Modern rotordynamic analysis relies on sophisticated computational methods and is guided by stringent industry standards to ensure safety and reliability.
Focuses on the radial bending vibration of the shaft. It determines critical speeds, unbalance responses, and stability margins (logarithmic decrements).
A steam turbine rotor failed during operation, leading to significant downtime and repair costs. A failure analysis was conducted to identify the root cause of the failure. The analysis revealed that the rotor had experienced a fatigue failure due to excessive vibrations. The rotordynamic design of the rotor was modified to reduce vibrations, and the failure was prevented in future machines.
) ; a negative log dec implies rapid, destructive vibration growth. Industrial Case Studies turbomachinery rotordynamics with case studies pdf
Modification of the seals (e.g., using honeycomb seals) or increasing bearing damping. 2. Steam Turbine Critical Speed Passage
Hydrodynamic Bearing instability, Seal Aerodynamic cross-coupling
Redesign of the rotor stiffness to move the critical speed away from the operating speed. Essential Topics to Look for in Resources A steam turbine rotor failed during operation, leading
The orbit of the shaft centerline rotates in the same direction as the shaft spin. Gyroscopic moments stiffen the system, raising the natural frequency.
Spectrum analysis showed a dominant frequency at 48 Hz while the machine ran at 100 Hz (
Unlike resonance, which is driven by unbalance, instability is a self-excited vibration (sub-synchronous) caused by internal forces, such as fluid forces in bearings or seals, which can lead to rapid failure. Why Study Case Studies? The rotordynamic design of the rotor was modified
A 50 MW power generation steam turbine experienced severe
), it was classified as a subsynchronous instability. The shaft orbit grew from a tight ellipse into a wide, chaotic circular path.
A large boiler feed pump experiences repeated fatigue failure of the shaft.
: ASME Turbo Expo 2020 Paper by D. Rouwenhorst et al.