Blades and vanes for steam turbines
The purpose of turbine blades is to convert the potential energy of compressed steam into mechanical work
Depending on the operating conditions in the turbine, the length of its working blades can vary from several tens to one and a half thousand millimetres. On the rotor, the blades are located in steps, with a gradual increase in length, and a change in the shape of the surface. At each stage, the blades of the same length are located radially to the rotor axis. That is due to the dependence on parameters such as flow, volume and pressure.
With a uniform flow rate, the pressure at the turbine inlet is maximum, and the flow rate is minimum. When the working medium passes the turbine blades, mechanical work is performed, the pressure decreases, but the volume goes up. That leads to a larger area of the surfaces of the working blade and, accordingly, to its bigger dimension. For example, if we take a 300 MW steam turbine, the length of the blade at the first stage is 97 mm, and at the last, 960 mm.
