INFLUENCE OF CENTRIFUGAL GROWTH ON THE ROTOR DYNAMIC STABILITY OF A ROTATING LABYRINTH SEAL

A computational framework based on a combined 3D-CFD/FE along with a second order rotor dynamics model is employed to assess a six-tooth straight through rotating labyrinth seal for a varying flow and operating conditions. Three-dimensional Reynolds Averaged Navier-Stokes compressible equations are solved to obtain the circumferential pressure distributions and are integrated further to calculate the seal fluid forces. Subsequently, the extracted rotor dynamic coefficients are compared to the one without considering centrifugal growth. All the six rotor dynamic coefficients shows distinct characteristics when the centrifugal growth is accounted for. The centrifugal growth has a substantial reduction on cross-coupled stiffness and direct damping and the influence increases with speed. The stability aspects of the seal are examined in terms of whirl frequency ratio and effective damping coefficient, presuming synchronous whirl. The results emphasis the consideration of the seal centrifugal growth effects, while conducting rotor dynamic stability analysis for a typical rotor system.