Response of a Rotor Under the Influence of Seal Forces

Application ID: 102621

The fluid flow in seals causes a strong restoring radial force, opposing the shaft motion. Also, there is a cross coupled force due to the axial variation of the circumferential flow. The first type of force always has a stabilizing effect on the rotor, whereas the second one in certain situations can cause an instability.

In this example, an axial compressor is modeled using the Beam Rotor interface. The compressor has 10 stages of impellers, with a seal near each impeller to avoid flow leakage. In addition, a balance piston seal is present at the end of the impeller stages. The time dependent response of the system is studied for a gradually increasing rotor speed. Two cases are considered for the simulation: excluding all seals and including the seals. The responses of the system for the two cases are compared. The result shows a better stability in the presence of seals.

This model example illustrates applications of this type that would nominally be built using the following products: