Analysis for rotordynamic coefficients of helically-grooved turbulent annular seals.
Academic Article
Overview
Overview
abstract
An analysis for helically grooved turbulent annular seals was developed to predict leakage and dynamic coefficients, as related to rotordynamics. The grooved surface pattern was formulated as an inhomogeneous directivity in surface shear stress. The governing equations, based on both Hirs turbulent lubrication theory and the fine groove theory, were expanded in the eccentricity ratio to yield zeroth and first order perturbation solutions. The first order equations define perturbations in the pressure, axial and circumferential velocity fields due to small motion of the rotor about the centered position. Numerical results are presented for proposed grooved seals in the high pressure oxygen turbopump of the space shuttle main engine and for a water pump application. The results show that an optimum helix angle exists from a rotordynamic stability viewpoint. A properly designed helically grooved stator is predicted to have pronounced stability advantages over other currently used seals.
