ROTOR-TO-STATOR, RUB-RELATED, THERMAL-MECHANICAL EFFECTS IN ROTATING MACHINERY

The thermal effects of rotor-to-stator rub, and their influence on the rotor vibrational response, are discussed in this paper. Based on mac hinery observations, it is assumed in the analysis that velocities of transient thermal effects are considerably lower than that of rotor vi brations, and thermal effects affect only rotor steady-state vibration al responses. These responses would change due to thermally induced bo w of the rotor, which can be considered slowly varying in time for the purposes of rotor vibration calculation. Thus uncoupled from the ther mal problem, the rotor vibration is analyzed. The major consideration is given to the rotor, which experiences intermittent contact with the stator due to predetermined thermal bow of the rotor, unbalance force , and radial constant load force. In the case of an inelastic impact, this causes an on/off step-change in the stiffness of the system. A sp ecially developed transformation is applied to the system model which contains discontinuities, and an averaging technique is then used to a nalyze stability of the different resonance regimes of rotor motion th at were obtained. These regimes are further used to calculate the heat generated during rotor-to-stator contact stages, as a function of the rmal conditions and rotor thermal bow modal parameters. The calculated heat input is used as a boundary condition for the rotor heat transfe r problem. The latter is treated as quasi-static, which allows the app lication of an asymptotic method to the problem. The solution at its f irst approximation is used to adjust the rotor thermal bow value. As a result of this calculation, an ordinary differential equation with co mplex variables is obtained for the thermal bow, and it is investigate d from the stability standpoint.