A New CFD-Perturbation Model for the Rotordynamics of Incompressible Flow Seals

A new, quasi-three-dimensional perturbation model is developed for the computation of rotordynamic forces for all incompressible flow seals with an axisymmetric geometry. The model assumes a small circular whirl motion of the rotor around the stator center. By avoiding the complicated perturbation coordinate transformation, the perturbation solution directly accounts for the disturbance of the wall shear stresses that are caused by the whirl motion of the rotor. The primary advantage of the present model is that it can immediately be applied to any radial-clearance seal of axisymmetric geometry without ad hoc adjustments. It was found from computations that include the upstream chamber that the magnitude of the first-order variables at the seal inlet are much larger and abruptly changing than was previously assumed.Copyright © 2000 by ASME