Dynamic Stability Study of Static Gas Bearing for Small Cryogenic Turbo-Expander

An experimental method is presented to analyze the dynamic stability of the gasbearing for small cryogenic turbo-expanders.The rotation imbalance response and the shape ofthe rotor orbit were obtained for different speeds up to 110,000 rpm,and the critical speed of therotor-bearing system was determined by a Bode diagram.An FFT signal analytical method wasapplied to identify the resonance frequency,and the waterfall plot was presented.During the wholeprocess of speeding up to the designed speed of 110,000 rpm,the rotor-bearing works stably withno whirl instability,which is validated in a waterfall plot.Also,the tested rotor-bearing modelwas analyzed theoretically.It was proved that the experimental results were highly consistentwith those of theoretical calculations.Thus the experimental method proposed here to analyzethe dynamic stability of the gas bearing is feasible.