What happens to the rotor speed after the fuel valve closes during shutdown?

When the fuel valve closes during shutdown, the rotor speed decreases. This occurs because the fuel supply to the combustion process is interrupted, leading to a reduction in the energy input to the system. Without fuel, combustion cannot continue, and the engine loses its driving force, resulting in a gradual reduction of the rotor speed due to the mechanical and aerodynamic drag present in the system.

As the energy from the fuel is no longer being converted into rotational energy, the kinetic energy of the rotor begins to dissipate over time, mainly through friction and other load factors until it eventually comes to a stop. This behavior is expected in many types of engines or turbines during shutdown procedures, as the fuel supply is essential for maintaining rotor speed. The implications of closing the fuel valve illustrate the fundamental principles of energy conversion and system dynamics in power engineering.