Catastrophe Performance Analysis of Steam Flow Excited Vibration in the Governing Stage of Large Steam Turbines With Partial Admission

Abstract

Steamflowexcited vibration is one of the main faults of large steam turbines. The catastrophe caused by steamflowexcited vibration brings danger to the operation of units. Therefore, it is significant to identify the impact factors of catastrophe, and master the rules of catastrophe. In this paper, the quantitative analysis of catastrophe performance induced by steam exciting force in the steam turbine governing stage is conducted based on the catastrophe theory, nonlinear vibration theory, and fluid dynamics. The model of steam exciting force in the condition of partial admission in the governing stage is derived. The nonlinear kinetic model of the governing stage with steam exciting force is proposed as well. The cusp catastrophe and bifurcation set of steamflowexcited vibration are deduced. The rotational angular frequency, the eccentric distance and the opening degrees of the governing valves are identified as the main impact factors to induce catastrophe. Then, the catastrophe performance analysis is conducted for a 300 MW subcritical steam turbine. The rules of catastrophe are discussed, and the system's catastrophe areas are divided. It is discovered that the system catastrophe will not occur until the impact factors satisfy given conditions. Finally, the numerical calculation method is employed to analyze the amplitude response of steamflowexcited vibration. The results verify the correctness of the proposed analysis method based on the catastrophe theory. This study provides a new way for the catastrophe performance research of steamflowexcited vibration in large steam turbines.