The Experimental Study On Vibration Characteristics Of High-Speed Turbo-expander Refrigerator Rotor

With the rotating machinery toward high speed,light,flexible development the gas bearing as the rotor bearing components of the bearing-rotor system in the high speed turbine is more and more widely used.In this paper,the vibration characteristics and stability of a high speed rotor under hydrostatic bearing lubrication are studied based on a high speed turbo cooling test bench.There are:The basic theory of finite element of rotor-bearing system is introduced,and the finite element model of the rotor,such as shaft section,wheel disk and bearing,is established for rotor of high-speed turbo-expander refrigerator.The rotor is modeled and analyzed by using ANSYS finite element analysis software.The critical rotational speed and mode of the rotor are calculated without consideration of the anisotropy of the bearing and the damping of the cross-rigidity.Considering the four unbalanced excitation forces and the bearing anisotropy imposed on the turbine wheel and the compressor wheel,Equilibrium response,in which the resonance separation phenomenon occurs in the rotor torsion under different excitation forces.The whole experimental system can be divided into experimental elements,include gas supply system,computer control and data acquisition system,etc.To improve system reliability the system is unified and coordinated,and a plurality of interfaces are reserved.The vibration signal data acquisition and analysis system is used to analyze the vibration and dynamics of a variety of spectrums such as spectrum analysis,three-dimensional spectrum,Bode diagram,axis orbit diagram,time amplitude curve,bifurcation diagram and time speed curve.The experimental study of the stability of high-speed turboexpanded refrigerator rotor supported by gas bearing is used to study the stability of the rotor.The experimental results show that the critical characteristics of rotor taper separation resonance,subsynchronous characteristics of half-whirl,periodic subsynchronous whip phenomenon and double-low frequency whirl phenomenon.The influence of the bearing gas temperature and the elastic damping rubber ring on the critical speed,low-frequency whirl and whip stability of the bearings is verified by the experimental method.The critical amplitude of the rotor is gradually increased with the increase of the bearing gas temperature,the rotor low-frequency whirl can be inhibited at high temperature.The experimental results show that the rotor of the silica gel experimental group exhibits low vibration amplitude and improves the rotation precision of the rotor.During the test,the low frequency characteristics of the bearing film are excited,but the vibration margin is still a distance to stability threshold.