Dynamic simulation of non-linear models of hydroelectric machinery

Cardinali, R.; Nordmann, Rainer; Sperber, A.

doi:10.1016/0888-3270(93)90003-f

Cited by 20 publications

(24 citation statements)

References 2 publications

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“…To perform simulations of unbalance response in vertical machines it requires that bearing parameters are updated in each time step with respect to eccentricity and load angle, which is time consuming. Cardinali et al [1] have performed nonlinear simulations of a vertical hydropower unit with tilting-pad bearings and White et al [15] performed simulations of a vertical pump with tilting-pad bearings.…”

Section: Introductionmentioning

confidence: 99%

“…The cause of this is that, in systems with vertical rotors, there is no predetermined operating point. In vertical machines such as hydropower units and pumps, it is the mass unbalance, the generator's properties, and the flow conditions in the turbine that determine the position of the rotor [1]. Commercial software uses algorithms designed for calculations of rotordynamic and bearing properties for machines with a horizontally oriented rotor.…”

Section: Introductionmentioning

confidence: 99%

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

Nässelqvist

Gustavsson

Aidanpää

2014

International Journal of Rotating Machinery

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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.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Nässelqvist

Gustavsson

Aidanpää

2014

International Journal of Rotating Machinery

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“…M. Cha et.al [8] shows the difference between horizontal and vertical orientation of TPJB's using Comsol Multiphysics where Reynold's equation is solved. R. Cardinall et.al [9] modelled a hydropower rotor with TPJB's and used Reynold's equation to describe the coefficients. All of these studies require that Reynolds equation is solved at each time step to update the stiffness and damping coefficients.…”

Section: Introductionmentioning

confidence: 99%

Influence of cross-coupling stiffness in tilting pad journal bearings for vertical machines

Synnegård

Gustavsson

Aidanpää

2016

International Journal of Mechanical Sciences

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“…The dynamic coefficients of journal bearings, bearing stiffness and damping, have major influences on the dynamic behavior of a LHG [7]. As illustrated in what follows, this behavior may experience significant and unpredictable changes due to fluctuations in the journal bearing operating conditions.…”

Section: Introductionmentioning

confidence: 99%

“…The upper bearing is composed of the generator upper shaft (3), pads (6), and bearing bracket (9). The lower bearing is a combined thrust and journal bearing, constituted by the generator lower shaft (4), the thrust block and pads (7), and the thrust bearing bracket (10). The turbine bearing is composed of the turbine shaft (5), pads (8), and turbine headcover (11).…”

Section: Introductionmentioning

confidence: 99%

Experimental Estimation of Journal Bearing Stiffness for Damage Detection in Large Hydrogenerators

Brito

Machado

Neto

2017

Shock and Vibration

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Based on experimental pieces of evidence collected in a set of twenty healthy large hydrogenerators, this article shows that the operating conditions of the tilting pad journal bearings of these machines may have unpredictable and significant changes. This behavior prevents the theoretical determination of bearing stiffness and damping coefficients with an adequate accuracy and makes damage detection difficult. Considering that dynamic coefficients have similar sensitivity to damage and considering that it is easier to monitor bearing stiffness than bearing damping, this article discusses a method to estimate experimentally the effective stiffness coefficients of hydrogenerators journal bearings, using only the usually monitored vibrations, with damage detection purposes. Validated using vibration signals synthesized by a simplified mathematical model that simulates the dynamic behavior of large hydrogenerators, the method was applied to a journal bearing of a 700 MW hydrogenerator, using two different excitations, the generator rotor unbalance and the vortices formed in the turbine rotor when this machine operates at partial loads. The experimental bearing stiffnesses obtained using both excitations were similar, but they were also much lower than the theoretical predictions. The article briefly discusses the causes of these discrepancies, the method's uncertainties, and the possible improvements in its application.

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Dynamic simulation of non-linear models of hydroelectric machinery

Cited by 20 publications

References 2 publications

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

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

Influence of cross-coupling stiffness in tilting pad journal bearings for vertical machines

Experimental Estimation of Journal Bearing Stiffness for Damage Detection in Large Hydrogenerators

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