Session: 27-03: Bearings Effects in Rotordynamics

Paper Number: 152932

Experimental Validation on Reverse Precession in Foil Gas Bearing Supported Turbomachinery 

Typical rotordynamic analysis of turbomachinery requires the identification of rigid body modes (RBM), bending critical speeds, and rotor orbit precession direction. Turbomachinery supported on hydrodynamic foil gas bearings (FGB) features a rotor-bearing system (RBS) designed to keep the RBM below the operating speed range. Adequate separation margins are required for 1st bending critical speed for a reliable turbomachinery operation. Identification of forward and reverse precession direction is also paramount during the design phase to ensure turbomachinery reliability. There is an abundance of literature published on reverse precession on turbomachinery supported on other types of bearings, such as rolling element and fluid film bearings. Reverse precession is seldom reported in real life on FGB-supported turbomachinery. This research paper aims to bridge this gap by providing information on reverse precession in FGB-supported turbomachinery. This research is motivated by the unexpected observance of consistent reverse precession during startup, steady state, and coast-down operation of FGB-supported motor-driven experimental turbomachinery in the research lab. This research delves into experimental observations about reverse precession corroborated by rotordynamic model predictions. It further explores the effect of FGB support structure stiffness anisotropy on reverse precession. This paper aims to provide a reference to future design engineers and researchers embarking on new turbomachinery RBS designs for challenging applications supported on hydrodynamic FGBs.

Presenting Author: Ali Shakil Collins Aerospace

Presenting Author Biography: Ali has over 20 years of experience in the design and development of turbomachinery, from a clean sheet of paper design to hardware build and testing. He has successfully designed & developed numerous machines such as Turbochargers, Turboalternators, Turboexpanders, Permanent Magnet Motors/Generators, Air Cycle Machines, Aerospace Gas Turbine Engines, & Test Rigs. Ali is an SME in Foil Gas Bearings for Collins Aerospace, a Raytheon Technologies Company. He has a BSME & MSME in Mechanical Design Engineering and an MBA in Entrepreneurship & Finance. His prior employment includes Honeywell, R&D Dynamics, Capstone Turbine, and Pratt & Whitney.

Authors:

Ali Shakil Collins Aerospace
Christopher Simpson Collins Aerospace