Analysis and testing for rotordynamic coefficients of turbulent annular seals with different, directionally-homogeneous surface-roughness treatment for rotor and stator elements

A combined analytical-computational method has been developed to calculate the transient pressure field and rotordynamic coefficients for high-pressure annular seals. The solution procedure applies to constant-clearance or the convergent tapered geometries of multistage centrifugal pumps which may have different surface roughness conditions on the stator and rotor seal elements. In experimental calculations with the method, the turbulent equations of Hirs (1973) are modified slightly to account for different surface roughness conditions, and a perturbation analysis is employed to develop zeroth and first order perturbation equations. Zeroth equations are also used to define both the leakage and circumferential flow due to shear stresses around the stator and rotor surfaces. The solution to analytical equations for four different surface roughnesses confirm the predicted net damping for the seals. A round-holed stator pattern yielded the highest net damping and lowest leakage of all the seals tested.