Xie Danmei

Sensitivity analysis of torsional vibration behavior of the shafting of a turbo generator set to changes of its mechanical parameters

Aiming at a 300 MW turbo-generator model, the sensitivity of natural torsional frequencies and modes of torsional vibration (TV) to the rotational inertia and stiffness of the turbo-generator were analyzed. Calculation results show that the variation of the rotational inertia or stiffness either of the rotor system as a whole (namely shafting) or only locally may both remarkably influence the TV characteristics of the rotor. The influence of localized variation is still notable although it is not as great as that of the rotor as a whole. The segments on the shafting, which contribute more to a certain mode of vibration, have a greater influence on the pertaining order of TV. Compared with the modal shape, a larger slope can be observed at these sections of the rotor for the particular mode. Thus, frequencies can be modulated by modifying the local construction of the rotor to make the natural TV frequency of a certain order avoid some specific value, herewith arriving at the objective of tuning. Therefore, it is very important, in the course of modeling for the purpose of studying the TV of the shafting of a turbo-set, to accurately determine the structural parameters of parts that have a relatively sensitive effect on the TV behavior.

Research and development of a high-quality thermal-stress online monitoring model for the 600 MW turbine

To monitor and control its thermal state, a rotor’s temperature and thermal stress fields must be calculated in real time. After some reasonable assumptions and simplification, iterative models of the rotor’s temperature and thermal stresses were obtained with an integral transform based on a two-dimensional axis-symmetry thermal conduction differential equation. The models can deal with some nonlinear factors such as material and boundary condition. An example is given to compare results computed by the finite element method (FEM) and one-dimensional models. The result shows that the analytical model gained has high quality and the computing course is very short. The iterative formulas could be used not only to analyze the rotor’s thermal states of turbine, but to monitor and control them online. The method adopted can be used to analyze the thermal state of other axis-symmetry objects having similar boundary conditions.