Rolf Gustavsson

Experimental and Numerical Simulation of Unbalance Response in Vertical Test Rig with Tilting-Pad Bearings

In vertically oriented machines with journal bearing, there are no predefined static radial loads, such as dead weight for horizontal rotor. Most of the commercial software is designed to calculate rotordynamic and bearing properties based on machines with a horizontally oriented rotor; that is, the bearing properties are calculated at a static eccentricity. For tilting-pad bearings, there are no existing analytical expressions for bearing parameters and the bearing parameters are dependent on eccentricity and load angle. The objective of this paper is to present a simplified method to perform numerical simulations on vertical rotors including bearing parameters. Instead of recalculating the bearing parameters in each time step polynomials are used to represent the bearing parameters for present eccentricities and load angles. Numerical results are compared with results from tests performed in a test rig. The test rig consists of two guide bearings and a midspan rotor. The guide bearings are 4-pad tilting-pad bearings. Shaft displacement and strains in the bearing bracket are measured to determine the test rig’s properties. The comparison between measurements and simulated results shows small deviations in absolute displacement and load levels, which can be expected due to difficulties in calculating exact bearing parameters.

Model Based Analysis of Coupled Vibrations Due to the Combi-Bearing in Vertical Hydroturbogenerator Rotors

The studies presented in this paper focus on analyzing how the combined thrust-journal bearing (commonly called combi-bearing) influences the dynamics of hydropower rotors. Thrust bearing is a comp ...

Experimental Verification of a Combi-Bearing Model for Vertical Rotor Systems

Combi-bearing is a combined thrust-journal bearing design used in vertical hydropower rotors. The dynamic characteristics of this component (combi-bearing) were analytically modeled by Luneno et al ...

Modeling of Visco-elastic Supports for Hydropower Applications

This paper presents a numerical model of how a visco-elastic support affects the dynamical response of a 42 MW Kaplan turbine that is experiencing resonance problems. The supports are placed between the bearing bracket and the supporting concrete structure. Since the supports are nonlinear, the nodal displacements are solved using a Runge-Kutta time integration method where the visco-elastic supports are implemented as a nonlinear force. To reduce calculation time the number of degrees of freedom of the rotor model is reduced using the Improved Reduction System. Excitation of the system is implemented as a stationary force in the runner with varying frequency. The resulting nodal displacement from the transient simulation is then compared to the system simulated without the supports to show how the machine dynamics are affected. The simulations show that the visco-elastic supports efficiently reduces the displacements in the lower vibration modes. The reduced vibration levels should decrease the probability of resonance problems occurring when running at operating speed.