Session: 25-02 Annular Seals 2

Paper Number: 81010

81010 - Circumferentially Grooved Seal Flow Field Analysis Based on Effective Film Thickness to Improve Bulk Flow Models 

Bulk flow modeling of circumferentially grooved seals uses simplified physics models to predict leakage and rotordynamic coefficients more efficiently than full computational fluid dynamics (CFD) simulations but at the expense of accuracy. Reducing bulk flow modeling inaccuracies, mainly a result of uncertainties in empirical quantities like friction factors and loss coefficients, requires a more fundamental and physical understanding of the flow features and their dependencies. This study utilizes CFD and an effective film thickness, a physical boundary between the jet and recirculating flows, to investigate Reynolds number effects on grooved seal flow fields and shear stresses. Simulations were run using ANSYS CFX for a single groove seal model assuming fully developed flow for a range of pressure differentials and rotor speeds. The effective film thickness boundary was defined by generating streamlines in the jet flow region that traversed the entire axial length of the model. Radial averaging across the local film thickness yielded bulk flow quantities used in processing and analysis. Flow structures, film thicknesses, shear stresses, and net flow expansion into the groove are found to be described completely by the ratio of circumferential to axial Reynolds number and the total resultant Reynolds number. The effect of groove aspect ratio on film thickness and shear stress is also quantified. This paper uniquely analyzes circumferentially grooved seal flow from the standpoint of the effective film thickness, and the results presented demonstrate the utility of the novel effective film thickness analysis for reducing empiricism in bulk flow modeling of circumferentially grooved seals.

Presenting Author: Nathaniel Gibbons University of Virginia

Presenting Author Biography: Nathaniel is a fourth year graduate student in the Department of Mechanical and Aerospace Engineering at the University of Virginia, working within the Rotating Machinery and Controls (ROMAC) lab. His research focuses on the fluid dynamics of incompressible seals.

Authors:

Nathaniel Gibbons University of Virginia
Cori Watson-Kassa University of Virginia
Christopher Goyne University of Virginia
Minhui He University of Virginia