Effect of Shaft Misalignment on the Dynamic Force Response of Annular Pressure Seals
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An analysis for calculation of the dynamic force and moment response in turbulent flow, annular pressure seals is presented. The fully developed flow of a cryogenic liquid within the annular thin film region is described by variable properties, bulk-flow equations with a turbulent friction factor based on Moody’s formula. The analysis considers arbitrary shaft center eccentric displacements and rotor axis misalignment angles. Solution to zeroth-order flow field equations determines the seal leakage, film forces, and moments. Dynamic force and moment coefficients due to perturbations in shaft center displacements and axis rotations are obtained from the solution of first-order (linear) flow equations. Numerical results on the effect of large static misalignment angles on the dynamic force response of a liquid oxygen damper seal typical of a cryogenic application are discussed in detail. The predictions show that a static misalignment mode relative to the seal entrance plane causes a large magnitude stiffening effect on the seal, while the opposite effect occurs for large misalignments about the seal exit plane. Alignment considerations are then shown to be of importance for adequate and predictable performance of annular pressure seals. © 1993 Taylor & Francis Group, LLC.
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