| In this thesis we investigate the gas flow in labyrinth seals for various geometries commonly found in turbomachinery. Labyrinth seals separate regions of high pressure from low pressure regions and they minimize the leakage of the high pressure gas. Equations governing the leakage rate for multicavity labyrinth seals are derived and their predictions, together with the associated pressure and circumferential velocity distributions, are discussed and compared to experimental results.; The detailed three dimensional, axisymmetric, steady flow in a single cavity is investigated by the use of standard Computational Fluid Dynamics (CFD) methods. The results so obtained, are in general agreement with published experimental results and indicate that the shear forces applied on the rotor are comparable to the pressure forces acting on it.; Small amplitude transverse vibrations of the rotor give rise to a three dimensional, non axisymmetric time dependent flow in the labyrinth cavities. Such a flow produces a nonzero net force on the rotor which under certain conditions may have a destabilizing effect. The rotor dynamic stiffness and damping coefficients due to those forces are calculated under the assumption that the flow can be modeled by bulk pressures and azimuthal velocities which are time dependent and non-axisymmetric. Comparison of the results with experimental data is satisfactory. |
