The phenomenon of violent vibration in a steam turbine at critical speed can lead to what problem?

The phenomenon of violent vibration in a steam turbine at critical speed can lead to physical damage to the turbine. When a turbine operates at its critical speed, it can experience resonance, which amplifies vibrations to levels that exceed the design limits of the machinery. This excessive vibration can cause various types of physical damage, including fatigue failure of components, misalignment, or even catastrophic failure if not managed properly.

The other options are unrelated to the consequences of operating a steam turbine at critical speed. Increased energy efficiency, improved performance, and lower operational costs are generally positive outcomes associated with proper turbine operation and maintenance, not a result of the vibrations caused at critical speed. In contrast, the physical damage arising from such vibrations signifies a significant operational risk, underscoring why understanding this phenomenon is essential for maintaining the integrity and functionality of steam turbines in service.