20 MW for small hydro power plant which allows environmentally friendly, local, and stable power supply.ere are several studies about the dynamic behavior of Pelton turbines and its failures. ese studies are mainly focused on the performance calculation [1, 2]; the bucket erosion [3,4,5,6]; and the bucket fracture [7,8,9]
Another axial force is due to the magnetic force on the rotor generator. is force should be zero if the axial position of the stator magnetic field center coincides with the axial position of rotor magnetic field center
A model of axial motion of Pelton horizontal turbine is proposed. e model needs a set of experimental data under different operating conditions in order to determine the unknown values of axial position of stator and rotor magnetic field centers, bearing position, and bearing clearance
Summary
Pelton turbines are widely used all over the world for electric power generation. is type of turbines with horizontal rotors is commonly used for power rates below 20 MW for small hydro power plant which allows environmentally friendly, local, and stable power supply. Computer fluid dynamics (CFD) simulations and most experimental studies are carried out considering that jet centerline coincides with bucket centerline Taking into account this consideration, there are no axial forces and there is no need to study the axial motion of horizontal Pelton turbines. Another axial force is due to the magnetic force on the rotor generator. A model for axial motion considering these forces will be presented and it will be used in two actual cases of horizontal Pelton turbines: one in normal operating condition and another presenting excessive axial motion with bearing failure as a consequence
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