Thermal Lubrication Study Of Multi Tilting-Pad Journal Bearing

The multi-tilting-pad journal bearings (MTPJB) are widely applied to large rotating machines such as hydrogenerator and heavy compressor, the performances of bearings directly influence the opeartions of the entire machine. Meanwhile, to manufacture and test on a MTPJB is high cost. But designers can get the function data of a MTPJB with analyses of the thermohydrodynamic lubircation (THD) and thermoelastohydrodynamic lubircation (TEHD) of bearings, which are acceptable for designing and optimizing the parameters of bearings. Thus, the study on the THD and TEHD of MTPJB has engineering values.In part 1, the engineering background of THD and TEHD analyse of MTPJB was described, and the journal bearing's structure, the pad and supporting, loading form, pad material, lubricating ways and bearing failures were briefly reviewed. A review on the THD and TEHD of tilting-pad journal bearings (TPJB) was presented in three parts:hydrodynamic lubrication of bearings, the lubrication of TPJB and experimental investigations on journal bearings. Finally, the topics of this thesis were proposed.In part 2, a film thickness equation of MTPJB was derived out, and the THD model of the bearing was established on the basis of previous theories, including the Reynolds equation, film thickness equation, the viscosity-temperature and density-temperature characteristics of lubricants, energy equation, heat conduction equation, the balance equations of force and torque and their boundary conditions were included. A FORTRAN program package based on the THD model was presented. The THD performances of the bearing under several conditions were analyzed.In part 3, the film thickness of MTPJB considering shaft misalignment were derived out, of which the tilting-pad has single or two degrees of freedom, and the computer program for these two cases were compiled, the effects of shaft misalignment on the THD performance of the bearing were comparatively examined.In part 4, a TEHD model of MTPJB was established, and the pad deformation due to pressure field was calculated. The computer program was compiled to slove the TEHD model. A variable accuracy was applied to reduce the computation time. The THD and TEHD performance of bearing, and the performance of THD and TEHD with consideration of shaft misalignment were computed and compared with each other, the effects of operating conditions on TEHD of bearing were analyzed.In part 5, the conclusions of this thesis were summarized, and the shortage of this work and the research topics in the future were briefly presented.