Session: 19-05 Rotordynamics in high speed turbochargers

Paper Number: 103344

103344 - Rotordynamics of a Rotor Supported by Foil Bearings Under Various Housing Excitation Frequencies 

Proton Exchange Membrane (PEM) Fuel cells are a rapidly growing technology in the field of automotive, especially in electric vehicles. In such applications, a motor-driven oil-free air compressor is one of the most critical auxiliary subsystems for the PEM fuel cell systems. Foil bearings are the perfect choice as oil-free bearings for fuel cell applications due to high rotordynamics stability and shock resistance. The platform of a motor-driven oil-free compressor can also be used as an electric turbocharger for traditional internal combustion (IC) engines. All electromechanical hardware for electric vehicles must satisfy vibration endurance requirements following ISO 16750-3:2012, characterized by certain g-loading at specific frequencies. Automotive PEM air compressors also follow the same ISO 16750 standard with the relieved g-loading requirement because it is expected that PEM and air compressors may be installed with additional vibration isolation mechanism. For the compressor to satisfy ISO 16750 requirement, detailed rotordynamics simulations with the compressor housing under certain g-loading are essential to design the foil bearings considering the static and dynamic loads to the bearing and rotordynamics stability. The main objectives of the current research are 1) to develop a six-degree-of-freedom (6-DOF) dynamic model of the compressor under external excitation to the compressor housing, 2) to simulate linear and non-linear rotordynamics of the compressor rotor supported by foil bearings, and 3) to provide appropriate design guidelines such as bump stiffness and axial length of the foil bearings for automotive PEM air compressors. The simulations show that the bump stiffness has to be increased further compared to stationary applications, and it is necessary to have a proper load distribution to the two radial bearings through either adjustment of inertia distribution or choice of different bearing lengths. Although linear simulations using linear coefficients are useful to identify natural frequencies, it is found linear methods do not predict rotor responses to the various housing excitation properly. The simulations with the nonlinear orbit method provide more accurate rotor-bearing responses under various housing excitations.

Presenting Author: Daejong Kim University of Texas at Arlington

Presenting Author Biography: NA

Authors:

Woongeon Lee University of Texas at Arlington
Daejong Kim University of Texas at Arlington