Session: 23-01, Foil bearings

Paper Number: 128199

128199 - Experimental Characterization of Darcy Friction Factors of Bump Channel Flows and Application to Cooling Flow Path Design 

Foil bearings are considered the most promising oil-free bearing technology for small high-speed turbomachines. Among many different underlying supporting structures, corrugated bump foils are the most popular. Due to the geometry of corrugation, the bump foils have clear gas flow passages, and cooling gas is introduced through these bump channels. The flow resistance through these bump channels are function of bump geometry and ambient conditions and type of gases. When multiple foil bearings are installed within a system, cooling gas flow passage design through the bearings requires proper understanding of bump channel flow resistances. Inadequate cavity pressures arising from the cooling gas flow passage design can create undesirable axial force to the thrust bearings. This paper presents experimentally measured Darcy friction factors of typical bump channels in both laminar and turbulent flow conditions, as a function of flow Reynolds number and hydraulic diameter determined from the bump channel geometry. This paper also presents experimentally measured flow characteristics of radial foil bearings and compared with the prediction using the experimentally extracted Darcy friction factors. Finally, the paper presents how Darcy friction factors can be integrated into the general cooling gas flow analyses using a test rig comprising two radial foil bearings and two thrust foil bearings, and introduces the formulation to calculate the cavity pressures along the cooling gas flow passages and the predictions are compared with measurements.

Presenting Author: Daejong Kim University of Texas at Arlington

Presenting Author Biography: Dr. Kim is an Associate Professor at University of Texas at Arlington. He earned PhD degree in Mechanical Engineering at University of Texas at Austin. He has published more than 30 journal papers on foil bearings and his other expertise are nonlinear rotordynamics, aerodynamics, energy system design/integration.

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