What is meant by critical speed in a steam turbine?

Critical speed in a steam turbine refers to the speed at which the turbine shaft naturally vibrates. This is a crucial concept because every rotating component, including turbine shafts, has specific speeds at which they tend to resonate due to structural and mechanical properties. When operating at or near the critical speed, the turbine can experience increased vibrations that may lead to mechanical failure or operational inefficiencies.

Understanding critical speed is essential for engineers because it helps in designing equipment to avoid these speeds during normal operation, ensuring stability and safety. When the turbine spins at its critical speed, resonance can occur, amplifying vibrations and potentially causing a failure. Therefore, maintaining operation below this speed is vital for longevity and performance, making this concept a fundamental aspect of turbine engineering and maintenance.

The other options describe different aspects of turbine performance but do not address the vibrational dynamics related to critical speed.