Study of Impact of Orbit Path, Whirl Ratio and Clearance on the Flow Field and Rotordynamic Coefficients for a Smooth Annular Seal
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The study of the effect of different orbit paths and whirl ratios on the rotordynamic coefficients of a smooth eccentric annular seal, using Computational Fluid Dynamics (CFD) was performed. The flow was simulated for two different orbits - linear and circular for orbit speeds ranging from 0 to 1. This was done using the FLUENT CFD code with a time - dependent solver which allowed the use of dynamic meshing and User Defined Functions (UDFs). The effect of clearance was also studied by simulating the flow through an eccentric seal with one-tenth the clearance and comparing the results. It was seen that the flow field varies significantly with both the change in orbit and clearance and this in turn affects the forces and rotordynamic coefficients. The linear orbit showed major changes in terms of both the flow fields and the resulting forces. The velocities, pressure magnitudes and forces were much larger than the circular orbit. Another important finding was that the behavior of the flow for the smaller clearance is viscosity dominated compared to the inertia dominated flow seen for large clearances. The computation of rotordynamic coefficients for the circular orbits used Childs' theory and it was seen that for larger clearances the CFD predictions were not in agreement with the expected trends from this theory. The smaller clearance simulations, however, show force predictions from which the rotordynamic coefficients obtained match the theory.
Sekaran, Aarthi (2009). Study of Impact of Orbit Path, Whirl Ratio and Clearance on the Flow Field and Rotordynamic Coefficients for a Smooth Annular Seal. Master's thesis, Texas A&M University. Available electronically from