Investigation On Dynamic And Static Characteristics Of High Efficient Tilting Pad Journal Bearing

With the high speed and high load developing trend in rotor machine,seeking the proper way to reduce the bearing power loss and increasing the efficiency of machine has been a research hotspot.In order to find the solution and at the same time ensure the safty of turbomachinery,simulation and test research of rotor bearing system has been developed.At first,a model concerns about oil film thickness in bearing clearance has been established,which is including the pad deformation due to load.Using the Reynolds equation in fluid film bearing to solve the oil film pressure through finite difference method.Combining with lubrication temperature viscosity effect,the energy equation is developed to solve the bearing pad temperature and bearing power loss.Bearing dynamic coefficients has been calculated by little perturbation method.Combine these models and calculations,a bearing calculation programme has been developed,which is called COMDYN_bearing.Comparing with the Texas A&M university testing results about the bearing dynamic and static characteristics.The results illustrates that eccentricity and bearing power loss at high speed fits the test data well,but the stiffness coefficients at high speed and high load and the damping coefficients at low speed high load shows large deviation with the test data.In order to find proper ways on decreasing bearing power loss without cut rotating safety margin,DyRoBes the rotordynamic analysis software is used to analysize the effect of bearing structure parameters on rotor transient unbalance response and rotor bearing system stability,which find that increasing bearing preload and bearing length diameter ratio could amplify the amplitude of rotor transient unbalance response and cut down the stability of rotor bearing system,meanwhile,it can also reduce the pad temperature.In test research,two magnetic bearing has been used to load the rotor bearing test rig.Oil supply temperature,bearing load and bearing clearance are investigated on the effect of bearing pad temperature and power loss.Increasing the oil supply temperature in a certain range,bearing pad temperature saw a increase,but when oil supply temperature reach a certain value about 50?,pad temperatue saw a drop trend.Under 10000r/min speed,bearing which support 8000N has 3-5 ? increase in pad temperature compared with 4000N.When the bearing with dimensionless radial clearance at 0.75‰ run at the 12000r/min,the pad temperature would reach at the shut down value 105?,which is not permitted in the engineering production.The bearing load shows a minor effect on power loss comparing with the influence of speed.The bearing power loss with dimensionless radial clearance at 0.89‰has 5kW increase comparing with 0.75‰ one at 8000N beaing load.Hence,efficiency,reliability and stability should all been take into account when design a bearing.The COMDYN bearing software and investigation on rotor bearing system could be the references of increasing the stability of rotor bearing system.The test results in this thesis is effective as a reference of optimizing bearing structure and increasing the unit efficiency.