Experimental study on the feasibility of alternative materials for tilting pad thrust bearings operating in transition to mixed friction

In hydrodynamic bearings traditional bearing alloys:Babbitts and bronzes are most frequently utilized.Polymer sliding layers are sometimes applied as a valuable alternative.Hard diamond-like carbon(DLC)coatings,which are also considered for certain applications may show some advantages,as well.Although material selection is of secondary importance in a full film lubrication regime it becomes important in mixed friction conditions,which is crucial for bearings with frequent starts and stops.Experimental research aimed at studying the performance of fluid film bearings in the specific operating regime,including the transition to mixed friction,is described in the paper.The tests were carried out on four tilting pad bearings of different material compositions:Steel/bronze,DLC/steel,steel/polyether ether ketone(PEEK),and steel/Babbitt.The tests comprised stopping under load and reproduction of the Stribeck curve by decreasing rotational speed to very low values,and observing the changes of friction force during the transition to mixed friction regime.Analysis of the transition conditions and other results showed clear differences between the tested bearings,illustrating the feasibility of less popular material compositions for bearings operating in specific conditions.More specifically,the DLC/steel bearing was demonstrating superior performance,i.e.lower friction,transition to mixed friction occurring at higher load,and more stable performance at start-stop regime over the other tested bearings.

Surface roughness characteristics effects on fluid load capability of tilt pad thrust bearings with water lubrication

The effects of surface roughness characteristics on the fluid load capacity of tilt pad thrust bearings with water lubrication were studied by the average flow model.The flow factors utilized in the average flow model were simulated with various surface roughness parameters including skewness,kurtosis and the roughness directional pattern.The results indicated that the fluid load capacity was not only affected by the RMS roughness but also by the surface roughness characteristics.The fluid load capacity was dramatically affected by the roughness directional pattern.The skewness had a lower effect than the roughness directional pattern.The kurtosis had no notable effect on the fluid load capacity.It was possible for the fluid load capacity of the tilt pad thrust bearings to be improved by the skewness and roughness direction pattern control.

通过轴承升级实现涡轮机械的可靠运行

Common fluid film bearing issues(mainly high bearing temperature)preventing reliable operation of turbomachinery will be addressed.Atheoretical review of radial and thrust bearing performance will be included for a basic understanding on how to handle the bearing issues.Some theoretical plots will be presented to demonstrate the effect of key bearing design parameters on bearing performance.Advanced bearing materials beyond babbitt will also be introduced as bearing upgrade options to overcome bearing issues.Case studies on radial and thrust bearing upgrades to mitigate or eliminate the bearing issues will be shared.Some of the common vibration problems preventing reliable operation of turbomachinery will also be described with suggestions on how to eliminate or mitigate the problems via changes to bearing design features or new bearing technology.A couple of case studies representing each vibration problem will be presented.