Experimental Research On Temperature Characteristics And Rotordynamic Performance Of SMA Spring Gas Foil Bearings

Gas foil bearings are a kind of sliding bearings using ambient air or other gases as the working fluid or lubricant,which have high reliability,high temperature resistance and maintenance free,so they are widely used in petrochemical,energy,aerospace and other fields.At present,in order to improve the performance of gas foil bearings,scholars at home and abroad have carried out a lot of theoretical and experimental research in the aspects of foil material,bearing structure and so on.The gas foil bearings also have some defects,such as insufficient damping and load capacity,etc.,which affects the wider application of the gas foil bearings.It is found that shape memory alloys(SMA)can transform the phase between martensite and austenite at high or low temperature,and restore their original shape size and Young’s modulus.When SMA is applied to gas foil bearings,makes it possible to control the stiffness and damping characteristics of gas foil bearings.This kind of bearing is simple in structure,easy to manufacture,has good stiffness and damping characteristics,and can achieve the purpose of active control of bearing performance by controlling temperature to make SMA spring in different states.The following experimental investigation has been done in this paper:The axial tensile tests were conducted in two states to obtain different stiffness values of the coated SMA springs.The SMA springs were heated to obtain the temperature-time relationship curve.The installation method of the SMA springs in the bearing cartridge was designed,and the SMA spring gas foil bearings were manufactured.A vertical static load test rig was designed and constructed to conduct a vertical static load test on the compliant support structure of the SMA spring gas foil bearing.The stiffness-displacement relationship curve of the compliant support structure was extracted from the obtained displacement-load curve.A static pull-push load test rig was constructed,and the static pull-push load test on the completed SMA spring gas foil bearing at martensite and austenite phases was performed.The nominal clearance and structural stiffness at different phases were extracted from the test data.The recorded data was compared with the first-generation bump type gas foil bearing of the same size.Based on the static push-pull test rig,the dynamic force experiments of SMA spring bearing were carried out in two phases of SMA springs by using the electromagnetic shaker.The relationship between the stiffness,damping and loss factor of the bearing in two phases with the vibration frequency and amplitude were obtained.Lift-off test was conducted on the SMA springs gas foil bearings to measure the lift-off speed and lift-off torque,the recorded data was compared with the firstgeneration bump type gas foil bearing of the same size,too.An 80.0 mm diameter SMA spring gas foil bearing was designed and manufactured,based on the lift-off test rig,temperature characteristics experiments with cooling air was conducted to observe the relationship between the friction torque and temperature during the bearing operation.A rotordynamic characteristic test rig was built,the SMA springs gas foil bearings were used as the support to conduct the rotordynamic experiment to analyze the rotordynamic response with different bearing clearance.