Dynamic force performance of annular gas seals at off-center conditions

A numerical analysis to predict the static and dynamic performance characteristics of gas annular seals at off-center conditions is presented. Isothermal rotor and stator surfaces are assumed according to conditions observed on an existing test rig. Heat flow to the rotor and stator is modeled by bulk-flow heat transfer coefficients. The non-linear differential equations for the turbulent bulk flow in the annular seal are solved using an efficient CFD algorithm. A perturbation method for calculation of the zeroth-and first-order flow fields determines the seal steady-state response and dynamic force coefficients. Numerical predictions for a test seal show that heat transfer from the bounding solid surfaces to the fluid film is important to correctly predict the temperature field. An adiabatic flow assumption leads to unrealistically large temperature drops across the seal length. The seal leakage and the direct stiffness coefficients are insensitive to the position of the rotor center in the seal, while the seal forces, the cross-coupled stiffness, and the direct damping coefficients increase with the rotor static eccentricity. (Authors)

Dynamic force performance of annular gas seals at off-center conditions Academic Article