Study On Dynamics For Hydrodynamic Journal Bearing Based On General Film Thickness Equation

Rotor machine is one of the most important mechanical equipment.With the fastindustry development of our state,such as electric power, aviation, mechanism,petrochemistry, rotoring machine play a great role.Journal bearing is an importantsupporting part in rotoring machine.In actual engineering programme,its staticcharateristic and dynamic charateristics are effective to equipment. There has alwaysbeen a huge demand for efficient journal bearings in machines like steam turbines,centrifugal compressors, pumps, and motors. Ideally the bearing achieves good damping,durability, negligible friction, and zero wear in the smallest possible space.This study is a part of National Natural Science Foundation Project”couplingfunction and cooperate theory between the three-dimension coned wedge-shape gapsand the hydrodynamic lubricate performance”(grant number:51005257).This paperstudied static charateristics and dynamic charateristics of journal bearings based ongeneral film thickness equation,getting new shape journal bearing that has betterperformance.Using writing codes by the method of numerical analysis and simulation ofsoftware,paper analysed the journal bearing shapes that were optimized byprevious.Performance results was researched.Author optimzed the jounral shape whichnot only statisfied load capacities but also had better stability.Main researches weresummarized as follows:①With CFD finite element softwares FLUENT and COMSOL Muliphysics, theauthor studied two optimzed bearing shapes of n=1and n=3, solid model and finiteelement model establishment，numerical simulatin analysis, getting static pressuredistribution figures.Imported static pressures, obtaining load capacities by matlabintegral solution codes.The result of CFD was in agreement with numerical method andverified the codes.Laid a foundation for dynamic and stability research.②Derived perturbed pressure Reynolds equations,stiffness coefficients anddamping coefficients from Reynolds equation combined with bearing profilestheory.Calculated circle and non-circle bearing8dynamic coefficients on differentconditions by matlab codes.Took rigid rotor for example,its stability index isdemensionless rotor quality Mst,analysed and calculated stability index.The resultsshow that the stablity of n=1is better than n=3.③Applied modal analysis principle and general process.Established solid model and finite element model.With dynamical modal analysis of rotor system by use ofANSYS software,the author got first order natural frequency and first critical speed.Theresults was uniform with numerical study.④According to analysis of dynamic characteristics,the stability which wasachieved by taking load capacity as objective function is not good.So,author tookstability as objective function,minimum oil thickness and bearing load capacity aslimited functions,searched new bearing shape with better stability by the method ofgenetic algorithm.The results show that,the bearing with satisfied limited load capacityand better stability can be achieved.