Numerical and experimental analysis of the rotor eccentric effect on the labyrinth seal

Labyrinth seals are widely used in turbomachines. In this paper, a transit simulation method is introduced to model the relationship between the journal offset in Labyrinth seals and the system stability based on Fluent UDF. A special dynamic mesh method has been adopted to ensure fine mesh quality during the arbitrary motion of the journal. In each time step, the transient fluid seal force on the journal surface is obtained by the solving Navier-Stokes equations. Then the displacement of the journal in the next step can be numerically solved by the FEM model of the rotor system. For every transient time step, the computed fluid seal force and the rotor motion displacement were coupled by data exchange. The experiment is carried out in a steam turbine with a position adjustable labyrinth seal. The experimental results show that the amplitude of the vibration decreases after the change of the relative position between the journal and the labyrinth seals and the numerical results show that the locus of the journal under different labyrinth seal offsets has some half-frequency components. Both the simulation and the experiment validates that the relative position between the journal and the labyrinth seals can greatly affect the stability in the coupled rotor-seal system.