Research On Load Carrying Property And Structure Design Of Water-lubricated Bearing In Integrated Motor Propulsor

To improve the flexibility,reliability and to reduce the noise of marine propulsion system,integrated motor propulsor(IMP)whose motor and propeller are integrated came into being.Water-lubricated bearing is the pivot of rotor and stator,and its technological level determines the operating performance,stability,reliability and service life of IMP.Now there is no matured IMP water-lubricated bearings in China.Research of IMP water-lubricated bearing with high performance is fundamental to improving survival capability of naval ships.Supported by project “Research on new material and structrue design of water-lubricated bearing used in equipment” and project “Design of water-lubricated bearing used in integrated motor propulsor”,this paper aims to establish the structural design method of IMP water-lubricated thrust and journal bearing,to design,produce and test IMP water-lubricated bearings,so that to provide guidance for developing IMP water-lubricated bearings.Considering the physical characteristics of water,this paper establishes the numerical calculation method suited to analyze the lubrication properties of water-lubricated bearings,studies the influence of working condition,bearing structure and journal misalignment on hydrodynamic lubrication properties of water-lubricated bearing,and proposes the optimization method of bearing structure parameters,design chart of bearing diameter and equation of minimum film thickness.The lubrication performances of water-lubricated thrust and journal bearing are tested by experiments and results verify the correctness of numerical calculation method.Finally,the structural design of water-lubricated bearings in one integrated motor propulsor is finished using the numerical calculation method and design chart obtained above.Water-lubricated bearings with PTFE-based composite material are prepared.The rationality of the designing scheme and PTFE-based composite material as water-lubricated bearing material are verified by experiment.The main research contents and conclusions are as follows:(1)Based on the theory of computational fluid dynamics,the numerical simulation method for hydrodynamic water lubrication is investigated.This method considers the physical characteristics of water as lubricants including the cavitation effect using an effective cavitation model.Proper mesh generation is studied.The rationality of the numerical calculation method is validated by data in the literature.(2)The influence of minimum film thickness,rotational speed,bearing structure and journal misalignment angle and direction on water-lubricated thrust bearing load carrying properties are studied and the optimization design method of pad number,step height and step position of step thrust bearing,inclined angle and taper-to-flat ratio of taper-flat thrust bearing,pad inclined angle and support position of tilting-pad thrust bearing are proposed.The design chart for diameter selection of IMP water-lubricated thrust bearing and equation for calculating minimum film thickness are proposed.A water-lubricated bearing test rig is built and the lubrication performance of water-lubricated thrust bearing is tested.By analysing the experimental result,it is found that the minimum film thickness-to-surface roughness ratio when lubrication state changes is about 3.6,and the correctness of numerical calculation method is verified.(3)The influence of eccentricity ratio,rotational speed,bearing structure parameters and journal misalignment angle and direction on water-lubricated journal bearing load carrying properties are studied and the optimization design method of bearing parameters is proposed.The design chart for diameter selection of IMP water-lubricated journal bearing and equation for calculating minimum film thickness are proposed.The lubrication performance of water-lubricated journal bearing is tested.It is found that the minimum film thickness-to-surface roughness ratio when lubrication state changes is about 3.5,and the correctness of numerical calculation method is verified.(4)The structural design of water-lubricated bearings in one integrated motor propulsor is finished using the numerical calculation method and design chart obtained above.The bearings are prepared using PTFE-based composite material our lab developed according to the designing scheme.An special test rig for the water-lubricated bearings is built and the water film distribution is tested.Results show that the designing scheme and PTFE-based composite material as water-lubricated bearing material are reasonable.