Determination Method of Engagement Position of SSS Clutch in NCB Steam Turbine and Analysis of Its Impact on Shaft System Vibration

An SSS clutch is incorporated into the shaft system of the NCB steam turbine in the gas-steam combined cycle unit. The benefit of this specific design is that the shaft system of the NCB steam turbine can disengage from and engage with the LP rotor during operation, enabling rapid and flexible adjustment between power generation output and heat supply. However, this mode of operation presents some special vibration issues in the shaft system. Analysis of the shaft vibration fluctuations that occur in NCB steam turbines before and after operating mode transitions indicates that this issue arises because the random engagement position of the SSS clutch induces changes in the shaft train’s balance and alignment conditions. Based on the measurement principle of shaft vibration phase and the dual keyphasor measurement system of NCB steam turbines, this paper proposes a novel methodology for determining the optimal engagement position of SSS clutches. This approach establishes quantitative correlations between shaft vibration characteristics and clutch engagement positioning, thereby enabling precise identification of the optimal engagement configuration. The research conclusions provide operational guidance for power plants to optimize shaft vibration in NCB steam turbines.