Calculation and analysis of critical speed of high-speed turbo-expanders

The advantages and disadvantages of the Prohl method, the Riccati recursive method and the finite element QZ(FEQZ) method in estimating critical speed of turboexpander rotor-bearing systems with anisotropic elastic support were discussed to ensure stable operation of high speed turboexpanders. It is suggested that the FEQZ method be the most effective way when the actual structure and practical application of turboexpanders are considered. The Matlab code was employed to design the program, and the results show that the program process is simplified and the calculation accuracy is higher. In addition, the effects of the support stiffness and the damping coefficient on critical speed of the rotor-bearing system of a turboexpander within actual working condition range were analyzed, and the calculation results were validated by the experimental data.