Exemplary embodiments of the present disclosure relate to a turbine nozzle box.
A large axial-flow steam turbine generally includes turbine nozzles (turbine fixed blades) which are referred to as stators, and blades (turbine moving blades) which are referred to as rotors. In addition, the turbine nozzles and turbine moving blades are installed in a multistage manner in the flow direction of steam (fluid).
An impulse steam turbine allows the thermal energy of steam to perform more expansion work using each turbine nozzle, and switches the flow of steam into a deflecting flow using each turbine moving blade after the expansion work is finished so as to guide the deflecting flow to a next stage.
A conventional turbine nozzle box typically includes a plurality of parts, and the parts are coupled using bolts or by welding.
After the steam in the turbine nozzle box is first redirected so as to axially flow, it is accelerated about the rotary axis of a rotor through nozzles located on the outlet plane of the nozzle box.
A partial arc operation refers to an operation for supplying steam to only a partial region of the quadrant of the turbine, and may be performed for electricity generation capacity if necessary.
However, the region of the turbine is uniformly divided into many sections during the conventional partial arc operation, and gas may not be introduced into a partial section due to the full blocking of passages for the region division, thereby leading to formation of a dead arc zone in which the partial section is not used.
In addition, the efficiency of the turbine may be reduced during the partial arc operation due to the formation of the dead arc zone.