Research On Oil-lubricated Multi-leaf Foil Bearing Characteristics With Compliant Support

The foil bearing is a hydrodynamic pressure bearing with flexible surface, which isgenerally applicable to high speed and light load. In view of this, two new multi-leaffoil bearings with compliant support are proposed in order to improve load capacity.The theoretical analysis includes calculating the static and dynamic characteristicsof the new foil bearings, comparing with fluid film bearings and multi-leaf foilbearings without compliant support. Then design and processing a multi-leaf foilbearings with single spring supporting structure. Finally, design and build a test rigfor researching on the static and dynamic characteristics of oil-lubricated multi-leaffoil bearings: experimental determination of the dynamic coefficients of the foilbearings and measuring its load capacity.According the geometric structure of the new multi-leaf foil bearings, calculate theelastic deformation of the film thickness; then calculate the overall compliancematrix including compliant support and foil leaves, which are modeled as curvedbeams and Castigliano’s theorem is used to obtain the foil deflections, while thecommercial software is application to verify the accuracy of the algorithm;Substitute overall flexibility matrix into the static and dynamic Reynolds’ Equationand solve the static and dynamic characters of the multi-leaf foil bearings withcompliant support. What’s more, Routh-Hurwitz bearing stability theory is used todetermine the stability of the structure of the foil bearing, which shows a highstability at high speed and load capacity has been improved.Secondly, oil-lubricated multi-leaf bearing with single spring support was designedand fabricated according to theoretical calculation. Then designed and builtidentification of foil bearing dynamic coefficients rig and load capacity test rig. Thedesign includes a rigid high-speed turbine rotor system, lubricating system, staticload system, dynamic load system, the foil temperature measurement system,parameter measurement system. The critical speed of the test rig is27200r/min.Then a load incremental method to measure the compliant support structure of radialstiffness test bed is built, the compliant support including a horizontal spring, bumpfoil structure.Finally, research and determinate the rotor dynamic coefficients of the oil-lubricated multi-leaf foil bearing and test the bearing load capacity from experiment. Proposeda rotor dynamic coefficients identification algorithm based on bearing responserelative to rotor and synchronous exciting. Calculate the rotor dynamic coefficientsof multi-leaf foil bearing using two sets of independent test data after FFT transform.The bearing capacity is measured according to the position of the rotor in thebearing. If foil bearing achieved the load capacity limit, the foil would connectedrotor and caused temperature fluctuation because frication. The test results arecompared with the theoretical value analysis to verify the accuracy of the theoreticalmodel.