Dynamic response of steam seal rubbing in steam turbine considering thermal effect

Steam seal rubbing is a common problem bothering the power plant. Usually the rubbing happens during the process of start-up or shut-down. Some of the rubbings would cause the failure of start-up or even greatly damage the rotor, but some would not. This paper presents the dynamic response of steam seal rubbing rotor by simulation. The rubbing problem was a thermal/mechanical problem, which was decoupled by sequenced method in the simulation, i.e. the rotordynamics equation was solved in frequency domain and the heat conduction equation was solved in the time domain. The simulated results showed that the stiffness and the preload of the steam seal structure would greatly influence the amplitude and phase of the 1× vibration for a rubbing rotor. The dynamic response with a big stiffness would develop into spiraling state, and the rotor would fail to start up due to rubbing. What's worse, the partial of the rotor would be heated and bowed permanently. Therefore, it is very important to adjust the steam seal structure to reduce the stiffness of rubbing.