Numerical Estimation of Torsional Dynamic Coefficients of a Hydraulic Turbine
The rotordynamic behavior of a hydraulic turbine is influenced by fluid-rotor interactions at the turbine runner. In this paper computational fluid dynamics (CFDs) are used to numerically predict the torsional dynamic coefficients due to added polar inertia, damping, and stiffness of a Kaplan turbin...
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| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Wiley
2009-01-01
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| Series: | International Journal of Rotating Machinery |
| Online Access: | http://dx.doi.org/10.1155/2009/349397 |
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| Summary: | The rotordynamic behavior of a hydraulic turbine is influenced by fluid-rotor interactions at the
turbine runner. In this paper computational fluid dynamics (CFDs) are used to numerically predict
the torsional dynamic coefficients due to added polar inertia, damping, and stiffness of a Kaplan
turbine runner. The simulations are carried out for three operating conditions, one at about 35%
load, one at about 60% load (near best efficiency), and one at about 70% load.
The runner rotational speed is perturbed with a sinusoidal function with different frequencies in
order to estimate the coefficients of added polar inertia and damping. It is shown that the added
coefficients are dependent of the load and the oscillation frequency of the runner. This affect the
system's eigenfrequencies and damping. The eigenfrequency is reduced with up to 65% compared
to the eigenfrequency of the mechanical system without the fluid interaction. The contribution to
the damping ratio varies between 30–80% depending on the load. Hence, it is important to consider
these added coefficients while carrying out dynamic analysis of the mechanical system. |
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| ISSN: | 1023-621X 1542-3034 |