| Rolling bearing is the core supporting component of gas turbine rotor system.Affected by harsh working conditions such as heavy load and high temperature,it has frequent faults,which directly affects the stability of rotor system and the reliability of the whole machine.Gas turbine bearings usually work in the mixed lubrication state of lubrication contact coexistence.Under harsh working conditions,the local rough peak contact of the interface brings problems such as stress concentration,too high flash temperature and too large dry contact area,which further induces the interface failure forms of gas turbine bearings such as wear,pitting,gluing and plastic deformation.Therefore,this paper takes the end ball bearing of a gas turbine power turbine as the research object,comprehensively considers the influence of typical working conditions and interface micro morphology of the bearing,establishes the interface failure prediction model of gas turbine bearing based on mixed lubrication,reveals the failure mechanism of bearing interface,and guides the tribological design of gas turbine bearing.The main research contents of this paper are as follows:Firstly,the coupling analysis model of mixed lubrication and wear of gas turbine bearing is established.The accuracy of the model is verified by comparing the lubrication results obtained by the coupling analysis method and the fitting formula.The effects of different working conditions and real surface roughness on the wear profile of rolling element and inner raceway are studied,the variation trend of surface profile with wear time is analyzed,the effects of load,slip roll ratio and roughness parameters on wear depth and wear volume are analyzed,and the variation trends of oil film thickness and oil film pressure before and after wear are compared.Secondly,considering the influence of non-Newtonian fluid and three-dimensional real rough surface,the theoretical analysis model of gluing failure of gas turbine ball bearing under mixed lubrication is established.The bearing temperature rise obtained by the coupling analysis method is compared with the numerical solution of Blok temperature rise formula to verify the accuracy of the flash temperature analysis model.The effects of surface processing technology,working condition parameters and roughness parameters on bearing surface temperature rise and friction coefficient are analyzed.Based on the gluing failure criterion,the gluing failure boundary under different load conditions is given.Then,based on the mixed lubrication analysis,considering the effects of plastic deformation and three-dimensional real rough surface,the elastic-plastic mixed lubrication analysis model of gas turbine bearing is established.The effects of bearing material hardening characteristics,load conditions and real surface roughness on the lubrication characteristics and plastic deformation of gas turbine bearing are discussed.The stress field distributions on the bearing surface and subsurface are obtained.Based on this,the relative fatigue life prediction theory of ball bearing is studied.Finally,the basic experimental research on ball disk contact tribological characteristics of simulated ball bearing is carried out.The effects of working condition parameters,oil types and contact pair materials on the friction coefficient are compared,and the friction coefficient obtained by the coupling analysis method is compared with the test results to verify the accuracy of the calculation model in this paper.At the same time,the surface morphology before and after wear is measured by three-dimensional topography instrument.By comparing the surface profile distribution after wear measured by coupling analysis method and test,the rationality of the wear failure model in this paper is verified directly by the test data. |
