A study of fault mechanisms in a rotor-seal system

A numerical method is described, which can be used for analyzing the fault mechanisms and the fluid-solid coupling function of gas flow-induced vibrations in a three-dimensional rotor seal system. Without resorting to a linear simplification the method features a direct numerical solution of the nonlinear aerodynamic force of a seal device flow field. Meanwhile, instead of conducting a decoupling simplification treatment by assuming beforehand a rotor vibration to be a simple harmonic one, a fluid-solid coupling model has been set up for a three-dimensional rotor seal. As a result, an analytical method is brought forth, which evaluates the gas flow-induced vibration problem of a rotor seal by taking into account the fluid-solid coupling effect. The influence of speed, pressure ratio and pre-rotation on the gas flow-induced vibrations of the seal was calculated followed by a comparison of this influence with that found in engineering practice and test results. On this basis, the reliability of several numerical calculation methods was verified. The basic characteristics of the seal gas flow-induced vibrations have also been identified. With respect to different speeds, pressure ratios and pre-rotations there are different amplitudes for each individual frequency component of a rotor vibration. However, there is always a frequency component of rotor first-order critical speed. Furthermore, the amplitude of the component will increase with the increase in speed, gas-flow inlet pressure and the positive-direction incoming gas pre-rotation. The above circumstance has been found to be in fairly good agreement with the phenomenon of seal gas flow-induced vibrations found in engineering practice and test results.