Numerical Estimation of Torsional Dynamic Coefficients of a Hydraulic Turbine
Journal article, 2009

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.

Author

Martin Karlsson

Scandpower-Lloyd's Register

Håkan Nilsson

Chalmers, Applied Mechanics, Fluid Dynamics

Jan-Olov Aidanpää

Luleå University of Technology

International Journal of Rotating Machinery

1023-621X (ISSN) 1542-3034 (eISSN)

Vol. 2009 349397

Subject Categories

Applied Mechanics

Fluid Mechanics and Acoustics

DOI

10.1155/2009/349397

More information

Latest update

5/14/2018