Research On The Load Carrying Capacity Of Large Water-lubricated Thrust Bearing And The Optimization Of Thrust Pad Profile

Hydrodynamic thrust bearings are widely used in large rotating machines, such as pumps,compressors and turbines, etc. It is mainly carried the axial loads. Therefore, it is the key partfor keeping the large rotating machinery operating stably and reliably. Moreover, the loadcarrying capacity and repair cycle of this kind of equipments are directly influenced. With thedevelopment of science and technology, the rotation speed and power of machinery becomemore and more high. Consequently, the thrust bearings are forced to operate on the high speedand high loads conditions. Thus, the higher requirement is put forward to the lubricationperformance of thrust bearing, especially the load carrying capacity. In recent years,water-lubricated thrust bearing has been widely applied in the canned motor pumps in specialenvironment due to its environment-friendly, economic and high security, low friction, lowtemperature rise and low power loss characteristics. However, the load carrying capacityremains to be further improved.In view of this, the water-lubricated thrust bearing of nuclear pump of the large cannedmotor pump is taken as the research object in this paper and the mathematic models areestablished both in laminar condition and in turbulent condition. Furthermore, the water filmthickness distribution and pressure distribution of the bearing are solved in the two conditionswith MATLAB programming. Moreover, the influence law of the main lubricationperformance of the thrust bearing is analyzed and calculated for the variation of the operatingcondition parameters, including rotation velocity and inlet pressure, and the geometricparameters of the thrust bearing, including the pivot location, the length-width ratio of thethrust pad and the thrust pad angle. As a result, it provides reference for the design of thethrust bearing. Then the study on modeling the surface profile of thrust pad is carried out. Meanwhile, the geometric models and mathematic equations of six different surface profile ofthrust pad are built. Simultaneously, the models are dealt with nondimensionalization,discretization and differencing on the basis of simplification of the sector-thrust pad.Consequently, the mathematic models are transformed into algebraic equations. Subsequently,taken one-dimensional infinite width slider and two-dimensional finite width rectangle slideras the research objects, the influence law of the main lubrication performance of the thrustbearing is solved with MATLAB programming by the use of the SOR (SuccessiveOver-Relaxation) method. Finally the cycloidal surface profile of thrust pad was confirmed tothe optimum surface profile because of the best lubrication performance in comparison withthe others. And taken surface roughness into account, the slider models with the cycloidalprofile of thrust pad are further to be optimized. The surface roughness models areaccomplished at the same time. In addition, one-dimensional infinite sliders at two differentsurface roughness modes, partial surface roughness and whole surface roughness, areanalyzed and calculated in comparison with each other. At last, the surface roughness modelsof two-dimensional finite rectangle sliders are further to be extended, including transversesurface roughness, longitudinal surface roughness and synthetical surface roughness. And thelubrication performance, especially the load carrying capacity of the cycloidal surface profileof thrust pad are solved in different surface roughness models. As a consequence, it provides aevidence for the design and optimization of surface profile of thrust pad.